[hpsdr] Penelope Performance Measurements

[Phil Harman]

After the Dayton Hamvention I had the great pleasure of spending an 
afternoon with John, N8UR. John has a most amazing basement laboratory 
dedicated to the measurement of all things time related.

We set up Penelope and the supporting version of PowerSDR developed by 
Bill, KD5TFD, in John’s lab and proceeded to measure performance. The 
plots are on the Wiki

<http://hpsdr.org/wiki/index.php?title=PENELOPE>

but here is the overall summary.

With Penny transmitting 0.25w at 14.1MHz the largest spurious response, 
the 3rd harmonic, was down by >50dB with no external filtering.

Looking at the carrier in a 1 kHz span, all close-in spurs were greater 
than 75 dB down.

We did some phase noise tests using John’s TSC-5120A phase noise 
analyzer, but the Penelope on-board TCXO wasn't really stable enough to 
get great results.

However, John suggested that the performance is significantly better 
than any HF transmitter he had tested so far (but in fairness, there 
was no big noisy power amplifier involved).

John believes the ‘glitch’ in the phase noise plot at 1kHz was due to 
drift of the 10MHz TCXO in Penelope. The results were repeatable so 
John considers the phase noise measurements to be valid.

Since we will be using basically the same FPGA code and components in 
Mercury we can expect similar results on receive.

We seem to be living up to the ‘High Performance’ of our project title!

73’s Phil
VK6APH


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