nooelec SAWbirdH1 Evals

[Alex P]

I ran  gain / bandwidth tests on two nooelec SAWbird LNAs .

Gains +39 dB for one, +40 dB for the other .. pass band filter ripple very similar

Alex Pettit

[b alex pettit jr]

PDF attached

On Wednesday, August 13, 2025 at 12:39:44 PM EDT, 'Alex P' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

I ran  gain / bandwidth tests on two nooelec SAWbird LNAs .

Gains +39 dB for one, +40 dB for the other .. pass band filter ripple similar

Alex Pettit

[Mike Otte]

Alex,

Tuesday, I too got out the VNA and used it.  It is always a learning experience.

My mission was to test the 4 x  snowbirds in my interferometer.  last July 28 it quit giving me results and would only give me noise of 100 -200 counts on the A/d,  usually 5-10 counts.

Were they good or bad?   Go -  No go test  not calibrated test.

So i have 4 sawbirds for the interferometer and 2 sawbirds for experimenting  and 1 sawbird barebones for reserve.

My setup was  a VNA - 2  , 1-  20dB attenuator for input and 1- 20 dB for the output.  I watched a couple of Utube videos and the one guy was very specific about the order of hooking up the cables.

I did this with the VNA live.

1 - output of sawbird to input of vna  > ch1

2- input of sawbird to output of vna > ch0 

3- hook up power to the sawbird

Do test - read numbers and see shape

4- unhook power

5- unhook input of sawbird   > ch0

6- unhook output of sawbird  > ch1

No, I did not use an isolator to block the DC and probably should have.  I knew that there was dc on the output but did not remeber.  There was a 20dB attenuator on both leads to the vna and i checked the sawbird output attenutaor and it was not changed nor destroyed.

Repeated for each of the 7 sawbirds.

Results were similar to what you saw.   All of them worked! All good.  problem is else where.

attached is a poor picture of my setup

Thanks Alex,   Good Info!

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Mike Otte W9YS

[b alex pettit jr]

The second half of the investigation was to eval acq software which uses freq shifting for  'drift'  correction.

Conclusion :

 The Sawtooth pattern in the RMS Time History is the result of the difference in SAWbird gain at 1420M and 1423M

                   Alex Pettit

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