KMDW tower frequency

[stk631]

I live a mile out from Midway Airport Chicago and have been monitoring Midway tower for over 30 years. A little over a month ago the tower frequency (118.7) has been broadcasting a carrier signal similar to having an open key on the channel. When either the tower or an aircraft transmits there is a whistle (again similar to an open key) during transmissions and has been very difficult to monitor and sometimes you can't even hear the aircraft transmissions. This cannot be squelched on any scanner that I use so you can't scan other frequencies becasue it locks on the channel. Does anybody have an explanation as to what is or has occurred on the Midway tower frequency?

 

[ATCTech]

I promise you nothing has happened on the frequency caused by or affecting the ATC radios or the tower would be using an alternate frequency. You have something near you radiating on 118.7 or causing a harmonic on 118.7. You may also have something on entirely different frequencies mixing and causing a weak carrier on 118.7 in your immediate area. You need to go mobile or handheld, move around your location, increase the squelch and/or remove the radio antenna and try to find a source. It could be a computer/network device, almost anything with a switching power supply, a TV set, lighting control or various other devices (and not necessarily wireless devices I might add). Don't rule out the neighbor's houses in your search.

It may be right 'under your nose' or something on a pole hundreds of feet away that you can't do anything about. We've chased down everything from leaky local oscillators to faulty gas-discharge lights to wireless camera systems over the years. Good luck!

 

[stk631]

That is something I never thought about. That's why forums like this are great. Thank you for taking the time to respond to my post. I located the problem within my house that was causing the interference. I feel stupid and happy at the same time. Thanks again !!!

 

[ATCTech]

Glad to help, but you have to tell us what the source was. Curiosity and all....

 

[stk631]

Hi, yes very good point. The problem was coming from an external DVD writer or more likely the transformer powering the writer. It was on a different floor in the house but I'd have to check further whether it was on the same circuit as the scanners. Either way it was only interfering with that one frequency and no others. Thanks again.

 

[majoco]

Switch mode power supplies strike again!

 

[ATCTech]

Excellent, glad you found it so easily.