The KJ4IIF 75 METER 1/4 WAVE COW
Using aluminum tubing scrounged from various and assorted places, friends, broken beams etc. etc, I decided, with the assistance of my son and daughter, to construct a 1/4 wave vertical for 75 meter phone in an excellent area of my property that was really well fertilized as antenna farms go....the cow pasture!!
I ended up using 44 feet of 2 inch army tent poles picked up at a salvage yard for the price of scrap aluminum. This pole is 44' long with a 4 inch taper end to fit into the next piece.
The top 13 foot section is a 2 inch boom from a salvaged 2 meter beam, slid inside the army tent poles easily and with some creative work I was able to attach all the pieces with self tapping metal screws. The top 13 feet of tube is a little bent but still works fine, a casualty of the hurricanes here in Florida but it served my purpose.
I attached the top section and 3 tent poles together, tied my guy ropes where the top section meets the 2 inch pole. I used four guy ropes 100 feet long purchased at the local flea market for $5.00 per 100 foot.
I attached a 10 foot piece of 2 inch galvanized pipe to an 8 foot 4"X4" pressure treated pole and buried it in the ground 4 feet.
I used muffler clamps to attach the vertical antenna (tent poles) to keep the base sturdy as I raised it up and my son put another piece of tent pole under it.
With the assistance of my old 1956 Ford 640 and a front end loader, I raised it as high as I could get it. With the antenna leaning against the front end loader we were able to get the antenna up in the air and guyed off.
My daughter assisted in holding one of the guy ropes and keeping the vertical from swaying to far to one side or the other.
When I reached the 37 foot mark I added four more sets of guy ropes.
I took house blocks and put the first set of four guy ropes under them and applied tension to keep the vertical upright. By doing this I was able to safely raise the antenna higher and get more tent poles under it. Adjusting the tension after each four foot of tent poles was added..
When I got 57 feet in the air I attached the RG213 coax with the center conductor attached at the base of the vertical sitting on a cement house block.
The shield of the coax is attached to an old well water head and radials attached to this same ground also. The coax run to the shack was about 30 feet.
Initially I added one ground radial 67 long to check the SWR with the antenna analyzer and got 1.7:1 in the center of the phone band. I decided not to add any more tent poles under the antenna and started adding more radials to see what happened.
After adding 5 more radials the SWR was terrific. The SWR curve at 3.600MHZ was 1.9:1 and 4.100MHZ was 1.9:1. with the full 75 meter band usable and broad banded.
I have added a total of 18 radials so far and SWR remains constant with no variation.
This vertical has done fantastic DX for me on 75 meters with numerous contacts into EU with great signal reports. Less than 500 miles it is not so good.
The receive is 12 to 24 DB better than my full wave 160 loop. But the down fall is the vertical has a lot more noise than the loop.
There is no comparison in the TX signal on the vertical compared to the loop. When working EU DX they could not even hear me on the loop but on the vertical the signal report was 5-9+, proving that the low angle of radiation on the vertical was working for great DX.
With the tuner I can tune all HF bands!
I feed the antenna with RG213. I am no engineer or expert but seems like I will have some loss in the feed line with the antenna not resonant on the other bands causing high current on the coax.
So in future experiments I hope to add a matching network at the base for other bands so no tuner is needed. And to keep the high current off the feed line.
The total cost for this vertical was $110.00. The barn yard antenna farm fertilizer was free and abundant. Labor supplied by son and daughter, .....priceless!
"I was so tickled right after my son and I got it up and
guyed it off. My first contact was the Netherlands, then Maldova and
the Russian stations all running 75 phone dx."
73 and happy DX, KJ4IIF - Ken