My ocf dipole ?...

[k8niv]

I have been running a endfed for a many years, all with good reports, but I wanted to try a ocf dipole to see how it would react to the noisy floor I seem to keep, it seems to have help some but don't think there's anyway to get rid of it all or enough to make a big differences, really hate the noise, because it comes in with the person you are trying to work.........the problem I seem to have with the ocf, finding the right place to hang it up.......all my trees in the yard are either on the edge of the yard near a creek, or out back at the foot of the mountains, I live in a valley, and no trees out in the middle of the yard......so having a problem getting the balun anymore than 35ft high and getting the legs up off the ground, at the present I have this one the balun is about 35ft high and the short leg stretched out and about 8-10ft off the ground, the longer leg, is stretched out cross the yard to a tree and hung the antenna wire over a tree limb and the insulator is about 8ft high off the ground.....this is about all I can do or put it up......don't like it but have to do for now.......oh by the way, I checked my swr with a NanoVna and for the most swr less than a 1.7, and I no your not suppose to get these 2 bands but on 160m and 60m bands the swr is a little high, but my internal tuner will handle it.....

Where does everyone else hang there ocf dipoles ?

 

[vagrant]

The kegs slope down on my OCF as well. I’ve worked the world on phone and just getting into FT8. I later put a choke balun from MyAntennas just below the feed point and it reduced my noise floor up to 2dB on some bands, a bit less on others. I initially tried a choke balun near the radio before and after the other one was installedat the feed point, but it made no further improvement. Others have noticed improvement with an additional choke balun near the radio.

I had previously tried other choke baluns and some I made, but nothing compared to the quality results I got from the MyAntennas choke balun. 2dB is significant. I took it off and on to test it on different bands to ensure it was not simply attenuation. ( I did not have an analyzer at the time )

I later installed another OCF that runs perpendicular to the other. The apex on that is also around 35’ and I have the expected improved results E & W with its lobe directions. A simple switch handles them. I installed another MyAntennas 1:1 choke when it went up.

 

[merlin]

OCF and end fed are hardly different. Your noise floor, not much you can do about that, especially below 40 meters.
I live in bit of a valley and only clear shot to near horizon is north. So, mountains south, east and west, don't play well with low angle propagation. 10 meters is marginal in good conditions. 6 meters is DOA.
My 84 foot longwire at 35 foot AGL enters to a remote ATU. Once tuned I get fair reception. Below 5 MHz, the noise is 10 ove S9.
TX is less than 2.5:1 across the spectrum
Results are not much different wether I use my Kenwood 440, my Barrett 980, or Airspy HF discovery.
My S/N improved by grounding the Pwaden on everything and a central power supply (grounded)
Computer and monitor also grounded and any wall warts have ferrite filters.
So, that is my HF/SWLing world.

 

[k8niv]

The noise I have is rough at times on 40m, 80m and 160m, rest of the bands seems ok......I have just been dealing with it but does aggravate a little trying to get the weak stations out of the noisy floor I seem to keep...


Does the balun on it stop any RF coming down the coax, like the end fed antennas do ?...

Just curious, if I may need to put a CMC choke inline or not on this ocf, have neighbors close, thanks...

 

[k8niv]

Have a question about the ocf dipole, if you was going to put a filter on one of these antennas which filter would you buy and where would you put it ?.....

Have neighbors close now to where I have the ocf up and really not sure if them bothers them or not, really don't want to chance it bothering there stuff, so thought about putting some kinda filter inline to maybe be on the safe side......this antenna does really well, have worked alot of stations on it I have needed to use my ended to work them because of the direction they was in........this fall, I'm planning on moving it and raise it up some and in a north/south direction, I like to experiment with these things.....will still have neighbors close by, this is something can't get away from unless I move it up the mountain some is the only way to get away from them, then would have a long run to the feed point...

 

[k8niv]

As far as RFI issues, haven't noticed anything been affected in the house, my neighbors I have you hardly ever see them...

 

[K6GBW]

Try also adding a choke at the entrance to the radio position. The coax shield is likely acting like an antenna as well and picking up RFI. Is the coax grounded? I've found coax grounding and choking before entry into the house to be a big big help. I used to run a choke inside the shack near the radio and it worked so so. Then I moved it outside the wall of the shack and it made a big difference. Turns out common mode was riding on the coax, through the wall (past the chicken wire behind the stucco), and into the operating position. So I added a choke outside and had a noticeable reduction in noise.

 

[k8niv]

Have a question about the 4:1 balun on this ocf dipole...

I took it down a few weeks ago and moved it, in the process of doing this noticed it had water in it, so I took the cover off it and sure enough it had water inside it covered the componence's, got all the water out, dried it out, cleaned everything inside, and put silicone on everything, sealed the cover, and around the hardware in the box, all with clear silicone.....

My question is, since I coated everything with silicone and hung it back up seems like it hasn't performed as well as it used to, silicone on all the connections affect it ?

I no the bands haven't been as good here the last few days, just curious if the silicone affects how it performs, thanks in advance

 

[ramal121]

Silicone gives off acidic fumes while curing. Sometimes no bueno for electrical connections.

 

[prcguy]

OCF dipoles are inherently imbalanced and most have common mode RF on the feedline, which can work both ways bringing noise induced onto the coax up to the antenna where it is received. There is a certain kind of 4:1 balun you should use on an OCF, I don't know what its called but it would be a current balun using two separate toroid's and I'll post a picture below. This type balun is a much better Bal-Un forcing the unbalanced coax to be more balanced on the antenna side. It will also have much better antenna to coax isolation and higher common mode current rejection.

Most companies do not use the "correct" type of balun on an OCF but MyAntennas does. I have their 80m OCF and don't detect any RF on the feedline, although I did add a good CMC choke for good practice after my initial testing. I would recommend a good CMC on any OCF antenna.

Here is a picture of the correct type of balun to use on an OCF, image poached from M0PZT.

 

[k8niv]

The Balun I have for this ocf has 1 of those in it, suppose to handle a kw .......it is laying here now on my desk, it got wet inside and now needs cleaned and hung back up.......have never saw water get inside one of these baluns/transformers before.....but it got inside this one....

While it was up here the balun was about 35ft or so and just had the legs hung up how ever to get them off the ground, and that thing did surprise me, alot less noise on it and tuned most of the bands, 7 or so.....I don't recall which bands don't have my notes handy but it did tune 160m using the internal tuner, do remember this...

What can I use to clean the connections inside the balun where the one at the bottom where the SO-239 is, it has a brown/yellow color on the connection, not sure if the guy who built this used some sorta glue inside the balun or what, but it is sticky, just wonder what I can use to clean this up, and hang it back up soon ?

 

[AK9R]

What can I use to clean the connections inside the balun where the one at the bottom where the SO-239 is, it has a brown/yellow color on the connection, not sure if the guy who built this used some sorta glue inside the balun or what, but it is sticky

Is it rosin from soldering the connections? If so, isopropyl alcohol will remove it.

 

[k8niv]

I talked to the guy who built it and he said the, yellowish color indicates oxidation--any electronic spray cleaner like Deoxit or CRC will clean the connection.......since I bought this one he has made changes on how to seal his balun's now...​

 

[prcguy]

I talked to the guy who built it and he said the, yellowish color indicates oxidation--any electronic spray cleaner like Deoxit or CRC will clean the connection.......since I bought this one he has made changes on how to seal his balun's now...​

Deoxit is a cleaner/lube, don’t use that one.