Thursday, October 17, 2013

A 30 Meter Inverted Vee Antenna. Post #234

The Thirty meter amateur radio band extends from 10.100 MHz to 10.150 MHz.  This sliver of the rf spectrum offers plenty of space for the die-hard cw fan as well as plenty of contacts for those into the various digital modes.  The operators who populate this band are generally friendly and willing to help out those unsure of the digital frontier.  You'll find plenty of action with PSK31 and RTTY as well.  Antennas for this band are simple and inexpensive.  While thirty meters is a good night time DX band, there are some interesting day time opportunities as well, especially towards sunset.  Besides, a few hours on thirty meters will give you some new contacts and an opportunity to improve your cw speed.

So, let's build a simple antenna for this band.  I built an inverted vee for thirty meters last weekend after I finished clearing some brush from my new home site in the Puna District.  I chose the inverted vee option because I had a spare fiberglass mast in my garage and didn't want to lay in a network of ground radials for a vertical antenna.  However, you could design the antenna as a ground plane using only 4 radials.  There are many choices in this area.  Choose the one that best suits your available space. For me, the inverted vee would be easy to build in back of my garage.

MATERIALS:

I decided to use #14 AWG housewire for the two antenna segments.  Using the general formula for a dipole (468/f(MHz)=L), I cut each element for the mid-point of the band (10.125 MHz).  The total length of the antenna would be 46.22 feet/14.09 meters.  Each antenna segment would be cut to a length of 23.11 feet/7.04 meters.

Two ceramic insulators attached at the end of each antenna segment.

Two, 7-foot/2.13 meters wooden posts.  The antenna segments would be tied off with insulators and attached to the posts to form the inverted vee shape of the antenna.

One Budwig HQ-1 center coaxial connector.  That's what I had in the "junk box".

Fifty feet/50.24 meters of RG-8X coaxial cable with UHF connectors. This would be the antenna feed line.

One, 33-foot/10.06 meters MFJ telescoping fiberglass mast.

One, 5-foot/1.52 meters wooden stake to support the mast.

Nylon ties, vinyl electrical tape, soldering tools.

One MFJ-941E Versa Tuner.

Station equipment, including an old Ten Tec Argosy II, dummy load, and a low pass filter.

ASSEMBLY:

The antenna was built on the ground and later hoisted into place.

The antenna elements were soldered to the tabs of the Budwig HQ-1 center connector.  The connections were wrapped with several layers of vinyl electrical tape.

Before I connected the RG-8X feed line, I made an 8-inch/20.32 cm diameter "choke" balun out of several turns of the RG-8X coaxial cable.  The choke balun was taped to the fiberglass mast about 6-inches/15.24 cm below the Budwig center connector.  I then connected the feed line to the center connector.

I taped the feed line to the fiberglass mast to a point just about 10-feet/3.04 meters above ground.

I then raised the mast onto its support stake, tied off the antenna elements to their wooden stakes, and adjusted the shape of the antenna slightly.

The now elevated feed line was run through a small hole in the shack window and connected to the MFJ Versa Tuner.  The Ten Tec Argosy II, the dummy load, and a low pass filter were connected to the MFJ Versa Tuner with some 3-foot/0.91 meter RG-8X patch cords.

INITIAL RESULTS:

With the Drake MN-4 in the system, I was able to keep a 1:1 SWR across the entire thirty meter band.  Without the transmatch, I kept the SWR down to less that 1.5 to 1 across the band.

I made most of my contacts from the late afternoon through the early evening.  I enjoyed both DX (mainland U.S., Canada, and Mexico) as well as local contacts.  My reports varied from 559 to 599 using 50 watts output from the old Argosy II.

As I grow to like thirty meters, other antennas for this band will be used.  But, for now, the simple inverted vee does an excellent job from the Central Pacific.

REFERENCES:

http://www.dxzone.com/catalog/Antennas/30M/.
http://www.k7su.com/verticalpage.html.
http://www.youtube.com/watch?v=xtwLdlm6wsM.
http://www.wa8lmf.net/ham/30m-magloop-ant.htm.
ht-antenna.com/012/.
http://www.arrl.org/hf-vertical.

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Aloha es 73 de Russ (KH6JRM).

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