ADF4351 signal generator

Richard Lee

Member
Did some testing this afternoon.. I checked the 300mm 1090mHz antenna that's installed on the tower.. Still working fine..
The testing with both Open and 50 ohm load was pretty good. The only weak area was up at 2400 mHz.
Not sure if the amp gain is too low, or if the signal generator output is low, or if the new directional coupler is more lossy at 2.4 gHz.

I did not use the either one of my portable frequency counters with this setup.
I found the numerical readout of the VOM was super stable, repeatable and easier to use.
I'll be using the counters when I do near-field directivity testing.

Notice the 100 mHz test.. I know that's below where the directional coupler should be working, but it seemed to indicating it was showing return loss.
I'll have to use it to test a TV antenna, to see if it's really working that low. That 2-stage amp is using 3.3vdc. My 5V supply had a problem.



P1030348.JPG
 
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Richard Lee

Member
Here's some data on the amp. Notice it's about 38 dB at 100 mHz, 33 dB at 1,000 mHz, but drops to 22 dB of gain at 2500 mHz.
I have no idea about the noise figure, but this might be a pretty good LNA for 1090 mHz.. Maybe 32 dB?

I ended up setting the sig gen to it's lowest power setting of -4 dBm, so it would work with my diode detector.
I have another diode detector that I want to test later, to see if it works better on 2.4 Ghz..
chart.jpg
 

Richard Lee

Member
I'm using the old one in the picture above. The input is 'N' and the DC output is BNC.
I use a female BNC-banana plug, directly into the VOM.
The other one is a newer model and smaller. I have no specs on either of them.

I saw some neat RF sensors on Ebay.. http://www.ebay.com/itm/172050526615
This one, looks amazing.. http://www.ebay.com/itm/181371214031
I think all the DC output is in mV, not just the first column. Put adjustable attenuation in front of it (to protect it), you would have a pretty good watt meter, up to 3 GHz..
 
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