(2020-08-01, 10:24 PM)dj11223344 Wrote: [ -> ]Thanks for all the suggestions. Still trying to figure it out. I got side tracked on other projects. I can't even seem to tune into known FM radio stations. Maybe I received a bad antenna or dongle.
I was in a similar position to you, having just purchased the RTL-SDR. Initially the ppm value would not converge. I then tried a much shorter dipole antenna (<100mm) as it appeared that it was possibly using GSM signals for the calibration (p.s. I'm trying to calibrate at home not on the boat) and found that it then converged rapidly to ~+-1ppm.
Having completed the calibration (0 ppm), I get background noise from the marine VHF channels on GQRX (too far from the sea!) but silence on (wideband) broadcast FM even though i have a good signal. Has anyone else experienced or fixed this?
Paul
I recently purchased a Nooelec NESDR Nano 3 RTL-SDR and I too was having problems with the calibration process like what was reported in the beginning of this post. The PPM was all over the place and at first it was looking like I would need to be using a crazy number like -800 PPM until I read to not worry about the calibration process. The unit is advertised as .5PPM from the factory so I entered 1 in the PPM and left the gain entry empty, hooked it up to the VHF aerial on the boat and found I was quickly picking up vessels up to 40 miles away. It did take a moment for the first vessels to display due to the slow response from the close anchored vessels. But once the harbour became busier the update rate was right on the mark and was as good or better than a Raymarine AIS receiver.
A good antenna is very very important, I first up tried to make do with a short wire antenna but that didn't work very well for the AIS, I could pick up local FM radio stations using CubicSDR program from
www.cubicsdr.com and I could also see the transmissions from vessels close by but you need a bit of height and a proper areal for it to work well.
Good luck
Cheers