My preferred method of calibration to have the kits ready built
and putting out some power.
Set the frequency to the highest practical band such as 28Mhz.
Press the right hand button to force a carrier out into some kinda dummy load
that has a simple tap off of it to feed a frequency counter, at a sensible level in order
to get an accurate reading.
Twiddle the blue pot slowly until the correct output frequency is seen.
Notes:
Using the 28Mhz band ensures? best accuracy, and usually coincides with maximum output power.
On 28Mhz the travel of the blue pot is narrow, so adjust slowly !
The final result will be good, but remember that it WILL change a bit because you're operating
the 125Mhz osc in the open air, and the lack of temp stabilization will cause some variation.
(Better when the unit is boxed and left to settle for 30 mins).
The variation might be enough to put a WSPR transmission slightly outside the narrow band.
That's when having a GPS can take over the finer adjustment.
Use Argo or similar to check for signal drift.
For a quick and universal drift check, you could also use the recently announced LiToPo
browser based monitor to watch for carrier drift, or see the final output wave form.
Feed some rx audio into the build in mic of your cellphone or PC (any OS) and ensure
that the browser security settings will allow acces to the mic or s/card input.
Tronald Dump