Cheap calibrated noise source, 35dB Bandwith 100kHz - 500Mhz.
http://www.elecraft.com/manual/N-gen...%20rev%20C.pdf
Noise performance of Mar's MMIC's should be noted on datasheets.
I have them "somewhere", with a little luck Google finds it too.
You can measure and calibrate your own noise generator.
Terminate receiver with 50 Ohm resistor, measure output and label it
zero dB.
Remove resistor, and switch ON the unknown ENR, Z = 50 Ohm.
The only thing to do is, ATTenuate in steps until you are at first measured
output labeled zero dB.
Add simply the dB's of the ATT units, this should be the ENR dB's.
Please correct me if I am wrong.
Homebrew ATTenuator pads can be build low as 0.1dB accurate enough.

Sources of how to measure NF are radio amateurs who do EME.
Google should come up with data if you search at "low noise" "EME" etc.
PS: Google for VE3DNL Using Noise Generators to measure Noise Figure.
Greetings Bas.

"Steve Kavanagh" schreef in bericht
om...
I've been playing with trying to make rough noise figure measurements
on the cheap and have a couple of questions:

(1) Are there any issues with the following setup and procedure for
making relative noise figure measurements (e.g. comparing two
receivers) ?

____________ __________ ________
| | | | | |
|Uncalibrated| | Step | |Receiver| Audio Out
| Noise |----|Attenuator|------| Under |-------*----o (0 dB)
| Source | | | | Test | _|_
|____________| |__________| |________| | |
| | 2.7k
|_|
|
*----o (-3 dB)
_|_
| |
| | 6.65k
|_|
_|_
///
Procedu
(a) For receiver 1 connect a high impedance AC voltmeter to the audio
output marked "0 dB". Record voltage with noise source off.
(b) Turn noise source on and measure AC voltage at "-3 dB" output.
Adjust step attenuator to get same voltage as in step (a). Record
step attenuator setting.
(c) Repeat steps (a) and (b) for receiver 2.
(d) The difference in noise figure between the two receivers is the
same as the difference in attenuator settings recorded in (b) and (c).
For example if the attenuation for receiver 1 is 10 dB and for
receiver 2 is 12 dB, then receiver two has a noise figure which is 2
dB less than that of receiver 1.

Assuming this is OK we move on to question 2:

(2) To avoid the expense of a calibrated noise source, I wonder if the
repeatability from unit to unit of simple low noise amplifier circuits
(perhaps a MAR-6 ?) is good enough to allow one to be used as a noise
figure standard, at least for fairly rough measurements at HF and VHF.
I am hoping that accuracies of +/- 1 to 2 dB might be achievable.
Has anyone measured the NF performance of simple MMIC amps at HF & VHF
? Or looked into noise figure repeatability ?

73,
Steve VE3SMA