HF reception problem with a Chinese BA5SBA SDR with Upconverter

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Jamieson Rowe
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Joined: Tue Jan 28, 2020 1:34 am

HF reception problem with a Chinese BA5SBA SDR with Upconverter

Post by Jamieson Rowe » Tue Jan 28, 2020 1:54 am

Hi,

I have struck a strange problem with two of the newish Chinese BA5SBA SDAs which have an Upconverter for LF and HF reception. I have had no problems with smaller 'dongle' RTL-SDRs which use Direct sampling (Q-branch), and have also assembled a kit using the same approach (luckily I succeeded in soldering the fine wires to the pins of the RTL2832U IC), with no problems, apart from not-wonderful HF sensitivity.

But both of the new (+Upconverter) models seem to be 'dead' in terms of LF and HF reception, even though they are quite OK on the VHF-UHF range. They both have a 100MHz upconverter oscillator, so I'm setting (in SDR#) the shift frequency to -100,000000 and leaving the sampling set for Quadrature sampling. I'm also turning off the RTL AGC and Tuner AGC, and setting the RF gain to maximum. But their LF-HF reception is non existent!

Can anyone offer any suggestions? Has anyone struck the same problem?

Thanks, Jim Rowe

rtlsdrblog
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Re: HF reception problem with a Chinese BA5SBA SDR with Upconverter

Post by rtlsdrblog » Tue Jan 28, 2020 3:17 am

Your settings sound correct. I'm assuming you're connected to the correct input.

If nothing works i'd ask for a replacement. I know that the defect rate on the BA5SBA direct sampling units is pretty high, so it might continue over to their upconverter version.

Jamieson Rowe
Posts: 3
Joined: Tue Jan 28, 2020 1:34 am

Re: HF reception problem with a Chinese BA5SBA SDR with Upconverter

Post by Jamieson Rowe » Tue Jan 28, 2020 9:47 pm

Hi,
Thanks for that response, but I'm a bit wary of just putting the problem down to both unit being faulty, since I got the second one from a different supplier when I discovered that the first unit was 'dead' on the HF range. The first unit was from Banggood, and is in a plain metal case with the word 'Convert' printed on it, whereas the second unit was from a very different supplier on eBay and had the black wrap-around dress label around the case.

They do look very similar inside, of course, so they may both come from the same manufacturer...

I've also tried looking with a DSO to see if there's any output from the 100MHz local oscillator when the range switch is set for reception on the HF range -- but there doesn't seem to be any output. So you're probably right: both units may well be faulty.
I guess I'll just have to 'write them off' as a bad purchase.

Anyway, thanks for your response and suggestions.
Jim Rowe

Jamieson Rowe
Posts: 3
Joined: Tue Jan 28, 2020 1:34 am

Re: HF reception problem with a Chinese BA5SBA SDR with Upconverter

Post by Jamieson Rowe » Wed Feb 05, 2020 7:54 pm

Hi again,
I've noticed that some of these 'upconverter' RTL-SDRs claim to have a 'bias tee' at the input to allow DC to be made available to external active antennas or RF preamps -- and I've seen a suggestion that the supply to the bias tee can be controlled by software. But it seems that apps like SDR# can't control this -- it has to be done using special batch files (one to 'turn on' the supply and another to turn it off.
Is there a possibility that the latest upconverter RTL-SDRs also have a feature to control the power to the upconverter, and SDR# doesn't have the facility to control this? It would explain why two different BA5SBA upconverter RTL-SDRs seem to be dead on the LF-HF upconverter range. Perhaps the units are not faulty, after all.
Has anyone discovered the answer? Is there yet another 'secret' software solution to 'unlock' the upconverters?

If so, please let us all know.
Thanks, Jim Rowe

rtlsdrblog
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Re: HF reception problem with a Chinese BA5SBA SDR with Upconverter

Post by rtlsdrblog » Thu Feb 06, 2020 12:51 am

No I don't think that the BA5SBA units would be that advanced to be switched via the GPIO. As far as I can see, the upconvert circuit on those units is simply controlled with the switch on the back.

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