Couple of RSP2 Newbie Questions...

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Glennfin
Posts: 5
Joined: Wed Jul 05, 2017 2:07 pm

Couple of RSP2 Newbie Questions...

Postby Glennfin » Tue Jul 18, 2017 11:12 pm

Hello players...

I've been looking over the RSP2 datasheet and I was hoping someone could answer a few questions.

Is it true that the two SMA antenna ports are only capable of receiving down to 1.5mhz? Am I forced to use the high impedance input for the broadcast band and LF?

It also seems that there are no bandpass filters below the 12mhz, only a low pass filter. On the high impedance input, only a 30mhz low pass.

Guess I got that right.

Glenn KZ4A
Last edited by Glennfin on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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Tech_Support
Posts: 196
Joined: Mon Jun 01, 2015 7:00 pm

Re: Couple of RSP2 Newbie Questions...

Postby Tech_Support » Wed Jul 19, 2017 8:01 am

Hello Glenn,
We do not recommend the use of ports A and B below about 1.5 MHz because there is a high-pass response which will lead to attenuation of the signals below this frequency. The roll-off is steeper on port B than on port A because of the influence of the bias-T circuitry on port B.

You care correct that there are no bandpass filters below 12 MHz on ports A and B. However there is an AM band notch filter. There is a straight conflict here between the desirability to have a very wideband receiver (up to 10 MHz) and RF pre-selection.

The Hi-Z port only has a low-pass response, but it has a very high dynamic range front end and generally gives a cleaner response at HF than either ports A or B.

Sincerely

SDRplay Tech_Support

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g1hbe
Posts: 195
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire

Re: Couple of RSP2 Newbie Questions...

Postby g1hbe » Wed Jul 19, 2017 8:34 am

Hi Glenn. The man speaks the truth. I think many of the observations about 'poor performance' of the RSP2 come from people who have not understood (or even read) the recommendations re the various antenna ports. I'm a MW and LF enthusiast and the difference between the Hi-z input and the two SMA ports is quite noticeable - Hi-z gives lower noise level and cleaner results, especially as you go lower in frequency. I'd recommend the Hi-z port for all HF listening up to 30 MHz, perhaps with the addition of a LPF or BPF of your choice depending on your bands of interest.
I use a set of switchable filters which includes a LPF which rolls off above 100 KHz for very low listening and another which goes over at 500 KHz for the beacon band. Save the SMA inputs for VHF & UHF.
I hope this helps, as the RSP2 is a very nice receiver for not a lot of money.

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Andy

Glennfin
Posts: 5
Joined: Wed Jul 05, 2017 2:07 pm

Re: Couple of RSP2 Newbie Questions...

Postby Glennfin » Fri Jul 21, 2017 10:15 am

Hi Andy (and tech support)

Thanks very much for the reply and explanation. Besides the lack of bandpass filters, my concern with using the hi impedance (balanced 1k) input is that in order to use it with HF coax fed antennas, I will need to use some sort of matching transformer or balun to match the balanced 1k input with unbalanced 50 ohm coax feed.


g1hbe wrote:Hi Glenn. The man speaks the truth. I think many of the observations about 'poor performance' of the RSP2 come from people who have not understood (or even read) the recommendations re the various antenna ports. I'm a MW and LF enthusiast and the difference between the Hi-z input and the two SMA ports is quite noticeable - Hi-z gives lower noise level and cleaner results, especially as you go lower in frequency. I'd recommend the Hi-z port for all HF listening up to 30 MHz, perhaps with the addition of a LPF or BPF of your choice depending on your bands of interest.
I use a set of switchable filters which includes a LPF which rolls off above 100 KHz for very low listening and another which goes over at 500 KHz for the beacon band. Save the SMA inputs for VHF & UHF.
I hope this helps, as the RSP2 is a very nice receiver for not a lot of money.
Last edited by Glennfin on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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DF1KZ
Posts: 12
Joined: Fri Nov 27, 2015 1:37 pm

Re: Couple of RSP2 Newbie Questions...

Postby DF1KZ » Sun Jul 23, 2017 7:14 am

Hello Everyone,

It is very simple to build a transformer for the HiZ-input of the RSP2. Just use a binocular core BN 73-202 (1€) with 3 turns primary and 13 turns secondary. You can also try 2 turns/9turns that may be better on higher frequencies. It takes 10 minutes to wind the transformer.
Using this transformer and a RF Systems DX-10 Professional antenna (50 Ohm) with an additional 20dB attenuator I can even receive the Russian Alpha on 11.9 kHz and SAQ on 17.2 kHz.
Without the 20dB attenuator the output of the DX-10 seems to be much to high for the RSP2 because there is only a 30MHZ low-pass filter for the HiZ-input. I fully agree with g1hbe that LPFs or BPFs should be used.

Wolfgang (DF1KZ)

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SDRplay (RSP1, RSP2 pro) with:
RFsystems DX-10 (14kHz to 50MHz), ICOM Discone AH8000 (10MHz to 2GHz)
12m above ground


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