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Mobile ATV in Snowdonia By Brian Davies GW4KAZ
  For some time I had been thinking of establishing a mobile / portable ATV station. This would be an ideal situation for getting me out of the house and the TV studio during the summer months. The repeaters mentioned are run by the Arfon Repeater Group.

 My ATV studio is located in the roof space of the house, so itís more like a sauna than a studio on a nice sunny day! We, here in North Wales, have some spectacular scenery. For ATV work this can produce fantastic pictures for transmission. On the other hand, the 1000 meters plus of rock known as Snowdonia, which for many years I have considered an obstruction, when trying to work stations on VHF to the south, now works to my advantage. It offers me access to sites, which are well elevated and have fantastic scenery. The equipment I use is shown in the photograph. 
Above Llanberis and the foothills of Snowdon
www.gb3arg.org.uk

     During this summer I have tested out three sites, all at about 200 meters a.s.l. to send pictures through GB3TM on our Tuesday night net. The equipment I use is shown in the photograph. This includes: A Maspro RX converted to 12v working and a small 5 in. mono TV as the monitor. A Worthing ATV TX, running about 800mW output, which is built into a 2U high x 19 in. rack chassis, where I have also included a home brew 950 to 1750 MHz RX, made from old Sat TV receivers. This RX may come in handy as a second RX for 10 GHz, with a suitable LNB.
Maspro RX, with the 5 in. TV monitor
and 19in. rack chassis

I have two cameras in use, one was marketed some years ago as a fun video camera for children, it is a mono camera with sound output. As you can see it is well anchored down under the headrest!  The second is a colour camera, which was purchased as a basic unit, and fitted into a plastic box. (Not shown in the pictures) All the above items work well from the 12v DC system in the car.

The antenna is a home brew Alford Slot mounted on an 8 in. dia. mag-mount. The antenna is housed in a suitable plastic tube and is connected to the RX and TX through a home-brew duplexer, so that I can use one antenna for RX and TX simultaneously. The duplexer was another experiment following on from my article in CQTV 190 , it works well in this situation. However, I have tested the duplexer on my home station with the TX running 12 W output and it works, but is a little sensitive on adjustment. No major problems though, even the RX pre-amp was not overloaded.
I set up the above equipment on the passenger seat, with the antenna on the roof. I have operated mobile with some success, sending video through GB3TM.The antenna stays firmly in place even at 40 mph! The distance from the two sites to GB3TM is about 20 miles, (Sites 1 & 2) and, if I pick my spot, I can get P5 signals through GB3TM. The other site is about 36 miles away (Site 3) and here I struggle to get a P2. However, with just 800 mW output, it shows that with "a little more coal on the fire" a P5 is more than possible. What is also interesting about site 3, is that I can receive and access both GB3TM and GB3DW, so there are possibilities here for the experimentation of linking the two repeaters in-band, by using sufficient band-pass filtering and some small beam antennas. Site 3.Maybe next summer! Watch this space.

Location of mobile sites plus GB3GW & GB3TM


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Garth RF Filters
Arfon Repeater Group
Amateur TV
contact brian (at) bvdavies.org.uk

  

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