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Using SDRplay RSP2 pro as panadapter w/Kenwood 830s

Posted: Thu Aug 09, 2018 3:42 am
by jimgar
Do you see any RF concerns when transmitting on my Kenwood ts-830s, when the IF out-1 connector on the connected to one of the antenna inputs on the SDRplay RSP2 pro? I have read post stating I need to purchase a TX/RX Switch to protect the SDRplay, is this switch necessary when using the IF out-1 RCA Jack on the radio to provide the received signal to the SDRplay?

I would like to ensure that I do not cause damage to the SDRplay RSP2 pro, I really like this receiver, but would like to use it as a panadapter.
I welcome any feedback you can provide on this issue, Much Appreciated!

Re: Using SDRplay RSP2 pro as panadapter w/Kenwood 830s

Posted: Sun Aug 12, 2018 2:52 pm
by hfsdpk11
Remarkable that your 830 is still on the air! I had an 830 in the '80s before eventually trading it in for an 850 which is still my primary HF rig. To your point, I've connected the IF Out RCA tap point on my 850 directly to the Ant1 input of the RSP2Pro without any special switching or isolation when transmitting. You'll have to check your schematic to see how the 830 IF tap is provided - I don't know that it's any different from the TS850 configuration but suspect it may be similar since the radios are of the same era.

Your tap at the 8.83 MHz IF is probably the same as mine in that the first IF is inverting so you'll have to set the RSP configuration to swap I/Q channels if you want to keep the convention of sigs below CF also displaying as below CF. Another thing you might see is the noise floor level varies a lot across the visible passband - maybe 20 dB. peak to peak. My guess is that's because there isn't any special matching going on at the radio's tap point since it's designed only for the narrow band centred at 8.83 MHz. passed by the first IF crystal filter. Nevertheless, you can see signals several 100's of kHz. away from centre frequency so it's still useful as a panadapter.

When transmitting, my 850's circuit does some muting/attenuation but you can still see a residual of the TX signal. It's much lower than the level of moderate RX signals & hasn't harmed my RSP2Pro over the past 1 year I've had it connected that way.

Again, check your schematic to make sure the IF tap has some protection from strong TX sigs. At worst, if you can lay your hands on a couple of 10 dB. attenuators, put those in line between the IF tap and your RSP to check the TX level and remove them as desired after verifying.

If you're using SDRUno for the spectrum display, I'd suggest my setup. Configure two RXers with SR=2 MHz and decimation of 1:

RX 0 = primary to set the RSP LO. Freq = 8800.000 kHz. This controls where the RSP LO is situated.
RX1 = used for the spectrum display. Freq = 8771.500 kHz.

This combination of RXers will place the radio's IF at nearly the centre of the RX-01 spectrum display while keeping the RSP's LO sufficiently offset from the region of interest.



Re: Using SDRplay RSP2 pro as panadapter w/Kenwood 830s

Posted: Sun Aug 12, 2018 11:06 pm
by jimgar

Thanks for the great response to my question, I really appreciate your taking the time to provide a detailed example of how you are using the RSP2 as a panadapter. I will verify whether the IF out-1 has protection and take your recommendation of using 10 db attenuators.

Now about the Kenwood TS-830s I bought it from the original owner and he had purchased it fully fitered, but it was rarely used. He had it recapped before he sold it to me and I looks and performs like new. I think this radio will out last me, as I am up in years as well.

73 de W7JRG