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Heterodyne Rockets

Feb 13th, 12:52

K0WUQ

Joined: Dec 3rd 2012, 11:13
Total Topics: 0
Total Posts: 0
This will probably get me the Dumb Question Trophy or else make me a finalist for the Much Ado About Nothing Award for 2022. Anyway ...

My kit-built receiver is set up so 180 degrees of tuning knob rotation covers the whole 40-meter band. Not as good as the Bandspread knob on my old receiver in the 1960s, but I can still tune SLOWLY up the band while listening to traffic. Anyway, I occasionally run across a half-second or so signal that starts at a moderate audio frequency and quickly flies upward in pitch until (at least to my ear) disappears. I call this brief phenomenon a "heterodyne rocket".

I am as smart as the next guy - I know this is a key-down transmitter doing ... something. I'm just not sure what. I have never heard a descending version of this, but of course the rising tone doesn't mean the sending frequency is increasing; just that between the two of us we're getting farther from some 'zero beat' frequency that existed a fraction of a second earlier.

Is this possibly another amateur 'tuning up' either the transmitter or an antenna tuner or some such? Thinking about it, I don't know why tuning anything to resonance would mean generating a frequency that rapidly shifts a few Hz (keep in mind that my theory knowledge is from the vacuum tube days of the '60s). Maybe it's something less subtle, like an operator changing a VFO setting to get to a clear spot in the band - but would that normally be a key-down procedure? Also, I wouldn't think I'd run across that as often as once or twice a week.

Anyone with experience that would clarify this? If it really could be another ham tuning up, somewhere near there would be a good place to listen for initial code transmission. Problems are, you don't know which direction to re-tune to listen, and that the sender will probably (actually, should) take a while listening before he/she starts hammering out CQs.

Thoughts from any 'old hands'? I am an old dog myself, but basically don't know squat about techniques of actually operating.

Larry K0WUQ

Feb 14th, 06:15

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
You may be close to an Ionosounder.
Feb 15th, 07:50

K0WUQ

Joined: Dec 3rd 2012, 11:13
Total Topics: 0
Total Posts: 0
After looking at the Wikipedia description of 'Ionosonde', I'll have to agree that this looks a lot more realistic than my hypothesis.

Maybe I am only as smart as the next guy ... sometimes ;-)

Thanks!
Larry K0WUQ

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