Funny thing happened on the way to a weather frequency

[WRUU653]

So I decided to see if any of the UHF weather frequencies that @Lscott posted came in near me and a funny thing happened.  First I had no success with UHF weather frequencies in my area. No big deal there, I do receive them on VHF. 

I put in 410.000 on my KG-S88G and immediately received the local medical dispatch in my area, loud and clear.  Here’s the thing they are on 463.000 and have no listing in the area on 410… So I grabbed my KG-935G Plus and put in 410.000 and nothing, not even a crackle. So I’m hearing it loud and clear on super het but nothing on SOC. I hear it just as good on both radios on the listed 463.000. So question, what is going on here? I mean it’s not a problem but I’m curious. 

My own theory is this, not far from our home is a location where one of the ambulances stages for response and I was wondering if the mobile radio to HT relay might be at play and I’m close enough to hear it.  I don’t really know. Any thoughts?

[WRUU653]

I tried investigating a bit further and turned squelch off completely on the SOC radio and still nothing at all at 410.000. I still hear the medical dispatch on the Super Het on 410.000 very clear even though it’s not listed to be there. I’m baffled by this. It is not like a faint reception or at a location I’d expect bleed over. I guess it’s just an RF mystery.

[OffRoaderX]

"Spurious RF emissions"

[Lscott]

8 minutes ago, WRUU653 said:

I tried investigating a bit further and turned squelch off completely on the SOC radio and still nothing at all at 410.000. I still hear the medical dispatch on the Super Het on 410.000 very clear even though it’s not listed to be there. I’m baffled by this. It is not like a faint reception or at a location I’d expect bleed over. I guess it’s just an RF mystery.

This is just a wild guess but you might be experiencing a case of intermod, inter-modulation interference.

https://www.everythingrf.com/community/what-is-intermodulation-distortion

https://static1.squarespace.com/static/53062f8de4b09e63a23ce552/t/532689a3e4b0825c71c80bc5/1395034531223/what_is_intermodulation_interference.pdf

 

[WRUU653]

10 minutes ago, Lscott said:

This is just a wild guess but you might be experiencing a case of intermod, inter-modulation interference

Well that is something I was unaware of. Add to the list of all the things I don’t know about RF. Interesting information. Thanks @Lscott.  This info along with @OffRoaderX mention of spurious RF emissions I remembered something else that happened awhile back on my KG935G Plus that involves the same local medical dispatch frequency. When the “simultaneous receive” option is turned on (this enables the radio to receive both upper and lower areas of the radio simultaneously) the same transmission comes in on GMRS 21 (462.700). I noticed this when I was scanning the upper area and had a local repeater frequency set in the lower.  I just turned off the simultaneous receive and forgot about it. So at least now I have a common frequency of 463.000 that is being received in two different areas on two different radios all be it different circumstances. Thanks for the responses. I get fascinated by this stuff.