A simple HF preselector for SDRs and older HF radios

[ka3jjz]

I've been on the lookout for a fairly simple to build HF preselector that you can use with these wide banded SDRs that cover HF (such as the Funcube, RTL-SDRv3, SDRPlay, etc.) that wouldn't cost an arm and a leg. If you have the parts and can wind a couple of torroids, this looks like a nifty little project...note that this will also work with old desktops that are single conversion and tend to overload easily.

Simple Tuned HF Preselector

This simple, low-cost, tuned, passive HF preselector will enhance reception of HF signals.

www.hamradiosecrets.com

Mike

 

[prcguy]

While interesting, I don't think the resulting filter is all that useful. I kind of remember a filter of this design has roughly 6dB per octave rolloff, so if tuned for 5MHz its only going to be about 6dB down at 10MHz, etc.

I bought one of these and am very happy with it even though its not a kit and I didn't learn anything from it. It works great in front of my RSP2pro and other receivers. *NEW* Multi Band Pass Filter HF+6m Upgraded version RTL SDR HAM Transceiver | eBay

 

[cmdrwill]

"New" Multi Band Pass filter KOOL.

 

[majoco]

You could try making two in series if you have a two-gang variable capacitor as long as both sections have the same parameters - a lot of the transistor radio variables do not comply as one section is for the RF stage and the other for the oscillator. This will give you only a quarter of the bandwidth and twice the slope...but then if you're feeling adventurous....