Carrier Interference on 462.6250

[WRUX266]

Here in the SE suburbs of Cleveland I have noticed a constant interference signal on 462.6250 (Ch 18). On my daily commute, my radio will stop on this frequency while scanning throughout my entire drive, encompassing parts of I-271 and I-480, between Bedford and Twinsburg. The signal sounds like a constant carrier and fluctuates between an S-5 and S-9, depending on where I am as far as terrain goes. I know it's not a birdie coming from my vehicle as it's there when the vehicle is off, and I also confirmed it with a hand-held radio while nowhere near my vehicle. There must be some sort of service/equipment either using this frequency, or some multiple of it causing this interference. Has anyone else encountered this, and if so, have you been able to pinpoint the source? Not that I can do anything about it, but curiosity has me intrigued.

[marcspaz]

This happens a lot in areas that have a high population or are heavily commercial.  There are all kinds of crap electronics being used in private and commercial settings that emit spurious emissions on frequencies they are not intentionally transmitting on. 

 

I have this problem driving around in many parts of Northern Virginia, Richmond, Tampa, and Orlando.  Near my house in VA, I have a fire house that has some kind of RF link to another FD building, on 462.000MHz.  Once I am within about 1.5 miles, that link is all I can hear on every FRS and GMRS radio, unless I have tone squelch enabled on every channel.  Even then, if someone transmits a tone, the FD transmitter wipes the other station to the point that I have no idea what they are saying. 

 

Sadly, complaints fall on deaf ears.  Once it starts I just turn the radio off until I drive far enough away from it.

[WRUX266]

Thanks, Marc. It's as I suspected. And since it only affects one frequency for me, I've just locked it out from the scan. I was just curious if others had this issue in other areas of the country.

[Lscott]

1 hour ago, marcspaz said:

This happens a lot in areas that have a high population or are heavily commercial.  There are all kinds of crap electronics being used in private and commercial settings that emit spurious emissions on frequencies they are not intentionally transmitting on. 

Good point.

1 hour ago, WRUX266 said:

Thanks, Marc. It's as I suspected. And since it only affects one frequency for me, I've just locked it out from the scan. I was just curious if others had this issue in other areas of the country.

Also radios have what are commonly called "Birdies" which are internally generated signals that appear to real. All radios have them. The designers usually do a good job of making sure they don't show up in the intended operational frequency range of the radio.

Also when running a radio outside of it's designed frequency range you can get cross modulation interference. This is caused by two or more frequency sources mixing together in the radio's front end electronics where the results may be in the pass band. This also shows up as a phantom signal. I have my old Kenwood TH-G71A dual band shows an almost full scale signal on channel 7. Turning the radio horizontal and rotating around I can null out the signal. Also taking the antenna off does the same thing so the source is external. However using a different model radio to monitor the same exact frequency shows nothing there. I did what you have, just locked that channel out of the scan on the G71A.