My old EME Setup

There is short description of my 23cm EME setup:

I must to write, that in  December 2013 my EME dish was damaged by hard snow load (snow in Israel !!! – I’ve not designed mechanics for this case), so since this time it is not operational for EME and used for Satellite TV.

  • First one is initial variant  that uses unmodified  1.8m dish and Azimuth/Elevation mechanic

 

My first QSO with PI9CAM was done at 8:40 UTC 10-07-2010 using 1.8m dish and 10W output power.

Further I had built single MRF-286 W6PQL amplifier that gave me 50W output to feed.

Next step –  I added to the dish above 1.8m dish “extra size”, extended it by mesh up to 2.6m diameter, shape is not exactly parabolic, but gave me gain improvements close to expected

 

Currently I had built 2xMRF286 amplifier of W6PQL design, it give me now near 100W only, but I have not finished its tuning yet.

So my present EME Setup is:

Transverter: self maid  1296Mhz/28Mhz + Yaesu FT897D / AFEDRI SDR (on RX)

Antenna: 2.6m dish (1.8m SatTV dish extended by mesh)

Feed: OK1DFC

LNA: G4DDK ~0.3dBNf

PA: 100W amplifier (2xMRF-286 W6PQL design)

There you can download and hear recorded I/Q file of DUBUS CW EME Contest that was done on my system using AFEDRI SDR receiver + 1296MHz/28MHz transverter.

next page has information about my dish’s Azimuth/Elevation control.

My EME dish Azimuth / Elevation mechanic and control


Azimuth / Elevation mechanic and control

Azimuth movements is done by AlfaSpid BigRAK rotator, controlled by its own control box.

Elevation movements is done by 36” linear actuator for Satellite TV, controlled by home maid control box with microprocessor MSP430F149 from Texas Instruments.

To calculate real elevation angle – the elevation controller uses simple algorithm, where number of pulses (from embedded in actuator pulse encoder), actuator and dish mounting geometric dimensions  are used in elementary triangle equations  see image below:

We can see triangle that is formed by dish support two sides “a” and “b” and linear actuator “c”,

where sizes of two sides “a” and “b” is constant and one side “c” – has  changing size that in reality defines elevation angle of the dish. Size is changing, but we can know it with relatively high resolution using actuator’s encoder pulses. relation between sides “a”, “b” and “c” is defined by next equation:

c2 = a2 + b2 – 2*a*b*cos(angle_between_sides_a_and_b);

So we can easy calculate angle_between_sides_a_and_b (in degrees) and from equation below find elevation angle:

elevation_angle = 180 – offset_angle – angle_between_sides_a_and_b;

where: offset_angle – is constant angle, that defined by dish support construction (can be easily measured or calculated).