Gary, WB9JPS wrote:
I built a noise source as described by Bill Sabin, W0IYH in QST (1995)
and EMRFD. Works fine, but now it's time for calibration. Chatting with
Bill, he reinforces the notion that the best way to go is comparison
with another calibrated source, or a direct measurement with a
calibrated noise figure test set. NoiseCom used to provide this service
to hams for $50, but now they claim they have dropped that offer (it's
about $600, now). So my question is, is there anyone in the SF Bay
Area (I live in Livermore) who might be able to help? If someone owns a
source or test set, perhaps we could get together. I'm open to other
suggestions, too.

FYI, this is primarily for testing HF rcvr performance. I'm building an
R2-style DC rcvr, and it's turned into a nice research and education
project, so I go a bit overboard sometimes, but it sure is fun. I'm
also using an IQPro DDS VFO. I wrote a couple reports on its
performance that are up on the AA0ZZ website.


Sorry I can't help with a calibrated noise source from this side of the
Atlantic. The amateur microwave community hold regular meetings that
always include a measurement session using calibrated professional test
equipment. Given a calibrated professional noise source and a NF test
set, it is very easy to transfer the ENR calibration to your HB source
(especially if the room temperature happens to be 290K :-)

However, you don't really need a professional test set. You can make
very accurate measurements of relative RMS noise power levels using a PC
sound card, and this opens the way to NF measurements. The only hardware
accessories needed are a simple linear downconverter of the type
described in EMRFD, and a noise source that can be gated by an output
from the PC. For details and software, see:


The only other issue is that almost all professional noise sources are
designed and calibrated mainly for UHF/microwave use. For your HF
application, you'll typically be limited to just one transfer
calibration point at 10MHz. You can rely on a professional source to
have no nasty resonances between calibration points, but the ENR will
probably roll off rapidly below 10MHz owing to the relatively low value
of the DC blocking capacitor.



--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek