DATV Contest 2022-08-21 LX/PE1ITR JO30BA
On August 21, 2022 I was QRV on 2m in the Dutch VHF DATV contest from Luxembourg. This has resulted in a new best DX for a number of stations. I was also happy to improve my own best DATV DX at 2m with a two-way connection over a distance of 336 km.
I left home at 06:30 UTC with a car full of radio gear. The first QSO was 10:02 UTC in the log. I had selected a location near Hosingen in the square JO30BA.
The station consisted of a 9 el dk7zb yagi on a 6m high mast. The transmitter was a Portsdown + limesdr mini + filter + SSPA. Output was 200 watts.
The receiver had the following parts. Pre-map, receiver to 9 MHz. MF Filter of 400 kHz and again an upconverter to 201 MHz so that the Minitiouner/Minitione software could receive and decode the signal.
Normally I also have a spectrum display in parallel, but I forgot my RTL-SDR. I found out that I can also hear the DVB signal in SSB audio. In this way the antenna could be perfectly aligned or I could estimate when it will decode.
I have worked 7 stations. Of these 4 two-way QSO's and 3 one-way QSO's. I've seen more stations that they could receive me. I was impressed with my receiver's performance. All QSO are made at 144.600 MHz with DVB-S SR 125k FEC 1/2 mode. Except in the QSO with PA3BYV I switched to DVB-S SR 66k FEC 2/3. Then This two-way QSO succeeded.
The QSOs above 300 km were special. I worked PA3BYV (JO32NX) 336km and PA3AOD (JO32NV) 325km.
All QSO had a lot of QSB on the signal. They were typical aircraft scatter signals. The signals were quite strong in the peaks, but the peaks were just too short for the receiver to synchronize and produce an image. But sometimes with a little patience it worked.
I also brought a 5 elements antenna for 51.7 MHz and a converter for the reception. I also only had receptions. Although I could receive beacons, I didn't see any DATV stations.
Good take-off towards North. 9 elements DK7ZB yagi on a 6m mast.
From top to bottom: Laptop, left the audio interface to the 144 MHz transceiver with the rotor control underneath.
On the right the minitioner receiver with MF flilter and upconverter. Then below that the Portsdown 2019 DVB tranmitter.
And below the Portsdown my homemade 2m tranceiver of which I use the receiver for DATV.
For this contest I had paid special attention to the MF filter. I use the frontend and VFO of my transceiver for DATV. This allows fine tuning with the VFO. The MF of the transceiver is at 9 MHz. I split the 9 MHz signal after the mixer. One tap goes to the SSB/CW filters the other tap goes to a 9 MHz MF filter for the DATV signals. Then to an upconverter for the Minitiouner. I think this setup helps me to decode the more difficult DATV signals. And it shows.
The block diagram below shows the receiver setup
In this photo the amplifier, 9 MHz bandpass filter and upconverter to the minitiouner can be recognized from the block diagram.
The Premap has a noise figure of approximately 1 dB. This is the most important part. The next important part is the 400 kHz wide band filter at 9 MHz in the MF section.
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