December 23rd, 2015
Today PI9CAM´s QSL for the first Satellite Bounce QSO via an unmanned spacecraft done by radio amateurs arrived by mail. As we know, there have been previous commercial attempts for Satellite Bounce in the early 60s using ECHO 1 and ECHO 2 which were inflated balloons with diameters of 30 and 41 m. The initial orbits were at heights of 1500 km and 1200 km.
The theoretical radar cross section (RCS) of ECHO 1 was 700 m², but measurements by military radar stations resulted in 900 to 1000 m² in the beginning. Later, the satellite deformed and shrunk. OKEAN-O, the one we used, has a radar cross section of 18 to 20 m² but is in a much lower orbit at a height of 650 km. This leads to quite similar unit power budgets, regardless the difference in size,
Enjoy the movie “The Big Bounce” about our predecessors 55 years ago!
While ISS Bounce took Jan, PA3FXB, and me 2 months of testing and improving to succeed, Satellite Bounce was a much bigger challenge. Despite the fact, Jan and the team of PI9CAM are operating the 25 m dish of the Dwingeloo radio telescope, it took us nearly 2 years, enormous patience and scores of tests until we finally managed to receive “Rs” to complete a QSO today (December 8th, 2015). As far as we know, it is the first time ever, a two way amateur radio contact could be completed by using an unmanned spacecraft as a reflector.Above screenshot shows the position of the satellite at the end of the QSO. The Satellite rose in SSE and set in NNW. A calculative common window opened at the point, marked “O”. Local obstructions were not considered. Due to safety reasons transmissions in Dwingeloo are limited to elevations above 10°. So the AOS (acquisition of signal) happend shortly before the groundtrack of the Satellite crossed the 40th degree of latitude northwards, as soon as PI9CAM started transmissions. Sum of slant ranges (distance between ground station and satellite) was 3400 km at the beginning and 2000 km at the end of the contact.
Much of the reflections remained below the noise floor, but this one of PI9CAM, right at the beginning (14:10:10 UTC), is a nice example, of what can be received:
And vice versa DJ5AR as to be heard in Dwingeloo (14:11:00 UTC):
The used object OKEAN-O (NORAD #25860) is a joint Russian-Ukrainian Earth observation satellite, launched on July 17th, 1999 by an Ukrainian Zenit-2 carrier rocket. The satellite is in a polar orbit of about 650 km height with an inclination of 98°. The mass is 6.2 tons and the RCS (radar cross section) is figured between18 and 20 m². It has been used for research of natural resources, ecological monitoring and hazards prevention. Designed for a life time of 3 years, it is out of service now.
In use by the ground stations were the 25 m radio telescope in Dwingeloo by PI9CAM with 120 W and a 3 m dish with 150 W at the feed by DJ5AR in Mainz. The mode used was digital JT9H that comes with the new WSJT-X software by Joe Taylor, K1JT. The transmit/receive periods were set to 10 seconds, working around a center frequency of 1296.300 MHz. The automated Doppler tracking (+/- 60 kHz) has been performed for the complete path on DJ5AR´s side with a homebrew tracking software. The calculative power budget during the QSO was about -154 dBm. This value is very optimistic, as it presumes the optimum reflectivity of the satellite, which depends on its orientation.
Conclusion: The main difficulties in this game are:
- Selection of suitable satellites, depending on radar cross sections and slant ranges.
- Compensation of the Doppler shift with a maximum rate of 600 Hz/second.
- Antenna tracking with dish of a mass of 120 tons.
To be continued…
From Monday, June 22nd to Wednesday, June 24th I will be QRV during the evenings on 23 cm and 13 cm using the special event callsign DL65DARC.
Skeds (aircraft scatter, tropo) are welcome via ON4KST, Facebook or email.
Rig will be a 3 m dish with 150 W on 23 cm and 75 W on 13 cm. The QTH locator is JN49CV. SSB, CW and WSJT modes are suitable. Operation on relays is not intended.
If I find some spare time, I will be QRV on June 25th, 26th and 28th as well.
On Saturday, June 27th, you can meet me in Friedrichshafen.
A long time monitoring of the beacon F1ZMT in JN07CX via Aircraft Scatter on 1296.872 MHz shows asymmetrical reflections on most of the crossing planes.
As the distance to the beacon is 624 km and it´s ERP of just 10 W (a panel antenna to the south combined with an omnidirectional big wheel) is rather QRP, only weak reflections can be detected from time to time. This ensures, that received signals were reflected on single airplanes. In this example can be seen, that the reception starts shortly before the plane crosses the path between DJ5AR in Mainz and F1ZMT in LeMans. Unexpectetly the signal can be seen for quite a while after crossing. There is a continuous variation of the doppler shift and no spread of the signal, as is usual for a moving solid reflector.
Last night, when I was going to switch off all the stuff in my shack, I saw an email from Malte, DE7LMS. I opened it and found a link to a video he recorded of my recent presentation in Weinheim.
After my complainments about using the ON4KST chat in March Contest and the response I received from Claus, OZ1FDH, and Kjeld, OZ1FF, recommending the KST2ME tool, I added my homebrew prototype of a selective ON4KST client extension to my station control software. It communicates via telnet with the server. While working satisfactorily under normal circumstances, it was a desaster under contest load. When the software didn´t crash, it at least slowed down, by computing hundreds of posts in shortest time. Between 300 and 400 users have been logged to the microwave chat during contest time. During the first contest hours I tried to solve the problems with certain bug fixes, resulting in a huge loss of contest time. So I had to return to the classic style in using the web client of the chat.
In total I logged 73 QSOs on 23 cm to 12 DXCC countries, spread over 39 grid squares (results). ODX was HG7F over 817 km. The use of the AirScout software, written by Frank, DL2ALF, has been essential. Most of the QSOs have been completed by assistance of aircraft scatter.
A nice example is the one with DJ5BV in JO30KI. The distance isn´t really far enough to do it via aircraft sctatter, but it seems, both antennas were pointing west and that resulted in effects of aircraft backscatter with significant dopplershifted reflections.
Jürgen, DK2AN phoned me tonight, to tell me, the new beacon DB0XY will be transmitting on 1296.910 MHz. It is located on the Bocksberg in the Harz mountains in JO51EU, about 750 m asl. The power is 10 W into a 4 times double quad, omnidirectional. The keying is in A1: callsign, locator, carrier, dashes, carrier….
In a first quick try it could be received here with 519 to 539 via tropo. When Planes crossed the path, the signal increased up to 559.
Another beacon will be installed on 13 cm soon. The intention is to provide beacons for monitoring via aircraft scatter.
Please spot any reception in the DX cluster.
After giving the presentation in english language in Clonbur, Ireland on August 25th, there will be two more dates in Germany:
September 13th, 2014 at the VHF/UHF/SHF Convention in Weinheim as a short version.
September 27th, 2014 at the “Distriktsservicetag” of DARC districts K (Rhineland-Palatine) and Q (Saarland) in Saarbrücken.
I will talk about how to surmount the horizon on VHF and up.
After giving an overview over the classic propagation modes Es, Aurora, MS and Tropo, I will explain, how aircraft scatter and ISS bounce work. EME will be subjected too and the presentation will be completed by an introduction to “Visual Moonbounce” as performed by Daniela de Paulis.
For the short version in Weinheim the overview over the classic propagation modes will be left out.
At present the HAM TV transmitter aboard the International Space Station performs blank transmissons until August 6th, 2014. No camera is attatched, so only signal levels can me measured.
This was an opportunity for me to check out the FSTV-equipment, I set up during the last months. So my very first attempt last night was successful. I used the pass at 23:50 UTC on July 30th, 2014.