ocf antenna

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WB3DYE

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Question: I plan on putting up an off center fed dipole antenna--I need it for 80/40 meters. anyone have recommendations. experience.?
de wb3dye
 

popnokick

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This link contains good info regarding the proper installation and operational characteristics of HF off-center fed dipole / Windom antennas. Between our club events and at my own station I’ve put them up dozens of times. The only thing I would add to this info is to keep the elements away from large metal surfaces... but that’s true of most long wire antennas.
Windom Antenna Home Page, and Handbook
 

prcguy

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I've seen and used many commercial type OCF/Windoms from Buxcom to Radio Works and can tell you the versions sold by MyAntennas is the best I've seen. The type of balun they use is regarded as the best, their quality is very high and they will handle full legal limit all day long.

I have their 133ft 80m version and of all the antennas I've used in my lifetime, this is now my go to home antenna for the lower bands. Here is a link to that model: https://myantennas.com/wp/product/ocf-8010e-3k-windom/

I would recommend a good common mode choke balun as by design, an OCF/Windom can have RF on the coax and my recommendation for the best common mode choke is, you guessed it, MyAntennas. Here is one of the best chokes for any 80/10m OCF antenna: https://myantennas.com/wp/product/cmc-130s-3k/

Most similar looking chokes have about 20dB of choking impedance on a good day with the wind behind them and the CMC-130-3K has about 40dB.
 

vagrant

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I have their 133ft 80m version and of all the antennas I've used in my lifetime, this is now my go to home antenna for the lower bands.
What height is the apex for your setup?

Do the legs have any bends in them due to space limitations?

I am using a home brewed OCF now around that length with a current balun and I plan on staying with an OCF for years to come due to it handling the lower bands. I have other antennas deployed, but I do like the wide coverage it offers.

The apex on my OCF is 10m AGL. My property size limitation requires that each leg has a bend which runs horizontally. I previously used a 40-6 m OCF and the legs never quite reached their anchor points. It sang pretty well on 40 and 20.

Man, I really want another property. A remote location for RX only gear away from RF and TX/RX here at home.
 

AK9R

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I'm very interested to read prcguy's answer.

I have a Buckmaster OCF for 80-10m. I tried using it in a configuration where the apex was about 16 feet off the ground (which flies in the face of Buckmaster's recommendation of 32 feet minimum) and the long element ran out for about 45 feet and then bent at a right angle. I was not happy with the antenna in that configuration and built a different antenna.
 

jwt873

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I would recommend a good common mode choke balun as by design, an OCF/Windom can have RF on the coax .

I'll second that... Some kits come with some sort of choke (Like the Carolina Windom). I tried a Buxcomm Windom quite a few years ago. It didn't come with a choke and I was getting RF burns from my CW key. I added one and the problem went away.

I wasn't impressed with the Buxcomm. Apart from not including a choke, the 4:1 balun wasn't waterproof and there was no drain hole at the bottom. It filled with water after a few rainfalls. I wasted an afternoon pulling the antenna down then drying out and weatherproofing the balun.

The antenna did work.. I made lots of contacts with it. But I eventually abandoned the Buxcomm for an 20 thru 6 meter Yagi and a dedicated full size inverted V for 80 meters.
 

prcguy

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I have the feedpoint about 3ft away from my tower with the long section horizontal at around 30-35ft high. The short section tapers downward from the feedpoint at about 35ft high to about 20ft high at the end which is supported by a push-up pole. Its not easy fitting a 133ft long antenna on a residential city lot.

A friend had the Buxcom 40-10m version and then he tried a MyAntennas 40-10m end fed. Soon after that he gave the Buxcom away. I still have a Radio Works 40-10m version with the choke that makes part of the coax into a vertical radiator. It was used on a job site in north east Canada up in some trees about 60ft high and horizontal. Not impressed with that one and a home made 40-10m end fed half wave sloping up a 75ft pine tree a the same location made more contacts.

At home I do supplement the OFC with a NA4RR Hexbeam for 20 through 6m. One problem with any long wire antenna is lots of lobes and nulls on the higher bands and you can't rotate the house to make use of the sweet spots. I really like the Hexbeam.




What height is the apex for your setup?

Do the legs have any bends in them due to space limitations?

I am using a home brewed OCF now around that length with a current balun and I plan on staying with an OCF for years to come due to it handling the lower bands. I have other antennas deployed, but I do like the wide coverage it offers.

The apex on my OCF is 10m AGL. My property size limitation requires that each leg has a bend which runs horizontally. I previously used a 40-6 m OCF and the legs never quite reached their anchor points. It sang pretty well on 40 and 20.

Man, I really want another property. A remote location for RX only gear away from RF and TX/RX here at home.
 

vagrant

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Thank you for those details. I guess I should test that with the long leg and see if it would help me toward Europe. I previously ran another 40-6 OCF perpendicular to the main OCF to complement it, which it did. Unfortunately, it pulled in more noise than I liked, as it was positioned horizontally over the house. It had to go.

At home I do supplement the OFC with a NA4RR Hexbeam for 20 through 6m. One problem with any long wire antenna is lots of lobes and nulls on the higher bands and you can't rotate the house to make use of the sweet spots. I really like the Hexbeam.
I do the same here with a K4KIO Hexbeam. I like it too, especially when I observed how well it initially performed at just 6' when putting it together and testing.

WB3DYE - I use coaxial cable for my OCF. I use 100 feet of LMR-400 that connects to an inline lightning arrestor at the base which is connected to a ground rod. The next run of coax runs up and connects to a current balun (choke) which is connected to a 4:1 balun that is attached to each leg. The apex is around 10 meters above ground level and sits off several feet from the mast. I have not observed much, if any, difference with or without the current balun inline, but I do have a long run of coax.
 
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