Phasing receive antenna for translator

FM does it with frequency!
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Joined: Thu Feb 17, 2011 3:28 pm

Phasing receive antenna for translator

Post by waveguide » Wed Feb 15, 2017 2:51 pm

Quick question... I have a translator, which is currently struggling to receive a good clear signal to rebroadcast.

I'm seeing a noise 35db on receive, (no desensitization happening), receive yagi gain is 5.5db.
If I use two yagis together (side to side), am I correct in thinking a second yagi will increase the gain by a further 3db upto 8.5db?

Whats the optimal spacing (at mid band) - the yagi have to be side by side - and whats the best way on combing the two receive antennas to the receive feeder cable? A t-piece or VHF mast head splitter - in reverse - or a low power splitter?


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Deep Thought
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Joined: Thu Mar 20, 2008 9:23 am
Location: La Grange, IL

Re: Phasing receive antenna for translator

Post by Deep Thought » Wed Feb 15, 2017 4:29 pm

You need to make sure the antennas are in phase where they combine together. That is dependent mostly on the connecting coax length and where the boom ends are with respect to each other, and the angle that the desired signal reaches the antenna(s).

Scala had some tech notes in their old catalogs regarding phasing for both increased gain and rejection purposes. I've attached a scan. They are written for TV reception but work for FM too. They might help you get a handle on your situation.

Use a "tee", not a combiner.
Scala antenna phasing tech notes
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Mark Mueller • Mueller Broadcast Design • La Grange, IL •

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