47 GHz EME Measurements

Home Up What's different 47 GHz 47 GHz feed for my EME system cooling lna image rejection 47 GHz EME Measurements

On 28 oktober 2020 I started my first measurements with the new LNA

WX was not very fine; temp 13C with 65% humidity and some clouds.
The infrared temp at the elevation angle of the sun was measured at 8 degrees

I started with measuring the Cold sky/ground Y-factor using my feed horn as antenna
Best value I measured was 1.5 dB

Then I mounted my RX system in the antenna and measured solar noise
Best value I measured was 8.1 dB at an sun elevation of 22 degrees

Then I measured the noise power level as a function of elevation angle between 3 and 30 degrees elevation
The result is this diagram

All these results were not good enough and I needed to understand the reason for this

I had to check the performance of the LNA and also needed to check the return loss of my feed

The LNA measured with the HP8970 noise figure meter and a noise com source

The LNA performance was good

Then I checked the return loss of my feed

Return loss measured better than 30 dB

On 3 november 2020 I again measured the Cs/G Y-factor
WX was better, temp 11.3 C humidity 69%
Ir temp at 20 degrees elevation below -20 C m the limit of my Ir temp meter
I measured Y-factor best value 2.0 dB Cs/G

I also measure Cs/G directly from the waveguide from the LNA without feed
The result of this was also best value 2 dB

Later I realised that measuring Cs with a feed as antenna with an opening angle of 120 degrees
would limit the visible Cs temp because it will look from 30 degrees elevation upward.
To have a better Cs/G measurement I will try to measure it again using a small horn antenna

Searching lecture I found a table showing brightness temperature over frequency as a function of the elevation angle.
I marked the 47 GHz frequency by a red line
The mentioned water vapour concentration is the level as defined in the standard atmosphere

This gives us the following atmospheric temperature as function of elevation

5 degrees 240 K
10 degrees 180K
20 degrees 120K
30 degrees 85K
60 degrees 55K
90 degrees 48K