Tag Archives: ISS bounce

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) darc.de

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

SM7FWZ finally worked via ISS Bounce

July 13th, 2015

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!

July 12th, 2015

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!

ISS Bounce News from Poland

June 14th, 2015

Michal, SQ5KTM, has been successful in receiving reflections of the french GRAVES radar from the International Space Station.

The radar system is used for space surveillance tasks, located in JN27SI and operating on 143.050 MHz. Karl, DK5EC, has written a very informative article about monitoring GRAVES.


Brendan Quest: Could it have been ISS Bounce?

February 21st, 2015

After giving a lecture about “Reflections on Air- and Spacecrafts” at the Dorsten GHz-Convention today, Alexander, DL8AAU, told me, he had discussed the possibility of ISS Bounce with Jeff, WA1HCO, when John, G4SWX, claimed to have received a burst of VC1T on 2 m across the atlantic ocean. Then he asked me about my opinion. Without knowing details, all I could answer was, that the inclination allows the ISS to cross at the latitudes of the stations and that it´s very likely, the stations will be inside the sight range of the ISS then.

First thing I did, when arriving back home in Mainz, was to retrieve an archived TLE file from 2014-07-06. The attempt to calculate a window between VC1T in GN37OS and G4SWX in JO02RF resulted in a direct hit, as the reception of the burst is claimed for  13:41:30 UTC on  July 6th, 2014:

25544 2014-07-06-13-40 VC1T G4SWX ISS(ZARYA) (25544) Elevation

As the the above graphs show, a short window of about 1:40 minutes for ISS Bounce opened at exactly the time, John claimed the reception of VC1T. And in fact this has been discussed in the WSJT Meteor Scatter Weak Signal Group as well.

The team members of VC1T and John, G4SWX, as well as those, involved in the discussion in Dorsten were informed to have the opportunity to check out my results. At least there is no doubt, there has been a matching window, exactly in these approximately 10 seconds, John received VC1T.

VC1T - G4SWX 2014-07-06 ISS BounceThe TLEs used for this calculation have an epoch date very close to the event:

1 25544U 98067A   14187.56731944  .00009245  00000-0  16720-3 0  9999
2 25544 051.6477 003.4946 0003495 212.8213 225.8239 15.50435882894337

Assumed power and antenna gain for VC1T have been 750 W and, as claimed on their website, 26 dBi. As I didn´t knew much about John´s rig, I assumed 20 dBi as antenna gain on his side. Differences can easily be added or subtracted to or of the above results. Also it hasn´t been considered that the ISS was not in the centers of the main lobes of the antennas. The radar cross section (RCS) of the ISS had been set to 348 m², as was given in the NORAD catalogue, as long as they provided this value there.


For the prediction of the signal level the value of the RCS is essential, as it depends on the frequency, the angle, the reflecing object is seen from the groundstations, the shape of the object, resonances, and eventually by effects resulting of the geometry of the object, as can be seen on corner reflectors. So it´s value should be handled with extreme much care. I don´t really know, whether the value of 348 m² (25.4 dBm²), I used, has been too small or too large. Both is possible.

At present Alexander, DL8AAU, is performing calculations on a digital model of the ISS using a special ray tracing software to get high quality values of RCS. This has to be done under consideration of the orientation and the heading of the ISS, as well as the angles, the ground stations have been seen by the International Space Station.

Path VC1T – G4SWX and Groundtrack of ISS

It is interesting to have a look on the relation of the direct path bethween VC1T and G4SWX in blue versus the Groundtrack of the ISS in red with the window marked green. The bearing of the VC1T antenna has been 62°, while the ISS passed the window under 68°. Vice versa the bearings at G4SWX have been directly 285° and 278° to the ISS.

The main questions are now:

How good is the quality of the assumed value of the RCS?, Can it be improved?
Could this constellation lead to a receivable signal level at G4SWX?

It has to be respected, that John, G4SWX, is a highly skilled operator with more than 30 years experience in 2 m EME and long distance MS over more than 3.000 km. Other propagation modes like meteor scatter, sporadic E or tropo, pure or in combination, are to be considered. There still is the possibility, that the match in time it is just a coincidence.

Joe Taylor, K1JT, has been involved in the above mentioned discussion and he stated there:

I should make it clear that I have no horse in this race. Like others
who have contributed here, I’m just a bystander with an interest in
knowing the truth about a reported phenomenon.”

This is exactly my point of view in this subject and it is up to the IRTS committee to recognize this contribution.

ISS Bounce or not, we have to respect, it has been a great achievement to cross the Atlantic Ocean on 2m! Applause!

When searching the web for more information, it seems, some had uncertain receptions just with fragments of a decode, finding it not worth to publish it. We are very interested in such “maybe” reception reports, to crosscheck it with a possible ISS window.

If you have any kind of information for us, please forward the exact time and your locator to dj5ar [at] darc.de


In this context it is interesting to know, that in 2007 Peter, SM2CEW and Petros, SV3AAF were very close to complete a QSO via ISS Bounce over a distance of 3136 km in CW!

Presentation “Reflections on Air- and Spacecrafts”

January 15th, 2015Banner GHz-Tagung 2015On February 21st, 2015 Jan, PA3FXB, and I will give a lecture in Dorsten at the GHz convention. It will be held in german and partly in english and is basing on the former lectures “Let´s Bounce”.

We will talk about unusual use of Aircraft Scatter and our experiences using ISCAT. Two years ago the idea, to try ISS Bounce, was born and discussed in Dorsten. We will show what we have done in the meantime in practising this propagation mode.

A big Dish, a big Bird and a big Signal

January 6th, 2015

Jan, PA3FXB, and I skeduled a very special ISCAT test on 23 cm for today. The CAMRAS team had planned to operate PI9CAM with the 25 m radiotelescope in Dwingeloo for some astronomical experiments this afternoon. Before starting with that, we used an ISS pass with low elevation to try ISS bounce with the big dish. Such a pass ensures slow variation of azimuth end elevation angles, which is essential to track moving object like the ISS (or other spacecrafts in low orbits) with an antenna of a weight of 120 tons.

DSC_0384aWe had very strong reflections right from the beginning, but no decodes. Maybe the signal level was to high? This has to be investigated. Then we changed to aircraft scatter, although the dish had to be kept elevated at 10° by safety reasons, I got strong reflections from airplanes quite close to PI9CAM. Not as strong as from the ISS, but decodable now and it was possible to work in CW too.

Despite the fact, we had no QSO via ISS bounce, we learnt, that it is possible to track objects in low orbits with the 25 m radiotelescope, as long as the elevation keeps low. This opens up a perspective to make use of other spacecrafts as reflectors.

ISS Bounce again: now in ISCAT

January 4th, 2015

Jan, PA3FXB, and I were discussing the use of digimodes on ISS bounce for quite a while. Today we tried it with ISCAT-B and were successful with the first shot. As in the tests with Ronald, ON7FLY, on AS, we used 15 seconds periods.


From the moment on, traces could be seen in the waterfall diagram, decodes were possible.

2015-01-04 12_14_58-

When the ISS culmiated and the variation of the dopplershift was fastest, the frequency correction came to its limits. But while I am used to ISCAT in the meantime, I needed no decodes to hear, that Jan was transmitting RRRRs.


At least I decoded a 73 from him. The experiences with ISCAT in ISS bounce are very promising, although the 15 seconds periods are too long. So we have to discuss it and try with shorter ones.2015-01-04 ISCAT QSO

Presentation “Let´s Bounce” IIa

October 21st, 2014

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.