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DSheirer / sdrtrunk

A cross-platform java application for decoding, monitoring, recording and streaming trunked mobile and related radio protocols using Software Defined Radios (SDR). Website:
GNU General Public License v3.0
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Retune Tuner to sweet spots #1277

Open Nokoa opened 2 years ago

Nokoa commented 2 years ago

Often SDRTrunk may define a center frequency for the tuner causing some of the channels to be on the edges, while all channels can very well fit in the middle area of the tuner spectrum. The edges signal quality is degraded.

GTR8000 commented 2 years ago

Yup, that's why some of us have taken to creating "dummy" channels to keep the centering optimized. I don't really like having extra channels running (even though they are decoding nothing), and it does make for a messy looking Now Playing screen, but it gets the job done.

Being able to define a static center channel per tuner would be a welcome feature.

cfc62 commented 2 years ago

Would the dummy channels be set for the highest and lowest frequencies for each SDR?

tvsjr commented 1 year ago

@cfc62 correct. For example, an Airspy is good for 8.9875MHz of coverage (aliasing happens on the outside 1MHz, so SDRTrunk won't use it). Good frequency pairs (what I affectionately call Dummy Lo and Dummy Hi) are 767.50625 and 776.49375 for 700. 800 is a bit more challenging since the entire split is 10MHz (851-861). If you wanted to split the band in half, you could do something like 847.0125-856.0000 and 856.0125-865.0000.

IMO, especially considering the low price of the tuners, using a static center frequency is actually the optimal configuration. Retuning the tuner to try to maximize coverage is a klugey thing that should be the second choice for when you don't have/can't afford/whatever enough tuners to cover everything statically.