Monday, February 6, 2017

Adding a Homebrew Front End to an RTL-SDR HDSDR Receiver

I started playing with the RTL SDR dongles again.  I wanted to use them to confirm that my BITX signal is NOT 9 kc wide (it is not).  I also wanted to try to confirm the aircraft band frequencies in use in this area.

So I got the HDSDR software running and plugged in the dongle that I had modified for HF use.  It worked great, but I could see (literally SEE) that it needed some bandpass filtering and perhaps a bit of RF gain.  So today I threw together this device.  Dual gate MOSFET (gates tied together) with an LC filter on the gate.  Power from Malaysia via the 9V battery.

It works great. It was fun to add a bit of homebrew to an otherwise soul-less commercial receiver.   But beware: that waterfall is addictive, even for a hardcore Hardware Defined Radio guy like me.
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5 comments:

  1. JohnFebruary 6, 2017 at 11:04 AM

    GM! Question about the construction: the base is a copper clad PC board...are the non-ground connection points just pieces cut from another similar PC board? I like the idea, just never tried it myself. Love the blog and read the book. 73, John/N6VTS

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  2. JwaharFebruary 6, 2017 at 11:13 AM

    It'll be great if you could share the circuit and the design parameters around the filter design.

    73 de kc1ccr

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  3. k8muFebruary 6, 2017 at 4:27 PM

    Nice use of black tape.

    Larry K8MU

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  4. Bill MearaFebruary 6, 2017 at 7:09 PM

    Gorilla tape! I use it a lot.

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  5. Bill MearaFebruary 6, 2017 at 7:11 PM

    John: The construction style is "Manhattan" -- as you surmised, the copper clad board serves as ground. Isolation pads are superglued wherever you need a connection above ground. I just cut the isolation pads from scrap copper clad board using tin shears. Quick and easy."

    Jawahar: I will try to post a schematic of the device tomorrow.

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