As the weather forecast promised heavy thunderstorms for today, I was looking out for scatter points on 13 cm. Pointing to eastern France, I found a heavily scattered signal of DB0UX in JN48FX in 204°.
But the sound was quite strange and rhythmic. When taking a look out of the window, I saw the dish pointing at two windmills in 1 km distance.
This kind of scatter is not very helpful, but a nice experience anyway.
After installation of new transverters for 23 and 13 cm with stabilized LOs a couple of months ago. I gathered some experience in using JT65C mode on EME. So I undertook a new attempt to receive and decode G8MBU via aircraft scatter today. As antenna I use a 3 m dish with a dual band ringfeed.
Path DJ5AR to G8MBU
The beacon is located at Cowes on the Isle of Wight, IO91IR37, 683 km from Mainz, JN49CV. It runs 2 W power into an omnidirectional dual alford slot antenna. The mode used is JT65c. Nominal frequency is 1296.800 MHz. To successfully decode the signal, the SSB dial should be set to 1296.7986 MHz, to get a tuning tone of 1400 Hz in WSJT.
There is a small window between the Isle of Wight and Mainz, where high flying aircraft can be “seen” from either places. But only a few airplanes cross the path within and fewer fly along the path. Reflections of G8MBU could be seen from time to time, but mostly too weak and too short to provide decodes. It took nearly 3 hours until the first decode happened at -22 dB and just some minutes later a second one appeared on the display at -21 dB:
The other day I had a look on Dominiques QRZ.COM page and saw, he claimed to have a beacon on 13 cm as well. The frequency seemed to be quite strange: 2308.037 MHz
It´s because the situation in Switzerland is different, than in other european countries:
2300 – 2308 MHz with special permission only
2308 – 2312 MHz License classes 1, 2 and CEPT
2312 – 2400 MHz with special permission only
My new Kuhne MKU 23 G4 transverter covers certain segements of the band. so I switched to 2304 – 2306 MHz and tried to listen on an IF around 148.037 MHz and was disappointed: nil. I expected a strong signal as the same beacon on 1296.050 MHz ist up to 40 dB above noise under normal conditions.
A weak trace can be seen at the IF of 1392.032 MHz (LO 916 MHz)
I contacted Dominique and he assured, the beacon should be on air. So I tried with the setup, I received ISEE-3 quite a time ago and monitored the path for airplanes. So after a short while, there was a trace to be seen on 2308.032 MHz. Even the keyed carrier could be heard deep in the noise, when larger aircrafts crossed or flew along the path.
Characteristic “hook” at the begin of the carrier after keying the call
So I proudly added beacon #23 to my 13 cm list.
HB9BBD/B: 2308.032 MHz, JN47GA, 1662 m. asl, PWR 8W, ERP 100W beaming north
March 23rd, 2017, Update
I had a second try with the MKU 23 G4 this morning and was able to receive the beacon with this gear as well on 2308.032 MHz.
Today I configured the MKU 23 G4, I ordered from Michael in Friedrichshafen to perform a RX test. Via aircraft scatter it was no problem to receive the beacons OZ7IGY in JO55WM over 670 km and OK0EK in JN89VJ over 689 km. The sun noise is at a level of 6 dB.
Beacons regulary receivable on 13 cm (green: TR / blue: AS)
The motivation is high now to configure the TX line as well 😉
During the morning I was able to monitor GB3FM in IO91OF on 1297.050 MHz and G8MBU in IO90IR on 1296.800 MHz. Now in the afternoon F5ZCS in IN87PT on 1296.959 MHz came out of the noise with a strong signal of 549 with fast QSB. It is my 53rd beacon on 23 cm. The weather here in Mainz doesn´t look like tropo: 8/8 cloudy and wind at 40 km/h.
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.
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.
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.
There are good tropo conditions to the east from here for quite a while. I worked OK1MAC on November, 26th with an outstanding signal. OK0EA, SR6LHZ can be monitored constantly. I missed OK0EL on 1296.940, but solved the miracle today. The frequency shifted to .942 and the signal has been covered by DB0AJA. It´s nice to listen, how OK0EL in 526 km distance is battling against nearby DB0AJA,131 km away. As can be seen, DB0AJAs signal is accompanied by several dopplershifted reflections on airplanes.
It is interesting to see, that F5LENs refractive index as well as Hepburns tropo index don´t really illustrate the real conditions today. The conclusions is: Always perform a beacon check before switching off! The result may be surprising.
Josemi, EA2TZ, informed me about the new setup of his beacon EA2TZ/B on 1,296.855 MHz.
The antenna is a stacked 2 x big wheel now, omnidirectional and the power is 10 W. The location is in about 630 m asl in IN93BF88CP, east of Bilbao.
Reports are welcome!