Friday, February 28, 2014

Minima Transceiver Module Testing

Jack - WA7KMR and I spent some time in his Lab, using his Test Equipment to characterize the first few modules of my homebrew implementation of Farhan's Minima Transceiver. We tested my; RF Mixer, Crystal Filter and IF Amplifier (see previous post).
Jack at the Controls
We first connected each module as a standalone device to ensure each worked as expected.  We were both most interested in the Crystal Filter performance measurements. My previous measurement attempts with the AIM-4170B were inconclusive, other than the shape of the bandpass.

Crystal Filter
With Jack's Lab Equipment we measured the bandpass and insertion loss of the Crystal Filter. The bandpass is 6KHz, and insertion loss is about 3db, with about 2db of ripple. With some tweaking, I think the ripple could be reduced.

We later checked the operation of the standalone RF Mixer, and then the IF Amplifier. The RF Mixer worked similar to one of Jack's known mixer. The amp provided about 30db of gain at 20MHz.

We connected all three modules together and I very pleased with the results.

RF Mixer, Crystal Filter, and IF Amplifier
Output of the IF Amp
Horizontal = 20MHz Center,  5KHz / Div
Vertical  = -30dbm at top line, -110db at bottom, 10db / Div
LO was 200mV RMS

The RF Signal was Detectable down to -90dbm
The Results: I am a very Happy-Camper.

More of my "Minima" module implementations will follow.

Thanks Jack, for the measurement help.

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1 comment:

  1. Great work!

    How did you make the oscilloscope to act like a spectrum analyzer?