23cm EME
Current 3.2m dish!
In August 2008 came the offering of a 3.2m dish originally used for SSETI for free collection so i jumped at the chance as it was only a few miles down the road in Stockton!
Here it was in it's sorry state..hi
The dish was in fair condition but did have a few holes in it from some wind damage when it was moved from it's original mount but these were easily fixed. The dish was given a good clean up and re-spray from light brown to more discrete black colour.. i'm hoping it does not stand out too much..hi
A hole was cut into one of the panels for the fibreglass feed pole and some modification was done to the original polar mount to make it good for my EME setup.
An old scrap trailer was aquired for nothing which was not what i was loking for but it has got my setup up and running, the trailer sides were cut off in a few minutes to leave a flat base to start work installing the mount. The mount is very simple, it is just a 3" bearing mounted on a plate which is on the top of four pieces of box section, the 3" tube from the dish mount slides through the bearing and down into the worm drive coupling made up at the base.
All very simple and is the way i like it..hi
Here are a few photo's... Not finished yet! Still not finished in June 2012!!
My first time QRV was 16th August and i heard RD3DA calling CQ but didn't get back in time to call him on JT65, i managed a easy QSO with Howard G4CCH and also one with Serge UT5JCW to my surprise when he came back to my calls and was also quite easy JT65 contact.
After everyone went QRT i thought i would try to hear my own echoes, maybe being a little optimistic!
Nothing was heard straigt away but afer another dash out in the rain to line up the dish a little better (by sight!) i did see on spectran and i did hear the odd weak tome after some cw tests.... GREAT :-)
My current setup is OK1DFC septum feed with choke ring attached (but not tweaked spacings yet)
TX: O/P ~100W @ Feed
RX: G4DDK LNA radio is Yaesu FT-736r.
Update 27th September..
Sun noise is measured at 7dB - Somthing not quite right yet...
Feed only: Ground/Cold SKy is ~3.2dB
maybe some matching problem between the feed and LNA?
Also heard DL0SHF in SSB! Yes i know he runs a big station but very nice to hear good SSB signals via the moon for the first time!!
Improvements October 2012
A new tracking system with the F1EHN controller board and US Digital Encoders has been installed giving a very precise indication of where i'm pointing, this is much better!
G4DDK 23cm lna has been tested on two analysers... measured 0.2dB and 0.3dB NF so in the right ball park!
LNA is now fitted to my newly constructed 1420MHz feed, performing much better than 1296MHz septum feed.......
Sun noise measurements now done with a Realtek RTL2832/E4000 dongle (AGC disabled) results below:
Solar Flux = 124
Sun Noise = 11.2dB
Moon Noise = 0.1dB The first time i have ben able to measure any moon noise!
VK3UM EME Calculator predicts 13.7dB Sun noise for SF124.
More Improvements November 2012
I have now built another feed in replacement to the square septum feed due to it's low poerformance for some unknown reason!
This is the VE4MA/W2IMU round fed with polarising screws and choke ring...
Last measurement with some tweaking of feed position is:
Solar Flux = 111
Sun Noise = 11.5dB
Things are looking better! Reception of ON0EME seems much better now compared to the septum feed and Sun noise has made a big leap! the isolation is not as good on this feed so some slight adjustment maybe needed before i connect the TX side but hopefully i can get that done soon.
This weekend 24/45th Nov i heard many stations on 23cm via the moon on CW/JT65
on CW:
I5MPK
I1NDP
OK1CS
G5WQ - hard to copy with my poor cw skills..hi
JT65C:
OK1CS -13
SP3XBO -14
I1NDP -5
G4CCH -8
YO2BCT -18
EA1RJ -23
PY2BS -7
ZS5Y -22
G5WQ -19
W3HMS -18
Some audio clips:
I1NDP(CW)
I1NDP(SSB)
I5MPK(CW)
G4CCH(CW)
ON0EME
LX1DB(SSB)
New feeds Nov 2012
1420MHz 'feed of plenty'
OLD 2m Dish
I have managed to hear some of the bigger stations about including OK1DFC, OE9ERC, ON7UN, G4CCH and probably a few others i could not positively identify!. All these stations have been on cw but have heard a few stations on JT65c also..
OE9ERC the strongest JT65 station i have heard..
The strongest cw station so far has been OK1DFC... could just read some of the cw very weak!
New dish mount AZ/EL motorised. 16th September 2006.
I've done some Sun Noise measurements with this setup and i'm getting around 4.3db of Sun Noise.
I Need to do a bit more optimising yet!
Update Oct 2007
The ARRL EME contest at the weekend spurred me on to get the dish back out and have a listen, to my surprise some stations made easy listening in cw with my poor efficiency dish at then moment.
Stations positively identified listed below, some recordings too.
On CW: LX1DB (weak ssb), OK1CA, SM4DHN, EA6VQ, G4CCH, OZ4MM.
On JT65C ES5PC, G4DZU
There were a lot's more stations out there but my cw is still quite poor and vy hard to identify with the fading and signlas being very weak.
On 30th October i managed my first QSO on 23cm EME with Howard C4CCH using the JT65 Mode, i was received at best -26dB. My output power was ~35Watts to the newly fitted Septum feed from OK1DFC.
The Dish that i built now has the Septum feed fited and looks something like this....
This is all there is to the dish and just some 12mm wire mesh for the reflector.
The Ribs are 15mm square tube.
I made a template up in wood first then formed them to shape by hand. I used a large mallet, holding the rib between two large wooden blocks and slowly formed the required shape. I'm sure someone else can come up with an easier method!
