Station interference

[greenie95125]

I noticed recently that if I plug in headphones to the headphone jack on my show computer I can hear faint but intelligible radio stations. One in is dominant and the other is very faint. If I unplug my ethernet cable that runs to my e1.31 controllers, the stations go away. This is my 1st year using e1.31, so it's never been apparent. The problem here is that the headphone jack is where I plug in my fm transmitter, so this phantom station can be heard on receivers between songs. 

 

I listened for a while, and determined that it's a 5000 watt AM station with it's broadcast towers about 12 miles from here. Has anyone experienced their e1.31 controllers (or cabling) picking up AM and passing it thru to the audio jack on a computer before? I tried it on another laptop, with the same result. Wierd...

 

Any suggestions to remove the interference? FYI, it's about a 50' cat 5 run from the computer to the 1st controller.

 

Thanks for any help...

 

Mike 

[Orville]

Strange that it would be an "AM" station being picked up on the "FM" bands, I've never heard of that one before.   Are you sure it's not FM stations that are being picked up from side frequencies?

 

I had a similar problem and had to locate an open FM frequency that was clear of any stations on either side of it, problem solved.   

 

But AM bleeding over to FM?

 

I'll have to leave that up to the more experienced radio folks here that have been DJ's or Ham Operators that are a bit more knowledgeable on this than I.    But I've never had an AM station bleed over onto my FM transmitter frequencies I've used in the past or today.  

 

And I know there are AM stations that broadcast on the lower end of the dial where my FM transmitter broadcasts on the FM band, but my transmitter does not interfere with the AM band and the AM bands don't interfere with my FM transmitter.   So yes, I find this very strange indeed.

Edited December 13, 2015 by Orville

[greenie95125]

Strange that it would be an "AM" station being picked up on the "FM" bands, I've never heard of that one before.   Are you sure it's not FM stations that are being picked up from side frequencies?

 

I had a similar problem and had to locate an open FM frequency that was clear of any stations on either side of it, problem solved.   

 

But AM bleeding over to FM?

 

I'll have to leave that up to the more experienced radio folks here that have been DJ's or Ham Operators that are a bit more knowledgeable on this than I.    But I've never had an AM station bleed over onto my FM transmitter frequencies I've used in the past or today.  

 

And I know there are AM stations that broadcast on the lower end of the dial where my FM transmitter broadcasts on the FM band, but my transmitter does not interfere with the AM band and the AM bands don't interfere with my FM transmitter.   So yes, I find this very strange indeed.

It only bleeds into the FM band when my transmitter is plugged in. Otherwise, it's only bleeding into my computer thru what seems to be the cat 5 cable that goes to my pixel controllers. It gets passed thru to the transmitter when it's plugged in. In other words, take my transmitter out of the equation, and I still hear AM radio from the headphone jack of my laptop when the cat 5 cable to my pixel controllers is plugged in. Strange right, especially when it happens on 2 entirely different laptops. Also, the station I'm hearing is 1591, so it's on the upper end of the AM band.

 

I'll do some investigating tomorrow and start eliminating stuff to see what's really causing it. Can't do it tonight while he show is running.

 

Mike

[PhilMassey]

If possible try a longer or a shorter cat 5 cable. I'm not an expert on radio, but it sounds like the cable is acting like an antenna.

Does it do it if the cable is connected to the PC but the controller end is disconnected?

Might be worth checking if the cable is running parallel to any power cords etc.

Would inserting an ethernet switch do anything to isolate the effect? 

Just a few random thoughts.

[greenie95125]

If possible try a longer or a shorter cat 5 cable. I'm not an expert on radio, but it sounds like the cable is acting like an antenna.

Does it do it if the cable is connected to the PC but the controller end is disconnected?

Might be worth checking if the cable is running parallel to any power cords etc.

Would inserting an ethernet switch do anything to isolate the effect? 

Just a few random thoughts.

Thanks for the ideas. I'm going to start isolating stuff hs morning, and I'll let you know.

 

Mike

[greenie95125]

If possible try a longer or a shorter cat 5 cable. I'm not an expert on radio, but it sounds like the cable is acting like an antenna.

Does it do it if the cable is connected to the PC but the controller end is disconnected?

Might be worth checking if the cable is running parallel to any power cords etc.

Would inserting an ethernet switch do anything to isolate the effect? 

Just a few random thoughts.

Well, I was able to shorten the run and re-route the cat 5 cable, and the interference is much better. It's still there, but if you have the volume up loud enough to hear it on a receiver, my music will blast you out of the car. Still very strange though.

 

Mike

[Greg Young]

Non-shielded CT cable runs (especially longer ones) can serve as receiving antennas, and are especially good at picking up AM signals. Think of the old cats' wisker receivers that allowed you to listen to am radio signals, without the need for any form of electrical power. 

Computers, and many of the plug in cards not only generate their own rfi, but they are very poorly shielded (if at all), and are subject to picking up extraneous signals/interference.

As you found a shorter run, or switching to a better shielded cable will help.