Dismantling the Rotor

After having serious issues with the elevation drive, I dismantled the BIG RAS Rotor last weekend. A construction to support the dish by keeping it in an upright position has been installed.

DSC_1124aAfter opening the case of the rotor, the failure could easily been seen: The cogwheel does not fit into the worm gear. Instead it slips over it. I hope to find a solution soon.


Update 2016-08-03: SPID offered to check and repair it as a warranty case! So it is on the way to Poland now. TNX to Jacek of SPID Elektronik!

VHF/UHF/SHF Contest May 2016 – Record breaking!

And another Contest is over. Again I learned a lot and I am happy with the results: With a count of 82 QSOs I broke my personal record in claimed QSOs in a 23 cm contest. Since October1990 the number has been as high as 78 QSOs.

RA-Maps JN49CV89KF 2016-05-08 14-32The claimed score is a little more than 30.000 points and a new personal record as well. The 82 Stations, worked on 1296 MHz, are from 12 DXCC countries and located in 41 different grid squares. Countries worked were 40 x DL, 1 x F, 3 x G, 2 x HB9, 1 x HA, 5 x I, 6 x OE, 14 x OK, 1 x OM, 1 x ON, 5 x PA and 3 x S5.  In most of the QSOs aircraft scatter was an important factor. 35 contacts were done in CW. ODX, as usual, was HG7F over 817 km, still my ODX via AS. Nice was to work 3 OE5-stations around local midnight within 10 minutes: OE5VRL/5, OE5JFL and OE5RBO.


VHF/UHF/SHF Contest March 2016

The contest is over and there are new ideas in my mind, how to improve for the next one. Even though I am using a homebrew KST-client beside the browser based one, arranging skeds in the ON4KST chat is still the bottleneck in operating the contest. I fear, many requests will disappear from the screens of many operators, before they can take notice. No reason to argue for me, instead I will continue working on my KST-client projekt.

RA-Maps jn49cv 2016-03-06 1296QSOs on 1296 MHz

I had much fun in using Aircraft Scatter on 1296 MHz for most of the 58 QSOs, logged on this band. The average was 372 km/QSO and I worked 37 grids in 12 countries. And again HG7F became the ODX with a distance of 817 km. Weather was very bad and many of the contest teams weren´t able to go to their usual locations. So this time only one Station could be worked from JN99, compared to seven in July 2015.

QSL for first Satellite Bounce by Amateurs arrived today


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!


A new Chapter in the Book of Bounce

2015-12-08 15_11_30-Radio Assistent for Space Communication by DJ5AR

Constellation at the end of the QSO

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.

x2015-12-08 15_43_11-WSJT-X v1.6.1-devel by K1JT


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…

ISS Bounce Tests with new WSJT-X

Following Jan´s (PA3FXB) suggestion, we tried the new experimental WSJT-X software. The mode, we chose was JT9 H. Also we agreed in trying full doppler compensation to be used on my side. Everything worked fine, as can be seen in the screenshot below.

2015-09-13 08_15_51-WSJT-X v1.6.1-devel by K1JT


ISS Bounce in JTMS

Back from our holidays Jan, PA3FXB, and I had another test via ISS Bounce on 23 cm today. As I located a bug in my Doppler correction software, causing unwanted steps, it could be fixed by finding a workaround for the malfunction in compilers NOW() routine, for returning the correct time in milliseconds. So the improved Doppler correction is working smoothly as can be seen and heard in the signals received.

2015-09-05 09-51-15 PA3FXB in JTMS

PA3FXB in JTMS received by DJ5AR via ISS Bounce. Center frequency was 1296.300 MHz.

094915  2.5 2270  3 36  248     DJ5AR PA3FXB
094915  6.5  520  2 26  276     PA3FXB DJ5AR
094915  9.7  360  1 26  310     PA3FXB DJ5AR
094945 12.8  180  1 26   64     PA3FXB R27 R27   DJ5AR
095115  3.1  300  2 26  268     DJ5AR PA3FXB R27 R27
095115  4.1  320  1 26  205     PA3FXB R27 R27   DJ5AR
095115  7.1  300  1 26  157     R27 R27   DJ5AR PA3FXB
095115  8.5  320  2 26  153     R27 R27   DJ5AR PA3FXB
095115 10.1 1560  8 36   65     PA3FXB R27 R27   DJ5AR
095115 11.7  300  5 26  138     R27 R27   DJ5AR PA3FXB
095115 12.3  820  7 26  111     R27   DJ5AR PA3FXB R27
095115 13.7  680  4 26   40     PA3FXB R27 R27   DJ5AR
095145  5.3  440  2 26  115     PA3FXB 73 73
095145  7.6  740  3 26  271     73 73 PA3FXB
095145  9.3 1440  3 36  283     73 PA3FXB 73
095145 12.0 1180  5 36  244     PA3FXB 73 73
095215 10.5 1120  3 36   56     WOW
095215 12.8 1520  3 36  190     WOW
095245  4.1  740  1 26 -116     SUPER
095315  2.1  420  1 26   -7     73
095445 16.0  140  2 26  252     DJ5AR PA3FXB
095615 14.7  140  4 26  231     73 73 PA3FXB          

We even had some kind of conversation at the end 😉

As further tests showed, the full doppler correction on my side is working very well now. This enables potential sked partners to work on a fixed frequency by just tracking the International Space Station with the antenna.

Sked requests are welcome:  dj5ar (at) darc.de

Modes, successfully being used so far: CW, SSB, ISCAT, JTMS

VHF/UHF/SHF Contest July 2015

When having a look on the claimed scores list, published today, I was really surprised by my preliminary result in the category 23 cm single operator. I did not expect at all to be No. 1.

It had been very hot that weekend and the activity in the ON4KST Microwave chat was extremly high. So I slowed down, made only little use of the chat and tried to find calling stations on the 23 cm band. There were a lot of signals from the east and when going to bed at midnight I counted 29 QSOs with an average of 524 km/QSO. Top DXCC count was OK (11) followed by DL (5), OM (4) and G (3).

QSOs on 23 cm. Saturday in red and Sunday in green

On Sunday morning I continued, but it was still very hot and not much fun. When the temperature in my shack exceeded 40°C at around 10:00 UTC, I decided to go QRT.

Finally I logged 45 Stations from 12 DXCCs in 27 squares with an average of 483 km per QSO.  17 stations were worked in CW, the rest (28) in SSB. 10 QSOs had a QRB > 700 km (7 x JN99) and the ODX was HG7F with 817 km. The total time of operation was less than 15 hours.


SM7FWZ finally worked via ISS Bounce

While yesterdays try for an ISS Bounce QSO failed by Ronny, SM7FWZ, missing my rogers, we tried again this morning. As this orbit culminated near the zenith for me, I decided to catch up the ISS on the descending part of the pass.

2015-07-13 09_50_40-Satellite Window Finder by DJ5ARSo I could avoid the singularity in the azimuth angle and we heard us right from the beginning with strong signals. As Ronny couldn´t copy any rogers yesterday, we had plenty of them today, as well as 73s!

Ground Track of the ISS versus the direct path between SM7FWZ and DJ5AR

It is remarkable, that Ronnys signal was audible on backscatter off the ISS, even when my elevation became less than 2 degrees. The slantranges to the ISS were about 2100 km for me and 1700 km for Ronny: A total distance of 3800 km!

This is the result of many tests and discussion before. Ronny transmitted and received on 1296.300 MHz during the whole pass and automatic Doppler compensation was done on my side for both of us.

It is funny, that we had a Moon Bounce QSO a couple of days ago, just to compensate some frustrating tests. EME is sooo easy!

Thank you, Ronny, for this fast and efficient QSO and enjoy your very special day!




Welcome Ronny, SM7FWZ, to the ISS Bounce community!

After many previous attempts Ronny, SM7FWZ and Jan, PA3FXB, managed to complete an ISS Bounce QSO on 23 cm today. The rigs used, were a 3 m mesh dish with 375 W on the dutch and a 4 m solid dish with 300 W on the swedish side.

Ground track of the ISS versus the direct path between SM7FWZ and PA3FXB

The window opened from 2015-07-13 08:07 to 08:17 UTC. While the antenna tracking was done automatically by both stations, only Jan could perform Doppler compensation. So they used a kind of mixed mode in tracking the frequencies.

25544 2015-07-12-08-07 SM7FW  PA3FXB ISS(ZARYA) (25544) DopplerRonny transmitted on 1296.300 MHz and tried to catch Jans signal manually. So I monitored the frequency, Ronny should be heard on my side. It is nice to see in the video, how Jan appeared on the very left, getting closer and closer to the frequency, Ronny could be heard.

Congratulations to this success!