Re: [AOCC] ARRL Sep VHF K7HP Single Op LP

John Klem

If I correctly understand, you saw multiple traces offset in frequency, not time?  I think many people have now seen this on 6 m (I'm among them), and it's not hard to believe the effect could be worse on 432.

In order to produce this frequency offset, I believe you must have some sort of dynamics in your path to induce Doppler or something similar.  Multiple static paths shouldn't do it.  I trust your receiver is linear enough that you shouldn't have observable mixing products (unless you have multiple strong signals already on different frequencies and an FT-817 like mine).  As Keith suggested, aircraft would do it, but the shift would vary with time (which I presume you didn't see).  I suppose some sort of atmospheric dynamics could produce this effect as well, and someone invoked that explanation in something I read recently.

I did a quick search on nonreciprocal propagation, and it appears this is generally recognized for ionospheric paths, but not obviously so for tropospheric paths.

Really interesting stuff.  It would be fun to do comparisons on different bands when you observe this, to see if the frequency offset scales with carrier frequency.

John AA5PR

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