Grampian Repeater Group

Introduction

It has not been a pleasant or easy summer for the repeater group and we fully realise that there is some disquiet amongst members regarding our decision to clear the decks and concentrate on the two meter repeaters.   We are a small group with limited capabilities so limiting our efforts to the basics really is necessary if we are to achieve anything at all.

While members seem to understand that AB and BA were not adding much (if anything) to Amateur Radio in the region there has been more reaction to the cancellation of the six meter GX project (see below).  When ETCC and Ofcom grant permission for a repeater they also impose an "on air" date and GRG had received extension to this several times but we had not found the time to progress the project to a point were we could honour this deadline.  To complete the project would have taken time away from GN and NG - both of which are running on very old gear and are at the end of their life. 

The ETCC are now actively policing failed repeaters by recommending enforced second Notice of Variations (withdrawal of Keepers permission to operate) to Ofcom. Voluntarily withdrawal of the application has received a warm response from Ofcom and ETCC and should help the group when we apply for new licenses in the future.

The Plan

We now have a clear plan that is manageable and unencumbered with projects that where taking time to plan but had no hope of being completed.

The first and most urgent job we have to do is rebuilding GB3GN and GB3NG.   Essentially, we will be commissioning two new repeaters from the ground up - this is a big job!

The first step will be to build the equipment cabinets at CME and MH, install overhead cable gantries and prepare the sites for the new Tait assemblies.  These will fit into the 19 inch racks which will also house the logic and cavity filters.   We estimate this will take 8 - 9 man-days (70+ Hours).  Once this is done and documented we will have a far more maintainable system - and tidy sites!  We expect to have this done by December 2009.

Step Two will be installation of the Tait system.  The Tait assemblies will house the new Tait T800 transmitter and receiver, diplexers and power supplies.   Workshop time (at least 20 hours) has to be found to build the Tait system and give them "personality".  If a transmitter were to fail then a new module could be fitted and it will pick up it's operating parameters from the Tait rack making maintenance a breeze!

Step Three will be to run tests on the new units and then install them on site before confirming compliance.  At this point we will have new repeaters running on old Logic.

It is going to take a while before we have the new repeaters are up and running but work is commencing now.

The Second Job is to design and build new Logic.  This is proving to be a complicated job as it is totally dependant on the groups future ambitions. The hardware and software that make up the Logic controller must be capable of running all features of any new build, so the group have spent a great deal of time assessing our remit in an attempt to predict future requirements.   Since NG came online the group has minuted a clear desire to link GN and NG.  So to build Logic we must first have a clear plan for linking.  To this end, we are in the final stages of preparing a proposal to the ETCC to link GB3GN and GB3NG, this has become a bit of a monster and deserves to be broken down a little bit.

ETCC Proposal

Increasingly, the ETCC are asking groups to justify existing repeaters and to prove that new applications serve a need, as they do with business radio. So the first part of our proposal is a demographic survey of the region, using population statistics, call book data and topography. Usage of repeaters has been assessed and clearly indicates that we lack wide area coverage. What we have found is that Grampian is a very large area (over 8,500 KM.Sq) and has a very low population density per kilometre squared - from this we can determine the need for expanded coverage rather than increased capacity. This will form the kernel of our argument to justify.

The second part of our proposal details the techniques that (our Group) could employ to achieve the link between GN and NG. We are asking for permission to link in-band and under one callsign but we also have to investigate the possibility of a UHF link. No other methods of linking could be employed at either site.

The third part of the proposal will be to present a clear plan to the ETCC on future development of a linked system so we can get feedback on what may or may not be possible from a licensing perspective. This will include asking for ETCC's opinion on a third "western" site (possibly near Huntly), Gateway stations to serve gaps in coverage (A Gateway would operate at UHF and serve to lift signals from a black hole onto the 2 meter backbone). While these are conceptual items, the ETCC's opinions can direct our planning and efforts.

As part of developing a long term plan we have approached Radio Clubs and Groups (and are continuing this process) in the service area, some have been forthcoming with advice and input while others have not. The Moray Firth ARS (operators of GB3SS) are very keen to work with GRG and talks between the two groups are commencing.  There is a real possibility that GB3SS could be included in the link in the future but in the meantime it is good to be working with an enthusiastic and forward thinking Radio Club.

We have a very long way to go before we are in a position to link.  Hopefully, the ETCC and Ofcom will respond positively to in-band linking which would leave UHF capability for other purposes (e.g., Gateways, isolated repeaters were need arises, or an overlay network should traffic capacity require it).

In the meantime both stations are operating.  NG has been suffering lock-ups that require a site visit to reset the unit.  GN is continuing to work well. Hopefully both boat anchors will continue to operate while replacements are made!

A site visit was made to Cairn Mon Earn a couple of weeks ago, a number of jobs were completed. The antennae and feeders were analysed for degradation but found to be nominal. Received Signal Level measurements were taken to determine if an in-band link could be established with NG by using various antenna (it can!) and GB3BA was decommissioned and equipment secured at the same time.

A similar site visit was made to Mormond Hill. NG has been suffering intermittent logic failures, it should be possible to use the old BA logic to secure NG until the replacement repeater control logic is ready.

We are planning to visit Cairn Mon Earn very soon to start work on the cabinets and gantries. It may also be possible to install the Six Meter antenna (if completed) at this time. While it may seem contradictory to be thinking about the 6M antenna at this time we intend to install it while other work is carried out, if not installed we may loose the rights to tower space. We then have the option to use it should time and technical resources allow.

To achieve our goals we also need a well ordered, enthusiastic and communicative committee to work on tasks and share the burden.  As the committee undertakes the work on behalf of members it is important we have the right skills incumbent.  While we have lots of offers of help registered we are in desperate need of technical skills, if you can help with engineering please do get in touch!