Paul Hudson
Vacuum Tube Member
I sometimes pick up radio stations in my audio. It is usually very faint but a problem. Does anyone have a solution for this?
Radio interference
- Thread starter Paul Hudson
- Start date
JordanBlock
Well-known member
Can you give us a rundown of your gear and how it's all connected, how you're using it, etc?
Richard Crowley
Veteran
It is a complex problem without a simple answer. Depends on the design and construction and state of repair of the equipment, what equipment you are using together, your location, etc. etc.
If you need specific help, specific information about the situation would be needed. There is no generic solution.
If you need specific help, specific information about the situation would be needed. There is no generic solution.
Paul Hudson
Vacuum Tube Member
Thanks for the reply. I have noticed it with different setups. Most commonly I find it running Lectronics right into the camera. I have changed to a hardwired Sony mic and the same problem. I have changed xlr's -- same problem.
Richard Crowley
Veteran
Were you close to the transmitter? Was there any pattern to WHERE it happened?
Paul Hudson
Vacuum Tube Member
Richard,
The transmitter and receiver where within 20 feet of each other. I first noticed this issue in New York about a year ago. It has occurred several times since, mostly in Arizona but once or twice in Dallas, TX.
Someone suggested using a ground lifter. Is there in validity in this?
The transmitter and receiver where within 20 feet of each other. I first noticed this issue in New York about a year ago. It has occurred several times since, mostly in Arizona but once or twice in Dallas, TX.
Someone suggested using a ground lifter. Is there in validity in this?
j1clark@ucsd.edu
Veteran
Have you tried ferrite beads, chokes, etc. on your cables to the mic, or between other pieces of equipment that are going in
to amplifiers?
A 'ground' lifter is usually to prevent ground loops coming in because two pieces of equipment are connected in two different places to 'earth' ground.
The Wife's hearing aid.... definitely 'ground lifted' picks up 60 Hz hum from a number of sources through radiative means.
paulears
Veteran
I think Richard means are you close to the radio station transmitter. If you can work out which station it is, I'd bet money on it being an AM station. AM signals, if they are strong, can get demodulated by being picked up on the cables, and then being introduced via the connectors, into the sensitive audio circuits. Ferrite rings were mentioned, and can be very useful. The usual process is to disconnect cables one by one until the culprit is found, then wrap this cable a few turns through the ferrite ring - this will in many cases, stop the RF getting through. It almost certainly will NOT be being picked up by any radio mic receiver you have, but by direct coupling into a longer cable - that works as an antenna!
A ground loop may well induce 50/60Hz hum (depending on your countries power supply frequency) but lifting the ground rarely works to remove RF, unless the RF is only on the screen - annoyingly, it often gets in by the centre conductor too!
Where the interference is permanent, then more extreme solutions such as j1clark mentions can do the trick - but the application of internal components is a last resort solution as it always invalidates warranties, and external solutions are rarely as effective - as there is still a signal path between them and the device internally that is doing the demodulation.
If you have the problem - the cheapest solution is a friendly radio ham - usually the older ones, who are often expert at solving RF interference problems. Many younger hams have little or no experience of Ancient Modulation (AM).
A ground loop may well induce 50/60Hz hum (depending on your countries power supply frequency) but lifting the ground rarely works to remove RF, unless the RF is only on the screen - annoyingly, it often gets in by the centre conductor too!
Where the interference is permanent, then more extreme solutions such as j1clark mentions can do the trick - but the application of internal components is a last resort solution as it always invalidates warranties, and external solutions are rarely as effective - as there is still a signal path between them and the device internally that is doing the demodulation.
If you have the problem - the cheapest solution is a friendly radio ham - usually the older ones, who are often expert at solving RF interference problems. Many younger hams have little or no experience of Ancient Modulation (AM).
Richard Crowley
Veteran
Paulears is correct, I was asking if you were close to the transmitter of the radio station you are complaining about. Do you only have this RFI problem with your wireless kit?
Paul Hudson
Vacuum Tube Member
Well in NYC and Dallas TX you are never far from a transmitter. What to do??
Richard Crowley
Veteran
If you are within 1/2 mile of a high power (thousands of watts) broadcast transmitter, then special measures must be taken to keep RFI out of your audio. Neutrik now makes special XLR connectors with built-in RFI filtering.
OTOH, if this happens simply around town, away from radio transmitters, then you may have a flaky cable or piece of equipment. You should NOT be getting RFI as a recurring situation out in the "normal" world.