R30 Cross A/B Band Interference

[eorange]

I've been noticing that scanning certain modes on one band causes interference on the other band.

A Band: scanning 200 MHz AM frequencies.
B Band: scanning 400 MHz P25 frequencies.

B Band scanning then causes a birdie on the A band, which persists even if I stop scanning the B Band.

Same thing happens in reverse - scanning 400 or 800 MHz P25 frequencies on the A band causes birdies on the B band scanning 200 MHz AM.

I've narrowed this down to P25 causing the issue. Anyone notice anything similar with other modes, like NXDN?

 

[bearcatrp]

Do you think its over modulation from P25 causing it? I get P25 very strong in my location from 4 different simulcast sites not to far from my location. What are you scanning for P25 in the 400 Mhz range?

 

[eorange]

I was trying to scan some recently activated 400 MHz federal frequencies, but they are too far away for me to pick up. And that's the strange thing...the cross-band interference (or whatever) was occurring even though I wasn't actually receiving any 400 MHz P25.

I just tried it again now. 400 MHz P25 B band scanning was causing a birdie on A band 260.200 AM. As soon as I changed the B band to something else (like AM airband) the birdie went away.

 

[vagrant]

Try your same scan again using a dummy load, or no antenna at all, as well as moving to a different location.

 

[vagrant]

@eorange Any update on the results when using a dummy load, or no antenna as well as relocating? Others may benefit from your results.

 

[eorange]

Ok, I'm back. Relocation made no difference with the antenna on. The extent was inside my house vs at the end of my driveway. Next time I'm out and about I'll do a better relocation test.

With no antenna...the interference seemingly caused by 400 MHz P25 scanning (with no stations received) disappeared. This was the case whether P25 A-band and AM B-band or vice versa.