[Milsurplus] Receiver LO Harmonic Generation for SCR-522

[Mike Morrow]

I don't have the Maintenance instructions for the SCR-522-A handy, but I'm sure that its receiver local oscillator harmonic generation scheme is the same as that used in the later R-77/ARC-3.

The Maintenance Instructions for the AN/ARC-3 has this description of the 6AK5 harmonic generator in the receiver local oscillator stage:

"The high RF voltage applied drives the grid hard enough to produce severe distortion, so that the output is rich in harmonics of high order.  A harmonic output of 1 to 2 volts may be obtained for any harmonic from the 11th to the 18th when the plate circuit is tuned to the frequency of the desired harmonic."

The SCR-522-A uses a 9002 as the harmonic generator.

Engineers of that era were clever.

Mike / KK5F

-----Original Message-----
>From: Hubert Miller <Kargo_cult at msn.com>
>Sent: Nov 17, 2018 5:46 PM
>To: "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net>
>Subject: Re: [Milsurplus] 1944 AAF Hand-Out for SCR-522
>
>Okay, so the transmitter crystal is 18th harmonic. Easy enough. 
>But, what I am puzzled by, is 11, 13, 17th harmonics are from prime numbers. If you try to generate power from say the 13th harmonic
>in one step, you end up with very small power. Enough for a heterodyne frequency meter, but not enough to drive an RF power am5p.
>All the online offerings are for 'Operating Manual', sans circuit explanation. BTW, the clearest scan is from the radio museum in Russia,
>for shame.
>I DO own the full tech manual for the SCR-522, but as it's not equipment I own, I relegated the manual to remote storage. So I guess I'll
>add this question to my to-do list for when I go to thin out my manuals again.
>-Hue