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)

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!

DL65DARC will be QRV on 23 and 13 cm

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.


10 GHz up and running!

DSC_2010bWith assistance from Franz, DF9ZT, I got my 10 GHz rig repaired and mounted it yesterday evening. Hope for the first QSOs soon with the 50 cm dish and 1.5 W. Beacons heard so far are DB0MOT (41 km), DB0MMO (90 km), DB0AJA (132 km), DB0ZDF (6 km), DB0FGB (263 km) and DB0ANU (182 km).

Thank you very much, Franz!

Asymmetrical Reflections on Aircraft Scatter

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.


Monitoring DX Beacons via Aircraft Scatter

The monitoring of distant beacons can be a boring job, even when using the waterfall diagram of a SDR. I prefer SpecJT of the WSJT package in JT65c mode. It is much more sensitive and even at slow speed faint refections can be seen clearly.

2015-05-05 12_07_28 F1ZMT

The example shows F1ZMT in JN07CX, 624 km from Mainz. The beacon operates 10 W into an omnidirectional antenna on 1296.872 MHz. The reflections in the screenshot were caused by 3 airplanes crossing the path one after the other.