Low-power EME world record
World Moon Bounce Day June 27, 2009
This year marks the 40th anniversary of the first human being walking on the Moon. To commemorate that in an appropriate way, Pat Barthelow (AA6EG, USA) and Robert Brand (Australia) devised a special day with many EME activities. A call was made to activate worldwide especially large dishes for EME at 23 cm so that it would be possible to make good SSB connections via the Moon. The project was named Echoes of Apollo and Saturday June 27, 2019, was named World Moon Bounce Day. Of course, the Dwingeloo radio telescope had to be there too!
The low-power EME experiment between Dwingeloo and Mount Pleasant
In the week prior to World Moon Bounce Day, Jan van Muijlwijk (PA3FXB) received an e-mail from Tasmania from Rex Moncur (VK7MO). He was busy preparing the 26-meter Mount Pleasant dish for 23 cm reception. At first, transmitting seemed not allowed because of the sensitive radio astronomical frontends which remained present. But transmission power of about 10 milliwatts could be admitted. And after some calculations, he came to the conclusion that an EME connection with this super low power might still be possible! Of course, if a counter station with a large antenna would be available. And the CAMRAS radio amateurs have such an antenna in Dwingeloo.
Jan, PA3FXB, and Rex, VK7MO, agreed to immediately try it on June 27 when the rising Moon reached an elevation of 10 degrees in Dwingeloo. In Tasmania, the setting Moon would then be around 15 degrees in elevation. That gave a lot of joint “lunar time”. Jan was joined in the radio telescope by Ard Hartsuijker, René Hasper (PE1L), John Lambo (PA7JB) and Fred Tak (PA0WTA).
The construction of the 23 cm station went very well with the help of the clear instructions from Eene de Weerd (PA3CEG). At the agreed time, Dwingeloo (PI9CAM) was ready to receive the signals from Tasmania. We used the JT65c technology for this, which makes it possible to receive approximately 10 dB better than the weakest Morse signal. Great was our enthusiasm when the first connection with a 10-mW signal from Tasmania was successful! Even with a 3-mW signal, the connection was established without any problems. As far as we know this is a world record. A signal of 1 mW was also tried, but it turned out to be too weak.
After the low-power EME connection, Jan van Muijlwijk gave a speech This is PI9CAM for the ECHOES OF APOLLO PROJECT JUNE 27, 2009 to the visitors of the dish in Tasmania. See blog post Radio Telescope Dwingeloo commemorates Apollo 11.
About this low-power experiment and World Moon Bounce Day Rex Moncur (VK7MO) and Justin Giles-Clark (VK7TW) offered the following text Echoes of Apollo – EME on three milliwatts! and photo’s to the Amateur Radio magazine of the Wireless Institute of Australia.
Echoes of Apollo – EME on three milliwatts!
Authors: Rex Moncur (VK7MO) and Justin Giles-Clark (VK7TW)
27 June 2009 was designated World Moon Bounce Day as an amateur radio contribution to the celebrations of the 40th anniversary of man’s first landing on the moon. The event was organized by a US group of amateurs who had access to the Stanford University 45 meter dish and they sought the involvement of some of the larger radio astronomy dishes around the world. A key objective was to involve and interest school children in science and amateur radio by allowing children to hear voices from the moon. The event was supplemented by amateur Earth Moon Earth (EME) stations all around the world and particularly those with SSB capability on 23 cm.
Within Australia the University of Tasmania agreed to take part using their 26 meter dish which was originally used by NASA in the Orroral Valley near Canberra between 1964-1985 after which it was gifted to the University and transported to Mt Pleasant near Richmond in Southern Tasmania. Our involvement was to provide amateur EME equipment, help set up and test the system and operate the station on the day. As it eventuated the availability of large dishes provided the opportunity to explore QRP EME at as low a level as possible and we are pleased to report completion of a JT65 EME contact between the University of Tasmania’s 26 meter dish and a Dutch 25 meter dish, PI9CAM, with the Tasmanian end running only 3 milliwatts.
– Setting up the University of Tasmania dish
While Dr Jim Lovell of the University of Tasmania willingly offered their dish and the support of the site technician Eric Baynes (VK7BB) it was first necessary to consider what was practical. At our first meeting it became clear that transmitting any sort of high power as required for SSB would be out of the question as the dish is fitted with five extremely sensitive liquid helium cooled receivers working from 4 to 22 GHz. There is no protection for RF and we could not risk damage to these receivers which are involved in ongoing international research programs. Accordingly, the Echoes of Apollo team where advised that we would contribute to the event but as a receive station only.
The feeds and receivers for the 26 meter dish are mounted in a small feed cabin (approx 2 meter cube) behind a Teflon window approx 1 meter in diameter. Within the cabin there is a remotely controlled 3 axis focus frame that allows the feeds and receivers to be moved into the correct focal position depending on which feed is in use. There is space for a 2 GHz noncooled feed and receiver which fortunately was not required around the time of the Echoes of Apollo event and the University agreed that this could be removed and replaced with a 23 cm antenna. Because of space limitations it was decided to use a small 3 turn helical. There is over 100 meters of LDF-4-50 coax between the dish and the control building where we could operate and for this reason we decided to down-convert at the feed and receive on 144 MHz. Eric, VK7BB, constructed a down-converter and the VK7MO EME station provided pre-amplifiers, 144 MHz receiver, GPS frequency reference, computer running WSJT and bandpass filters at 1296 MHz and 144 MHz to limit interference from microwave systems at the nearby Hobart airport.
A few weeks prior to the event tests were conducted with Dave Scott (VK2JDS) with JT65c signal levels much worse than expected at -9 dB and no prospect of copying SSB. A sun noise test gave around 18 dB compared to 27 to 28 dB determined with the VK3UM EME Calculator. The time for testing was limited as this is an operational radio astronomy research facility but the system was gradually refined with additional pre-amps and filters and through adjusting levels at all stages – as well as resolving the occasional ‘Murphy’ problem. Finally, we decided that the helical feed must be the remaining limitation and did some estimates to see if a Septum feed and choke ring could be physically mounted. Initially it fouled other equipment but after a redesign of the mount it was successfully installed. In the end we achieved a sun noise of 25 dB which was within a few dB of what could be expected. Every time the system needed adjustment Eric, VK7BB, had to do a safety harness and go up in a cherry picker.
Tests were now conducted with Doug McArthur (VK3UM) who runs 400 watts and an 8.6 meter dish. Doug’s SSB came through at 5/6 sufficient to be heard in a room filled with children – so with just four days to go we reported to the Echoes of Apollo team we were ready to go.
– Could we transmit QRP?
With the RX side resolved our minds turned to the possibility of transmitting QRP at a few tens of milliwatts to avoid any possibility of damaging the radio astronomy receivers. A quick calculation suggested that we should be able to work the 25 meter Dutch station PI9CAM at less than 10 milliwatts using JT65 and after an email Jan van Muijlwijk (PA3FXB) told us they would be delighted to try JT65 at 10 milliwatts. While we did not have time to test the system until the day of the event WSJT echo testing on the day gave a signal level of -31 dB at 10 milliwatts and this was improved to -27.8 dB by careful adjustment of the focus of the feed.
– The day of the Event
Because of uncertainty about working the Stanford group with SSB at an adequate level for a room full of children the university decided not to actively advertise the event to the public but agreed that we could advertise on the VK7WI broadcast for hams to come along with children and friends. Our first reception was from Doug, VK3UM, at 5/7 who we worded up by telephone to talk to the children. It was a joy to see the smiles when they heard their names off the moon. While as hams we could copy Dave, VK2JDS, on SSB at 5/2 it was not quite strong enough for the children to resolve the voice, but using JT65 messages such as the following, Dave produced a great reaction from the children who then got out their cameras to photograph their names coming back from the moon.
082700 7 -10 0.2 38 10 * HI JESSICA 1 0
082800 8 -8 0.1 30 11 * HI NICOLE 1 0
082900 9 -9 0.2 19 11 * MOON ECHOS 1 0
083000 6 -9 0.3 8 10 * MOON ECHOS 1 0
083100 9 -7 -0.3 -5 10 * HAVE FUN 1 0
The Stanford group was received at around 5/7 for a short period but then had to remove their feed to repair a pre-amp. Later we had various children and the media visit and arranged for Doug, VK3UM, to be the voice from the moon with great effect.
As the European window opened, we could copy Dan, HB9Q, on his 15 meter dish calling CQ on JT65c at -1 dB. The university technician agreed we could up to power to 30 milliwatts and Dan responded to our call giving us a -23 dB report. Power was then reduced to 10 milliwatts and with some effort we again completed with Dan at -29 dB. It is noted that given the 18 dB isolation of the Septum feed we did not need to use a TX relay as 18 dB down on even 30 milliwatts is quite safe for a low noise pre-amp.
The PI9CAM team using a 25 meter dish completed quickly with us at 10milliwatts giving us -22 dB and again at 3 milliwatts with signal levels of -26 dB. An attempt at 1 milli-watt was not successful. Never-the-less with a 3 milli-watt completion we were “over the moon!”.
Other Stations copied on SSB were VE3KEP, 4/1; W5J, 5/8; N6JMC, 5/8; VK5MC, 5/6; KF6JBP, 5/7; SP6JLW; 5/6; N6BDE, 5/8 and RD3DA at -5 on JT65.
We also took many hours of video that will be cut into a TV-presentation in the near future.
We acknowledge the support of the University of Tasmania and Dr Jim Lovell in providing access to the dish and especially the efforts of the site technician, Eric Baynes (VK7BB) in making this a very successful exercise which allowed us to explore the limits of QRP EME.
Video low-power EME
Some more World Moon Bounce Day in Dwingeloo
This success was followed by an EME connection with a group in Switzerland. HB9MOON is a club station that has a beautiful 10 meter dish. A number of enthusiastic volunteers from this club had decided to use World Moon Bounce Day to promote amateur radio and EME in particular. During the day there were about forty children who spoke greetings in many languages towards the Moon so that this could be received by other groups around the world. It was very nice to make a connection through the Moon with these Swiss children. Some of them had such a microphone fear that only a timid “hello” was heard, while others read their text clearly and loudly so that it was perfectly understandable in Dwingeloo. (Added later Since February 2011, the club station is no longer operational because the owner sold the dish.)
In addition to these prearranged EME contacts, we also made thirty other connections in Dwingeloo. Many in SSB with the somewhat larger stations, and with the help of JT65 also with a number of small stations. The smallest was probably RA0ACM this time with a single yagi of 45 elements and only 70 watts.
During the day, several visitors came by, most of them radio amateurs who wanted to see the Dwingeloo Radio Telescope live. After explaining how you can sing “Father Jacob” with the Moon, a few children were able to imitate it flawlessly.
The webSDR receiver developed by Pieter Tjerk de Boer (PA3FWM) is really a great success. It has functioned throughout the event and again there were dozens of listeners.