On Thu, Jun 01, 2017 at 01:29:10PM -0700, Greg D wrote:
One of your challenges is going to be knowing exactly what the conversion equation is, i.e. where exactly your LO ended up. Given the frequencies and multipliers involved, a very small offset in the LO crystal can result in a large offset in actual receive, making it difficult to find the satellite the first time. I think mine was off by something like 50 mhz on AO-40, even after tweaking the LO with a frequency counter. Very touchy.
For testing, and given that there's not much ham-related stuff on that band, you might scan the horizon and count microwave ovens (2450 mhz -ish), though they are not very frequency-stable. Best is around dinner time :) I also had good results listening for the 17th harmonic from a 2m transceiver fed to a diode as the load (144*17 = 2448). You might even try that with the 18th or 19th harmonic (2592 or 2736 mhz) on an unmodified unit, to be sure it's still working.
Greg,
That's a great idea on the 2m rig as an exciter for a diode comb generator. I'll have to try that out tonight on my unmodified unit! I assume that you attached the diode on the other side of a 20 dB pad to give some sort of reasonable return loss for the rig?
Many thanks go to Alan [email protected] for providing the requisite crystal. My alternate plan was to replace the LO generation in the unit with a custom PLL board. That might be interesting to do and then compare the xtal modification with the custom PLL for phase noise and overall performance.
--- Zach N0ZGO