Reader David Forsman, WA7JHZ, read the round-up of RTLSDR upconverter choices and sent me a photo and build schematic of one he designed which was featured in the January 2013 issue of QST, the ARRL‘s monthly magazine.
This circuit up-converts frequencies between 2.3 MHz and 43 MHz by 125 MHz (127.3 MHz to 168.0 MHz) for driving the Realtek RTL2832 quadrature decoder DVB-T device with Elonics E4000 tuner chip with USB 2.0 output. It also incorporates an input bandpass filter (BPF), diode limiter, RF attenuator, and amplifier.
The filter’s response curve:
David reported he’s built two of these up-converters with good sensitivity on 20 and 15 meters. I think I have all the parts except the crystal and coils to build this on hand, so this might be a good excuse to sting my antenna up again and try it out. Thanks David for sending this in!
RETROVOLTAGE 
I like it. My first dongle took about 30 microvolts to produce a signal at 105mhz. I couldn’t pick up aircraft in the local area so it definately needed an amp.
Could you tell me what the cores are for the .25 uh chokes are and the core for the output coil at the mixer.
Thank you very much
Marv K0BJB
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