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Ctrl Panel & Main SP different freq.

Posted: Sat May 27, 2017 2:30 pm
by K3WKM
New to SDRUNO opened 3 RX...why do the RX for 01 and 02 show passband for different freq. than entered in the RX Ctrl.
Thanks for the help
73
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Re: Ctrl Panel & Main SP different freq.

Posted: Sun May 28, 2017 12:21 am
by PG3
With a SR of 10 MHz and a DEC of 1 in the main window you have an IF bandwidth of 8 MHz. Each of your spectrum displays appear to be zoomed in and SCROLLED to different sections of the total IF bandwidth.

Re: Ctrl Panel & Main SP different freq.

Posted: Sun May 28, 2017 10:15 am
by K3WKM
OK thanks but the first issue is why in RX 01 and RX 02 is the RX control frequency different than what shows in Main sp 01 and 02?

If u understand the solution to my problem can u explain what and how I should be able to fix it?

Thanks

Re: Ctrl Panel & Main SP different freq.

Posted: Sun May 28, 2017 10:26 am
by K3WKM
OK so what do I do to fix it?

Thanks

Re: Ctrl Panel & Main SP different freq.

Posted: Sun May 28, 2017 1:35 pm
by hfsdpk11
You can tune a VRX only within the sampling rate bandwidth centred on the LO of VRX0. In your case, VRX-0 sets the LO to 446.753637 MHz. and you're using a sampling rate of 10 MHz. That means the VFO tuning range of <ALL> VRXs is limited to 446.753637 +/- 5 MHz, or roughly 441.75 to 451.75 MHz. You are attempting to use VFO's of 147 and 162 MHz. in VRX1 and 2 respectively, however the LO and SR bandwidth will not allow you to do that. Instead, it will tune to wherever the VFO/LO math tells it to within the allowable BW (I'm too lazy to figure out why those particular freqs in your situation).

Re: Ctrl Panel & Main SP different freq.

Posted: Sun May 28, 2017 2:10 pm
by K3WKM
Thank you for the explanation....If I understand correctly that would mean you can not listen to two different freq. that are not within the 10 MHZ sampling rate.....my objective was to listen to two repeaters at the same time.....one on 2 meters the other on 70cm....(this can't be done is what I think u are telling me)....

I appreciate ur help....

73 Steve K3WKM

Re: Ctrl Panel & Main SP different freq.

Posted: Sun May 28, 2017 5:21 pm
by hfsdpk11
I think you've got it. In essence, you can tune the VFO of any VRX across: LO +/- SR/2 but not outside of that. Since the RSP has only one LO, you're limited to the bandwidth around it and no more. Look on the VRXs as taking a chunk out of the passband provided by the LO and sampling of the ADC and then doing the demodulation/processing on that chunk.

Re: Ctrl Panel & Main SP different freq.

Posted: Sun May 28, 2017 5:27 pm
by K3WKM
Excellent...thanks for straightening me out!
73 Steve K3WKM