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SITE LAST UPDATED ON: Thursday, 12/03/2015 @ 01:37 UTC.

DVU37 - Output 439.4625 MHz - Input 430.4625 MHz.

GB7JB is funded solely by donations from its' users and supporters. There is no club or group to join and no annual membership fee. We rely totally on your good will.

The system is located in South Wiltshire, in IO81vc, co-sited with GB3JB, and provides coverage across South Wiltshire, South Somerset and North Dorset.

GB7JB is a 70 cm Digital voice repeater, based on DMR TDMA Mototrbo technology.
It provides TWO simultaneous channels. One is for local chatting, whilst the other is connected to the Regional Cluster / Network.

Repeater Hardware

GB7JB Hardware

The principle system for GB7JB is of course the repeater itself.  This is a Motorola DR3000, the specification for which is shown below.

The TX and RX sockets are connected to a normal wide bandwidth duplexer, which is all that is necessary to allow successful operation, at the 9 Mhz split, between the input and output frequencies.

In the image above, you will see a typical duplexer lying on top of the repeater unit.

You will also note that, in the bottom left had of the unit, there is a mains power supply, this of course is basically redundant at the "JB" site, but it does enable safe connection to the high current and fully regulated 13.8 volt dc feed, since the entire site is run from a 24 volt battery system, which is float charged by a 35v / 45v Solar Power system.
Basic System Schematic

The output of the duplexer is then connected to the antenna, via a lightning arrestor and 50 feet of LRM400 coax.

The system is single antenna working, with a 4 stacked dipole array, similar to the image shown below.

This page is still under construction, and it's content and layout may well change without notice and in due course..