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ftg

Made a quick combination of DC-block, volume control and BNC to 3.5mm adapter for testing a rather vintage Wiltron made 4GHz detector.

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ftg

Here is it all hooked up and the detector is shown in all of it's glory.

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ftg

Here's a short video of it detecting some 1kHz AM modulated X-band and C-band emissions.
youtube.com/shorts/Jho39mk2GrE

YouTubeGigaHertz crystal set with vintage detectorBy oh2ftg
Alexander Knochel

@ftg Does this work like a diode detector, and you amplitide demodulate it with the cap and all that?

ftg

@quantensalat
It very much is the diode detector in the Wiltron RF detector.
This kludge with the BNC, 3.5mm jack and 1µF plastic cap is a combination of DC block and adapter.

The AM modulation is internal to the HP 8684B signal generator.
It can also be fed external modulation for AM or FM, if desired.
For example 10GHz FM ATV is possible with this thing.

polprog68k
@ftg @quantensalat am I right that with an FM modulation it would require a steep low/highpass filter before the diode detector?
ftg

@gorplop @quantensalat
Yeah if I wanted to use the diode detector for FM reception I'd need a decently high-Q filter before it so that I can then push the transmission into the filter skirt and then slope detect it.

Because then:
Higher deviation = More RF "peeks" from the filter slope and looks like AM modulation to the diode detector.

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