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Author Topic: Directional antennas for *finding* interfering sources?  (Read 5246 times)

Scott Helmke

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Directional antennas for *finding* interfering sources?
« on: November 04, 2016, 09:50:48 am »

Any recommendations for very directional UHF antennas for tracking down interference & uncoordinated sources?

I do the frequency coordination for a local Big Ten football stadium, and we have a couple TTi spectrum analyzers and a nice R&S FSH spectrum analyzer. Handy gear for checking on things, beyond the Axient spectrum manager that keeps scanning the bigger picture. 

I rarely have problems with non cooperating media, but it would be nice once in a while to have something really directional to try to track down unknowns. What's available (or could be built reasonably) in the UHF TV spectrum?  I really can't justify something huge to carry around, though.
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Pete Erskine

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Re: Directional antennas for *finding* interfering sources?
« Reply #1 on: November 04, 2016, 09:59:33 am »

Any recommendations for very directional UHF antennas for tracking down interference & uncoordinated sources?

I do the frequency coordination for a local Big Ten football stadium, and we have a couple TTi spectrum analyzers and a nice R&S FSH spectrum analyzer. Handy gear for checking on things, beyond the Axient spectrum manager that keeps scanning the bigger picture. 

I rarely have problems with non cooperating media, but it would be nice once in a while to have something really directional to try to track down unknowns. What's available (or could be built reasonably) in the UHF TV spectrum?  I really can't justify something huge to carry around, though.

A standard directional UHF Paddle like a Sennheiser A2003 will work.  Additionally you will need an adjustable pad to control the level so that it is not overloading your meter or SA.  The trick is to start at the back of the room., for example, and to aim the back of the antenna and turn it to minimize the signal.  The direction that the back of the antenna faces is the direction where the freq is on your first heading.   Then move to the side of the room and to the same.  the intersection is where your freq is.
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Pete Erskine
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Jason Glass

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Re: Directional antennas for *finding* interfering sources?
« Reply #2 on: November 04, 2016, 10:00:35 am »

Hi Scott,

These are perfect:

http://www.wa5vjb.com/products1.html

Just add a cable, connector, and a handle made of PVC pipe.

Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.

Scott Helmke

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Re: Directional antennas for *finding* interfering sources?
« Reply #3 on: November 04, 2016, 10:35:24 am »

I usually do carry a Sennheiser A2003 for trying to find stuff... but it's generally not been something I've had much success at.  I do like Peter Erskine's null approach, though. Will have to try that next time.
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Jason Glass

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Re: Directional antennas for *finding* interfering sources?
« Reply #4 on: November 04, 2016, 11:40:01 am »

I usually do carry a Sennheiser A2003 for trying to find stuff... but it's generally not been something I've had much success at.  I do like Peter Erskine's null approach, though. Will have to try that next time.
Pete's method works well. Also, it helps to disable the instrument's preamp and add any internal attenuation that it may have.  I also find that orienting the antenna for horizontal polarization helps.

Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.

Pete Erskine

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Re: Directional antennas for *finding* interfering sources?
« Reply #5 on: November 04, 2016, 11:45:00 am »

I usually do carry a Sennheiser A2003 for trying to find stuff... but it's generally not been something I've had much success at.  I do like Peter Erskine's null approach, though. Will have to try that next time.

The back of the antenna has a sharper null than the front which is very wide.  Couldnt find an actual plot but this shows what i mean...
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Pete Erskine
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Russell Ault

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Re: Directional antennas for *finding* interfering sources?
« Reply #6 on: November 04, 2016, 04:11:47 pm »

This may be a stupid question, but, at your level, do you ever use Doppler-shift-based antenna arrays for finding RF sources?

Thanks!

-Russ
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Lyle Williams

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Re: Directional antennas for *finding* interfering sources?
« Reply #7 on: November 04, 2016, 08:39:20 pm »

I don't do large wireless audio installs, but my experience of doppler systems (I have a simple one) is that they are better suited to wide area work where you just want to be able to drive to the vicinity of a signal than to close in work.

I agree with previous posts that a desireable feature in a handheld search antenna is a sharp and deep null.
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Russell Ault

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Re: Directional antennas for *finding* interfering sources?
« Reply #8 on: November 05, 2016, 01:39:14 am »

I don't do large wireless audio installs, but my experience of doppler systems (I have a simple one) is that they are better suited to wide area work where you just want to be able to drive to the vicinity of a signal than to close in work.

That makes sense. I was thinking of a Doppler system in combination with a hand-held antenna: mount a Doppler system at the side of the room and use it as one of the two points of directional reference for triangulation (bonus points if the if the system can be remote-controlled).

-Russ
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Dan Currie

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Re: Directional antennas for *finding* interfering sources?
« Reply #9 on: November 05, 2016, 04:29:30 am »

Scott,
  Maybe a receiver like an Icom R20 would help.  It has easily adjustable gain settings and a pad which are useful in zeroing in on the source.  It can also demodulate FM signals which you can listen to on it's internal speaker.
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Re: Directional antennas for *finding* interfering sources?
« Reply #9 on: November 05, 2016, 04:29:30 am »


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