Pro Stick Plus Freq Adjustment - SDR Sharp

I just started getting into ADS-B tracking, mainly because my ~4yr old loves planes and insists on asking everything possible about the ones that fly by. I picked up a Pro Stick Plus and basic Nooelec 5dBi antenna. When I fired up SDR Sharp, it looks like the signal peak I see is ~1.0896 instead of the expected 1.09. This is with a 2.4 MSPS rate, gain set to 48. Is this “off” enough to have any impact on messages? I know I can make the PPM adjustment, but when I do in SDR Sharp then I start getting multiple spikes, so not sure if I’m testing / adjusting properly. Thanks!

Current prosticks have a TCXO so they should be within +/-1ppm or so - so within 1kHz or so - definitely not as much as 400kHz, even the uncompensated crystals are better than that.

What’s the “peak” you’re seeing? Mode S isn’t a continuous signal so any steady signal you see is probably an artifact; maybe you are just seeing the “DC spike” in the dongle itself?

Yeah, it’s a solid spike up to around -5dB: May be an artifact.