Category Archives: Propagation

Windmill Scatter

August 30th, 2017

As the weather forecast promised heavy thunderstorms for today, I was looking out for scatter points on 13 cm. Pointing to eastern France, I found a heavily scattered signal of DB0UX in JN48FX in 204°.

But the sound was quite strange and rhythmic. When taking a look out of the window, I saw the dish pointing at two windmills in 1 km distance.

This kind of scatter is not very helpful, but a nice experience anyway.

Disappointing Morning / Amazing Evening

August 17th, 2017

The whole morning I monitored EA2TZ/B in IN93BF on 1296.854 MHz over a distance of 1072 km, peaking up to 30 dB. The vertical profiles of 0:00 UTC from Paris and Bordeux showed an inversion at 1000 m altitude. F6DKW from Paris was booming here, but nothing could be heard of beacons close to the path or in tests with F6CIS, IN94WL and F6AJW, IN93EK. The duct was just too high.

Tonight Paolo, IK7UXW, JN80XP, asked me in the KST chat, to give it another try. We had discussed the possibility of combined propagation with aircraft scatter and tropospheric ducting before.

The path is perfect, as there is one hop over the Alps and a plain track over the Adriatic Sea.

On Tuesday last week, while I was watching the other Paolo aboard the International Space Station via HAMTV on 13 cm, Paolo had initial QSOs in this propagation mode with Daniel, DL3IAE, in JN49DG on 23 and 13 cm. That was a great effort! So I was more than poised for a try.

Paolo has a 2 m dish and QRO, so he started calling me in CW. I heard “musical noise”, EMEers know, what I mean, with very strong bursts from time to time, lasting for some seconds. After a while we decided to try in JT65c. And from the start I could decode Paolo in most of the periods.

The better decodes always correlated with airplanes, crossing the path within a specific window soutwest of Munich defined by a path with a virtual end at the coast of the Adriatic Sea.

Most impressive was the crossing of an A380-800

At the end some bursts could be seen again (after 30 seconds)

The whole Test took almost an hour to complete, as my TX power is about 10 dB less than Paolos. It is evident that JT65 with 60 second periods is not very useful.

Paolos reference for ducting on the Adriatic Sea is IQ3ZB/B. Tonight it was at S9 + 30 dB. With good conditions it can be at S9 + 60 dB. So we agreed in continuing the tests in other  digital modes and in CW as well as on 13 cm.

G8MBU – JT65c Beacon via Aircraft Scatter

July 5th, 2017

After installation of new transverters for 23 and 13 cm with stabilized LOs a couple of months ago. I gathered some experience in using JT65C mode on EME. So I undertook a new attempt to receive and decode G8MBU via aircraft scatter today. As antenna I use a 3 m dish with a dual band ringfeed.

Path DJ5AR to G8MBU

The beacon is located at Cowes on the Isle of Wight, IO91IR37, 683 km from Mainz, JN49CV. It runs 2 W power into an omnidirectional dual alford slot antenna. The mode used is JT65c. Nominal frequency is 1296.800 MHz. To successfully decode the signal, the SSB dial should be set to 1296.7986 MHz, to get a tuning tone of 1400 Hz in WSJT.

There is a small window between the Isle of Wight and Mainz, where high flying aircraft can be “seen” from either places. But only a few airplanes cross the path within and fewer fly along the path. Reflections of G8MBU could be seen from time to time, but mostly too weak and too short to provide decodes. It took nearly 3 hours until the first decode happened at -22 dB and just some minutes later a second one appeared on the display at -21 dB:

1158 -22  4.0 1282 #* G8MBU IO90IR
1206 -21  3.9 1268 #* G8MBU IO90IR

In total I monitored G8MBU for 5 hours. The propagation conditions were normal today, no tropo at all.

Moon Bounce on 13 cm

April 28th, 2017

Sometimes you hear words that hurt. Especially if they are true: Some years ago I tried 13 cm EME with Dan, HB9Q, and couldn´t copy anything of him. His comment after the test: “There is no way, not to hear me!” This is frustrating.

So I forgot Moon Bounce on this band and had fun with other activities, mainly on 23 cm. But the over 30 year old equipment caused more and more problems. So I started collecting parts and modules for a new transverter system covering 23 and 13 cm. It had been finished for the last VHF/UHF/SHF contest in March and was tested with good results. In the end of March I tried EME again after 2 years of absence. On 23 cm it worked fairly, but on 13 cm the drift was a serious problem. In a test with Alex, ZS6EME, I could decode his strong Signal, but not vice versa. So I added 10 MHz Double Oven Controlled Oscillators as references to stabilize the transverters.

PY2BS in WSJT-X Wide Graph

Today I tried with Bruce, PY2BS, and heard him strong in the speaker during his prior test with Toshio, JA6AHB:     1131  -6  2.5 2305 #* JA6AHB PY2BS GG66
At this time his elevation was -1.7° and the moon still under the horizon. After the moon set in Japan, we started:

1155  -8  2.9 1184 #* DJ5AR PY2BS GG66
1157 -13  3.6 1157 #* DJ5AR PY2BS GG66
1159 -10  2.7 1137 #* DJ5AR PY2BS GG66
1200  Tx      1500 #  PY2BS DJ5AR JN49 OOO
1201 -10  3.1 1114 #* DJ5AR PY2BS GG66
1202  Tx      1500 #  PY2BS DJ5AR JN49 OOO
1203  -9  3.3 1089 #* DJ5AR PY2BS GG66
1204  Tx      1500 #  PY2BS DJ5AR JN49 OOO
1205 -10  2.9 1066 #* DJ5AR PY2BS GG66
1206  Tx      1500 #  PY2BS DJ5AR JN49 OOO
1207  -9  3.1 1043 #* DJ5AR PY2BS GG66
1208  Tx      1500 #  PY2BS DJ5AR JN49 OOO
1209  -9  2.7 1019 #* DJ5AR PY2BS GG66
1210  Tx      1400 #  PY2BS DJ5AR JN49 OOO
1211 -10  3.0  994 #* DJ5AR PY2BS GG66
1212  Tx      1400 #  PY2BS DJ5AR JN49 OOO
1213 -11  2.2  969 #* DJ5AR PY2BS GG66
1214  Tx      1400 #  PY2BS DJ5AR JN49 OOO
1215 -22 -2.5  946 #  RO
1216  Tx      1400 #  RRR
1217 -10  3.1  919 #* RR -20 DB
1218  Tx      1400 #  73 BEST -8

As he switched his RX from 2304.070 MHz to my TX frequency 2320.070 MHz at about 12:14, we completed very fast. I am very pleased now with my first initial on 13 cm, a new grid square, a new ODX, a new DXCC and a new continent! After setting up a new Initials List for 2320 MHz and writing this blog entry, I enjoy my “Radio Operators High”!

Nice Tropo this Afternoon

December 20th, 2016

There is some nice troposheric propagation this afternoon. It looks promising for the NAC, IAC and UKAC this evening on 23 cm. When looking for DB0XY I saw this situation:

2016-12-20-14_00-23-cmHopefully it will last for some hours!

Strange Tropo today

September 28th, 2016

During the morning I was able to monitor GB3FM in IO91OF on 1297.050 MHz and G8MBU in IO90IR on 1296.800 MHz. Now in the afternoon F5ZCS in IN87PT on 1296.959 MHz came out of the noise with a strong signal of 549 with fast QSB. It is my 53rd beacon on 23 cm. The weather here in Mainz doesn´t look like tropo: 8/8 cloudy and wind at 40 km/h.


Listen to F5ZCS:


QSL for first Satellite Bounce by Amateurs arrived today

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!


A new Chapter in the Book of Bounce

December 8th, 2015

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

September 13th, 2015

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

September 5th, 2015

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)

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