THE HISTORY OF THE BRISTOL 70cms REPEATER GROUP

All the above systems performed well, with only minor outages mainly caused by mains power failures when the hospital was testing their backup generators.

In 1996 we were contacted by the hospital management to inform us that they suspected GB3BS was causing access issues to motor verticals on site, this was a shock, and the group were concerned that we would be asked to vacate site. However working with the Hospital management we investigated the problem, and it was confirmed that GB3BS output was causing the problem on site. This was not due to GB3BS becoming faulty, but as a direct result of the poor design of the receivers used in the Car Keyfob system (for more information on this subject please visit Ofcoms website and search for RAKE). Once we had confirmed that the fault was not with GB3BS we were able to design and implement a solution that the Hospital were happy with

The Solution was a 418MHz Encoded transmitter that operated from a control box in the porters lodge. Pressing a “Stop button” on the front of the box transmitted a signal to GB3BS. The Receiver simply operated a small relay which was inserted into the repeaters Squelch line, thus breaking the line, and forcing the logic to think that the QSO had finished and no further traffic was using the repeater and moving the repeater back into standby mode.

This design was submitted to both ofcom and the Repeater Management Committee (Now the Emerging Technologies Committee) and was approved for use by both parties. We understand our solution has been used by several other repeater groups that suffered the same problems.

It simply offered the Hospital staff a method of forcing GB3BS to stop transmitting for a short period of time (Approx 2.5 Minutes). Because the solution only broke the Squelch line, it did not turn power off to the repeater so no issues to our licence conditions in reference to authorised persons turning on and off the repeater.

This solution stayed in place until 2007. When we were contacted by the new local administrator of the Hospital who informed us that we were now causing problems to the local Doctor’s surgery. We conducted several tests that suggested this new problem was not actually being caused by GB3BS, but obviously with our history of car keyfob problems it was not so easy to convince the hospital.

The Group decided to investigate the feasibility of moving GB3BS to one of the newly allocated wide split. Once we were happy that this route would fix our keyfob problems once and for all (Transmitting a 100W signal directly next to a car that we knew suffered from GB3BS blocking its keyfob on a wide split channel had no affect). Within a couple of day’s of us conducting our last tests we were again contacted by the new hospital manager, who was un aware of the button solution that we had already put into place, she was concerned that with the increased usage of the hospital the problem was becoming more and more disruptive. At the meeting we put forward our plan’s to move, and results of our tests we had been conducting. Thankfully the hospital Manager we were meeting was interested in our pro-active approach to the problems, and our attempts to resolve the issues prior. She also understood that the issues were not with GB3BS but the car alarms.

All was fine, Car alarm problems gone, well, all except one elderly Gent who was convinced that GB3BS was still causing him issues with his old Skoda, a new set of batteries in the keyfob soon had the gent back on the road so to speak.

Although GB3BS was on the bench for such a long time, we did find a few bugs and quirks with the live production version. These we worked with Ken Arc in the USA (Who I must say is one of the most helpful people I have ever spoken to) and have resolved most of the problems. In fact we bought a spare logic unit and spare radio parts so that in the event of failure we have all the parts we would need to get the box back on air quickly. We use the spare logic as a “Sand pit” environment for testing, and have been able to Beta Test software for Ken.

All has been fine with GB3BS until May 2009 when, out of the blue we were served noticed to leave site by South Gloucester Primary Healthcare trust (The new owners of Cossham Hospital). Although this was not un-expected due to our knowledge that Cossham was due to have a £18m refurbishment, it was still a shock

The Group had several meetings which were to plan what we were going to do, if we were going to attempt to re-gain access to Cossham once the refurbishment was complete (Finding a Temporary site while the work was being done), find another site, or just simply turn the box off, walk away and add it to the ever increasing list of repeaters that are going off air.

I am glad to say we went for the second option of finding a new home!

Mark and I drew up battle plans, we did have some restrictions with potential sites due to the very high saturation of UHF repeaters around the Bristol area. Also the lay of the land so to speak had a big influence on potential sites.

It was decided we would create an information pack that we could send to potential sites, both to introduce our selves, but more importantly to make a direct request for help with securing a site for the repeater. We nicked named the pack “The Sales Brochure” as it was trying to sell the group to a potential site.

10 packs were sent directly out to a number of high profile sites, some instantly wrote back stating Health and Safety restraints on accessing their sites. One company offered us some tower space but wanted £5K Plus a year in rent, something we would never be able to afford!

Another site did offer us some space, and we started exploring working with them, at the same time I cold called a few more sites, and finally hit a site manager that was already knowledgeable of Amateur Radio, and what it can bring to the community, we were invited to forward an information pack to him.

Which of course we did. A follow up call was made a week or so later, primarily to ensure delivery of the pack. While speaking to the site manager he requested we contact BANES Raynet Group as they already have a presence on site, and to ensure that our equipment would not interfere with their operations.

I contacted the Area coordinator, and after a site visit, meeting up with Phil from Raynet and the site manager, it was discovered that we as a group could benefit Raynet, and they could benefit us.

We have been continuing to work with the site owners, and at the start of September we received an official invite from Avon Fire & Rescue to use their site at Lansdown.

Further meetings were held to finalise where we could go equipment wise, and we were put in touch with another company that are already onsite. I was put in contact with a lady who was the third party companies senior technician. Working with the 3rd party company it became apparent that they were about to abandon one of the buildings they occupied and they were more than happy to sign the building back to Avon Fire & Rescue, and for us to take over ownership of this building. What was also a surprise was the building came with its own 3KW Generator.

November 24th 2013 the repeater group applied for a N.o.v. to operate a Digital Mobile Radio repeater.  DMR is a true digital mode, providing internet linking,  very narrow bandwidth and two situations QSO on a single channel. On top of this,  this new mode also allows features such as checking a person has their radio switched on and tuned to the same timeslot you are using, send them a simple text message or request a private QSO with them, although the latter is frown on as not being in the spirit of repeaters,  or amateur radio.

On the 20th January 2014 we were issued a NOV by Ofcom  for GB7BS,  we were not expecting such a fast turn around as normally delays are in excess of 7 months. 

Also in January we took delivery of some radio samples from BFDX in china,  these radios are DMR hand portables,  the TD501.  The radios are brilliant for the money, BUT lack CTCSS which make them useless for Ham Radio use. BFDX then sent us some samples of the BFDX TD503 (we had serial 003 and 004 !!) These looked better, and had the CTCSS, and a nice colour display.  BUT again were no good as they had several issues with firmware, something BFDX were not willing to talk to us to find a fix, even after we sent them a full technical breakdown of the faults.  It was decided not to continue working with BFDX as we were not getting anywhere with customer services.

On the 20th April (after a lot of research and conversation between Mark and I) we had a brand new shiney DR3000 repeater in our hands, funded by Mark and I and not the Repeater Group as funds would not allow it. We selected the Motorola DR3000 over the Hytera repeater, not on Technical engineering, but simply on compatablity grounds.

The long and short of it was the Repeater Group had a problem with our main antenna, or its feeder.  what ever happened,  we needed a tower climb to inspect the coax and antenna. With the cost of hire of a crew to climb it made financial sense to simply replace the antenna (the most likely fault).

If needed, we had enough feeder spare to replace the existing run.  On the 21st September the Antenna WAS replaced and a visual inspection of the feeder showed it to be water tight and in good conditio (good old Denso tape :) ) .  See our 2014 newsletter for the full story and autopsy of the antenna. Durring testing a problem was identified and resolved with the circulator and the steel chassis it was mounted to.   Also some fine tuning "Tweaks" were needed to finalise isolation of the two repeaters.

2021/2022 were an interesting couple of years for the Bristol 70cms Repeater Group. We were barred from attending site to do anything but emergency repairs (Thankfully nothing broke!) thanks to the Covid 19 pandemic.  In fact during a number of months in the period 2020 – 2022 we were not even allowed out of our homes!

However it did give us time to investigate solutions to our number one and number two issues we faced with DMR Radio and the Southwest Cluster from the get go.

These were the number of repeaters we could support (limited to 15 by Motorola design) and the fact we could ONLY support Motorola equipment.

Although there is commercial equipment available to resolve the above limitations, the price was a major crippling restriction. This was made worse as Mat ran up a bit of a large phone bill just calling their sales team to find out about the system and its hardware requirements and bottom line cost.

Thankfully the FreeDMR team helped us get a system up and running. There were a few problems on the way with our first virtual server and or the early release of the modified FreeDMR which resulted in us having to purchase a second hand physical server and the FreeDMR team re-writing large parts of the server system.

The 1^st of October 2022 was our official launch of the SWC FreeDMR server. We had to change GB7BS from being the Master repeater to a ‘Peer’. Not long after other cluster members moved over to.  Within two weeks everyone was on the new network system.

The new network (Described else where on this site under GB7BS) maintained the cluster as per its original design, but also through dial on demand (DoD) it opened up new features of external cluster communications.

February 2023 saw a small tweak to our system. Driven by the need to make the server 99.98% available as well as a need to move the hardware maintenance and upgrade issues away from  the group onto someone else’s shoulder whilst also driving down our energy consumption and operating costs, the Bristol 70cms repeater group invested in moving away from our physical server over to VSP system or PaaS to give it another name. Most know it as being a cloud based system.

As of the 25^th Feb, we are running both physical and virtual servers to give other cluster members a chance to plan site visits to re-program the repeater to start using the VSP solution all at the same time maintaining a view into the system as a for our users via the live dashboards.

Once all repeater groups have moved over, then we will shut down the physical server