Proposed ATV Repeater
to cover the Bournemouth/Poole Area.

Chuck Hobson (CH) G0MDK, Chairman of FRARS, welcomed all the guests. He then introduced John Fell (JF) G0API as chairman for the meeting.

JF thanked CH and FRARS for the use of the club facilities for the meeting.

John Saunders (JS) M1BAI intervened to welcome and thank, three SCART members for their support in coming: Alan G1APD (Secretary), John M0JTT (Treasurer) and Eric G3KXE.

JF introduced himself by giving some of his background within the South Coast Beacon and Repeater Group (SCR&BG). In particular he spoke of his involvement in setting up and running 2 local FM voice repeaters, GB3SC on 2m in 1980 and GB3SZ on 70cm in 1984. SCR&BG also set up and run the microwave beacons that have recently been refurbished and moved from the Purbecks to Bell Hill.

JF requested those present to sign lists to be passed round, so that names email addresses etc would be known of those interested in the project proposals, also to know of what support may be available.

JF introduced the other three of the project team i.e. JS, Tony Ault G3KTU (TA) and Norman Goddard G3UXR (NG).

Discussion followed indicating that there is support from the four local amateur radio clubs: ‘Flights’, Poole, Christchurch and Bournemouth. Representatives of these clubs present said this would probably be confirmed in writing and hopefully by a donation (JS for BRS and Poole in their absence, Bev G7PNW for Christchurch and JF for Flights).

JF disclosed the identity of the proposed site and informed us of possible/ probable facilities. In summary:

• Location is Alderney Hospital in the BH12 district (NGR SZ042946)
• The antenna mast, triangular in section, is used for data communications with other hospitals in the area. This is well above our 23cms (i.e. 30-40GHz region) so unlikely to cause mutual problems. Slight concern was raised that there might be problems (on 2m) with pager signals in the area.
• The repeater antennas would be near the top at about 100 feet above ground. Access is by a permanent ladder up the outside face of the mast (no hoops!) and there is a platform at the top.
• There is a solid garage style, secure building next to the foot of the mast for the communication equipment, supplied with mains power.
• There is a possibility of redundant coax feeds (LDF4-50) from the antenna area to the building becoming available to us. This is approximately 120 feet.
• The authorities’ communications manager for the site is G4GHP, a keen member of the South Coast Repeater and Beacon Group (unfortunately not present as he is on holiday in USA).
• The site, mast and existing antennas were clearly visible.

It is clear that me must consider some ‘payback’ to the site owners. JF suggested that this could be in the provision of emergency video linking. Bev confirmed that RAYNET might now have an interest in this.

Also the payback type role to the RSGB and Amateurs is important by way of using otherwise sparse amateur frequencies (including the other bands likely to be used in future expansions).

TA showed a topography map on laptop to illustrate the good position of the proposed site.

Mike G8LES and Roy G8CKN, travelling from central Hampshire through the storms, were welcomed and thanked for coming.

JF suggested, given the chance to choose, GB3SQ was one of the last call signs available in the GB3S series used in this area.

Dave G8AJN asked about trials. These would probably not start until the latter part of June depending on the availability of G4GHP, coax and aerial riggers etc.

During a discussion of RF power, JF told of the availability of a 4 brick amp (80W out) that could give more than 25W erp from a test Alford slot fed via LDF4-50.

Roy and others discussed filter possibilities linked with TX-RX antenna separation advantages. It was noted that additional TX filtering may be needed to satisfy local 23cm narrow band users.

A wide discussion arose on the possible ways of repeater control, ranging from basic facilities using PIC, use of proven software on an Amiga, through to sophisticated systems controlled by a PC. (Paul G7EYT donated an Amiga at the meeting). TA suggested start simple and expand with sophistication with the experience of time.

Mike G8LES suggested we look out for Farnell 5 volt 40A PSUs at rallies; these can be tweaked to say 6.5v and used in series to fulfil the high power requirements.

Roy G8CKN told us of his experiences in connection with obtaining a licence. It appears that the procedure has improved recently and it is realistically possible that a licence could be obtained within 6 months.

Mike warned us, especially with a high power amp in use, to watch out for RF getting on the DC supply leads and, of course, employ good practice like the use of screened boxes.

A show of hands was requested to see what proportion present where in favour of continuing with the repeater proposal. Everyone, 18 at that time, were in favour with no abstentions or dissenters.

At the completion of the main business of the open meeting, Mike came to the white board and gave us a most useful and interesting guide to the many options, problems and solutions available in the planning of a new ATV repeater. Much technical input was also supplied by Roy from the floor, with a steady flow of questions from the audience to steer the speakers. A few of the many subjects covered were:

Flat plate antenna (bowtie) mounting, phasing etc

Preamp design, construction &use (2 per box with ~20dBgain & ~1dB NF, use of twinax cable/ sockets)

Use of 2^nd AF channel for passing permission to link

PTT on TX (via DTMF) to kill o/p during DX receiving conditions

Problem using 567 line sync detector if black vertical line on video, producing apparent 32KHz (use video clamp/ cutter)

Need for audio sound squelch as repeater sound not switched

(I could fill a book with the information given!)