{Collins} Xtal Calculator



Hi All,
I recently did a minor mod to my 75S-3B to allow injection of my Fluke 6062A sythesized generator into the crystal oscillator (a poor man's AOR DDS-2) to allow general coverage operation. This works great, but I needed a convenient way to quickly calculate the proper crystal frequency (or signal generator injection frequency), preselector band, and preselector tuning for a given desired receive frequency. Although I suspect there are many computer programs out there already, I haven't actually seen one. So I created an Excel spreadsheet that does this. In addition, you can input a known crystal frequency and it will calculate the receive frequency. The program calculates only the ideal frequencies and stttings per the Collins manual, not other possible frequencies due to image, spurious, etc.

If anyone would like this spreadsheet, just drop me an email and I'll send it to you. Also, if you want details on the modification, I'd be happy to pass it on. It is very simple, requiring only installation of a piece of miniature coax from the grid of V3B to the spare RCA jack on the back panel, and disconnection of C78, which has about the same capacitance as the unterminated piece of coax. (C78 is omitted in the 75S-3C for the same basic reason)  The beauty of this scheme is that when you disconnect the signal generator from the coax connector on the rear panel, the 75S-3B returns to normal operation, using its installed crystal bank. Of course, you really need to have a synthesized signal generator lying around to pull this off for good SSB operation.

Don
W5QN 
Sponsored by the Collins Collectors Association http://www.collinsradio.org
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