Wednesday, 11 March 2015

BBGen - Noise is your friend!

I acquired a Broadband White Noise Generator from RFDesign (UK) last Sunday at local Wythall rally. - BBGen
 - 100Khz to 5000MHz
 - Flat output with, typically ~24dB ENR (Excess Noise Ratio).
          -This equals to approx -90dBm/Mhz or -120dBm/Khz.
 - 11-15V input voltage with reverse polarity protection

Once I wired it up, I used it to do an approx. calibration on my SDR S-meter and compare the floor noise on the various bands, which seemed ok with the 30m slightly down. It will certainly come handy when I build the G11 multiband board, which I hope to kick off within the next few days.

I recently realized  that the S-9 signal generator I homebrewed last summer had the wrong spec of led diode (Vf) and gives a higher output than S9. My friend Micky is trying to measure the output for me with some pro equipment.

BBGen under the magnifier glass
I still need to configure the recommended software to take some measurements with my laptop soundcard, it will be an interesting experiment to compare the sensitivity my various radios.

NFM (Noise Figure Meter) software by Owen Duffy VK1OD

G11 SDR Audio improvements:
I am  pleased with the audio improvements I made recently - USB galvanic isolator and RG174 audio cables. (described here).  I got the subjective impression that I was able to hear weak signal (on the noise) way better than before, there is no hum noise whatsoever and the panadaper looks flatter/cleaner.

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