Category Archives: Propagation

Moonbounce by Accident in 1943

September 27th, 2023

I have been in contact recently with Cindy Stodola Pomerleau, W2AXO, the daughter of Edwin K. Stodola, chief scientist of project Diana, about a text by Dr. Stepp, an engineer of the German Telefunken company, describing reflections from the moon with a radar system in 1943. The text has originally been published in a german nautical journal and been reprinted in CQ DL later. So it is in German only and as I think, it could be of some interest to the moonbounce community, I did a quick translation to English.
Btw.: If interested in Project Diana, the book, written by Cindy, is a must have!

Not much is known about the German technicians picking up reflections from the moon, while testing newly developed radar equipment on the island of Ruegen. Later one of them, Dr. Stepp, published a short report, he wrote:

“Back in 1943 Telefunken was to develop a system for detection and measurement of near to ground targets – ships, low-level attack aircrafts and vehicles – with a maximum outreach.

The mission to detect close to ground objects required among high transmission power and receiver sensitivity the use of least possible short waves. As the capabilities of those times allowed, a stationary facility was erected with the following characteristics:

TX pulse power:                  120 kW
Pulse duration:                    1,5 µS
Wavelength:                         53 cm, abt. 564 MHz
RX sensitivity:                      12kTo
Antenna surface:                45 m²
Polarization:                         horizontal
Number of dipoles:            8 per row horizontal
                                          80 per column vertical

The antenna could be turned around the vertical axis. It had a very narrow vertical beam with zeroes in the diagram 1.3° beside the main beam direction.

The system was named Wuerzman. In late 1943 the system was erected in the south of the island of Ruegen on a hill called Bakenberg for field testing.

The results confirmed the reckoned outreach: Ships of mid sizes could be detected up to the horizon at about 50 km, airplanes up to a height of 1000 m and up to a distance of 100 km. Under convenient weather conditions it detected targets in the harbor of Danzig (Gdansk) and the Gulf of Finland.

After the first tests I instructed Willi Thiel, a high-achieving technician, to mind the system by himself and to operate it continuously. A couple of weeks later I returned to the island of Ruegen for tests nearby Goehren. On the last day of my stay, a couple of hours before my journey back to Berlin, I visited the Bakenberg again. The sky was very cloudy and the night extremely dark. On our way to the Bakenberg W. Thiel told me about a strange fault, he mentioned the day before at the same time, but couldn´t find the reason, as after about two hours it gradually declined and at least disappeared.

After starting the operation of the Wuerzmann I made following observation: The fault appeared again, it had a length of several pulses and a bigger pulse amplitude than the strongest close targets. It appeared about two seconds after the start of transmission and disappeared pulsing analogous later after the stop of transmission. All other targets disappeared in the moment of switching off the transmitter. The fault happened only when the antenna beamed east, disappeared at once after larger changes of the bearing and appeared with a two seconds delay when beaming east again. It seemed, we targeted the moon behind the clouds. The degrading disappearance I explained as the slow movement of the reflecting body out of the narrow horizontal pointing beam together with a growing height over the horizon.

Soon after the system went into destinated operation, I never heard of further observations.“

German original in: Der Seewart, Band 35, 1974, Heft 2, S. 71
Reprint in CQ DL 1979, Heft 7, S. 328
Translation by Andreas Imse, DJ5AR

A picture of the system can be found here:
Website: http://www.deutschesatlantikwallarchiv.de/radar/germany/rd_.htm
Picture: http://www.deutschesatlantikwallarchiv.de/images/radar/germany/053748.jpg

Addendum November 6th, 2023

Cindy, W2AXO, did a great job in further investigations and published a very comprehensive history of early moonbounce on her website:
https://www.projectdiana-eme.com/the-moonbounce-zeitgeist.html

Nice Opening tonight

November 29th, 2020

As predicted in the Hepburn forecast, there happened an opening to the west tonight. No really breathtaking distances, but at least three new squares on 2 m (two of them I already worked on 23 cm 😉 ) IN86, IN87 and IN89.

On 23 cm I tried with Grant, G1SDX in IO80FL, first in FT8, but I could only copy him via aircraft scatter due to significant doppler, inhibiting decoding of his signals. He copied me via tropo up to -11 dB, but we had a difference in power of 13 dB (36 element yagi and 10 W vs. 3 m dish and 200 W). So we tried MSK144, where I could decode him via AS, but he had no decodes of me.

It´s a very interesting path, as half of it is over water. It should be an opportunity for combined sea ducting and aircraft scatter. I hope for a chance to try.

Activity as EI8HH is over now

October 21st, 2020

QSOs in October 2020: MS in red, FT8 in green and SSB in blue

While refurbishing our irish home, I found some time in the mornings and the evenings to be active on 2 m. At least I worked 31 squares. Even on 23 cm I got 3 Calls to the log. The rig so far is an IC-9700 with a 7 element yagi and a linear amplifier with 200 W on 2 m and a 69 element yagi on 23 cm,

Now I have to close the station and take the antennas down. It has been a lot of fun and I hopefully will be back next year, if pandemic allows. Many ideas are in my mind now, how to improve the station over here.

Many thanks to Joe, EI3IX, his N adapter female-female allowed me, to run 2 m and 23 cm simultaneously 😉 .

EI8HH on Air

October 2nd, 2020

As some work at our families house in Ireland has to be done, I am spending 3 weeks over here in IO53HN. I got my new IC-9700 with me and have antennas for 2 m and 23 cm. As I have to restrict my movements by government order, no portable activites are possible in the first two weeks. So I will try to work in the UHF/SHF Contest on 23 cm from the southern lake shore of Lough Mask. My favourite direction is to GI/GM. Maybe I can go to a better QTH later in the 23 cm UKAC. On 144 MHz I will focus on meteor scatter in the morning hours.

In a first test on 2 m I worked GI and GM in FT8. GM7PKT came back on my very first CQ. Later I tried meteor scatter with my german neighbour Mathias, DH4FAJ. As he has massive QRM, he couldn´t hear anything, but I copied him twice with +4 dB. So better to try in the morning again.

Tropo to Belarus this Morning on 144 MHz

September 9th, 2020

A nice inversion could be seen out of the window of my shack this morning, promising good conditions. In fact I have been a little too far south for the duct, but at least I had two QSOs to Belarus in FT8.

Green: worked – Red: heard via tropo – Blue: heard via meteor scatter

The stations worked and heard via tropo have been in distances up to 1300 km. Occasionally signals appeared from more distant stations, 1500 and more km away. These could be decoded in one or two periods, then disappeared. Some reappeared later in the same manner, so it´s very likely, it has been meteor scatter, as it happened in the early morning, when conditions are good for sporadic meteors.

Worked Hrd Tropo Hrd MS 
SP6URZJO71mdSP6EJO71kkUT4UEPKN49wv
SP1MVGJO74jaSQ6POMJO71vqUT2EMKN67qv
SP6CVBJO80veHF1JJO73fiUS4IEKKN87ux
SQ5ESMKO02hcSP1NENJO73fiUR7IMMKN88tr
EU3CZKO12JBSP1WSRJO73gjUS3ITUKN88wa
EU3AIKO22CESP6LTMJO80fuUT6LXKN89cj
SP3NJO81xkUS8ARKO60sr
SO3ZJO82kkR3LQKO64hk
SQ2SATJO83xg
SP1FJZJO84ee
SP9BCVJO90wb
SP7CKHJO92qf
SP2CHYJO94go
SP8NFOKN09ps
YL2IVKO06lm
EW3AAKO12TC
EU3ACKO12wd
SP4MPHKO14lc
UR4WWTKO20ec
LY1LRKO24ph

New Bands down to DC

May 7th, 2020

Yesterday I added a logarithmic periodic antenna for the range 28 to 150 MHz to my little antenna farm. So I am QRV now on the amateur bands from the highest DC band 28 MHz up to 2400 MHz.

Antennas at DJ5AR

Recently I got an IC-7300 with extended frequency range to cover the 50 MHz and 70 MHz, as well as the new Irish bands 80 MHz and 60 MHz.

So I am looking forward to have some cross band QSOs to Ireland soon!

I took down the 3 cm dish for some work on the rig. And I know, the 70 cm yagi is much too close to the new antenna, but I have been too lazy to dismount it.

Addendum May 18th, 2020

First PI4 decodes of EI1KNH in IO63VE on 40 MHz.

AirScout V1.3.3.0 released

May 3rd, 2020

The VHF/UHF/SHF contest on 2nd to 3rd of May was a good opportunity to spend a few hours trying the new AirScout version 1.3.3.0 released by Frank, DL2ALF. In principle it works like it´s predecessors, but is more stable in collecting the aircraft data. My favourite in this case is planefinder.net.

Most impressed I am by the new feature to monitor a number of paths to certain stations simultaneously! This provides more efficiency in arranging skeds, particularly in times like these, when there are a few planes only are available.

Find more details on the AirScout Site.

Strange Conditions Today

January 1st, 2020

I got up quite early today and decided to check the beacons on 23 cm. When beaming to LA1UHG, there was a noticeable signal in F1 about 1 kHz above its frequency. It was easy to read it as DB0LB from the back of the dish. But it seemed, there was another faint signal right beside the spacing carrier. With the help of my SDR radio I could set very narrow filters and after a while of listening, I identified it as LA1UHG, JO59FB, 1028 km. Wow!

But the signal faded out more and more and at least it disappeared.

LA1UHG just 140 Hz below the space carrier of DB0LB

Later this morning, the dish still pointing north, I heard Kurt, OE5XBL, chatting in SSB with Rudi, OE5VRL/5, both with very strong signals on 23 cm. Expecting a huge signal, I turned the antenna to Kurt, but there was no significant increase in signal strength. I called in and the three of us were talking about the conditions and to meet for a beer at the GHz convention in Dorsten next February, when Kurt was called by Dave, G4RQI. I had tried with him earlier without any success, and so, to be honest, I was a little annoyed by this. Even, when turning the dish to the UK, I couldn´t copy anything of Dave’s transmissions, while he was working Kurt and Rudi. These were enough indications, that the inversion was at a too high altitude for me, to enter it. So I went for a long walk with my XYL in the nearby vineyards.

The inversion is at an altitude of about 1000 m (Courtesy DWD)

In the evening I performed another beacon check. It was funny to see beacons, the dish was pointing to, as well as others from the back of the dish

Dish pointing southeast: DB0UX, DB0VC, DB0AAT (from left to right)

Turning the dish, confirmed the experience I had in the the morning: Pointing southeast I saw DB0VC, JO54IF, next to DB0AAT, JN67HU. Turning the dish towards Kiel in the north, the signal of DB0VC increased just a little. Maybe, it has been reflected by a mountain range about 50 km southeast of me.

Dish pointing north: DB0UX, DB0XY, DB0VC, OZ7IGY (from left to right)

F5ZNI: Beacon #34 on 13 cm

December 29th, 2019

By performing my daily beacon check, I noticed a weak keyed carrier in between the spacing of the F1 signal of DB0UX on 2320.900 MHz. I assumed to see F6DWG/B, which I monitored around the .900 before. But it didn´t take long to find out, that the real signal (mark) was the lower carrier and after a while I learned, it was F5ZNI using reverse F1 keying. Later in the evening the signal increased due to good tropo conditions, as can be seen in the pictures. F5ZNI is the 34th beacon I received in the 13 cm (S) Band

F5ZNI and DB0UX in PowerSDR

I am always happy about new beacons, but this case is an example, why beacon coordination and using standards is most important. First of all, reverse F1 keying is always bad, as you are used to listen to the upper carrier of the signal. In case there is an unkeyed carrier in between the text, you can easily identify the mark, where to listen. But if there is text keyed nearly all the time, as F5ZNI does, it is rather time consuming until the mark is identified.

The DB0UX signal was strong and the frequency is locked to a reference, while F5ZNI is drifting a little. So it was obvious, that there was a second signal in place. If the french beacon would have been locked to 2320.900 MHz too and would use the standard A1 or F1 keying, there would have been no chance for me to monitor or even to take notice of it.

An excerpt from BEACONSPOT.UK shows the situation on 2320.900 MHz:

BeaconNominal FrequencyLocatorLast SpottedLast FrequencyStatus
F6DWG2320.900JN19BQ2019-05-312320.898Dead/lost
HG3BUC2320.900JN96CC2019-10-112320.897Operational
OZ5SHF2320.900JO45VX2019-08-242320.900Operational on spot date
DB0MJ2320.900JO31UB2019-12-292320.905Operational
ON0TB2320.900JO30BM2019-09-202320.897Dead/lost
DB0UX2320.900JN48FX2019-12-292320.900Operational on spot date
F1ZCC2320.900JN08XSUncertain - new spot required
SR1SHS2320.900JO73PG2019-12-302320.900Operational
IQ5FI2320.903JN53SR2019-12-282320.901Operational
F5ZNI2320.904JN19BQ2019-12-302320.899Operational on spot date


Depending on the location and the conditions, there will be more or less interference on 230.900 MHz

So I am urging all beacon keepers to make use of the service provided by the
IARU R1 VHF/UHF/MW Beacon Coordinator. When designing a beacon, please respect chapter 11 “Beacon Requirements” in the IARU-R1 VHF Handbook.