Thursday, June 20, 2013

Antenna Topics: A Simple Multiband Vertical Antenna. Post #203

While I was searching for some antenna projects on Thursday (20 June 2013), I came across an antenna book I bought 25 years ago to help a new amateur radio operator make his first HF antenna.  The "Novice Antenna Notebook"  by Doug DeMaw, W1FB (SK) contains a wealth of simple, effective antenna ideas suitable for any license class.  I was drawn to this book a quarter century ago because it explains complex antenna theory and design in a simple, easy to understand manner.  I've used several of DeMaw's designs for my portable and emergency antennas.  All have worked successfully.

I decided to return to my own novice/technician days (1977-1978) and create one of the simple antennas that got my friend on the air.

The simple multiband vertical antenna described by DeMaw is easily made, cheap, and performs very well.

As DeMaw says, "you may want to keep things simple when you erect your first multiband vertical...simplicity denotes reduced cost for materials, and this is an appealing factor to most of us!"  I thoroughly agree.  So, with that caveat in mind, I gathered the materials needed for this ultra simple vertical antenna.

As designed by DeMaw and modified for my location, here's what I used:

Two 30-foot (9.14 meters) pieces of #14 AWG house wire.  One wire would serve as the vertical element.  The other wire would serve as an elevated radial or counterpoise.  As designed, this antenna would cover from 40 to 10 meters and would be fed with 450-ohm ladder line to a 4:1 balun and an antenna transmatch.

Fifty feet (15.24 meters) of 450-ohm ladder line. This would be the feed line.

Four ceramic insulators.  Two insulators would be for the vertical section and two insulators would be used for the counterpoise or elevated radial.

Fifty-feet (15.24 meters) of monofilament fishing line with sinker attached.  The fishing line would be attached to the vertical element and then shot over the branch of a nearby tree.  The extra fishing line would be secured to the base of the tree to hold the vertical element at a 45-degree angle.  I used a slingshot to place the line at a suitable notch in the tree limbs.



Four 7-foot (2.13 meters) wooden stakes.  One stake would be used as the center tie-off point for the vertical element.  One stake would be used to tie-off the elevated radial.  And two stakes would be used to keep the ladder line off the ground until it reached the 4:1 balun on the garage wall.

One W9INN 4:1 balun.  The ladder line would be connected to the balun.

Twenty-five feet (7.62 meters) of RG-8X coaxial cable with UHF connectors.  The cable would be attached to the balun and would be run into the shack through a plexiglass window pane.  The RG-8X would be connected to a suitable transmatch.

A transmatch.  I use an old Drake MN-4 ATU for my multiband antennas.

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

ASSEMBLY:

Per DeMaw's instructions, I cut two, 30-foot (9.23 meters) pieces of #14 AWG house wire.  I attached insulators to each end of the wires.

I pounded the central wooden stake into the ground with a hammer.  This would serve as the tie-off point for both the vertical element and its elevated radial.

I attached the vertical element to the fishing line and shot the combination through a notch in a nearby pine tree with my slingshot.  The limb was approximately 35-feet (10.67 meters) above ground.  The fishing line was tightened a bit before I tied it off to the base of the tree.  The vertical element was led to the central stake at an angle of 45-degrees.

I attached the elevated radial to the center stake and stretched it out to a nearby wooden stake. I attached one lead of the ladder line to the vertical element and then attached the other lead to the elevated radial.

I led the ladder line to a wooden stake 25-feet (7.62 meters) from the center connection stake.  The ladder line was kept off the ground and eventually was connected to the 4:1 balun attached to the garage wall.

All connections were soldered and wrapped with vinyl electrical tape.

Twenty-five feet (7.62 meters) of RG-8X ran from the 4:1 balun into the shack, where it was connected to the Drake MN-4 ATU, Swan 100-MX, a dummy load, and the low-pass filter.

RESULTS:

For a simple, inexpensive antenna, I have no complaints.  I can bring the SWR down to 1.3 to 1 or less on 40, 20, 15, and 10 meters.  I've enjoyed some excellent contacts on 40 and 20 meters with reports ranging from 569 to 599 for CW and 56 to 59 on SSB.  I've been running the old Swan 100-MX at around 25 watts.  Fifteen and ten meters have been a little weak in my area, but I've manged to bring in some good contacts from Asia and the U.S. mainland.  If I added a few more elevated radials and fanned them out around the antenna, my results would have been better.

This antenna was a joy to build and produced some good contacts.  I will build a few more of DeMaw's novice antennas before summer ends.  These antennas work.

REFERENCES:

DeMaw, Doug, W1FB.  "Novice Antenna Notebook".  American Radio Relay League, Newington, CT, 06111.  First Edition.  Copyright 1988.  pp.60 to 61.

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

For the latest amateur radio news, please visit my news site at http://kh6jrm.com.  I've included a few headline stories at the bottom of this post.

Thanks for joining me today!

Aloha es 73 de Russ (KH6JRM)

BK29jx15--along the beautiful Hamakua Coast of Hawaii Island