OCFD attic antenna build...

justrfb · May 2, 2015

Hello All.
Here are pictures from my build of a Off Center Fed Dipole attic antenna. I used all the information gathered here by these fine people. Check out my other threads for the information. Thanks for all the help. Here are some pictures...

Sincerely,
Rich

justrfb · May 2, 2015

More pics...

More pics...

br0adband · May 2, 2015

Have you done any monitoring so far and had a chance to see if it's doing well? I made an OCFD last year at one point and I swear I either did it wrong or I just live in some particular position in the universe where that particular antenna serves absolutely no purpose whatsoever.

I built one of those simplistic quarter-wave antennas with one main element plus the four grounding ones at 45 degree downangles off the SO-239 connector and I swear that thing yanked in more signals across my typical monitoring bands than anything else, was very pleased with it overall. But I did the OCFD hoping it might improve some aspects of things and it just performed much worse for me so, basically the parts are standing behind the door of my studio apartment. Maybe I'll give it another go sometime, who knows.

I'd be interested in hearing your experience with the OCFD, regardless.

dmg1969 · May 3, 2015

Looks good! I would also be interested in how your reception has changed across various bands. I don't use it quite that much anymore, but it is still in my attic with coax run to my monitoring area.

prcguy · May 3, 2015

Get that antenna away from all those metal ducts and struts!
prcguy

N3JI · May 4, 2015

prcguy said:
Get that antenna away from all those metal ducts and struts!
prcguy

My thoughts exactly...

justrfb · May 5, 2015

Hello All.
Thank you for your comments and I am sorry I haven't replied til now... I am a revert to scanning and am still learning but the "new" OCFD is doing a touch better than the temporary wire one I built last week. I haven't gotten to add more channels that I want to listen to but the ones I have in there now are amazing me as to which ones I am hearing. I am getting hits from local towns pretty far away. Much more distance than the telescoping supplied antenna. I am very excited to get my new OCFD away from the metal flue and garage door supporting members. I will report back with more news when I get the antenna in a better spot and I add more channels. Thank you for your help and support.

Sincerely,
Rich

nanZor · May 5, 2015

Wow - good job!

You may want to consider adding at least 4 choking ferrites (such as RadioShack #273-105 snap on's near the feedpoint. More is better, but you may not want to spend that much on this type of antenna. The ocfd is inherently unbalanced (despite the balun) and the coax shield actually becomes part of the antenna, which is usually undesirable from both a direct reception standpoint, and also ingress from the shack back to the antenna itself.

From the pic, I'd extend the antenna out a bit to get the lower element away from the box.

While mounting in the clear is recommended, this is a GREAT example of how reflections from nearby objects can actually help with the crazy reception lobes at uhf and above, and why the ocfd may work (to a degree of course) ok in less-than-perfect locations.

Remember that this bad boy is very wideband, and sometimes lesser scanners can be overloaded, typically from FM broadcast and the like - it all depends on your environment.

justrfb · May 13, 2015

Hello All.
Finally got to spend a little time with my antenna and scanner last night. I moved the antenna away from the metal and it seems to have increased my scanner's ability to receive just a little more, a little better. I programmed in a bunch more local (and not so local) township PD's but didn't get a lot of time to listen... I did get a hit from Denville (my hometown) which was a surprise to me as far as distance away. I also got a hit from Rockaway which is a little closer to me than Denville but still surprised me. I am not to sure how I can measure or monitor the improvement of this antenna. Nothing to compare it to (except for the provided telescoping antenna) and nothing to "measure" the performance with... All I know is I am getting more than I did before which makes me wonder, can I get more with this antenna set up different or something else easy to build. I am willing to try... Any suggestions as to building something as relatively easy as the OCFD. Thank you again for all of your help and suggestions.

Sincerely,
Rich

N3JI · May 13, 2015

justrfb said:
Hello All.
Finally got to spend a little time with my antenna and scanner last night. I moved the antenna away from the metal and it seems to have increased my scanner's ability to receive just a little more, a little better. I programmed in a bunch more local (and not so local) township PD's but didn't get a lot of time to listen... I did get a hit from Denville (my hometown) which was a surprise to me as far as distance away. I also got a hit from Rockaway which is a little closer to me than Denville but still surprised me. I am not to sure how I can measure or monitor the improvement of this antenna. Nothing to compare it to (except for the provided telescoping antenna) and nothing to "measure" the performance with... All I know is I am getting more than I did before which makes me wonder, can I get more with this antenna set up different or something else easy to build. I am willing to try... Any suggestions as to building something as relatively easy as the OCFD. Thank you again for all of your help and suggestions.

Sincerely,
Rich

Excellent! So did you mount it outside, or just move it away from the metal? How far away are those agencies you mentioned? I'm just curious.

FWIW, I found that the RadioShack Discone is now half price online, so I ordered one ($34). A steal IMHO -- couldn't pass it up...

OCFD attic antenna build...

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