coupled diode, cat 3 testing, discovery spectrum

["Rick Brooks" <ribrooks@xxxxxxxxxxxxxxxxxx>]

Title: coupled diode, cat 3 testing, discovery spectrum

Hi all.
I wanted to start to follow up on my action items from the July 2000 meeting.

Category 3 Cable:

I tested the coupled diode discovery prototype against CAT 3 cable.
The method worked virtually the same as for CAT 5 cable.
I tested 98 and 304 meters, with clip leads at each end, both distances worked fine.
The results will be posted to the reflector soon (I sent them to David Law to post already).
next step: zip cord, monster cable, coax, and barbed wire.

Spectrum analysis:

Also, I have been looking at spectrum analysis of the drive and receive signals, I probed them directly.
I'll send a file as soon as I find a working scanner....

Using the pseudo random idle times, as I showed in my presentation, here is a summary of what I saw:

10 kHz to 30 kHz:
     at the spectrum analyzer noise floor

30 kHz to 100 kHz:
     flat noise in the range of 26 to 30 dBuV,
     about 3 to 6 dB above the noise floor of the spectrum analyzer (1 kHz resolution bw, 100 Hz video bw)

above 100 kHz:
     at the spectrum analyzer noise floor

Just out of curiosity, I changed my code to allow fixed frequency detection, i.e. fixed idle times.
When I looked at this, the noise was a lot higher, as expected; a peak every 10 kHz.
Still the highest harmonic was at 57 kHz, with an amplitude of about 45 dBuV.
The spectrum was back to the noise floor at 1 MHz and above.

Anyway, this all looks pretty clean, I'll send along the plots when I can.

However, the real test will be radiated emissions, that will come later.
I believe that the power supply will be the thing that is harder to quiet down.

Please send me your thoughts, or if you are interested in working on this.

thanks,
- Rick