Antenna at OH2AXH used for 1296, 2304, 3400, 5760 and 10368 GHz EME.
The hamshack was built by OM Pertti, OH2AXH ( 60k ) as a temporary affair onto the trailer ( 105k ) of his Massey Ferguson tractor. This is what the shack ( literally ! ) looked like inside ( 73k ). There was also a bed for the operator and spare room for other necessary devices like a refrigerator etc.
This is a photo of of the 6.4 m dish at the Sipoo EME Racing Team site care of OH2AXH. At the feed you can see the 10 GHz transverter ( 14 kb ) that I put together for this one time experiment. The noise figure is around 1.5 dB and the output power from the SSPA is about 13 W. The SSPA used was the AMSAT Phase III D satellite prototype built by our payload design team at AMSAT-OH. The system polarisation is continuously variable by a small servo. The unit at the feed is complete less power supplies. The IF used was 144 MHz split mode. Frequencies were continuously checked with a 10 MHz ( yes - another Fletcher project ) TV-line secondary standard ( Rubidium ).
This is what the antenna feedhorn ( 41 kb ) looks like. The feedhorn is a modified Ku-band TVRO feed retuned down to 10.4 GHz. The final matching is achieved with a separate waveguide matching section ( 46 kb ) constructed with five tuning screws. Five screws were used so as to facilitate retuning at other frequencies too further away from 10.4 GHz. To fit five 2 mm brass screws with lock nuts at a distance of an eighth of a wavelength, the screws were alternately fitted on each side of the TE10 waveguide. The waveguide transition ( 44 kb ) was also modified from an existing Ku-band transition by extending the guarter wave sonde in the waveguide.
The antenna is motor driven and pointing was manual via an optical system. Stations worked were VE3ONT, WA7CJO ( 162 kb sound file ) and SM4DHN. Heard also were WB5LUA, DL0SHF and F6KSX.
Here is a photo of a second waveguide ( 52 kb ) feed constructed in a similar manner from a Ku-band feed. The feed is going to be used actively at OH2AXH. This ( 42 kb ) is a close-up photo of the modified waveguide probe inside the circular waveguide section. Sometimes the whole
probe needs reconstructing to achieve good matching and low ellipticity as a function of polarisation angle in linear operation.
Since the first tests I have now added 40 Watt TWTA for more oomph in 1999. The top reading is the incident power and the bottom reading is reflected. Using the OH2AXH 6.4 m ( 4.5 m effective ) dish and OM Pertti's NE32584C LNA own echoes are excellent. Moon noise is ~2dB above cold sky, sun about 18 dB above cold sky and ground/sky is around 5 dB. Approximately 3 dB ( estimate ) of the TWTA output is currently being lost in the waveguide run, three sections of coaxial cable and the T/R relay.
