How to set the bandspread to neatly match a given ham band
Posted: Tue Nov 01, 2016 9:04 am
We had the question recently from an SDRuno user who asked the question: "How can I set the bandspread such that it covers exactly the 40m amateur band?"
This was our answer:
There are two ways to the frequency span that you want (or close to it). It may not always be possible to get the exact span, but you should be able to get reasonably close. The displayed frequency span is determined by the final sample rate used by SDRuno. If you open up the advanced tuner settings panel (ADV) from the main panel, you will see the Final SR at the lower left hand corner of the ADV window. It is also displayed in the top right hand corner of the Main Panel.
Now, firstly, ensure you are in Zero IF mode. Next select the closest IF BW value that is lower than the final span that you want (it must be lower than). Now select an RSP SR (ADC sample rate) of 2.8 (2.8 MHz) and a Decimation factor (DEC) of 8. You will now see a FINAL SR of 0.35 MHz displayed. With this method and in this case, you will see some slight roll off at the band edges. This is because the closest IF filter bandwidth to the desired frequency span is 300 kHz and the IF filter will slightly attenuate the edges of the spectrum relative to the centre. It will not affect your ability to receive signals at the edges of the displayed window.
Now, open the Receiver window by pressing Rx in the Main panel. Now click on the frequency display with your mouse and type in your desired centre frequency and hit the enter key. Open up the SP1 display and you will not see the 40m band displayed with a span of 350 kHz.
A simpler way (but less accurate) is simply to type your desired frequency span in the BW window in on the Main panel. This is a quick frequency span setting window. If you type 0.35 into the BW window, you will see the Final SR change to 0.3. This is because the software tries to pick the closest available tuner IF bandwidth first (which in this case is 300 kHz) and then set the sample rate that is appropriate for the IF bandwidth, so in this case, you will not get the full desired 350 kHz display.
Jon, SDRplay
This was our answer:
There are two ways to the frequency span that you want (or close to it). It may not always be possible to get the exact span, but you should be able to get reasonably close. The displayed frequency span is determined by the final sample rate used by SDRuno. If you open up the advanced tuner settings panel (ADV) from the main panel, you will see the Final SR at the lower left hand corner of the ADV window. It is also displayed in the top right hand corner of the Main Panel.
Now, firstly, ensure you are in Zero IF mode. Next select the closest IF BW value that is lower than the final span that you want (it must be lower than). Now select an RSP SR (ADC sample rate) of 2.8 (2.8 MHz) and a Decimation factor (DEC) of 8. You will now see a FINAL SR of 0.35 MHz displayed. With this method and in this case, you will see some slight roll off at the band edges. This is because the closest IF filter bandwidth to the desired frequency span is 300 kHz and the IF filter will slightly attenuate the edges of the spectrum relative to the centre. It will not affect your ability to receive signals at the edges of the displayed window.
Now, open the Receiver window by pressing Rx in the Main panel. Now click on the frequency display with your mouse and type in your desired centre frequency and hit the enter key. Open up the SP1 display and you will not see the 40m band displayed with a span of 350 kHz.
A simpler way (but less accurate) is simply to type your desired frequency span in the BW window in on the Main panel. This is a quick frequency span setting window. If you type 0.35 into the BW window, you will see the Final SR change to 0.3. This is because the software tries to pick the closest available tuner IF bandwidth first (which in this case is 300 kHz) and then set the sample rate that is appropriate for the IF bandwidth, so in this case, you will not get the full desired 350 kHz display.
Jon, SDRplay