The Softrock uses an FST3253 switch as a mixer. Here I have used a Softrock like the Ensemble with a 47MHz BPF and an Si570 programmable oscillator. Subharmonic mixing is used with Softrocks as they will not work using an oscillator at four times the received frequency of 47.05MHz. I have used about a 20KHz offset but with "subharmonic mixing" I think a much lower offset may be used as there is no signal present to feedback into the receiver's IF. If your SDR oscillator is lower than the IF frequency this figure will be negative. The station on 999KHz (999000Hz) is seen at 1008177Hz when you hover your cursor over it's carrier. Like all major broadcasters the BBC usually maintains very good frequency accuracy.Ĭhoose a station on it's own with no other strong signal close by so there is no confusion. I have used a local BBC medium wave station on 999KHz. WWV, or one of the major shortwave broadcasters may be used. This time tune to the frequency on the external receiver. My method for setting the various offsets is to tune to a strong, steady AM station of known, preferably accurate, frequency. You will need to set that frequency in "Mirror RF Spectrum for Tune", see above. "Swap I and Q Channel for RX Input" and "Mirror RF Spectrum in general" will seem to have the same effect but for a few rigs the sideband setting will change above a certain frequency. The tuning will not match between the receiver and the SDR so the tuned signal will only be heard on the SDR. Tune in several SSB stations with this receiver if the sideband heard on the SDR is not correct for the selected band (LSB for 40 metres, for example) then tick "Swap IQ channel for RX Input". Tune to an amateur band on the conventional receiver but listen to the audio from the SDR. When CAT control is established the first stage must be to check that the "Swap IQ channel for RX Input" is correctly set.
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