GB50EMJ Earth Moon Jodrell.


In May of 2007 Jodrell Bank were planning their First Light Festival, being 50 Years since the first commissioning of the Telescope in 1957. Part of the proceedings was to be co-ordinated with the Times Literary contest. In which children were invited to write poems which would be transmitted to the Moon and bounced back to Earth and received by the Jodrell Bank Telescope.

The problem was that Jodrell Bank is in a Radio quiet zone so the uplink could not be sited anywhere near the telescope. They approached Ofcom to see whether anyone in Amateur Radio may be able to help. Ofcom then approached everyone who held a high power Licence for 70cm. It had to be 70cm because the antenna feed they intended to use was the one they had used for the ill-fated Beagle 2 mission to Mars.

I agreed to help using my EME station (G4RGK) which Licenced for 30 dBW . I told them I would need a special licence as the power levels and public broadcast was not permitted under the normal Amateur Radio licence. As time was very short, I asked them to handle the admin. Within ten minutes JB had Ofcom fax me a Form at work, which was filled in and faxed back immediately. Amazingly, after only a 20 minute wait the GB50EMJ licence appeared down the fax from Ofcom.

Initial tests met with some problems getting an SSB signal into the Dish at sufficient strength and intelligibility, the receiving feed at the Jodrell dish was made for the Beagle 2 venture and was circularly polarised, this automatically netted a 3dB penalty because my antenna array was using Linear polarisation. The receiver at their end was just an IC706 running on 28 MHz. Initially it was not possible to resolve the modulation. After some discussion, I asked them to relay my audio back to me where it became obvious that the sidebands were being inverted. This was because their Local Oscillator was running at 460 MHz and because of this my USB transmission was being inverted. A quick change to transmit on the opposite sideband at my end solved this, and intelligible communication was established.

On the day of the festival, thankfully the weather was calm with little wind, so there were no pointing problems. The audio was to be carried from the Jodrell Bank Festival Marquee to my station via VOIP where it was fed into the audio stages of my transmitter and then transmitted to the Moon. I new the VOIP link could be problematic, so this was a worry, but in the end it all turned out fine and the transmitted audio was heard as received by the Jodrell Bank dish returned to Earth 2.6 seconds after transmission, the delay caused by the distance involved.