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replace dongle power supply

Posted: Fri Feb 15, 2019 2:35 am
by nospam
Has anyone tried disabling the internal 3.5V switching supply and supplying an external linear regulated supply also independent of the USB 5V? Just wondering if this would reduce LO jitter and background noise.

Re: replace dongle power supply

Posted: Fri Feb 15, 2019 4:50 am
by rtlsdrblog
There is no 3.5V switching regulator, only a 1.2v one. The 3.3V rail is powered by an LDO, unless you have a really cheap and rare RTL-SDR as some of those use 3.3V switching regulators.

Yes some people have tried using a 1.2V LDO before, however the effect isn't really big, and the power draw of the dongle rises to about 400mA IIRC. You might get a little fewer birdies on HF in direct sampling mode but that's about it.

Re: replace dongle power supply

Posted: Fri Feb 15, 2019 2:49 pm
by nospam
tks for responding. I should have thought about it and realized that the new stuff would run at 1.2v. Nevertheless, it sounds like people have tried that with no beneficial effect. Mine is older but not real old, its got the E4000 tuner. I've got a homebrew upconverter. I've been using it to do WSPR reporting. At first it did just fine but lately it seems there's some jitter somewhere. It could be in the LO in my upconverter too plus its time to update the WSPR decoding software. Lots of variables. I think the software is adequate as I've connected a real good quality receiver and it decodes fine with lots less jitter showing on the wspr waterfall. Anyway, sounds like hacking that PS on the dongle is the last thing to try.

Re: replace dongle power supply

Posted: Sun Feb 17, 2019 2:03 am
by rtlsdrblog
Are you meaning frequency drift? If it's an older generic brand, it won't have a TXCO. For WSPR that could be a problem as when the temperature changes the frequency will drift.