GB3DR and GB3SD

SOUTH DORSET REPEATER GROUP: ABOUT THE STATIONS

(Updated 10/07/2022 by Mike G0LQI)

In order to use GB3DR and GB3SD you must use a 71.9Hz sub-audible tone.

The Voice Repeater GB3SD

This is the original South Dorset Repeater. It was first switched on at 1200 GMT on the 3rd of July 1976. It is on channel RB14 with it's input on 434.950MHz and output on 433.350MHz. A CTCSS tone of 71.9 Hz must be used for access. The station complies with the 25KHz specification. Separate aerials are used for transmit and receive.

Back in April 2012 the external PA on GB3SD failed and was replaced with an identical spare that Edward, G3VPF purchased at the same time as the original. Unfortunately after only 10 days service that also failed. For a few weeks GB3SD operated at a reduced power of about 10dB down on normal. As both units were very old and the devices used in the PAs were believed to have a limited shelf life it was decided not to attempt an expensive repair but to replace the ageing F496 repeater with modern equipment that does not need the external PA. Chris, G6WHI managed to obtain a couple of Motorola GM340. These are high quality PMR units that are intended for repeater use and are also current equipment.

Chris designed and built the new hardware and software control system and assembled a brand new GB3SD. It has full battery back-up and a number of new features. From the users point of view the new control logic is an improved version of what we have been using on GB3DR for some time, including the Voice ID (see GB3DR information below). One major change is that the new GB3SD, (like GB3DR) now requires a continuous sub-audible tone of 71.9Hz to enable talk through and is not accessible using the old and now largely obsolete 1750Hz tone burst.

GB3SD and GB7SD LOCATION - RIDGEWAY HILL NGR: SY677858 - midway between Weymouth and Dorchester, 3/4 of a mile east of the A354. The site is at approximately 500ft above sea level and the aerials 40/50 ft above average ground level. Both GB3SD and GB7SD use the same aerial for TX and the ERP is approximately 25W.

You can see the official details including a coverage maps here: GB3SD GB3DR

GB7SD is a Digital Voice Repeater. For information about see GB7SD

AERIALS You can see pictures of the aerials here.

In October 2021 new receive antennas (full-wave dipoles) for GB3SD and GB7SD were fitted by Rob G0ECX aided by Kelvin G4TRW. The old antenna connectors were badly corroded due to water ingress and preliminary tests indicate that the new antennas have given an improvement in the receive coverage.

The storms Dudley, Eunice, and Franklin in February 2022 caused significant damage to the Ridgeway tower. Many thanks to Rob G0ECX, John G8IKP, and Kelvin G4TRW for their repair work. More information in the latest newsletter .

The Voice Repeater GB3DR

The Voice Repeater GB3DR has been installed in it's new location on Portland and is now operational (May 2022). Input on 145.1375 MHz and output on 145.7375 MHz. A CTCSS tone of 71.9 Hz must be used for access. It seems that the coverage is as good as expected from the simulations and tests (maps). The new repeater is analogue and Yaesu Fusion compatible. By the way, there are no "pips" between transmissions; when you drop carrier so does the repeater. If you are using an analogue only rig, it's best to use tone squelch, if available, to avoid hearing the Fusion data signal. In this situation, it is important to check your S-meter before calling in analogue mode to avoid possibly blocking a Fusion QSO. The repeater does not work in digital and analogue mode simultaneously; it's one or the other. More information in the May 2022 newsletter.

Historical notes

History of the original GB3DR system.

This was a 2M Repeater that until 2014 was located on the same site as GB3SD. It was switched on at 0900 UTC on Saturday the 13th of August 2005. It is on channel RV59 with it's input on 145.1375MHz and output on 145.7375MHz. A CTCSS tone of 71.9 Hz must be used for access. The station complies with the 12.5KHz specification now adopted as a standard for all 2m repeaters in the UK. A single folded dipole is used for transmit and receive. The power output is approximately 20 Watts ERP.

The original repeater was built by David, G4RQI and uses a Kyodo KG110/BSR150 base station. This Repeater beacons every 5 minutes, sending "GB3DR B". As with GB3SD the letter B inserted after the callsign indicating that we are in CTCSS Region B (71.9Hz). The beacon changes to "GB3DR DORSET" once every 25 minutes following closedown. The first of these is always the fifth beacon after the repeater was last used, i.e. the repeater must be idle for at least 25 minutes so don't expect to hear it often if this repeater is in use! The logic was designed by David Osborn GD4HOZ.

In April 2008 a replacement repeater was installed, still using a Kyodo KG110/BSR150 base station but with a new control logic built by Chris, G6WHI. In order to prevent the transmitter being held on for very long periods if QRM or QRN is present a 5 minute transmit time-out is in operation but otherwise the logic is very 'user friendly'. The repeater beacons every 15 minutes by sending GB3DR in Morse code.

A short Voice ID has been added to the logic as was proposed, discussed and approved at the 2011 AGM. It simply says 'GB3DR.co.uk' and is intended for stations new to the area to know which repeater they are listening to and where to find out about it. The Voice ID is only sent when the repeater is idle and not in use. If you enable tone squelch on your rig you won't hear either the Voice or CW ID when the repeater is idle as they are both sent without the sub-audible tone. Please note however that some older rigs might not have the ability to use tone squelch. To comply with licence regulations the CW ID must be sent when the repeater is in use but this is at a low deviation which does not interfere with QSOs.

INTERNET LINKING OF GB3SD (Echolink is not in operation at the moment - 2023.)
Tests were first conducted in June 2003 but were discontinued after a few weeks.

At the 2005 A7GM, Rob Mott, G0ECX volunteered to provide a link using EchoLink and this was gratefully accepted. On the 25th of November 2005 at 1320 UTC the new facility was switched on and was operational in 'attended mode' most evenings and weekends.

In July 2012 provision of the Echolink facility was taken over by Geoff, G0EVW who was the original Echolink NOV holder for the SDRG. In September 2015 Geoff moved QTH and the facility was one again taken over by Rob, G0ECX. GB3SD-R is Node Number 112689 and is currently operational 24/7 most days.

You can find full details about EchoLink on the web site at www.echolink.org and how to use it on this page www.echolink.org/Help/dtmf_functions.htm Also, by popular request, Rob, G0ECX produced a brief guide to using the link that you can read here echolink guide Please note that the file is in Adobe Acrobat (PDF) format.

PACKET RADIO The two Packet Radio Nodes, WEY2 (GB7SD) and WEY23 (GB7SD-1) were closed down in April 2005 to make way for GB3DR. WEY2 was subsequently moved to a new QRA at the QTH of John, G0PGT. However the supporting Network collapsed and WEY2 (G0PGT-2) was closed permanently in August 2007. Full details can be found here.

DOCUMENTS Various SDRG documents and relevant information sheets can be found here Documents.

THANKS Over the years many individuals have contributed to the success of our group, far to many to name here. The Archive of activities available to read on this site provide some idea of the effort needed to commission and maintain an Amateur Radio Repeater Station. The Group has seen success and occasionally failure in its endeavours but it is important to remember that everyone involved has been a volunteer. The full support of current users is needed to maintain what we have and to continue to provide a facility in the future.