I've been monitoring AO-73 (FUNcube-1) extensively over the past few months and noticed significant frequency variations in the transponder passband. The passband may be up to 15kHz higher depending on on-board temps. Lower temperatures give higher freqs!

During winter passes, I'm consistently seeing the transponder 8-12 kHz higher than the nominal 435.150 – 435.130 MHz LSB uplink and 145.950 – 145.970 MHz USB downlink. Has anyone correlated this with the telemetry data to confirm the temperature relationship?

Would be interesting to create a lookup table for SatPC32 based on orbital position and season. The telemetry downlink is functioning with about 70mW output so data should be available.

Yes, this is well documented in the FUNcube telemetry archives. The crystal oscillator frequency increases as temperature drops - classic behavior. I've seen swings of nearly 20 kHz on deep winter eclipse passes.

New to AO-73 but I've noticed this too. Is there a recommended way to predict the offset before a pass starts? Sometimes I spend half the pass just finding the transponder edges.

Check Colin VK5HI's SatBlog - he tracks this data religiously. The FUNcube Dashboard correctly decodes the data and uploads it to the FUNcube Data Warehouse where you can examine the correlations. I use his reports to pre-tune my radio before each pass.