QTH: near Oral, SD
Class: Amateur Extra
AMSAT # 41247
QRP ARCI # 16638
NAQCC # 9880
Firefly # 61
QRPGuys Tri-Band Vertical
I recently purchased a QRPGuy's tri-band vertical antenna. This antenna covers 20, 30 and 40 meters and comes as a kit for $15 and is rated for 10 watts.
Everything to build the antenna is included in the kit...except the wire for the 4 radials and the radiator.
There are 2 swiches and a BNC connector to solder to the board, 2 toroids to wind and solder to the board and a couple of bolts to attach.
Total build time was about 1 hour.
Each toroid requires a specific number of turns on the wire that is wound around it. The manual called for 24 turns on the 30 meter toroid and 38 turns on the 40 meter toroid.
I used 26 guage "Silky" wire that I had purchased from "The Wireman" for the 17 foot radiator and the four 10 foot radial wires.
After assembly, I suspended the antenna from my 20 foot Shakespeare Wonderpole and connected 25 feet of RG-8X coax to my antenna analyzer for testing.
I found the initial settings to be OK on 20 and 30 meters, but the SWR was over 10:1 on 40 meters. It is crucial to tune 20 meters first, because this antenna is a quarter-wave vertical for the 20 meter band.
After trimming the radiator to achieve the best possible SWR on 20 meters, 30 meters tuned up perfect with the flip of one of the onboard switches.
40 meters however, was still over 10:1 SWR. I decided to remove a few turns from the toroid to lower the inductance to see if that would improve the poor SWR reading. By the time I got 40 meters tuned up good, I had removed 4 turns from the toroid.
Now, all 3 bands tune up with an SWR of 1.4:1 or less.
I rolled the 17 foot radiator wire and the four 10 foot radial wires up around the printed circiut board and held the loose ends in place with the two rubber bands that I used to firmly attach the antenna to the base of the Wonderpole.
During my testing, I moved the antenna up to the top of the Wonderpole and tested SWR and found that the SWR was best when the feedpoint of the antenna was as close to the ground as possible.
I also loosely laid out the 4 radial wires and tested SWR, then staked the 4 wires taught and retested. I found no difference between the loosely laid out wires and the tight ones. This made me happy because I didn't want to pack 4 extra tent stakes.
The entire antenna weighs in at 3 ounces.....that is including the 57 feet of wire used to build the antenna. (17' radiator and four 10' radials)
I have used this antenna several times while out field portable.
Always on 20 meters, and with fantastic results. I couldn't be more happy with this antenna...super lightweight and effective.