47 GHz EME

Home Up What's different 47 GHz 47 GHz feed for my EME system
 

During the testing of my gearbox I already found that it was turning much too fast for reliable tracking.

I searched for possible solutions and decided to try if a pulse width modulated power supply for the electromotor would help

I found these small PWM motor controllers and decided to try if this would give me the solution

On 12 march I received this unit and first indication during a test looked promising.

As soon as weather permits I want to test this on the gearbox and hope that it will work out as hoped for.


At 3 march 2020 I made my first solar noise measurement using the 1.8 mtr dish and my home made feed

I had, as can be expected. to optimize the position of the feed for best performance

My first solar noise measurement resulted in a bit more than 2 dB.
After first adjustment I had around 5 dB
After the second adjustment I had 6.4 dB solar noise

This is already a nice result after only 20 minutes of trying.
It must be repeated but for this I need to improve the gearbox drive to turn much slower

I also measured hot earth cold sky resulting in about 0.8 dB

 


In December 2019 I started with a first setup for 47 GHz EME

Hearing from several stations working to be QRV with low power I joined in and see what would be possible

My first trial will be to test RX on 47 GHz and see if my antenna would be useable

I had a gearbox available for this but it needed an other electro motor because the original motor was turning
 the antenna at 360 degrees per second and this is way too fast

After removing the motor I build a replacement able to mechanical fit at to place of the old one

Old Electro motor, quite heavy with special coupling element to fit to the gearbox
Replacement motor with small gearbox

Replacement motor with special coupling element    

Gearbox ready for use with the 47 GHz
Precision 1.8 mtr prime focus dish
Dish mounted

1.8 mtr precision instruments dish f/d =0.4

After the modification of the gearbox the antenna was still turning much too fast.
 I am now trying to control rotation speed using puls width modulator in stead of a DC power supply.
I expect that in this way I should be able to reduce rotating speed to acceptable speed for following the moon

I also had to make a feed holder. I started with the original 11 GHz feed which was a feedhorn for 11 GHz with a round feed and several chokes.
I removed the 11 GHz feed part of it leaving the holding of the hub with a possibility to mount the 47 GHz feed

The original 11 GHz feed with hub feeding support

The modified feed hub ready for mounting the 47 GHz feed

 

 

 


To understand the possibilities to make a 2 way QSO using WSJT or CW I tried to make calculations based on station parameters which are possible by now

My first calculation trial is based on 1Watt output and a noise figure of 5 dB
At this moment I found that the atmospheric attenuation is still not very well known and I had to search for information on mm wave atmospheric attenuation but then based on EME propagation through the atmosphere, so aiming at the moon.

I found a nice presentation from UA3AVR
https://www.moonbouncers.org/Orebro2017/UA3AVR_Calibrations of mm-wave antennas and RX systems
using Moon radiation_Orebro2017.pdf

explaining atmospheric attenuation

Take a look at 47 GHz EME performance data from several stations