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Would T-bias benefit from LC filter?

Posted: Mon May 02, 2016 11:51 pm
by arjscott
Apologies if this is a stupid question.

I have seen DC regulators with LC filters to reduce high frequency noise.

I'm guessing - I could be wrong - the power supplied by the T-bias has some HF noise up there.

Would an LC filter reduce this, and as a result get better performance from an LNA?

Thanks in advance.

Re: Would T-bias benefit from LC filter?

Posted: Wed May 04, 2016 1:10 pm
by rtlsdrblog
What frequencies are you listening to? There is some HF noise generated by the switching regulator in the dongle. There is already an inductor on the bias tee to block signals from getting through to the power rails, but lumping in more inductors might help. Also ferrite beads.

Re: Would T-bias benefit from LC filter?

Posted: Thu May 05, 2016 5:07 am
by arjscott
Thanks for your reply.

I'm listening on L-band but not having much success. I guess there could be other issues like the cheap patch antenna.

I'll try an LC and ferrites and see what happens.

Cheers.

Re: Would T-bias benefit from LC filter?

Posted: Thu May 05, 2016 11:57 pm
by rtlsdrblog
I think the main problem with L-band would be the antenna, and possibly the need for a filter depending on if you have strong out of band signals in your area. Homemade LC filters at L-band frequencies probably won't cut it unless designed very caregully, but Adam 9A4QV sells some good L-band filters for a reasonable price, at lna4all.blogspot.com.

Also, check that you aren't having any heat related issues at L-band, and perhaps try the modified driver. http://www.rtl-sdr.com/beta-testing-a-m ... at-issues/