Wednesday, May 29, 2013

Antenna Topics: A simple, indoor multiband dipole antenna. Post #197

Over the past few days, mother Nature has released a torrent of heavy showers over the Hamakua Coast of Hawaii Island, making outdoor antenna work very wet and potentially dangerous.  When the weather turns bad, I usually lower all my verticals and inverted vees to ground level, disconnect antenna feed lines, and unplug my rig from the electrical mains.  I usually run my station off of deep-cycle marine batteries charged by photovoltaic panels, but sometimes, I use the electrical grid to run a bit more power (i.e. more than 50 watts) from my venerable Swan 100-MX.

During today's passing showers, I decided to revive one of my old indoor antennas, a 10, 15, and 20 meter segmented dipole fed by a short piece of 50-ohm cable (RG-58).  This certainly isn't a new idea.  I've used the concept for outdoor antennas as well.  You can choose which of these bands to use by clipping or unclipping dipole segments.  AK7M and NV5I have published versions of this antenna in various ARRL publications.  I will cite the appropriate reference at the end of this post.

I was able to find all of the antenna materials by carefully searching my storage bins in the garage, a place I call the "radio room annex."

So, with the rain falling down, I decided to "homebrew" another indoor dipole.  Hopefully, I could use this simple antenna to make a few contacts before dinner.

MATERIALS:

Approximately 12-feet (3.65 meters) of RG-58 coax for the feed line.  I had a 12-foot (3.65 meters) piece of RG-58 cable with "pigtails" left over from an old Hustler Mobile Antenna.  This coax would be sufficient to reach the Drake MN-4 transmatch ("tuner").

One PL-259 connector.

A 50-foot (15.24 meters) spool of AWG #22 insulated, solid copper wire.  You could use any wire available.  I chose this gauge because I had some stored in the shack.

At least six test leads with alligator clips.

A box of thumbtacks.

A SWR bridge or a transmatch capable of reading SWR.  My old Drake MN-4 was able to handle the SWR chores.

Small pieces of nylon cord to support the ends of the 20 meter segments of the indoor dipole.

ASSEMBLY:

After I attached the PL-259 to the coaxial cable, I wound approximately 8-feet (2.43 meters) of coax nearest the pigtails into a "choke balun" and held the winding together with nylon ties.  Hopefully, the coil would keep rf from running down the shield of the coax into the shack.

Using the general dipole formula ,468/f (MHz)=l(ft), I determined the length of wire needed to make each element of the dipole at 28.400 MHz.  That worked out to be 8.23 feet (2.51 meters) per element.

Next, I cut two wires to this length and attached them to the feed line, one to the center connector and the other to the shield braid.

At this point, the clip leads play their role.  To get the dipole operating at 21.200 MHz (15 meters), I attached a clip lead to the end of each 10 meter segment; calculated the length of wire needed to complete the 15 meter segment (an additional 2.80 feet/0.85 meters for each element); and to complete the 20 meter segment, I added another clip lead to each antenna element and attached an additional 5.34 feet (1.62 meters) to each side to bring the 20 meter elements to a resonant frequency of 14.200 MHz.

Like NV5I, I used thumbtacks to secure the pieces of wire to the ceiling of the radio room.

With all elements connected by clip leads, I had a 20 meter antenna that exhibited a 1:7 to 1 SWR without the Drake MN-4 in line.  For 15 meters, I got a 1.8 SWR without the Drake MN-4 in line.  The 10 meter segment showed a SWR of 1.6 to 1 without the Drake MN-4 in line.  When I used the Drake MN-4 in the antenna system, I was able to get a SWR below 1.3 to 1 on all bands.  With a little trimming, I could use this antenna without a tuner.  In such a case, you may want to cut your antenna elements a little longer than the formula provides.

INITIAL PERFORMANCE:

I was pleased with this "homebrew" antenna.  As NV5I states in his article, "it's inconspicuous, non-hazardous and efficient."  Running 10 watts CW through the old Swan 100-MX, I was getting reports between 559 to 589, depending on propagation.  SSB reports were a bit weaker, ranging from 54 to 57, with approximately 10 watts output.  The antenna works and was easy to build.  Best of all, I didn't have to go out in the rain to adjust the antenna.  This antenna was just right for a bad weather day.

Perhaps this indoor dipole will useful for those amateur radio operators subject to the restrictions of HOAs and CC&Rs.  This could be the answer to some of your antenna problems.  As long as you run low power and use digital modes, you shouldn't have any problems with rfi or nosey neighbors.

REFERENCES:

Barry, Larry A., NV5I.  "An Indoor Dipole Antenna."  Reprinted in "Hinks & Kinks For the Radio Amateur", 13th Edition, ARRL, Newington, CT., 06111, Copyright 1992, pp. 7-26 and 7-27.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

You can leave comments on the form at the bottom of this post.

Aloha es 73 de Russ (KH6JRM)

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.

Saturday, May 25, 2013

Antenna Topics: Reworking a basic 10 meter ground plane antenna. Post #196

Reworking a basic 10 meter ground plane antenna.

After two fun-filled days of experiments with my horizontal 10 meter dipole, I decided to lower both masts, disassemble the dipole elements, and store them in the garage for possible emergency or portable use.  For some reason, the second mast made my "antenna farm" noticeable from the street and I opted to use only one mast for my next 10 meter antenna project.  I selected the fiberglass mast with the light green paint for antenna projects because it blended in well with the garden and the surrounding vegetation.  The spare MFJ mast would be used as a backup and emergency mast.

Still, I wanted to work a bit more with 10 meters, which has shown some excellent propagation during the past month.  I had already used a 10 meter vertical dipole with great success during the past year.  This time, I wanted to experiment with a 10 meter ground plane antenna that could be easily built, erected, and taken down without undue problems.  With four elevated radials, I hoped to avoid an extensive radial field and to get a good match for some RG-6 coax I had stored in the garage.  Although the RG-6 is a nominal 75 ohms (versus a nominal 50 ohms for RG-8X, RG-8, and RG-58), I felt any small mismatch could be handled by my trusty Drake MN-4 matchbox ("tuner").

As I mentioned a few days ago, I had a supply of RG-6 left over from a radio station studio rebuild several years ago (I was working as a news person then).  I was able to get a few Radio Shack "F" to "UHF" connectors to make using the RG-6 easier.

MATERIALS:

Since this was going to be a busy weekend (I had to announce the "Memorial Day Drag Races" at the Hilo Drag Strip), I lined up all supplies on Thursday and built the 10 meter ground plane on Friday (24 May 2013).

One 33-foot (10.06 meters) MFJ telescoping fiberglass mast.

One 5-foot (1.52 meters) support stake for the mast.

One Budwig HQ-1 center coax connector (available from Fair Radio Sales in Lima, Ohio).

Five ceramic or plastic insulators.  One insulator would be attached to the top of the mast and would support the vertical element of the 10 meter antenna.  The other four insulators would be attached to each elevated radial.

Four, 5-foot (1.52 meters) wooden or metal fence posts to tie-off the radial elements.

Some dacron rope to attach the end insulators of the elevated radials to the posts.

Fifty-feet (15.24 meters) of RG-6 coaxial cable.  This would be the feed line.  The feed line would be connected to the anti-static unit beneath the shack window.

10-feet (3.04 meters) of RG-6 coaxial cable to run from the anti-static unit, through the shack window, and onto the Drake MN-4 matchbox.  Small pieces of RG-6 coaxial cable would connect the Drake MN-4 to the Swan Transceiver, a low pass filter, and a dummy load.

Approximately 50-feet (15.24 meters) of #14 AWG housewire.  Although the length of the vertical element and its four elevated radials would amount to only 41.15 feet (12.55 meters), I wanted some extra length, just in case I needed to trim the antenna.  Some antenna experts advise making the radials about 5% longer that the radiating element, but I preferred to keep all antenna lengths the same.

Nylon ties, vinyl electrical tape, dacron rope.

ASSEMBLY:

The mast was lowered to the ground for ease of antenna installation.

I wanted the antenna to be resonant at 28.400 MHz, right in the center of the novice/technician phone band (28.300 MHz to 28.500 MHz).  I find there is a lot of action in this portion of the band when 10 meters is open.

Using the general formula, 234/f (MHz)=l (ft), I cut each wire (the vertical element, plus four elevated radials) to a length of 8.23 feet (2.51 meters).

I attached an end insulator to the top of the mast and connected the vertical element to it.  I led the vertical element down from the top 8.23 feet (2.51 meters) and secured the wire to the fiberglass mast with nylon ties.

I attached the vertical element to the + side of the Budwig HQ-1 center connector.  I attached each elevated radial to the - side of the Budwig HQ-1 center connector.  All connections were soldered and covered with several layers of vinyl electrical tape.

End insulators were attached to the end of each elevated radial.

Before I connected the RG-6 feed line, I wound a "choke balun" near the "F" to "UHF" connector.  The balun would help keep stray rf from entering the shack by the shield of the coaxial cable.

Once erected the mast, the feed point of the antenna would be approximately 25-feet (7.62 meters) above ground level.  I ran the feed line down the mast to a level of approximately 16-feet (4.87 meters) above ground level.  The feed line was secured with nylon ties.

I hoisted the mast onto its wooden support stake and spread out the elevated radials, separating each wire by 90-degrees.  The elevated radials were led off the mast to pre-positioned wooden fence stakes.  Although the angle was not at an optimum of 45-degrees, the elevated radials appeared evenly spread around the mast at a uniform height at the post tie-off point.  The elevated radials offered some support for the mast.

I then led the feed line to the anti-static unit beneath the shack window.  A short length of RG-6 went from the anti-static device, through the shack window, and onto the Drake MN-4 matchbox ("tuner").  Small patch cords connected the Swan 100-MX transceiver to the Drake MN-4, the low pass filter, and the dummy load.

INITIAL PERFORMANCE:

With the Drake MN-4 in the antenna system, I was able to get a 1.3 to 1 SWR in the 28.300 MHz to 28.500 MHz segment of 10 meters.  A little trimming will probably improve that figure.  I was able to get a SWR of 1.7 to 1 across the entire 10 meter band with the help of the Drake MN-4.  Tuning was a bit "touchy" at the bottom 50 KHz of the band.  For now, I'm satisfied with the performance of the ground plane.

I've made only a few contacts on 10 meters since I erected the antenna on Friday.  So far, CW contacts have reported 559 to 579 on my signals, while SSB contacts have ranged from 54 to 57.  Nothing spectacular, but the antenna works.  The rig runs cool and the old Drake MN-4 seems able to take care of any mismatch on the band.  I've been running the old Swan 100-MX at 20 to 30 watts.

The antenna was assembled at little cost, since I had most of the materials in the shack.  I'm sure you can find  mast sections, wire, and rope at the nearest hardware store or home improvement center.  I leave the choice of coaxial cable up to you.  I used RG-6 because I had a supply of the cable from my old days at KKBG-FM/KHLO-AM.  "F" to "UHF" connectors for the RG-6 can be found at Radio Shack stores.

If you want a simple 10 meter antenna that requires only one support and doesn't need an extensive ground radial system, try the ground plane antenna with elevated radials.  The antenna is fun to build and it works.

REFERENCES:

http://www.dxzone.com/catalog/Antennas/10M.
http://www.youtube.com/watch?v=aLgFeTpIX4A.
http://radiosurvivalist.com/antennas/for-10-meters.asp.
http://www.comport.com/~w5alt/antennas/?pg=3.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

You can leave comments on the form at the bottom of this post.

For the latest in amateur radio news and trends, please check out my news site--http://kh6jrm.com.  I've included a few news updates at the bottom of this post.

Aloha es 73 de Russ (KH6JRM0.

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.




Thursday, May 23, 2013

Antenna Topics: A simple 10 meter dipole. Post #195

A simple 10 meter dipole antenna.

One of my favorite amateur radio bands is 10 meters.  It's unpredictable, capricious, and fun!  When propagation is favorable, you can works the world at QRP levels.  Basic antennas for this band are simple, cheap, and forgiving.  Most of the parts needed for this antenna can be bought at your neighborhood hardware store or home improvement outlet.

Although 10 meters has been a bit sporatic over the past few days, I've been able to make some good contacts during daylight hours from my location on Hawaii Island--the island with the active Kilauea Volcano.  We live dangerously over here.

MATERIALS:

Two fiberglass or pvc masts, ranging from 20 to 30 feet tall (6.09 meters to 9.14 meters).  These masts will support the 10 meter half-wavelength "flat top" antenna.  Fortunately, my backyard can support two masts approximately 30 feet (9.14 meters) apart.  Anything more requires my dipoles to be in the inverted vee configuration.  For this project, I had two, 33-foot (10.06 meters) fiberglass masts in storage.

One Budwig HQ-1 coax center connector (available from Fair Radio Sales in Lima, Ohio).  You make a center connector out of plexiglass, tough plastic, or even a long, ribbed end insulator.  I had a spare HQ-1 in the shack, so I used that for the center connector.

Two ceramic insulators. These would be used to tie off each dipole element to its mast.

A 6-foot (1.82 meters) wooden or metal fence post to support each mast.

Fifty-feet (15.24 meters) of 50-ohm coaxial cable (RG-8X, RG-8, RG-58).  Since I didn't have any RG-8X around the shack, I used the RG-6 coaxial cable attached to my 15 meter vertical dipole.  I disconnected the inverted dipole and stored it in a plastic storage bin for later use.

A suitable length of #14 AWG house wire for the dipole elements.  I wanted the antenna cut for 28.400 MHz, right in the middle of the novice/technician phone band for 10 meters (28.300 MHz to 28.500 MHz).  Using the general formula for a half-wave flat top dipole (468/f (MHz)=l(ft), I cut a piece of #14 AWG wire to a length of 16.47 feet (5.02 meters).  Each dipole element would be 8.23 feet (2.51 meters) long.

10-feet (3.04 meters) of dacron rope for each end insulator.  The rope would be used to tie-off the dipole elements.

ASSEMBLY:

I built the antenna with both masts nested to the ground.

I attached each dipole element to the center insulator.  Each connection was soldered and wrapped with several layers of vinyl electrical tape to seal out salt air and rain.

Each antenna element was attached to its end insulator.  A 10-foot (3.048 meters) piece of dacron rope attached each element to the top of its respective mast.

I attached the RG-6 coaxial feed line to the Budwig HQ-1 center connector.  The cable already had a "choke balun" from the previous 15 meter vertical dipole.

I hoisted the masts into position, leaving a little sag in the flat-top dipole to account for wind movement.

The antenna height above ground was approximately 31-feet (9.45 meters), allowing for some sag in the antenna.

The RG-6 coax feed line was led off the dipole at a 90-degree angle, finally reaching a plastic hook in the garage.  The hook was approximately 16-feet (4.87 meters) above ground.  The cable was then led to the anti-static unit beneath the shack window.

A 10-foot piece (3.04 meters) of RG-6 coax went from the anti-static unit, through the shack window, and then onto the Drake MN-4, low pass filter, dummy load, and the Swan 100-MX transceiver.

INITIAL PERFORMANCE:

With the Drake MN-4 antenna matchbox ("tuner") in line, I was able to keep SWR below 1.5 to 1 from 28.300 MHz to 28.500 MHz.  I've been able to establish a few mainland U.S.A. and Asian contacts, with reports varying from 549 to 579 on CW and from 53 to 57 on SSB.  I've been running the old Swan 100-MX at 20 to 30 watts.  Nothing outstanding, but I do get contacts on a band that has been "up and down" for several days.  I'll keep the flat top around for a few days and see what it does.  I may also shift the antenna to a vertical dipole arrangement as I did with my 15 meter antenna.  The conversion will be simple and will require only one mast.  In any case, I won't need a ground radial system.

Try a simple 10 meter horizontal dipole...it works; it's easy to build; and it's cheap.

REFERENCES:

http://www.hamuniverse.com/easydipole.html.
http://www.arrl.org/files/file/Technology/tis/info/pdf/9106023.pdf.
http://www.youtuve.com/watch?v=quXF2MHIn-w.
http://www.youtube.com/watch?v=8KHzsKYs

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

You can leave comments on the form at the bottom of this post.

For the latest in amateur radio news, visit my news site--http://kh6jrm.com.  I've included a few items of general interest at the bottom of this post.

Thanks for joining us today!

Aloha es 73 de Russ (KH6JRM).

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.


Wednesday, May 22, 2013

Antenna Topics: A simple 15 meter vertical dipole. Post #194

A simple 15 meter vertical dipole.

One of my favorite amateur radio bands is 15 meters.  The band is usually open during daylight hours and provides plenty of DX for those of us operating from the central Pacific.  Although most of my antennas are designed to be used on several bands (using ladder line, a 4:1 balun, and an antenna matchbox or "tuner"), I sometimes want to use an antenna specifically designed for a single band using whatever coaxial cable I have around the shack.

In my location, I prefer using verticals, inverted vees, and loops because my backyard is small and room for a decent radial field is non-existent.  If I can't use a horizontal flat top dipole, I can always go up using a vertical dipole.  These antennas are simple to build, erect, and take down.  They are ideal for portable use with a telescoping fiberglass or pvc mast.  Once I finish testing a vertical dipole for a chosen band, I keep the pre-assembled antenna in a plastic storage box for future emergency and portable use.

Since I was't teaching today, I decided to use the sunny and somewhat voggy (volcanic smog) morning to build a portable 15 meter vertical dipole.  All of the antenna materials were found in the storage room near the garage.  Feel free to substitute materials you have available.  Most of the wire and mast materials can be obtained from a hardware store or home improvement center.

MATERIALS:

One 33-foot (10.06 meters) MFJ telescoping fiberglass mast.  You can also use pvc pipe, surplus military mast sections, or even wood.

Approximately 30-feet (9.14 meters) of #14 AWG house wire.  You could use any wire you have available, since the antenna elements will be secured to the mast.

One Budwig HQ-1 center coax connector.  You could also strip a piece of 50 or 75-ohm coaxial cable and use the pigtail to connect the upper and lower sections of the vertical dipole to the feed line.  I happened to have an extra HQ-1 center connector in the shack.  Fair Radio Sales of Lima, Ohio sells these connectors.

Fifty-feet (15.24 meters) of 50 or 75-ohm coaxial cable.  If you prefer 50-ohm coax, you can use RG-8, RG-8X, or RG-58 coaxial cable.  I used 75-ohm RG-6 coaxial cable for this project because I had some cable left over from a studio remodeling job at my former radio station.  I found "F" to "UHF" connectors at the Hilo, Hawaii Radio Shack store--this allowed me to use the RG-6 without cutting off the "F" connector and soldering on a "UHF" connector.

A 5-foot (1.52 meters) wooden stake to support the MFJ fiberglass mast.

Nylon ties and vinyl electrical tape to secure the antenna elements to the mast.

ASSEMBLY:

As is my usual practice, I built the antenna on the ground.

Using the general formula 468/f (MHz)=l (ft), I cut the dipole to a length of 22.02 feet (6.71 meters).  This would put antenna resonance at 21.250 MHz in the 15 meter band.  Each antenna element would then measure 11.01 feet (3.35 meters).

I attached each antenna element to the Budwig HQ-1 center insulator.  The top half of the vertical dipole was connected to the + side of the connector.  The bottom half of the vertical dipole was connected to the - side of the connector.  Each connection was soldered and wrapped with several layers of vinyl electrical tape to protect the connection from wind, salt air, and rain.

The center connector was secured at the 16-foot (4.87 meters) point of the fiberglass mast.  Each element was run along the mast and secured with nylon ties and vinyl electrical tape.

I wound a "choke balun" out of several turns of the RG-6 coax before I attached the coax to the center connector.  The "choke balun" would keep unwanted rf out of the shack.

Once I finished building the antenna and securing the elements to the mast, I hoisted the mast onto a wooden stake.

The RG-6 coax was led from the mast at a 90-degree angel to a plastic hook under the garage roof.  The cable maintained a 16-foot (4.87 meters) height above ground until it was attached to the support hook.  At this height, the feed line presented little risk to people, pets, or vehicles that might pass near the mast.

The RG-6 coax was led down to the anti-static unit near the shack window.  A 10-foot (3.04 meters) piece of RG-6 coax was attached to the anti-static unit and led through the shack window to the Drake MN-4 antenna matchbox ("tuner").  Small patch cords made from RG-6 connected the Swan 100 MX transceiver to the Drake MN-4, the low pass filter, and the dummy load.

PRELIMINARY RESULTS:

This antenna has been a joy to use.  With the Drake MN-4 in line, I've kept SWR below 1.3 to 1 across the 15 meter band.  Using 50 watts or less, I've been able to get CW reports of 569 to 599 and SSB reports of 55 to 59, depending on propagation.

This antenna requires only a few minutes to erect or take down, making it perfect for emergency or portable use.  I'm in the process of building similar vertical dipoles for 20 and 10 meters. All of these antennas will be tested and kept in storage for future use.

So, if you have a few hours and want to build an effective, cheap, and efficient mono-band antenna, consider erecting a vertical dipole.  Best of all, this antenna doesn't require a ground system.

Have fun!

REFERENCES:

http://www.hamuniverse.com/kl7jrverticaldipole.html.
http://www.arrl.org/files/Technology/info/pdf/9106023.pdf.
http://www.arrl.org/hf-vertical.
http://www.wolfington,net/articles/dipole/

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

You can leave comments on the form at the bottom of this post.

For the latest amateur radio news, please visit my news site--http://kh6jrm.com.  I've included a few items from that site at the bottom of this report.

Until next time,

Aloha es 73 de Russ (KH6JRM).

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.

Monday, May 20, 2013

Antenna Topics: RG-6 coaxial cable for antenna feed lines. Post #193

RG-6 coaxial cable--an alternative to RG-8X, RG-58, and RG-8.

Most amateur radio operators are familiar with the RG-8, RG-8X, and RG-58 family of coaxial cables.  These moderately priced cables are used for antenna feed lines and patch cords around the ham shack.  With a nominal impedance of 50 to 52 ohms, they work well with both contemporary transceivers and the old "boat anchors" we love to hate.  Many amateurs (such as yours truly) also use 300-ohm tv twinlead and 450-ohm ladder line to feed our antennas. With a suitable transmatch and a 4:1 balun, we can use an antenna on several bands.

What if you don't have any ladder line, tv twinlead, or 50-ohm coaxial cable to feed your antenna?  Is there any other cable that can be used?  There certainly is.  RG-6 coaxial cable, the type used by cable companies , can often be used the same way as 50-ohm coaxial cable.  RG-6 usually refers to a cable with an 18 AWG center conductor and a 75-ohm characteristic impedance.  Usually, this cable comes with "F" connectors.  All you have to do is get a "F" to "UHF" adapter from Radio Shack and you're ready to connect the RG-6 to your equipment.  Many amateur radio operators use RG-6 to make matching sections for loop antennas.

As luck would have it, I acquired several 25-foot (7.62 meter) and 10-foot (3.04 meters) pieces of RG-6 when my radio station (KKBG-FM/KHLO-AM) did a studio remodeling job and had some RG-6 left over.     At that time (2010), I was still working as the news director and had a good relationship with the station engineer, who also was a ham.  I secured these "left overs" at no cost...they even had the "F" connectors still attached.  I bought several Radio Shack "F" to "UHF" connectors to convert the cables for amateur radio use.  The cable has been stored in plastic containers since that fortunate day 3 years ago.  Now was the time to modify my antenna feed system.

When I researched the characteristics of RG-6 coaxial cable, I was surprised by the attenuation figures I found:

For 1 MHz, the attenuation (dB/100-feet/30.48 meters) was 0.2 dB.  For 10 MHz, the figure was 0.6 dB.  For 100 MHz, the number was 2.0 dB.  And for 1,000 MHz, the attenuation was 6.2 dB.  Those numbers would serve my purposes very well.

I tested the RG-6 on my recently erected 40 meter delta loop.  First, I replaced the 450-ohm ladder line/4:1 balun combination with 50-feet (15.24 meters) of RG-6 fed directly into the Drake MN-4.  The old Drake was able to get the SWR on both 40 and 15 meters below 1.5 to 1 on both bands.  I didn't try the antenna on 20 meters because the mismatch would be too great for the Drake MN-4.

When I reconnected  the 450-ohm ladder line/4:1 balun combination, I replaced the usual RG-8X coaxial cable from the balun to the static discharge system and the RG-8X cable from the static discharge system to the shack with RG-6 coaxial cable.  As before, the Drake MN-4 transmatch was able to bring the SWR to 1.5 to 1 on 40, 20, 15, and 10 meters.

Following a few on-air tests, I removed the RG-8X coaxial cables from the antenna system and stored them in the garage.  I'll be using the RG-6 coax substitutes for awhile, just to see if I run into any problems.  So far, the Swan 100-MX runs cool, the SWR is below 1.5 to 1, and the loop performs as well as before the substitution of cables.

So, if you want a good, general purpose feed line for your antennas, consider RG-6.  You can buy RG-6 in various lengths at the nearest hardware store or home improvement outlet in a variety of lengths.  You might be able to get some RG-6 for free from your cable company service technician.  If you don't want to worry about converting the "F" connector, just buy some "F" to "UHF" connectors from Radio Shack.

Try some RG-6 for your next antenna project.  You might be surprised how well it performs.

REFERENCES:

en.wikipedia.org/wiki/RG-6.

http://www.broadbandutopia.com/coaxial.html.

http://www.bluejeanscable.com/articles/rg6.htm.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

If you want the latest amateur radio news, please visit my news site--http://kh6jrm.com.  I've included a few news items at the bottom of this post.

Thanks for joining us today!

Aloha es 73 de Russ, KH6JRM

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.

Saturday, May 18, 2013

Antenna Topics: A simple 40 through 10 meter delta loop. Post #192

A simple 40 through 10 meter delta loop.

One of the quietest and most versatile antennas I've used over the past few years has been a 40 through 10 meter delta loop fed with 450-ohm ladder line.  Used with a 4:1 balun, an antenna matchbox (i.e. "tuner), and a few feet (meters) of 50-ohm coaxial cable, this easy to build antenna will give you hours of both local and DX contacts.

I built my original 40 meter delta loop with tuned feeders back in 1977, shortly after I passed my novice amateur license exam.  Since space was at a  premium (small backyard), money in limited supply (I was just starting my broadcast radio career after time in the Air Force), and I was recently married, extra funds for a tower and a super sophisticated rig were unavailable.  Like many of my fellow amateurs, I depended on wire antennas, used rigs, and basic designs to work the world.  My first rig was the venerable HW-101, a rig I must have rebuilt several times.

Anyway, I found simple antennas, such as dipoles, inverted vees, and loops were easy to build, cost me very little, and were more than satisfactory for my needs.  Even though my fortunes have improved since those early days, I still prefer making my own wire antennas.

So, on Friday, I opened my antenna logbook for 1977 and found a simple delta loop design I used in November of that year.  Today (Saturday, 18 May 2013), I rebuilt that antenna with supplies I had in the garage.  The antenna works very well and only took me a few hours to build, erect, and test.

MATERIALS:

One 33-foot (10.06 meters) MFJ fiberglass mast.

Three ceramic insulators.  One positioned at the top of the mast and two placed at the bottom of the delta loop.

Two 6-foot (1.82 meters) metal fence posts to tie off the bottom of the delta loop.  I used two 5-foot (1.52 meters) of dacron rope to tie the bottom insulators to the posts.

One 6-foot (1.82 meters) metal fence post to support the fiberglass mast.

A sufficient length of #14 AWG house wire for the delta loop.  Using the general formula for a loop, 1005/f (MHz)=l(ft), and the chosen frequency of 7.088 KHz for the loop, the delta loop was cut to a length of 141.78 feet (43.22 meters).  Each side of the delta loop would equal 47.26 feet (14.40 meters).

A 50-foot (15.24 meters) length of 450-ohm ladder line.

A W9INN 4:1 balun.

A 20-foot (6.09 meters) piece of RG-8X coaxial cable.  This would run from the 4:1 balun to the anti-static system near the shack window.

A 10-foot (3.04 meters) length of RG-8X coaxial cable.  This cable would run from the anti-static unit through the shack window to the Drake MN-4 antenna matchbox (i.e. "tuner).

Short pieces of 50-ohm coax cable to connect the Drake MN-4 to the Swan 100-MX, the low pass filter, and dummy load.

ASSEMBLY:

The antenna was built on the ground.

I fashioned the antenna wire into a rough triangle shape.  I attached a ceramic insulator to the top of the mast and passed the antenna wire through it to the far right end insulator.  At the lower left insulator, I attached the 450-ohm ladder line, with one wire connected to the wire running towards the top of the mast and the other wire attached to the lower wire running to the far right insulator.  All connections were soldered and wrapped with several layers of vinyl electrical tape.

You can attach the feed line at any corner of the delta loop, depending on what kind of polarization you desire.  I attached the feed line to the bottom left of the delta loop because it made maintenance simpler for me.  I expect my signal will be vertically polarized.

I hoisted the fiberglass mast onto its support stake and tied-off the bottom portion of the delta loop to two stakes.  The sides resembled an equal lateral triangle.

The ladder line was led away from the lower left insulator at approximately 6-feet (1.82 meters) above ground.  The ladder line was attached to the 4:1 balun on the garage wall (approximately 6-feet/1.82 meters) above ground.

The 20-foot (6.09 meters) length of RG-8X was attached to the balun and run to the anti-static unit.  The balun was later covered with thick plastic sheeting to protect it against rain and wind.

From the anti-static unit, I ran a 10-foot (3.04 meters) of RG-8X through the window of the shack and onto the Drake MN-4, the Swan 100-MX, and associated equipment.

PRELIMINARY RESULTS:

Using the Drake MN-4 and the 4:1 balun, I was able to keep the SWR below 1.5 to 1 on 40, 20, 15, and 10 meters.  Although propagation has been down a bit since the last CME from the sun, there have been some excellent contacts using less than 50 watts from the old Swan 100-MX.  Depending on the band and time of day, most CW reports range from 549 to 599 and the SSB reports vary between 54 and 57.  Local interisland contacts usually range from 579 to 599 on CW and 57 to 59 on SSB.

The loop does an excellent job for local area nets with coverage out to about 250 miles (approximately 400 kilometers).  I'm probably getting more horizontal polarization than vertical polarization.  The loop makes an excellent NVIS (near vertical incident skywave antenna).  Those into emergency communications may want to consider a low-level loop for strong local coverage.

So far, I'm satisfied with the performance of the delta loop.  It's quiet, cheap, and simple to make.  I've been thinking of making another delta loop and using the pair as a 2-element beam.  I should get some gain out of this arrangement.  The antenna was an enjoyable project.

REFERENCES:

"How to build a delta loop antenna."  http://www.youtube.com/watch?v=WF1TIfbI8Xo.
"Dual Delata Loop for 10 and 12 Meters."  http://www.hamuniverse.com/kl7jrdualdelta1012.html.
"Delta Loop for HF--W5SDC Homepage."  http://w5sdc.net/delta_loop_for-hf.htm.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

For the latest amateur radio news, visit my news site...http://kh6jrm.com.  I've added a few stories from that site to the bottom portion of this post.

Thanks for joining me today!

Aloha es 73 de Russ, KH6JRM

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.


Thursday, May 16, 2013

Antenna Topics: A multi-band half-wavelength sloper covering the 40, 20, 15, and 10 meter amateur radio bands, post #191.

A multi-band half-wavelength sloper antenna.

This has been another beautiful, slightly windy day on Hawaii Island--a perfect time to build another antenna for DX adventure.  Although I've been happy with my 40 meter vertical with tuned counterpoise, I wanted to experiment a bit with another antenna I used frequently in my novice license days almost four decades ago.

I quickly found my antenna experiment log book on the shelf of the radio room and turned to the pages marked "November-December 1977."  Those were some unusually dry months at my old QTH in Honokaa.  I was able to build several working verticals, loops, and slopers for my then new novice station.

By feeding the sloper with 450-ohm ladder line and a 4:1 balun, I was able to cover three novice segments  in the 40, 15, and 10 meter amateur radio bands with few problems.  I knew the antenna would work on 20 meters, but I didn't hold a higher license (i.e. general, advanced, or extra class) to  qualify for that band.  Of course, after the passage of 37 years, I eventually got my general, advanced, and extra class licenses, so the old novice restrictions didn't apply.

Like a child in a toy store, I relished the idea of rebuilding an old antenna that could serve my current license class (Amateur Extra Class).  Since I have a limited budget in my retirement years, I decided to continue my practice of building my own antennas with wire, pvc masts, and parts available locally.  I also build my antennas with another purpose--they are collapsable and transportable for mobile, portable, or emergency use.

MATERIALS:

One MFJ telescoping fiberglass mast, 33-feet long (10.06 meters).  The top of the sloper would be attached to the tip of the mast, with the rest of the antenna running at a 45-degree angle to a tie-off stake.

66.02 feet (20.13 meters) of #14 AWG house wire.  The sloping dipole was designed to resonate at 7.088 KHz, the frequency of the Hawaii Afternoon Net.  During construction of the sloping dipole, the wire would be cut into two equal portions (33.01 feet/10.06 meters).  Each piece would form the elements of the dipole.

Two ceramic or plastic insulators to tie-off the sloping dipole.  One insulator would be at the top of the mast, while the other would drop down at a 45-degree angle to a wooden tie-off stake.

Two small pieces of dacron rope to tie-off the ceramic insulators.

One ceramic insulator at the center of the antenna.  The 450-ohm feed line would be attached here.

50-feet (15.24 meters) of 450-ohm ladder line.  This would serve as the antenna feed line.

One W9INN 4:1 balun.  Any 4:1 balun would work.  I happened to have a spare W9INN balun in the shack.

20-feet (6.09 meters) of RG-8X coaxial cable to run from the 4:1 balun to the anti-static discharge unit near the window of the shack.

A 10-foot (3.04 meters) piece of RG-8X cable to run from the static discharge unit  through the window pane and then on to the Drake MN-4 matchbox.  An antenna "tuner" is necessary for this antenna to work properly.

Small coaxial patch cords to connect the Drake MN-4 to the Swan 100-MX transceiver, a dummy load, and a low-pass filter.

ASSEMBLY:

The mast was placed on the ground.  Each antenna element was attached to a ceramic insulator and to the center ceramic insulator.  The top half of the antenna and its corresponding insulator were attached to the tip of the MFJ fiberglass mast and secured with nylon ties.  The bottom element was attached to the center insulator.  The end of this element was attached to its insulator and later tied-off at a wooden stake.

The 450-ohm ladder line was attached to each element, with the center insulator supporting the connection.  All connections were soldered and covered with several layers of vinyl electrical tape.

The mast was hoisted and placed on its wooden support stake.  The support stake was a metal fence post, 6-feet long (1.82 meters).  The post was driven into the ground approximately 2-feet (0.60 meters).  The antenna was brought off the top of the mast at a 45-degree angle and secured to a 5-foot (1.52 meters) wooden stake.

The 450-ohm ladder line was led off from the center connector to the W9INN 4:1 balun attached to the garage.  The feed line remained approximately 16-feet (4.87 meters) off the ground until it reached the balun just below the roof of the garage.  The balun was later wrapped in plastic to protect it from the rain and sun.

20-feet (6.09 meters) of RG-8X was attached to the 4:1 balun and directed down to the anti-static unit below the shack window.  The anti-static unit is attached to an 8-foot (2.43 meters) copper ground rod.

A 10-foot (3.04 meters) piece of RG-8X entered the shack through the window pane and was connected to the Drake MN-4 and the rest of the station equipment.

INITIAL PERFORMANCE:

If you change the direction of the stake supporting the bottom half of the sloping dipole, you can get some directivity to your signal.  Since I planned to aim my signal to different parts of the world, I decided to put stakes facing NW, NE, SW, and SE of my QTH.

Initial tests were encouraging.  With the Drake MN-4 in line, I was able to get a 1.5 to 1 SWR on 40, 20, 15, and 10 meters.  Signal reports varied from 559 to 599 on CW and 54 to 59 on SSB, depending on propagation and time of day.  Because of the recent CMEs from the sun, propagation on 15 and 10 meters has been poor to fair over the past few days.  Most of my contacts were made using less than 50 watts from the old Swan 100-MX.  The rig is old and I didn't want to stress the finals too much.

As is my usual practice, I disconnect and ground the feedline after the operating day is over.  I also lower the mast to reduce visibility and the chance of a lightning strike.  The mast is painted a dull green and seems to blend in well with the surrounding trees and vegetation.  The mast is hardly noticeable from the street.

So far, I'm satisfied with the overall performance of this "homebrewed" antenna.  My cost was minimal because I had most of the materials stored in the garage.  What I didn't have, I could have bought at the nearest hardware or home improvement center.

If you want a simple, multi-band antenna that works, try this sloping dipole.  You won't be disappointed.

REFERENCES:

"A Two band Half Sloper Antenna" http://w5gzt.us/8006032.pdf.
"MF/HF Slopers--ARRL."  http://www.arrl.org/mf-hf-slopers.
"Sloper Antenna Tests."  http://www.hard-core-dx.com/nordicdx/antenna/wire/sloper.html.

If you want the latest Amateur Radio News, please check my news site -- http://kh6jrm.com.  I've included a few news items at the end of this post.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Thanks for joining us today!

Aloha es 73 de Russ (KH6JRM)

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island


Sunday, May 12, 2013

Antenna Topics: A 20 meter vertical antenna with tuned counterpoise, post #190

KH6JRM's Amateur Radio Antenna Topics:

A 20 meter vertical antenna with tuned counterpoise.

This weekend has been outstanding on Hawaii Island.  Weather conditions were partly sunny and a bit cooler, thanks to the return of gentle trade winds.  Most of the vog (volcanic smog) has been blown off and most of us can finally breathe normally.  In other words, this was a grand day to build antennas.

In my last post, I described a 40 meter vertical with tuned counterpoise that has performed well on the 7 MHz and 21 MHz amateur radio bands (the 15 meter antenna uses the third harmonic of 40 meters and works as a 3/2 wavelength antenna on 15 meters).  Since I built the antenna for the 7.088 MHz Hawaii Afternoon Net, it functions well around 21.264 MHz in the SSB portion of the 15 meter band.

Now that I've enjoyed some success with this vertical, I decided to make another vertical antenna with a tuned counterpoise for 20 meters, concentrating on a frequency of 14.200 MHz.  Like my 40 meter version, I opted for an elevated tuned counterpoise instead of a radial field to complete the "missing half" of the vertical antenna.  My yard is quite small and an extensive radial field is not possible at this time.

This antenna was built for use without a transmatch or antenna tuner.  My trusty Drake MN-4 is waiting for a general cleanup and maintanance check before I return it to service.

MATERIALS:

A fiberglass, pvc, or wooden mast to support the vertical element.  All I had in the storage room was a homebrew 20-foot (6.09 meters) pvc mast I used for another project.  So, I grabbed that mast and began the project.

A sturdy 6-foot (1.82 meter) wooden or metal fence post to support the mast.  I had a metal fence post that would meet that requirement.

Nylon ties to secure the mast to the support post.

Sufficient wire to make the vertical and counterpoise elements.  Using the general formula 234/f(MHz)=l(ft), I cut a piece of #14 AWG house wire to a length of 16.47 feet (5.02 meters).  This length would make the antenna resonant at 14.200 MHz.  Although many antenna experts recommend that the tuned counterpoise be lengthened by approximately 5%, I decided to keep both vertical and counterpoise elements the same lengths.  So, the counterpoise wire was cut to a length of 16.47 feet (5.02 meters).

Two ceramic or plastic end insulators.  One to support the top of the vertical element and the other to tie off the end of the counterpoise.  A 3-foot (.91 meters) wooden stake would be the tie off point for the counterpoise.  The end insulator would be connected to the wooden stake with a 3-foot (.91 meters) length of dacron rope.

The counterpoise as well as the bottom of the vertical antenna element would be approximately 3-feet (.91 meters) above ground.  This slight elevation would serve to reduce some of the ground losses..

One Budwig HQ-1 center coax connector (available from Fair Radio Sales in Lima, Ohio).  The vertical element would be connected to the + terminal and the counterpoise would be connected to the - terminal.

Fifty feet (15.24 meters) of 50-ohm coaxial cable with UHF connectors.  This would serve as the antenna feed line.  I had some RG-8X coax in the shack for this purpose.  You could also use RG-8 or RG-58.

Before I attached the coax to the center connector, I made a "choke balun" out of 8 turns of the coax measuring approximately 6-inches (15.24 cm) in diameter.  This balun would help keep stray rf off the shield of the cable and prevent rf from entering the radio room.  The "choke balun" was built about 3-inches (7.62 cm) before the center connector.

ASSEMBLY:

The 20 meter vertical was built on the ground.

I attached the center connector to the vertical element and the counterpoise wire.  The connection was made about 3-feet (.91 meters) above ground.  This would help reduce some of the ground losses.  I then attached the top ceramic insulator to the tip of the mast, ran the wire up the mast, attached the wire to the ceramic insulator, and finally secured the vertical element with several nylon ties.  The counterpoise was stretched out along the garden and ran to the end insulator and tie off post.  All connections were soldered and wrapped with several layers of vinyl plastic electrical tape.

I attached the RG-8X coaxial cable (with the "choke balun) to the center connector.  The cable was run a few feet above the level of the lawn to the anti-static unit placed near the radio room.  A short length of RG-8X cable (10-feet/3.04 meters) went from the anti-static discharge unit to the Swan 100-MX transceiver.  I used several short patch cords to connect a dummy load, low pass filter, and the SWR meter to the transceiver.  If the Drake MN-4 was available, the outside cable would have been connected to it first.

When the operating day is done or bad weather approaches, I disconnect the antenna feed line from the anti-static unit, wrap up the coax as far as the antenna mast, and store the unconnected cable in a sealed plastic storage bin at the base of the mast.  The cable will be out of sight and not connected to any station equipment.  I once lost a 33-foot (10.06 meters) pvc mast to a lightning strike.  Thankfully, my feed line was disconnected and grounded at the base of the mast.  The mast took a terrible beating, but none of my equipment was damaged.  As a matter of safety, I always unplug my equipment and ground all antennas when I'm not using them.

PRELIMINARY RESULTS:

The 20 meter vertical with an elevated, tuned counterpoise works very well.  Without the Drake MN-4 in the antenna system, the SWR ranges from 1.5 to 1.7, depending on what portion of 20 meters is being used. A little trimming would help reduce the SWR even further.  I could get better SWR readings if I had installed a few radials, but I chose to avoid that part of the project.  The counterpoise seems to keep things under control.  Once I get the Drake MN-4 back on line, I should be able to cover the entire 20 meter amateur radio band with a SWR of less than 2 to 1.

So far, the antenna has performed as expected. There is no gain, but DX coverage to the mainland U.S.A. and Asia is quite good, with reports of 56 to 59 on most contacts.  I'm running about 50 watts from the old Swan 100-MX.  The rig stays cool and the SWR remains fairly low.

I was fortunate to have most of the antenna materials around the shack.  I've found hardware stores and home improvement outlets a good source of basic antenna materials.  This antenna was an enjoyable experience.  Best of all, it works.

REFERENCES:

http://www.arrl.org/hf-vertical
http://dxzone.com/catalog/Antennas/20M/20_meter_Vertical.
http://www.youtube.com/watch?v=8hvHQuR1CoA.
http://hf-antenna.com/018.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

If you want to catch up on the latest Amateur Radio News, please visit my news site--http://kh6jrm.com.  I've included a few news items from that site at the bottom of this post.

You can leave comments on the form at the end of this post.

Thanks for joining us today!

Aloha de Russ (KH6JRM).

BK29jx15--Along the beautiful Hamakua Coast of Hawaii Island.

Saturday, May 11, 2013

Antenna Topics: A simple inverted vee dipole that doesn't require a tuner, post #189

KH6JRM's Amateur Radio Antenna Topics:

A simple inverted vee dipole that doesn't require a tuner.

Hawaii Island has been enjoying some excellent, if somewhat voggy, weather the past few days--a perfect time to design and build a simple antenna for my favorite amateur radio bands.  Although I enjoy working 10 and 20 meters, I've found plenty of contacts and even some decent DX on the 40 and 15 meter bands.  During the day, there are plenty of Hawaii hams to chat with on a variety of nets.  Early afternoon chats on 15 meters range from locals to the exotic realms of the southwest Pacific and Japan.  If I decide to work 10 or 20 meters on a whim, I can always switch to my 40 meter vertical with tuned counterpoise to capture a few elusive contacts on 10 meters.  This antenna uses tuned feeders (450-ohm ladder line) and can work amateurs from 40 through 10 meters with the help of a 4:1 balun and a good transmatch, such as my Drake MN-4.

However, this week, I've had the Drake MN-4 apart for its semi-annual maintenance check-up.  The tropical air in Hawaii sometimes leaves a small layer of salt and other contaminants on metal surfaces, particularly on antenna wires and other connections. So, every few months, I clean and lubricate all the contacts, switches, and dials on my equipment--a necessary task in the tropics.  While I have the Drake MN-4 on the workbench, I have no readily available "tuner" or transmatch available.  I have an old MFJ 941-E in storage, but I didn't want to unpack it this weekend.  I guess I'm just lazy.

Anyway, I had a spare MFJ 33-foot (10.06 meters) telescoping fiberglass mast in the garage just waiting to support another homebrew "special".  This antenna would be used on 40 and 15 meters.  The 15 meter operation would run as the third harmonic of 40 meters and would give me a low SWR if I cut the antenna elements properly.  If I cut the 40 meter portion for the lower part of the band (i.e. around 7.088 Mhz--the Hawaii Afternoon Net frequency), I should get decent performance at 21.264 Mhz in the 15 meter band.  That would place me in the region for SSB contacts on 15 meters.

Of course, with the Drake MN-4 in line, I would just cut the antenna elements for my favorite 40 meter frequency and use the old Drake to minimize SWR.  Since I didn't have the MN-4 available, I reached a compromise--CW on 40 meters and SSB on 15 meters.

Since I was using 50-ohm coaxial cable for the feed line (RG-8X), adventures into 20-meter land would be out of the question because of high SWR and loss of power in the coax.

With the sun shinning early this morning, I began the project.

MATERIALS:

One 33-foot (10.06 meters) MFJ fiberglass mast.

Three, 5-foot (1.52 meters) wooden posts.  One post would serve as the mast support.  The other two posts would be used as tie-off points for the inverted vee.  I chose the inverted vee format because of limited space in my backyard.  A regular flat-top dipole using two masts would be preferrable, but I used what I had on hand.

I chose a 40 meter operating frequency of 7.088 Mhz--a favorite Hawaii net frequency.  The antenna would also be usable on the third harmonic, 21.264 Mhz.  In this case, the 40 meter antenna would serve as a 3/2 wavelength antenna on 15 meters with a fairly small SWR.  I cut two pieces of #14 AWG house wire for the 40 meter elements.  Using the general formula 468/f(Mhz)=l(ft), the total length of the inverted vee dipole worked out to be 66.02 feet (20.13 meter).  Each antenna element was then cut to 33.02 feet (10.06 meters).

The antenna was assembled with the MFJ mast on the ground.

One Budwig HQ-1 center coax connector (available from Fair Radio Sales in Lima, Ohio, USA).

Two ceramic or plastic insulators attached to the bottom end of each antenna element.

Two wooden posts to tie-off the antenna elements.  I used some dacron rope I had stored in the garage.

A 50-foot (15.24 meters) length of 50-ohm coaxial cable with UHF connectors.  You can use RG-58, RG-8, or RG-8X.  I used a spare reel of RG-8X in the storage room for the feed line.

ASSEMBLY:

With the MFJ mast on the ground, I attached the top portion of each antenna element to the Budwig HQ-1 center coax connector.  I soldered each connecction and wrapped several layers of vinyl plastic electrical tape around each connecction.

I then attached the bottom portion of each antenna element to a ceramic insulator.

Before I attached the coax feed line, I made a "choke balun" out of several turns of the coax, secured the coils with vinyl plastic electrical tape, and attached the "choke balun" to the mast with nylon ties.

I attached the feed line to the Budwig HQ-1 center connector.

I ran the coax feed line down to the mid-point of the fiberglass mast (about 16 feet/4.87 meters) and secured  that portion with nylon ties.

I then hoisted the MFJ mast onto its wooden support stake.  I tied off each antenna element to a pre-positioned stake.

The coax feed line was led to the garage and secured to a plastic hook.  The coax was allowed to sag a little,   with the line approximately 15-feet (4.57 meters) above ground from the mast to the garage.

The feed line was connected to my static discharge unit near the shack window.  A 15-foot (4.57 meters) piece of RG-8X coaxial cable ran through a window opening to the Swan 100- MX.  Separate cables  ran to a dummy load and a SWR meter.  If the Drake MN-4 was in service, the cable would have been connected to the MN-4 first and then to the station equipment.

PRELIMINARY RESULTS:

Initial tests were good.  The SWR across the lower 100 Khz of the 40 meter amateur band ranged from 1.5 to 1.7 to 1 without the "tuner" in the line.  On the upper portion of 15 meters, the SWR ranged between 1.6 to 2.0 to 1.  Obviously, some adjustments must be made, but, for now, the equipment seems to work without overheating.  Once the old Drake MN-4 is put into its normal place and a bit of trimming is done, I should have lower SWR readings.  Running 50 watts out of the trusty Swan 100-MX, I get CW reports ranging from 559 to 599 and SSB reports varying from 55 to 59, depending on the band selected and the time of day chosen for operations.

This antenna won't bust a DX pileup, but it will get you contacts at moderately low power levels.  Since I had the materials on hand, my costs were minimal.  Most of the materials for this antenna can be found at your nearest hardware or home improvement outlet.  Mast materials can be made of pvc pipe, wood, long fishing poles, or even expandable aluminum poles used to clean swimming pools.

I had fun building this simple antenna.  It works.

REFERENCES:

http://www.youtube.com/watch?v=8KHzsKYsZL0.
http://hamuniverse.com/easydipole.html.
http://arrl.org/file/Technology/tis/info/pdf/9106023.pdf.
http://ehow.com/how_4528486_that-doesnt-require-antenna-tuner.html.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Thanks for being with us today!

Aloha es 73 de KH6JRM
BK29jx15
Along the beautiful Hamakua Coast of Hawaii Island.

Tuesday, May 7, 2013

Antenna Topics: A tuned counterpoise antenna for 40-10 meters.

KH6JRM's Amateur Radio Antenna Topics:

A tuned counterpoise antenna for 40-10 meters

In my last post, I related the experience of making a segmented inverted v dipole antenna covering the 20, 15, and 10 meter bands.  The antenna required some adjustment, particularly in the 20 meter segment, which was cut a bit short.  With all the segments connected together with alligator clip leads, I found the 20 meter section approximately 5 inches (12.7 cm) short on each side.  With the addition of some extra wire, the 20 meter section tuned up nicely on 14.200 Mhz.  It pays to cut your antenna elements a few inches (several centimeters) longer than expected.

After using the segmented v for a few hours, I lowered the mast and stored the antenna segments in some plastic storage bins near the radio room.  I can reassemble this antenna again if the need arises.

A NEW ANTENNA

Since my backyard is rather small, I prefer verticals, inverted vees, and loops for most of my HF work.  The only drawback to this scenario is the lack of space to accommodate a radial field.  Vertical antennas need a ground radial system to function efficiently. As I was storing the segmented inverted vee in the garage, I discovered a spare 100-foot (30.48 meters) spool of 450-ohm ladder line.  With the weather mostly sunny and hot today (Tuesday) and most of my antenna materials available, I decided to erect a new vertical antenna using a tuned counterpoise to supply the "missing half" of my vertical antenna.  Normally, a ground radial system would be used in this instance, but I decided to use a counterpoise to save time and space.  I ran across an article in the 14th Edition of the ARRL Antenna Book that gave me hope.

According to the article, "the performance of vertical antennas...depends a great deal on the ground system.  You have no way of knowing whether or not you have a 'good ground' in the rf sense.  If you can eliminate the ground connection as a part of the antenna system, it simplifies things...the system is completed by a wire...of the same length as the antenna.  This makes a balanced system somewhat like the center-fed dipole."

Armed with that advice, my old 33-foot (10.06 meters) MFJ fiberglass mast, enough wire for a 40-10 meter vertical (33-feet/10.06 meters), wire for the 33-foot (10.06 meters) counterpoise, and 70-feet (21.34 meters) of 450-ohm ladder line, I was ready to build a new vertical antenna.

PROCEDURE:

I built the antenna on the ground.

I attached 33-feet (10.06 meters) of #14 AWG housewire to the mast and secured the vertical element with nylon ties.

I laid out another 33-foot (10.06 meters) of #14 AWG housewire along the border of a hedge row.  This wire was attached to a ceramic insulator and tied off on a short stake.

I attached one lead of the ladder line to the vertical element and one lead to the tuned counterpoise.

I hoisted the fiberglass mast onto a support stake and ran the roll of ladder line along a back hedge to my garage.

I connected the ladder line to a 4:1 W9INN balun which was attached to the garage side.

From the garage, a 20-foot length (6.09 meters) of RG-8X ran into the shack.  The coaxial cable was then attached to my Drake MN-4 transmatch (tuner).  From there, short coaxial patch cords connected the tuner to the dummy load, low pass filter, and the Swan 100-MX transceiver.

450-ohm ladder line or 300-ohm TV twin lead should be used for the feed line in this system.  On most bands, the SWR will be quite high.  You will lose a lot of power in the system if you use coax for your feeder.

PRELIMINARY RESULTS:

With the help of the 4:1 balun and my trusty Drake MN-4, I was able to get the SWR below 1.5 to 1 on 40, 20, 15, and 10 meters.

The results have been excellent, with performance on par with my segmented inverted vee.  Depending on the band in use, I've been getting mainland U.S. contacts ranging from 569 to 599 on CW and 57 to 59 on SSB.  I've been running the old Swan 100-MX at the 50 watt level.

So far, this antenna combining vertical and horizontal conductors is doing well.


REFERENCES:

"Combining Vertical and Horizontal Conductors".  The ARRL Antenna Book, 14th Edition.  ARRL, Newington, CT., 06111.  p. 8-8.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Thanks for being with us today!

Aloha es 73 de Russ (KH6JRM).

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.  

Monday, May 6, 2013

Antenna Topics: A 20, 15, and 10 meter segmented inverted vee dipole. Post #187

KH6JRM's Amateur Radio Antenna Topics:

A 20, 15, and 10 meter segmented inverted vee dipole.

In my last post, I described a 40/15 meter inverted vee dipole using aligator clip leads and short pieces of wire to improve the SWR on 15 meters.  The short additional length of wire on each end of the inverted vee lowered the SWR for 15 meters and provided a slightly better match for the RG-8X coax used as the feed line.  When I wanted to use 40 meters, I just unclipped the short lead.  By selecting the correct length of wire for each band and using the clip leads to add or subtract a small amount of wire length, I was able to use this antenna without an antenna match or tuner.

This past weekend, I was able to modify this idea to get an inverted vee that would cover 20, 15, and 10 meters without a tuner.  As in the case with the 40/15 meter inverted vee, I incorporated some ideas from Edward M. Noll (W3FQJ) and Larry Barry (NV5I) to make a homebrew tri-bander inverted vee that has proven to be effective from my location on the Island of Hawaii (the island with the volcanoes).

MATERIALS:

One 33-foot (10.06 meters) fiberglass, pvc, or wooden mast.

Approximately 35-feet (10.67 meters) of antenna wire.  I used some #14 AWG housewire stored in the garage.

One Budwig HQ-1 center coax connector (available from Fair Radio Sales in Lima, Ohio).

Three 5-foot (1.52 meters) wooden or metal stakes.  One will support the mast and two will be used to tie off the ends of the inverted vee.

Eight alligator clip leads.

Six ceramic or plastic insulators.  These will be used to segment the antenna elements.

Fifty feet (15.24 meters) of RG-8X, RG-8, or RG-58 coaxial cable with UHF connectors.  This will be your feed line.

Ten feet (3.04 meters) of RG-8X or other 50-ohm feed line to connect your station to the main antenna system.  My antenna feed line is connected to a static discharge system below the shack window.  This small length of cable will connect the static discharge system and antenna feed line to the shack's equipment.

ASSEMBLY:

I built the antenna on the ground.

First, measure and cut the dipole elements for 10 meters.  Using the general formula 468/f(Mhz)=L(feet) and a frequency of 28.4 Mhz, the 10 meter dipole was cut to a length of 16.47 feet (5.02 meters).  Each dipole element was cut to a length of 8.23 feet (2.51 meters).  I attached each dipole element to the ends of the Budwig HQ-1 center coax connector.  Before tied off each end of the dipole elements to its insulator, I attached an alligator clip lead.  This lead would be connected to the next segment of the antenna element--the 15 meter portion.

Using the above formula for a frequency of 21.250 Mhz, the full-length dipole would measure 22.02 feet (6.71 meters). Each dipole element would then be 11.01 feet (3.35 meters).  Since I already had a 10 meter antenna length of 8.23 feet (2.51 meters) for each side, all I had to do was clip a small length of wire to the 10 meter clip lead on each side to make a full length 15 meter dipole. In this case, the additional wire length was 2.78 feet (0.85 meters).  I attached an alligator clip lead to the top and bottom of each 15 meter segment before I secured the 15 meter portion to the bottom of the 10 meter insulator.

Using the above formula for a frequency of 14.200 Mhz, the full-length 20 meter dipole would measure 32.95 feet (10.04 meters).  Each dipole element would then be 16.47 feet (5.02 meters).  As in the above examples, all I would need to complete the full 20 meter antenna element for each side is a short piece of wire added to the clipped together 10 and 15 meter elements.  In this case, the additional wire length was 4.97 feet (1.51 meters) for each side of the inverted vee.

I attached an alligator clip to the top of each 20 meter segment and tied off the ends at the final insulator.

The total length of the connected elements came to 15.98 feet (4.87 meters) for each side of the inverted vee.  By connecting the appropriate segment, I would be able to select any one of the bands (20, 15, or 10 meters) without encountering excessive SWR.  Later, I had to adjust the length of the 20 meter segment because the chosen length was a bit short (about 2.5 inches/6.25 cm) per side.

After I attached the RG-8X to the center connector, I wound approximately 6 feet (1.82 meters) of the coax into a "choke balun" and secured this coil together with nylon ties.  I hoisted the mast on its support stake and tied off the end insulators to nearby stakes.  The antenna elements added some support to the mast.  Trade winds haven't affected the mast too much.  I will later install some guy ropes to further stabilize the mast.  All antenna connections have been soldered and covered with several layers of plastic vinyl electrical tape.

I ran the RG-8X halfway down the mast (approximately 16 feet/4.87 meters), secured the coax to the mast with nylon ties, and led the cable to the anti-static unit beneath the shack window.  A short piece of RG-8X connected the shack's equipment (Drake MN-4, if needed, a low pass filter, a dummy load, and the Swan 100 MX transceiver).

PRELIMINARY RESULTS:

So far, results have been good.  SWR on 10 and 15 meters stays below 1.7 to 1 without the Drake MN-4.  With the Drake MN-4 connected to the antenna system, SWR stays below 1.2 to 1 across each band.  The results on 20 meters are less satisfactory, with SWR readings of 2.0 to 1 without the Drake MN-4 and 1.5 to 1 with the Drake unit in the antenna system.  A little trimming will be needed to bring the 20 meter portion of the antenna into a better SWR reading.

Despite this minor problem, all bands covered by this antenna work well.  The antenna is a project in progress.  I could possibly add further segments to cover 40 and 80 meters, but, by that time, I will have run out of room to accommodate a larger antenna.  My backyard is a bit small.

With the old Swan 100-MX running 20 to 30 watts CW, I'm getting reports of 569 to 599. SSB reports vary between 56 to 59, depending on propagation and band conditions.  This antenna has its flaws, but it keeps me on the air with a minimum of cost and maintainance.  I'll work on this "skyhook" for a few weeks before I build another antenna.  Right now, my collection of wire and feed line is running low, so I'll have to visit the nearest hardware store and pick up what I lack in the storage room.

I have about 100 feet (30.48 meters) of 450-ohm ladder line which is waiting for a project.  I think a doublet antenna is in the planning stages.

Have fun building your next antenna!

REFERENCES:

Noll, Edward M.(W3FQJ).  Easy-Up Antennas for Radio Listeners and Hams. Limited Edition, 1991.  MFJ Enterprises, Inc. Mississippi State, MS, 39762.  pp. 111-113.

Barry, Larry A. (NV5I).  Hints and Kinks for the Radio Amateur. 13th Edition.  ARRL, Inc.  Newington, CT, 06111. pp. 7-26 and 7-27.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Thanks for joining us today!

Aloha es 73 de Russ, KH6JRM

BK29jx15--along the beautiful Hamakua Coast of  Hawaii  Island.


Saturday, May 4, 2013

Antenna Topics: A simple multi-band inverted V dipole for 40 and 15 meters, post # 186

KH6JRM's Amateur Radio Antenna Topics

A simple multiband inverted V dipole for 40 and 15 meters.

If you have a small backyard and only have room for a few antennas, a segmented inverted V dipole covering two to three bands of your choice is an option worth considering.

It is quite easy to build an inverted V dipole antenna for two-band operation, with each leg of the dipole separated by a ceramic or plastic insulator.  A jumper clip associated with  each of the two insulators is closed for 15 meter operation and left open for 40 meter operation.  While 15 meter operation is possible with just a 40 meter inverted V (using the third harmonic of your 40 meter frequency), you could risk high SWR on 15 meters, depending on what 40 meter frequency you use.

For example, a few years ago, I used my coax fed 40 meter inverted V on 15 meters with few problems since my prime 40 meter frequency was 7.088 Mhz ( the frequency of the Hawaii Afternoon Net).  With the antenna cut for 7.088 Mhz, I had only a small mismatch on my 15 meter frequency of choice--21.264 Mhz.).  I was able to use much of the 15 meter phone frequencies without cutting any antenna elements.  When I got lazy, I just used the Drake MN-4 match box ("tuner") to reduce the SWR.

Although this plan allowed me some frequency selection, I wasn't happy with constant adjustments to the Drake MN-4.  There had to be a better way.

An obvious solution was to use 450-ohm ladder line and a 4:1 balun in combination with a tuner to provide all band coverage from 40 to 10 meters.  I built a few of these ladder line fed antennas, and they worked very well.

However, when I wanted to revisit the old 40/15 meter inverted V, I had no 450-ohm ladder line or 300-ohm TV twin lead at my disposal.  I did have a spare 33-foot (10.06 meters) MFJ telescoping fiberglass mast, a 50-foot (15.24 meters) piece of RG-8X coax with UHF connectors, and a 100-foot (30.48 meters) spool of #14 AWG house wire.  Coupled with my Drake MN-4, a static discharge system near the shack window, and my trusty Swan 100-MX transceiver, I had the makings of a simple, cheap, and easy to erect inverted V that would give me great contacts with low SWR.

MATERIALS:

A 33-foot (10.06 meters) mast.

Three wooden stakes.  One to support the mast and two to support each inverted V element.  I used three, 6-foot (1.82 meters) wooden stakes for this purpose.  The choice of stakes will depend on what's available in your area.  I had a few stakes left over from an old vegetable garden.

One Budwig center coax connector (available from Fair Radio Sales, Lima, Ohio).

Four ceramic insulators--two for each antenna element.

50 to 75 feet (15.24 meters to 22.86 meters) of #14 AWG housewire for the antenna elements.

A few feet (a few meters) of dacron rope to tie off each antenna element.

ASSEMBLY:

The inverted V was built on the ground.

I first determined the length of the 40 meter elements using the general formula 468/f(Mhz)=L(ft).  Since my preferred 40 meter spot was 7.088 Mhz I made each antenna element 33.01 feet (10,06 meters).  I attached a clip lead to the end of each 40 meter segment before I attached an end insulator.  My chosen 15 meter frequency was 21.050 Mhz ( I like CW).  To make the 40 meter elements into a 3/2 wavelength 15 meter antenna, I added a wire segment of .33 feet or 3.96 inches (10.05 cm) to each side.  A clip lead was attached to the upper end of this very small segment, with the remaining portion attached to an end insulator.
To run a 40 meter schedule, I used only the 40 meter portions of the antenna.  To use 15 meters, I attached the small outrigger wires to the 40 meter clip leads.  With all the leads connected, the inverted V would run as a 3/2 wave length antenna with low SWR.

Before I attached the RG-8X feed line to the Budwig center connector, I wound several turns of the feed line into an 8-inch (20.32 cm) diameter "choke balun" to prevent rf from entering the shack by the feedline.

All connections were soldered and covered with several layers of plastic vinyl electrical tape.

I then hoisted the mast and secured it to the wooden support stake.  I tied off the ends of the inverted V to two pre-positioned wooden stakes.  The antenna elements also helped support the light fiberglass mast.

I ran the RG-8X to my static discharge system and used a 10-foot (3.04 meters) piece of RG-8X to connect the antenna to the Drake MN-4.  Short  coaxial patch cords connected the rig, low pass filter, and dummy load to the Drake MN-4.

PRELIMINARY RESULTS:

Without the tuner in the antenna system, I was able to get a 1.5 to 1.7 SWR across the 40 meter band and a SWR of 1.7 to 2.0 across the 15 meter band.  Obviously, I have a bit of trimming to do.  With the Drake MN-4 in the system, I was able to reduce SWR across both bands below 1.5 to 1.  Results have been good, considering propagation conditions.  Using 50 watts CW into the antenna, I'm  getting 569 to 599 reports on 40 meters and 549 to 579 reports on 15 meters.  Not terribly outstanding, but the antenna works and the equipment stays cool.  I've been able to get satisfactory results on the SSB portions of each band by adjusting the Drake MN-4 for minimal SWR.

Most of the materials can be found at the nearest hardware or home improvement outlet.  The same design principal can be use to create segmented dipoles for 80/40 meters, 20/15 meters, and 15/10 meters.  I'll investigate those varieties later. But, for now, I'm having fun with an inexpensive antenna I built myself.

REFERENCES:

The ARRL Antenna Book,22nd Edition, ARRL, Newington, CT, 06111.

Noll, Edward  M., W3FQJ.  Easy-Up Antennas for Radio Listeners and Hams.  Limited Edition, 1991. MFJ Enterprises, Inc., Mississippi State, MS, 39762.  pp.117-118.

You can follow our blog community with a free email subscription or by tapping into the blog RSS feed.

Check out the latest Amateur Radio News by scrolling down to my news blog at the bottom of this post.  you can also follow Amateur Radio News and Trends by visiting my news site--http://kh6jrm.com.

Thanks for being with us today!

Aloha es 73 de Russ, KH6JRM
BK29jx15--along the beautiful Hamakua Coast of Hawaii Island.





Thursday, May 2, 2013

Antenna Topics: A simple 15 meter vertical dipole, post #185

KH6JRM's Amateur Radio Antenna Topics:

A Simple 15 meter vertical dipole.

Like many of my fellow amateur radio operators I'm "horizontally challenged" by a small lot without many trees or tall structures to support a half-wavelength, flat top dipole.  So, I've usually resorted to inverted vees, small loops, and random length wires.  All of these antennas have performed well, considering the lack of space available.  I've also tried verticals, with uneven results.  With a good radial or counterpoise system, vertical antennas can do a good job.  Perhaps, I'm getting old, but I don't get excited putting radial wire in my backyard.  Although I've used elevated counterpoise wires with some success, I just don't enjoy running wire all around my back yard, especially with neighbor children and pets running around.  Besides, the ground conductivity in my area is very poor.  The thought of "planting" a large number of radials in my small backyard just doesn't appeal to me.

With all this in mind, I decided to attach  dipole elements  to a vertical fiberglass or pvc mast and run the antenna structure as a vertical dipole.  Hopefully, I could get a workable antenna without ground radials that would perform as well as my earlier flat top antenna projects.  Last weekend, I assembled a test vertical dipole antenna for 20 meters.  It works very well, is fairly inconspicuous, and, most of all, it's cheap because I had all of the material on hand.  What you don't have around your QTH can be bought at the nearest home improvement or hardware store.

MATERIALS:

A 33-foot pvc or fiberglass mast (10.06 meters).
A Budwig HQ-1 coax center connector (available from Fair Radio Sales).
33-feet (10.06 meters) of hookup wire.  I usually use #14 AWG housewire for antennas, but all I had in the shack was a 50-foot (15.24 meters) spool of #22 AWG hookup wire.  So, I used that spool for the antenna wire.
Two ceramic or plastic insulators to tie off each dipole element.
Fifty-feet (15.24 meters) of 50-ohm coaxial cable for the feed line.  I had some RG-8X cable in the shack for this purpose.  You could also use RG-58 or RG-8.
A wooden stake to support the mast.  I had a spare MFJ 33-foot (10.06 meters) mast in the garage.  The mast will slip over the stake.  The stake should be at least 5-feet (1.52 meters) long to provide enough support for the flexible mast.
Nylon ties and vinyl electrical tape to secure the vertical elements to the mast.

CONSTRUCTION:

The antenna was built on the ground and then hoisted over the support stake.

For the 20 meter vertical dipole, I selected a frequency of 14.200 MHz.  Using the general formula 234/f (MHz)=L (ft) and allowing for a few inches of overlap, I cut each dipole element to a length of 16.6 feet (5.06 meters).
The top half of the 20 meter dipole was attached and soldered to the + terminal of the Budwig connector.  The bottom half of the dipole was attached and soldered to the - terminal of the Budwig connector.
I attached a ceramic insulator to the end of each dipole element.
The top insulator was tied off with nylon ties and vinyl tape.  The bottom insulator was similarly tied off.
Each vertical element was secured to the fiberglass mast with several nylon ties and vinyl electrical tape.
Before I attached the RG-8X to the Budwig center connector, I wound several turns of the coax into a "choke balun" to prevent rf from running down the coax to the shack.
The RG-8X feedline was attached to the center connector at the mid-point of the mast (approximately 16-feet (4.87 meters) above ground.
The coax feed line was led to a plastic hook on my garage.  The hook was 16-feet (4.87 meters) above ground.  The cable had a little sag, but was nearly perpendicular to the mast.  Hopefully, this step would keep the radiation pattern from being skewed.
The feed line was attached to a static discharge system and copper ground rod just below the shack window.
A 10-foot (3.04 meters) length of RG-8X from my Drake MN-4 match box (tuner) was threaded through a window space and attached to the static discharge system.  Small patch cords connected the MN-4 to the dummy load, low pass filter, and the old Swan 100-MX transceiver.

PRELIMINARY RESULTS:

Results have been favorable.  Without the Drake MN-4 in the line, my SWR measured 1.7 to 1, indicating that some trimming may have to be done.  With the MN-4 in the line, I was able to keep SWR below 1.3 to 1 over the entire 20 meter band.  Not perfect, but it works.  The vertical dipole seems to work as well as my 40-10 meter inverted vee fed with 450-ohm ladder line.  Of course, the 20 meter antenna is strictly a one-band affair, while the inverted vee can be used on other bands from 40 through 10 meters.

While this vertical dipole has its limitations, it has the advantage of taking up little space, requires no radial system, and is inexpensive to make.  I've painted the fiberglass mast a dull green, which blends well into the surrounding vegetation.  The thin antenna wire can't be seen from the street running past my house.

Since my mast is collapsable, the antenna is suitable for portable or emergency use.

I'm enjoying this "homebrewed" antenna.  It's brought me many hours of enjoyable contacts with Japan and the mainland United States.

You can follow our blog community with a free email subscription or by tapping into the blog's RSS feed.

If you want to check on current amateur radio news, scroll down to my news site below this post.  Or, you can direct your browser to http://kh6jrm.com.

Thanks for being with us today!

Aloha from the Big Island of Hawaii,

Russ Roberts, KH6JRM, BK29jx15.