Tag Archives: 144 MHz

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!

EI8HH – Active in the Perseids

August 17th, 2014

Despite a lot of work in the garden and at the house I found some time to setup my old 16 element F9FT yagi. In the night from August 12th to August 13th and in the morning I logged at least 16 QSOs.

The list of sked requests became longer and longer during the night. Although I did my best to work all interested stations, it wasn´t possible to make QSOs with all of them. Sorry! The conditions weren´t too good, but improved a little during the morning of 13th.

I worked: 8 x DL, 2 x I, 1 x LA, 2 x OK, 1 x PA, 2 x S5 in 15 different squares. ODX was S51AT in JN61GW over 2,075 km.

DSC_0923

I am located at the southern shore of Lough Mask with the mountains of Connemara to the south and the west (IO53HN).

EI8HH in IO53hn

DSC_3732My best take off is to GM and LA.

Please QSL via DJ5AR.

Article in “Funkamateur” magazine July 2014

June 22nd, 2014

German Funkamateur mgazine has published my article “Abenteuer Bakenbeobachtung von 144 MHz bis 10 GHz” in its recent issue July 2014. As many topics are related to posts on this website, some of them are compiled here. Links to certain other websites can be found in the link list to the right.

Weather, rainscatter:

Rainscatter on 23 and 13 cm
Impressive Thunderstorm

Weather, troposheric ducting:

Another strange constellation (Update)
Strange Conditions
Opening September 21st 2013

Aircraft scatter (video):

PI7ALK via Aircraft Scatter

List of beacons, heard by DJ5AR in Mainz, JN49CV

My new beacon list