alantlk wrote:I noted the 12dB difference in 2nd harmonic strength between the SAS and a calibrated SA on the forum
I cannot find any post comparing the levels between the SAS and a calibrated SA. Could you post a link to the post your are referring to ?
alantlk wrote:Two other SDR software and hardware combinations had wildly different readings as well, -35dBm, and -68dBm. While some variation is to be expected with such a simple test setup I was surprised at the 85dBm range of values.
Could you provide some details, such as which software you are using. Some software, such as SDR# does not display signals in actual dBm, and the reported signal level will vary with SDR gain settings.
alantlk wrote:I queried my results with SDRPlay Support who replied to say there are calibration tables within the API that mean the SDRUno reported signal level is within 0.5dB of actual and that they are available to 3rd party software. While I note replies about zero IF, so I'll try again when I've got some more time, does SAS use those API calibration tables please?
I've compared levels between SDRuno, a signal generator and the SAS. The difference in levels are usually within 1-2 dB. There is some slight loss with SAS due to (currently) uncompensated windowing loss. The values you are reporting seem to be wildly out compared to what I've seen so far. Can you provide some more detail about the tests you have made ?
The total system gain, and gain reduction figures are obtained from the API which uses the gain tables to calculate the returned values.