RSP2 no BBC Radio 4 on LW?

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StandingWave
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RSP2 no BBC Radio 4 on LW?

Postby StandingWave » Mon Feb 18, 2019 10:07 pm

I just received my RSP2 today. It is supposed to tune down to VLF frequencies, but having had a casual play tuning into different bands I noticed that there was a complete abscence of a signal at 198kHz LW where there should be a very strong signal from BBC Radio 4. I tried both with a small whip antenna and with the longwire in the gardn. I checked with the old analog radio and sure enough Radio 4 was broadcasting with a nice clear strong signal, but nothing on the SDR? Shannon volmet came in quite clear with a bit of fading on 5505kHz and FM broadcast band came in clear. If its deaf at 198kHz does it really receive down to VLF?
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Mike2459
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Re: RSP2 no BBC Radio 4 on LW?

Postby Mike2459 » Tue Feb 19, 2019 12:49 am

The Hi-Z antenna port begins to rolloff a little around 20KhZ. This is the preferred antenna port for HF and LF. Are you sure you didn't mistakenly enter 198 Mhz instead of 198 Khz.

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Paul
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Location: SW UK

Re: RSP2 no BBC Radio 4 on LW?

Postby Paul » Tue Feb 19, 2019 8:08 am

It would be heloful to post a screenshot of your RSP2 on 198 KHZ, preferably with LO IF and perhaps a SR of 8 for clarity.

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g1hbe
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Location: Cheshire, UK

Re: RSP2 no BBC Radio 4 on LW?

Postby g1hbe » Tue Feb 19, 2019 9:23 am

Oh yes, the RSP2 does indeed receive well down to VLF. It's my 'go to' LF receiver, as it works well right down to 15 kHz at least. It's all there, BBC R4, MSF (60 KHz) and all the other stuff including SAQ on 17.2 kHz on those special occasions.
The Hi-Z port is best for LF, but you should get results even on port A. Below (I hope) is a shot of my RSP2 from 0Hz to about 200 kHz. The big hump is navigation sigs and you can see the stuff at 20 kHz at good strength. It's worth bearing in mind that strong MW and LW broadcast stations can overload the RSP and raise the noise level and drown out the weaker LF signals. Try the MW rejector or better still make a 250 kHz LPF.

lfsmall.jpg
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Andy

StandingWave
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Re: RSP2 no BBC Radio 4 on LW?

Postby StandingWave » Tue Feb 19, 2019 10:47 am

Thanks for the replies. Indeed using the Hi-Z input did work. Its still quite noisy but at least its there. I also got it on the internal whip, but only just.

I'm not sure where I find the MW rejector? The MW/FM box disappears (if that's the one) when I select the Hi-Z antenna.
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g1hbe
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Location: Cheshire, UK

Re: RSP2 no BBC Radio 4 on LW?

Postby g1hbe » Tue Feb 19, 2019 11:13 am

Yes, the MW/FM rejector disappears in H-z mode. A homebrew LPF (or a commercial one) is a good idea, as is careful control of the RF gain/attenuation slider.

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Andy

fotoralf
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Re: RSP2 no BBC Radio 4 on LW?

Postby fotoralf » Tue Feb 19, 2019 11:30 am

StandingWave wrote:Its still quite noisy but at least its there.


It always helps in such cases to know where people are located. From your screenshot, the French radios périphériques appear to be a lot stronger than R4.

Ralf

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StandingWave
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Re: RSP2 no BBC Radio 4 on LW?

Postby StandingWave » Tue Feb 19, 2019 2:53 pm

I am in the central England, i.e. in Leicestershire, the midlands, a long way from France.

Those peaks are mostly a loud hum, very likely mains hum. Not sure what its coming from yet but its something I need to figure out. Having said that, my antenna connector is not properly set up for the Hi-Z input at present. The RSP2 Hi-Z inputs are unmarked and in the absence of being able to find any information other than pictures of the inputs on the RSP2 Pro, I connected the co-ax shield to GND the inner core to P. Given that there is a P and N connection, I presume that ideally it should be a dipole using a balanced feed to P & N with optionally GND connected to the ground rod? I guess an LPF would help to filter out some of the hash but it probably won't solve the hum that I am experiencing at the moment. Still, I have put it on my todo list to have a look at.

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g1hbe
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Location: Cheshire, UK

Re: RSP2 no BBC Radio 4 on LW?

Postby g1hbe » Tue Feb 19, 2019 5:09 pm

Wide, buzzing carriers from switch-mode PSUs are a pain in the neck on LF. The best you can do is to use a loop antenna sited as far as possible from any suspected source of noise. Not easy these days!
For feeding the Hi z connector with coax, link N to G and connect outer to G and inner to P. For a proper balanced feed, ignore G.
There's an illustration on the main site under 'documentation' /datasheets I think. The coax from my Wellbrook loop goes to a ferrite transformer and then into the P/N terminals. This works well and breaks the Earth loop than can cause so much grief. Use LF-spec ferrite if you want to go L-O-W.

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Andy

Paul
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Location: SW UK

Re: RSP2 no BBC Radio 4 on LW?

Postby Paul » Tue Feb 19, 2019 7:18 pm

Hi again "Standing wave"
Firstly, there are folks answering your post who really know thier onions and I'm just stumbling along, learning a little here and there along the way.
However, I did notice on your screenshot that your RF Gain/Attenuation is set at the "top."
As you are probably aware the default setting is "gain reduction," but can be changed by the operator to Gain if desired.
The best starting point for this slide is generally around the mid-point and I would recommend from my shallow experience that it's a reasobale starting position..
Either extreme, in gain, or gain reduction will generally produce poor results.
As for the HI-Z connection, here's SDRPlay's explanation and imagery that may be of assistance:
https://www.sdrplay.com/wp-content/uplo ... uidev2.pdf

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