Looking to test my land for interference before build. Nothing nearby so I suspect it's ok but what is simple way to check? Walk around with an AM radio tuned to a quiet frequency at the lower end of the dial and listen for static or buzz? Walk around with my wireless mics listening for noise?
testing for spurious RF interference?
- Thread starter firehawk
- Start date
Jim Feeley
Veteran
If your wireless receive has a little spectrum scanner, use that feature. (search the manual for "scan").
Here's a short video on how to find likely clear frequencies on a Sennheiser G3:
And here's a six-minute video on how to do a RF Scan on a Lectrosonics receiver.
Some useful background info, and then the procedure is shown starting at about 2:00 in:
And yes, also walk around with your wireless receiver and listen for noise (as you say). You may need/want to turn on your transmitter so your receiver is trying to get an actual signal. If you're worried about intermittent problems, perhaps record for an hour or so, and then look at the waveform on your computer (and maybe scrub through) to see and hear any little spikes of interference. Or just read a book on your land as you monitor....
Consider different RFI at different times of day. A nearby church or sports stadium?
Or since you're looking at building, consider hiring a good location-audio person who might have a spectrum analyzer and local knowledge of what frequencies now (and in the near future) are good or bad bets). I have an RF Explorer spectrum analyzer that's really helpful. But it's not free http://rfexplorer.com . Or lean on a location-audio person you know for local knowledge.
What wireless systems are you using (or planning to use)? In the 500MHz range, 1.9GHz, 2.4GHz, other? Are you going to use DMX?
A couple good backgrounder articles (I'm sure there are others):
The Radio Frequency Spectrum Puzzle
https://www.local695.com/magazine/the-radio-frequency-spectrum-puzzle/
A Few Notes on the Radio Spectrum and a Brand-New Licensing Guide!
https://www.local695.com/magazine/a-few-notes-on-the-radio-spectrum-and-a-brand-new-licensing-guide/
HTH a little.
Here's a short video on how to find likely clear frequencies on a Sennheiser G3:
And here's a six-minute video on how to do a RF Scan on a Lectrosonics receiver.
Some useful background info, and then the procedure is shown starting at about 2:00 in:
And yes, also walk around with your wireless receiver and listen for noise (as you say). You may need/want to turn on your transmitter so your receiver is trying to get an actual signal. If you're worried about intermittent problems, perhaps record for an hour or so, and then look at the waveform on your computer (and maybe scrub through) to see and hear any little spikes of interference. Or just read a book on your land as you monitor....
Consider different RFI at different times of day. A nearby church or sports stadium?
Or since you're looking at building, consider hiring a good location-audio person who might have a spectrum analyzer and local knowledge of what frequencies now (and in the near future) are good or bad bets). I have an RF Explorer spectrum analyzer that's really helpful. But it's not free http://rfexplorer.com . Or lean on a location-audio person you know for local knowledge.
What wireless systems are you using (or planning to use)? In the 500MHz range, 1.9GHz, 2.4GHz, other? Are you going to use DMX?
A couple good backgrounder articles (I'm sure there are others):
The Radio Frequency Spectrum Puzzle
https://www.local695.com/magazine/the-radio-frequency-spectrum-puzzle/
A Few Notes on the Radio Spectrum and a Brand-New Licensing Guide!
https://www.local695.com/magazine/a-few-notes-on-the-radio-spectrum-and-a-brand-new-licensing-guide/
HTH a little.
Jim gave you very good notes. But what interference are you referring to; What are you concerned about; health, wireless interference, something else?
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Thank you very much Jim and Paul.
I am currently using 500Mhz range Sennheiser G3 mic systems and AVX 1.9Ghz. I plan to use those for the foreseable future. I do plan on using DMX but have to figure that out.
Another very helpful guy recommended I test for spurious Radio Frequency interference at different times over 24x7 periods at various points in the site to see if I will need to cover the place place in chicken wire, like he nearly had to do, before he settled on a star ground electrical wiring system.
That is above my head, but I figure if it's going to be a problem I better find out and figure how to deal with it. I thought if all my wireless systems worked on the site without interference from nearby I was ok. But maybe the wiring in my own building can cause me problems too.
I am currently using 500Mhz range Sennheiser G3 mic systems and AVX 1.9Ghz. I plan to use those for the foreseable future. I do plan on using DMX but have to figure that out.
Another very helpful guy recommended I test for spurious Radio Frequency interference at different times over 24x7 periods at various points in the site to see if I will need to cover the place place in chicken wire, like he nearly had to do, before he settled on a star ground electrical wiring system.
That is above my head, but I figure if it's going to be a problem I better find out and figure how to deal with it. I thought if all my wireless systems worked on the site without interference from nearby I was ok. But maybe the wiring in my own building can cause me problems too.
Another possibility along the lines of what Jim suggests is to get in touch with a local ham radio operator. These guys are usually pretty sharp and may have a spectrum analyzer and a lot of local knowledge about what RF is in the area as that is a big part of their hobby.
You never know what might interfere. I have some LED tubes that interfere with the FM radio in the garage.
You never know what might interfere. I have some LED tubes that interfere with the FM radio in the garage.
paulears
Veteran
Spectrum scans are blunt tools. Buy a cheap RF Explorer, or even a cheap SDR receiver. Then you can see the RF environment. You will be surprised. Scan systems built in to radio mic systems look for wide band interference that behaves like a used radio channel. Interference often doesn’t. Often with these proper monitors you see interference spikes just where you don’t want them, but they are intermittent, so unless your scan was on the right frequency at the right time, it gets missed.
often, interference to radio mics comes from devices OUT of the band, that are close enough to have harmonics in our bands. We’re expecting transmitters with 20-50mW outputs, but you could have 50W of nasty digital radio at a frequency exactly half of your radio mic one, that has 4 or 5 Watts on harmonic. Worse, these digital systems are silent and then burst into a few seconds of life every now and then. Not just when people are speaking! Many venues have these things on the highest point, usually right above the stage area!
a proper monitor lets you observe what is happening. Scanning is in my humble opinion a totally rubbish feature.
often, interference to radio mics comes from devices OUT of the band, that are close enough to have harmonics in our bands. We’re expecting transmitters with 20-50mW outputs, but you could have 50W of nasty digital radio at a frequency exactly half of your radio mic one, that has 4 or 5 Watts on harmonic. Worse, these digital systems are silent and then burst into a few seconds of life every now and then. Not just when people are speaking! Many venues have these things on the highest point, usually right above the stage area!
a proper monitor lets you observe what is happening. Scanning is in my humble opinion a totally rubbish feature.