Category Archives: ISS Bounce

Presentation “Let´s Bounce” II

September 1st, 2014

ISS Bounce Title

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.

Presentation “Let´s Bounce”

June 22nd, 2014

On July 24th, 2014 on 19:00 CEST I will talk about how to surmount the horizon on VHF and up at the local DARC Club in Bodenheim near Mainz.

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.

Deutscher Amateur-Radio-Club e.V.
Ortsverband Bodenheim
Haus der Vereine
Laubenheimer Str. 22
55294 Bodenheim

The admission is free, but please register via email to
DK2FQ (at)   or to me   dj5ar (at)

ISS Bounce even in SSB

February 17th, 2014

After getting familiar in working us in CW via ISS Bounce, Jan, PA3FXB and I were looking for a new challenge. So we decided to try it in SSB. After some tests in the last days and finding a workaround for a bug in my PowerSDR, we completed a two way contact in SSB on a center frequency of 1296.300 MHz tonight. The doppler compensation worked well on both sides. Just minor corrections with the RIT were neccessary. The signals weren´t as strong as they were in the days before, but strong enough to copy even some 73s at the end. It seems to be the first SSB QSO via reflections on a spacecraft at all.

The audio recording starts with my recording of PA3FXB on one channel synchronized with Jans recording of my signal on the other channel.

Just another ISS Bounce QSO

February 13th, 2014

Tonight I had a sked with Jan to try ISS Bounce once again. We agreed in trying SSB after getting in contact in CW. Jan appeared shortly after rise of the ISS and it was no problem to exchange reports and confirmation with strong signals. Then we switched to SSB and I could hear Jan clearly, but my tracking software refused to stay in SSB mode. So I have to fix this bug for our next test.

Later we tried to detect reflections from Iridium 4. We expected to see something about -19 dB, but nothing was to be seen in the waterfall diagram. Maybe that the choosen pass wasn´t too high in elevation and we will try again. When Jan was operating PI9CAM on February 2nd, faint traces of reflections on COSMOS 1823 could be detected by Hannes, OE5JFL, Dan, HB9Q and myself. As it is quite time-consuming, to find reasonable passes of satellites, I wrote a small Excel tool get an overview over satellites, passes and elevations. It can be found for free download here: Visibility

Macros have to be enabled in your Excel. Just enter the date, time, period and the locators of the two stations in the approriate cells, click “Calculate” in the “ADDINS/Satellite Overview” menu and the worksheet will be updated. Don´t forget to fill the TLE worksheet with the latest data of your choice.

ISS bounce VI: Feedback

June 5th, 2013

Once the news about our QSO were spread out over the internet, Jan and I had an overwhelming feedback from all over the world. Many sent just congratulations, but a number of hams supported us with additional information. Domenico, I8CVS did calculations using the radar equation. His results concerning the expected signal levels correlate very well with our recordings.

A lot of details about earlier attempts were reported by GW4DGU (ex G4DGU), VK3UM and VA7MM. Here a summary in brief:

Chris, G4DGU and John, G4ANB performed tests with Ben, SM6CKU in 1980 on 70 cm. Ben was able to copy a SSB burst of Chris reflected on a COSMOS 3 stage launcher.

Dough, VK3UM had several QSOs with Graham, ZL3AAD on 432 MHz in the 1990s by bouncing signals off the Russian space station MIR. It seems, they were the first to complete a QSO using a space craft as reflector!

In an AMSAT forum Miles, WF1F, reports about reflections of Joe´s, W2KQ, signal bounced off the MIR on 2 m while arranging school schedules with one of the cosmonauts in 1994.

We knew that Mark, VA7MM and Cor, VE7BBG (sk) had their first tests on 23 cm on May 16th, 2004, as Mark published on his website. He now told in an email about four(!) QSOs they had on May 23rd, May 25th, May 31st and June 5th, 2004. As far as we know now, this team was the first to complete a QSO via ISS bounce at all.

In end of 2007 a lot of activities happened on 144 MHz. Rob, PE1ITR tried with Mike, DK3WN, who received reflections. Peter SM2CEW nearly completed a QSO with Håkan, SM7WSJ and tried also with Petros, SV3AAF (more). Frank, PE1NFE and Rune, SM5CUI were able to copy the signals from Sweden as well. Bernd, DF2ZC completed on 2 m with Frank, DH7FB on December 9, 2007. They had three more QSOs in 2008.

Addendum May 2016:

I found a link to the website of Philippe, F6ETI, where he described the successful experiments with F6AGR to bounce reflections off the Russian MIR space station on 144 MHz in February 2001. As he told me, they performed just a one way test and had no QSO.

To be continued ……


ISS bounce V: The QSO!

May 23rd, 2013

STS-133 International Space Station after undocking 5

(Copyright by NASA [Public domain], via Wikimedia Commons)

After a lot of tests and improvements have been done in tracking the doppler shifted signals, Jan, PA3FXB any I had another try around 1296.300 MHz this morning. Both of us performed compensation of the own doppler component as well in receiving as in transmitting. We agreed in using  the EME QSO protocol and periods of 30 seconds.

PA3FXB as received by DJ5AR

Jan appeared within my filter bandwidth as soon as the ISS became visible to both of us. His signal strength was peaking up to nearly 20 dB above noise and was easy to copy. The tracked frequency seemed to be stable until the ISS culminated. Then the variation of the doppler shift became so rapid that the compensation mechanism was not fast enough anymore. But that happened to the very last part of our QSO while we were transmitting our final 73s. So I can state that the best signal quality can be expected during the ascending and the descending parts of the pass.

In the meantime I received Jan´s recording. Listen how DJ5AR sounds on his side:

DJ5AR as received by PA3FXB

Many thanks to Jan for his cooperation and his patience in numerous tests before.

This success is dedicated to our fathers, who suffer from the same disease!

If you are interested in a try, do not hesitate to contact Jan or me. You can find us in the HB9Q 1296 MHz EME logger or in the ON4KST microwave chat, when QRV.


ISS bounce IV

May 10th, 2013

Today Jan, PA3FXB and I used ISS passes to improve doppler compensation.


The first pass of three was disappointing because no reflections could be detected. In the second one I found Jan shortly after his window opened. But it sounded more like a strange kind of music than CW, Jan stated after listening to the audio file, I recorded of his signal. The reason were too long steps in timing for the frequency correction. I reduced it for the last try from 100 ms to 10 ms. After some recalibration of frequency and rotor control I started the system again when the ISS rose.

2013-05-10 13-43

I could hear Jan without any manual corrections immediately after he started transmissions. The frequency tracking worked quite smoothly and reading his CW was possible without any problems.

PA3FXB as received by DJ5AR with QRG tracking every 10 ms

The audio file contains Jan´s signal in three periods. From 0:00 to 1:00 the signal raises while being on the upper flat part of the doppler curve shown above. During the second period from 1:00 to 2:00 the signal passes the steep part and even an adjustment every 10 ms leads to a kind of jumping signal. When receiving the third period, the signal was quite stable again and faded out, while the ISS moved to the eastern horizon.

In between his TX periods Jan tried to catch my signal without doppler compensation, just playing with the RIT. He successfully got a short part of my transmission:

DJ5AR as received by PA3FXB without QRG tracking

Doppler compensation on my TX part did not work. It seems that the SDR does not accept CAT commands for frequency change while transmitting. So we will work on another strategy, where TX frequencies remain fixed and both stations will do full doppler compensation only while receiving.

ISS bounce III

April 30th, 2013

The doppler shift was the problem to be solved for performing further steps in ISS bounce. There are two practical strategies: If every station will compensate its own doppler component, so even random QSOs would be possible. The other solution is, when the whole compensation will be done by one of the stations. That would open ISS bounce to stations that are able to do antenna tracking on the ISS, but not to compensate the doppler. In this case it is required to arrange skeds, because the compensating station is required to know the coordinates of the other one.

Basing on DC9ZPs E-Book I extended the software, I use for station control, by satellite tracking. That opens the possibility to calculate the relative speed and the resulting doppler shift of the ISS pertaining to given locations and given frequencies.

DJ5AR-EI8HH Elevation DJ5AR-EI8HH DopplerAbove diagrams show the elevation with the according doppler components on 1296 MHz for a window between DJ5AR, JN49CV in Mainz (green) and EI8HH, IO53HN near Galway (blue). If the full doppler compensation will be done by one of the stations, the red line with a total span of 120 kHz will be relevant. The window in this example would open for about five to six minutes.

ISS bounce II

April 8th, 2013

Another test tonight with the experience of the one two days ago, was more efficient in finding the reflections. The ISS passed south of our QTHs. So I could track the whole pass from rise to set. Jan´s signal could be detected most of the time during his window. The picture shows his signal shortly after the rise of the ISS. Caused by the doppler effect it moves from right to left. The shift in this detail varied between 47 kHz and 38 kHz, while PA3FXB was transmitting on 1296.300 MHz in CW.  By a length of about 25 seconds there was a variation of 400 to 500 Hz per second.

PA3FXB shortly after rise without QRG tracking

PA3FXB 2013-04-08 shortly after rise Audio

PA3FXB shortly after rise

PA3FXB shortly after rise with manual QRG tracking

Jan was transmitting his callsign “PA3FXB” followed by “T”s. The variation of the pitch in the first audio file is caused by manually tracking the signal. The second audio file gives an impression of the speed of the doppler variation. An effective  compensation of the doppler effect seems to be most important.

There have been earlier attempts to realize QSOs by reflections on the ISS. SM2CEW reports about nearly completing QSOs on 144 MHz with SM7WSJ in 2007 and he tried also with SV3AAF (more). DF2ZC claims the first ever QSO via ISS scatter on 2 m with DH7FB on December 9, 2007. They completed three more QSOs in 2008. It seems that these were the only four QSOs via ISS bounce since then. VA7MM reports about tests on ISS bounce with VE7BBG on 23 cm in 2004. PE1ITR tried with DK3WN in 2007.

ISS bounce

April 7th, 2013

Tonight Jan, PA3FXB and I tried, what we were discussing about for quite a while. There was a prediction of an ISS pass shortly after local midnight and both of us had no other appointments. So we agreed that Jan should make a transmission on 1296.300 MHz as soon the ISS became visible to him and tracking it as long as possible. My part was to monitor the pass of the International Space Station on my SDR. We used 3 m dishes on both ends and Jan had approximately 375 W in CW.

PA3FXB via ISS Beginning

PA3FXBs signal at the very right

Here is the result. Jan appeared with a relatively strong signal (on the very right), faded out and came back with weaker signal strength. I interpret it, that the first appearance was backscatter and the second was forward scatter, what has to be discussed. Doppler was extremely strong and more than 40 kHZ at the beginning.