mikefox whiskey
Accomplished DX-er
Registered: 02-2009
Location: Northern Ireland
Posts: 403
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 New OCF Dipole/Windom type antenna & photos!
I built this antenna with a 4:1 balun and isolator from a Radio Works Carolina Windom Short 80 and basically just replaced the wires with longer ones and added a longer 'Vertical Radiator'.
I am lucky to have some public land I can use to fit the antenna.
I remember the first time I used the Short 80 antenna a few years ago and was surprised how well it worked, though it was a bit short. Anyway the weather had been good here recently so I dug it out of the attic and thought I would see what I could put together.
The wire I used is a military spec antenna wire which for the life of me I could not get hot enough to take the solder so I vouched for the brass insides of 2 block connectors instead to join the antenna wires to the balun, the wire seems to be steel clad copper or something. After searching about online for dimensions I decided to cut the antenna wire 90ft(30M) one side and 45ft(15M) the other, the vertical radiator is RG59 50 Ohm coax and is 22ft(7M) long and goes to the isolator.
The PL259 connectors are wrapped well with self amalgamating tape to make the plugs water tight and also take the strain of the weight.
My old doublet antenna feed point on the ground with the wires still up in the trees, ready to be replaced with the new ariel.
The new antenna being hoisted up, the pull wire line to the pulley on top of the pole is Kevlar and is virtually unbreakable, this antenna is quite a bit heavier than my doublet, the feed point is about 37ft (12M) or so up, my only real gripe is that the vertical section of the antenna runs parallel to the aluminium/steel mast.
The 90ft section is running towards the South and the 45ft section is towards the North East.
Conditions have not been great on lower HF recently so I have not really tested it out in a big way yet, judging by the signals coming in from Italy etc so far I am pleased though.
Being used to doublet and G5RV SWR readings (off the chart!)I was quite surprised at the SWR readings from this antenna, here are a few examples:
86m 1.3
45m 1.9
80m 1.5
40m 1.2
20m 2
17m 1.1
15m NOT HAPPENING...!?!
12m 1.3
11m 2.5
10m 1.5
These readings were taken with NO TUNER!
I have a tuner though which will sort out any discrepancies.
My plans are to probably replace the balun and perhaps the isolator with smaller lighter versions, the Radio Works ones are rated at 2KW or something daft like that to suit the American market I would suppose. I also will change the 50 Ohm coax of the 22ft vertical radiator to a piece of 75 Ohm cable to the isolator then 50 Ohm to the transceiver.
I've also found a calculation online for the lengths of OCF/windom type dipoles, and it is as follows:
(Long side of ariel) 468 divided by the Frequency in MHz - multiply the answer by .64 to get the length in feet.
(Short side of ariel) use the same calculation as above though this time multiply the answer by .36 to get the length in feet.
Any other suggestions are appreciated. 
Last edited by mikefox whiskey, 11/Aug/2009, 10:53 am
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(Forum user name is now SuperNasty)
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19/Mar/2009, 12:33 am
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