Coming back to an earlier post, Noise source design, I wanted to post the final results, and the looks of these noise sources.
The case is an aluminum extrusion design, and the lids are milled to accomodate the BNC and SMA connectors. The SMA is a really high quality connector. No point in using a noise source with a cheap connector – you are normally going to connect and disconnect this often.
The constant current supply is optimized for the maximum noise output, normally, about 8 mA. The design is a current mirror, with a TL431 precision reference.
The noise section is soldered with 0603 SMD mostly, on a FR4 board.
Foam and copper tape to avoid any foreign signals getting into it. Spurious signals can mean big trouble with noise measurements.
Return loss, I think it is pretty good.
SWR.
After some optimization of the circuit, the ENR output is now pretty flat, even with no specially expensive noise diode.
After all, pretty happy with the device, and others are happy two, as I give them away at low cost. If you need one, let me know.
Reading the postings since you began with HP 8970A, now about developing noise source. Is 2019/09 last posting in this topic? Thank you for interesting material!
Indeed, but last year built a batch of new sources still same design.
It seems to be useful for several people and up to 1.5 Ghz even some company uses it for their production line because the connectors wear out on their expensive sources.
Your information: special function 9.2 (measure input) is valuable to discover problem with 8970A here. You explain how -93 dBm (30 MHz carrier) can match ENR (15). I tried this today 5 July in my workshop (HP 8660C generator HP 436A power meter HP 8484A power sensor). In this test, 8970A displays 18.36 (not 15!) with averaging = 16. I then test with my noise source (cheap chinese “0.2-2000 MHz” kind, modified by removing 2 MMIC and replacing with 1 jumper and 1 SOT86 20 dB attenuator, and using 10 dB output attenuator, then calibrated earlier against borrowed noise source so 30 MHz ENR = 14.6). With noise source ENR 14.6, special function 9.2 display 18.46 with averaging = 16. From this new information, I think cheap chinese noise source ENR 14.6 is probably close to -93 dBm equivalent carrier power. However, HP 8970A has severe adjustment problem because special function 9.2 is reading 18.36-18.46, not 15.0! I just downloaded manual 9018-05510-2 and I am searching for way to adjust response to 30 MHz -93 dBm carrier response with special function 9.2. I think this is why when I measure 432 MHz LNA (expect ~0.4 dB NF) instead HP 8970A display -0.2 dB NF. Thank you again for excellent teaching about dBm and ENR relationship!