Thursday, 15 August 2019

A dedicated portable Narrowband/ DATV system for 6cm

Having previously used  parts of my 6cm eme system for portable DATV operation from Titterstone CleeBrown Clee and Cleeve common it was very apparent that the large numbers of interconnecting cables and its lack of waterproofness was a handicap. A dedicated, waterproof system was needed , in the style of the 24 GHz system.

Having not used the Fujitsu amp in the 6cm FMTV system I had an amplifier. I also had a DB6NT preamplifier, however I needed a compact Transverter. The DB6NT mk4 had good performance but cost a lot. I looked around for a second hand one to no avail. In a conversation with G4DDK at Heathrow airport on our way to Frederichshaven we were discussing what we were looking for. He was toying with the idea of a 6cm DB6NT mk4 xverter to upgrade the mk2 in his eme system. I offered to buy his mk2 and this convinced him to go ahead with the plan. Problem solved

Sam shipped the transverter which produced over 200mW (too much for the Fujitsu amp) and could hear the GB3OHM beacon on a patch antenna, time for encapsulation.

I found another waterproof box like the one used on 24 GHz in which the Fujitsu amp just fitted. The Transverter was mounted on a plate on the sidewall of the box, the amplifier was mounted in the base of the box.

To offer some protection and to allow monitoring when masthead mounted a PIC controller was deployed. It monitors  positive and negative volts, current and temperature. It also sequences the antenna change over relay and bias control

Tuesday, 13 August 2019

More 6cm FMTV upgrades

When operating on 6cm FMTV from cleeve common having multiple boxes in the system was a handicap. It meant a lot of cabling had to be changed when swapping bands. What I really needed was to have a display built into the control box, removing the need for an external monitor. Looking on ebayusa I found an unboxed cheap 7" LCD display with the usual selection of HDMI/VGA/Composite inputs that would run off 12V. The quoted dimensions convinced me it would fit in the control box.

When it arrived it worked fine and fitted easily in the control box, as shown below. The controls were mounted on the side of the box. There was still room left in the box; perhaps I can squeeze in the microphone amplifier and audio amplifier so it can have WBFM voice qsos?