ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: FM transmitter and WL mic receiver proximity  (Read 2455 times)

Riku Ylinen

  • Newbie
  • *
  • Offline Offline
  • Posts: 6
FM transmitter and WL mic receiver proximity
« on: March 16, 2016, 01:04:03 pm »

Have you guys any opinion about clearance between a FM Transmitter antenna (typically max 5 Watts,  87.5-108 MHz) and wireless microphone receiver antennas (470 MHz and up, UHF-R, ULX-P etc.)?

Those frequency ranges are quite far from eachother, but how likely would much stronger FM transmission cause excessive load or interference into the microphone receiver, if being only a few meters from eachother? Many times it would be handy to mount all antennas up to the same mast.

Typically there would be an announcer with a wireless mic within 150 meters or so from the mast and it (among other program) would then be distributed over a much larger area with the FM transmitter. All this outdoors.

What minimum physical distance between antennas should be used? Has anybody experience with this kind of setup, or should I just test it.


Best,

Riku
Logged

Keith Broughton

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3312
  • Toronto
Re: FM transmitter and WL mic receiver proximity
« Reply #1 on: March 16, 2016, 06:50:00 pm »

Many times it would be handy to mount all antennas up to the same mast.





Riku
While I can't give a specific distance, mounting on the same mast should be avoided.
Considering the FM TX is 5 watts, get it as far away as is practical.
Logged
I don't care enough to be apathetic

Mac Kerr

  • Old enough to know better
  • Administrator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 6793
  • Audio Plumber
Re: FM transmitter and WL mic receiver proximity
« Reply #2 on: March 16, 2016, 07:04:08 pm »

While I can't give a specific distance, mounting on the same mast should be avoided.
Considering the FM TX is 5 watts, get it as far away as is practical.

Assuming they are both omni antennas, mounting them one above the other will put each antenna in the null of the other. This may actually be better isolation than could be achieved in a reasonable horizontal distance. Antennas with natural gain will have better nulls than 0dB gain whips.

Mac
Logged

Keith Broughton

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3312
  • Toronto
Re: FM transmitter and WL mic receiver proximity
« Reply #3 on: March 16, 2016, 07:09:34 pm »

Assuming they are both omni antennas, mounting them one above the other will put each antenna in the null of the other. This may actually be better isolation than could be achieved in a reasonable horizontal distance. Antennas with natural gain will have better nulls than 0dB gain whips.

Mac
Good point.
Logged
I don't care enough to be apathetic

David Buckley

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 565
Re: FM transmitter and WL mic receiver proximity
« Reply #4 on: March 16, 2016, 11:05:29 pm »

A station I do tech work for (though I'm not the RF guy!) has a 1KW TXO FM transmitter, and a STL receiver on 465MHz, and there is also a bunch of stuff for other organisations on 83MHz, 152MHz, and a lot of walkie talkie repeater stuff around 450MHz.  Our STL receiver just works.  The FM Tx has a filter on it to keep it clean.

I'd suggest trying it.  Or, if you want to be more scientific, get an RF guru to work out the products to check no nasties are going to appear, but with just one transmitter, that is relatively unlikely.  Worst case you'll need a filter.
Logged

Jens Palm Bacher

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 317
    • Lydfabrikken
Re: FM transmitter and WL mic receiver proximity
« Reply #5 on: March 17, 2016, 03:09:36 am »

Have you guys any opinion about clearance between a FM Transmitter antenna (typically max 5 Watts,  87.5-108 MHz) and wireless microphone receiver antennas (470 MHz and up, UHF-R, ULX-P etc.)?

Those frequency ranges are quite far from eachother, but how likely would much stronger FM transmission cause excessive load or interference into the microphone receiver, if being only a few meters from eachother? Many times it would be handy to mount all antennas up to the same mast.

Typically there would be an announcer with a wireless mic within 150 meters or so from the mast and it (among other program) would then be distributed over a much larger area with the FM transmitter. All this outdoors.

What minimum physical distance between antennas should be used? Has anybody experience with this kind of setup, or should I just test it.


Best,

Riku
My guess would be that the RX antenna and front end would provide much of the neded isolation. If you are worried, throw a couple of highpass filter in, and use rx antennas without amplifiers: http://194.75.38.69/pdfs/BHP-500+.pdf
Logged

Riku Ylinen

  • Newbie
  • *
  • Offline Offline
  • Posts: 6
Re: FM transmitter and WL mic receiver proximity
« Reply #6 on: March 17, 2016, 07:25:27 pm »

Thank you all for sharing your thoughts!

I think Ill try keepin antennas in their others nulls and also get some additional RF highpass filters to be on the safe side.
Logged

Scott Holtzman

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 5906
  • Ghost AV - Avon Lake, OH
    • Ghost Audio Visual Systems, LLC
Re: FM transmitter and WL mic receiver proximity
« Reply #7 on: March 18, 2016, 12:18:37 am »

My guess would be that the RX antenna and front end would provide much of the neded isolation. If you are worried, throw a couple of highpass filter in, and use rx antennas without amplifiers: http://194.75.38.69/pdfs/BHP-500+.pdf

That's interesting, an RC network filter.

I am much more familiar with mechanical filters (cavities) arranged as notch or bandpass filters.

Logged
Scott AKA "Skyking" Holtzman

Ghost Audio Visual Solutions, LLC
Cleveland OH
www.ghostav.rocks

ProSoundWeb Community

Re: FM transmitter and WL mic receiver proximity
« Reply #7 on: March 18, 2016, 12:18:37 am »


Pages: [1]   Go Up
 



Page created in 0.03 seconds with 22 queries.