Building a Transceiver (Pixie V3) 

Thanks for the info, I didn’t realise. Yes, different crystals or perhaps a variable capacitor to provide some wriggle room?

@@ianxfs Yes. A last vestige of "incentive licensing", I suppose. You need to get that highest level license to get the bottom 25 kHz of both the CW and phone portions of 80, 40, 20 and 15. The pixie seems the ideal way to let our lowest class license get their feet wet on HF, since, otherwise they are restricted to 10m and up, and often only have a Baofeng. I don't know where those 7.023 MHz crystals come from. They certainly must be being used in some non-Ham application. They're not 2x the color burst frequency, so I have no guesses. For the sake of round numbers, lets say we wanted to move it up 3.5 kHz, making it 7.0265MHz, giving a comfortable 1.5 kHz clearance from the sub-band edge, for tolerance, drift, and key clicks (not that the FCC is going to care about clicks that exceed the sub-band, but not the band). That-s 0.05%. In this frequency range, even cheap crystals are going to have very good Q, so I don't know if 0.05% is doable. My understanding is that the load capacitor would have to be reduced in order to move up in frequency. Too low a load capacitance might cause problems with oscillator startup, but the oscillator isn't keyed, so as long as it eventually starts (even seconds), it should be OK. I suppose that there could be other effects such as increased phase noise, but that shouldn't be a problem for this usage. If you have any small value capacitors lying around, say between 1 and 10pf, it would be instructive to know how much the transmit frequency changes, as heard on you base station rig, if you temporarily tack one of these directly across the crystal (and if soldering, after giving the crystal 5 minutes to cool. Looking at the circuit, the load capacitance is the two 100pf capacitors in the Colpitts divider, C3 and C7, and the capacitance of the tuning diode, D2, all in series. (C4, I believe, can be ignored, because the base of Q2 is a high impedance at RF.) If they were all 100pf, that would give a 33.3...pf load capacitance. Specified load capacitance is normally in the 20pf to 30pf range for most crystals (according to my readings, see this article: www.electronics-notes.com/articles/electronic_components/quartz-crystal-xtal/crystal-resonator-frequency-pulling-trimming.php ), so I'm guessing that the tuning diode capacitance is a bit smaller. So, if the crystal can move far enough, it might work to reduce C3 and C7. But I suspect that I should look for a cheap source of 7.040 MHz crystals. 73, Bill - KE1G

@@KeepEvery1Guessing Thanks for the licensing info Bill, and the explanation of the design. I don’t have similar caps in the shack, but I’ll keep this in mind when I next come across some to “borrow” or buy. Like you say, a crystal would be the most straightforward approach. 73.

Thanks Daniel!

Thanks!

Thanks Scott! Determined to make a contact with someone now…🤞🏻

Would have to come with a magnifying glass for my eyes. Looking forward to seeing a contact video Ian.

@@ianxfs Go get 'em!