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Guest Message by DevFuse

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2 OTA Antennas on one mast


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10 replies to this topic

#1 OFFLINE   visionman

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Posted 27 September 2010 - 02:29 PM

Will I have any interference issues doing this? Say, if one antenna is 4-5 ft. above the other and connected to different and separate equipment? Thanks

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#2 OFFLINE   Stewart Vernon

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Posted 27 September 2010 - 02:49 PM

Hi, and welcome..

I don't think there is a definitive answer here.

You might get interference depending upon how close the antennas are, how strong the signals are, the channel frequencies, multi-path interference, and how you combine the signals.

There's probably a lot of math you could do to figure it out, but ultimately hooking everything up and trying it out is the best way to find out.

I'm using a dual antenna setup indoors, a few feet apart, because I need it to pickup a particular channel.

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#3 OFFLINE   visionman

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Posted 27 September 2010 - 02:58 PM

I'll give it a shot. I'm not combining the signals. Getting close to snow time so I'll have to test quickly! Thanks for your ideas.

#4 OFFLINE   Stewart Vernon

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Posted 27 September 2010 - 05:21 PM

If you're not combining them, then hopefully you will be far enough apart to not interfere with each other.

I'm not aware of my indoor ones interfering with each other when separate... but they do interfere a little when I combine the signals.

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#5 OFFLINE   Davenlr

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Posted 27 September 2010 - 05:41 PM

The actual formula specifies 1 wavelength separation at the lowest frequency. For channel 2, that would be about 24 feet apart. For channel 7, that would be about 6 feet. For UHF, a couple feet would be sufficient.

If they are different bands i.e. one VHF and one UHF, then its not quite as important. I have my channel 7-13 yagi 4 feet below my UHF yagi and have no appreciable pattern distortions.


Check Amateur Radio Relay League antenna book, or the ARRL on google for lots of info.

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#6 OFFLINE   visionman

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Posted 28 September 2010 - 06:51 AM

Channel 7 could be the spoiler. I've learned alot from these responses. Thanks guys..

#7 OFFLINE   AntAltMike

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Posted 03 October 2010 - 05:36 PM

I've installed commercial antennas on highrise buildings for 15 years. A quarter wavelength spacing is fine. 4-5 feet for VHF highband (channels 7-13) is as much or more than I ever use.

#8 OFFLINE   FarmerBob

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Posted 03 October 2010 - 11:58 PM

I had this set up during the transition. I used a 4' pole to distance the two and a simple combiner to "mix' the two then ran it to my distribution system using a Diplexer. It worked out great. I took it down after the completed switchover, but will probably need to put it back up since I am finding out that the AntennasDirect CS4 (shown on the bottom) that I was guaranteed by their President would cover 7-69, over exaggerated the 7-13 capability as I am finding out, they no longer listing it in their specs and their TS now mentions. But mind the weight of the extension pole if you do it as I did. If too heavy, it'll put a ton of stress on the mount (standard DISH J mount) and it could pull it out. Mine was anchored in concrete and I could see it starting to work its way out.

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#9 OFFLINE   visionman

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Posted 04 October 2010 - 10:03 AM

Looks like it's worth a shot then. A pre-amp is not recommended if there are any splitters in the line, correct? Before the transition, I was refused a waiver for NBC which is 65 miles away. I bought the antennas and amplifier the engineers told me to buy but of course nothing worked due to terrain. Finally, after the switch over, I was granted the waiver. I was stuck with the UHF ant. and amp...
Thanks for all the feedback..

#10 OFFLINE   doctor j

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Posted 04 October 2010 - 01:43 PM

I had this set up during the transition. I used a 4' pole to distance the two and a simple combiner to "mix' the two then ran it to my distribution system using a Diplexer. It worked out great. I took it down after the completed switchover, but will probably need to put it back up since I am finding out that the AntennasDirect CS4 (shown on the bottom) that I was guaranteed by their President would cover 7-69, over exaggerated the 7-13 capability as I am finding out, they no longer listing it in their specs and their TS now mentions. But mind the weight of the extension pole if you do it as I did. If too heavy, it'll put a ton of stress on the mount (standard DISH J mount) and it could pull it out. Mine was anchored in concrete and I could see it starting to work its way out.


Might I suggest:

http://www.ronard.com/4424.html

or at least:

http://www.ronard.com/ychim.html

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#11 OFFLINE   FarmerBob

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Posted 04 October 2010 - 02:07 PM

Might I suggest:

http://www.ronard.com/4424.html

or at least:

http://www.ronard.com/ychim.html

Doctor j

Thank you for your suggestions but my chimney is 30'+ wide and I have bit up there. Plus I really like the "clean covert" look that I have now. All those straps are a bit much. I have a good base to work with. It just needs to be done methodically, instead of "I've two more jobs after this." When I get an once of energy I am taking the foot that I got from the guys that just reinstall my two dish set up and have a seriously more secure anchoring method in mind. Now that I have gotten rid of the 1k2 dish that catches the wind more and was hammering the far right mount, secure since 1994 until the 1k2, and have my 500s back, of which I never had any torq issues, with the "reinstall" I have in mind it might be a bit over kill. But solid forever, "pretty" from the ground with finite mount tuning capabilities.

Thanks again.

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