Electronics > Projects, Designs, and Technical Stuff
Tracking Generator Alternative: 1GHz Wideband Noise Source
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alterbaron:

--- Quote from: LaserSteve on August 14, 2015, 03:06:57 pm ---I ordered one of the EBAY units for 20$.  I'll take it to a friend's RF lab and see if I can get some real numbers.  My AVCOM PSA-37 is by no means flat enough for a meaningful measurement.  However I can measure total noise power very accurately.

Will let you guys know what I find..

--- End quote ---

Awesome, I'm really curious to see how it performs.


--- Quote from: G0HZU on August 14, 2015, 11:53:06 am ---I have a couple of homebrew noise sources here that use such diodes. One is a precision high level noise source I made in the 1990s that puts out about -85dBm/Hz up to 180MHz and is flat to about +/- 0.2dB across this full range and really flat across most of the range.

I also made a noise source for receiver testing that is flat to about +/- 0.3dB to just over 1GHz. I used a packaged noise source diode rate to 500MHz but I actually depackaged it to get it to give it the (above) flat response up to 1GHz.

--- End quote ---

That's a pretty damn good result! How do you measure the flatness of the noise source to that amount of accuracy?

I'll keep my eyes open for a noise diode. What's a typical price?
Also, it would be fun to compare and contrast the performance of different RF transistors as noise sources. Hmm . . .
G0HZU:
I measured them on several Agilent PSA spectrum analysers at work. Both noise sources are designed to have a very good source match so this minimises measurement uncertainty. I actually see a flatter result on the analyser display than I quoted but I allowed a bit extra for various contributors to uncertainty etc. But it's really difficult to measure stuff accurately across such a wide bandwidth. The PSA is still one of the best analysers on the market in terms of response flatness vs frequency.

There was (allegedly) a time when you could get noise diodes for a special low price (a few dollars) from Noisecom if you were a ham/hobby experimenter. I/m not sure if this is still the case though... However, I salvaged mine from scrap equipment so got them all for free.
alterbaron:
Update: Board layout nearly done, here's a preview:

LukeW:
I put this together recently... haven't tested it yet.

The power supplies are on a separate board, one 30V supply for the avalanche bias (constant current) and a 12V supply for the MMICs.
tggzzz:

--- Quote from: LukeW on October 13, 2015, 06:32:54 am ---I put this together recently... haven't tested it yet.

--- End quote ---

Translation: "I did work".

I will be interested in seeing the results of your work, and hearing the pain points and lessons you learned.
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