+- ARCHIVE: Australian Ham Radio Discussion Forum ( AHRDF ) (https://www.ahrdf.net/forum)
+-- Forum: SPECIAL INTERESTS (https://www.ahrdf.net/forum/forum-30.html)
+--- Forum: E.M.E. (https://www.ahrdf.net/forum/forum-21.html)
+--- Thread: EME : VK7 to VK7 (/thread-861.html)
EME : VK7 to VK7 - VK4ADC - 14-09-2019
From text edition for SEPTEMBER 15 2019 - VK NATIONAL NEWS BROADCAST ON VK1WIA : http://www.wia.org.au/members/broadcast/wianews/
Also in MP3 edition of news available at: http://www.wia-files.com/podcast/wianews-2019-09-15.mp3
Back on August 31, Richard VK7ZBX and Rex VK7MO completed the first VK7 to VK7 EME contact over a distance of 720,000 km even though their stations were only 22 km apart here on Earth.
Operations were at 10 GHz using the QRA64 digital mode.
Richard was running a 75cm dish and 60 watts - to Rex running a 113cm dish and 90 watts.
At the time the Moon was nearly as close as it can get but even so this resulted in a propagation loss of 289 dB!!
However spreading was around 35 Hz producing an additional loss of around 3.4 db. Signals were solid and a degradation test with added noise showed there was 5 dB in reserve.
On the following day the Moon had moved a further 1562 km away due to its elliptical orbit but this cost only an additional 0.1 dB But the spreading was now down to 3 Hz reducing the overall loss by around 3.3 dB compared to the day earlier. With this extra 3.3 dB in hand Richard tried out a 60cm dish and just 30 watts and again a QSO was completed.
This time degradation tests showed there was nothing to spare.
This second QSO is believed to be between the smallest dishes ever to complete an EME QSO with power of just 30 watts at one end.
Critics might ask how we are sure the signal got to the Moon and back rather than direct between us. The answer is that the signal took 2.5 seconds to arrive which relates directly to the time it takes at the speed of light to get to the Moon and back. In addition Doppler shift calculated at around 20 KHz proved to be within about 5 Hz once it was automatically compensated - again confirming the signal was being reflected from the Moon.