GB3XX, Daventry Repeater.

Antennas and Cavities
 

The Receive Antenna
This is on top of the mast with a clear view all around; the received signal goes through 2 cavities both
of which are tuned as band pass filters.
 
The Transmit Antenna
This is on the north west side of the mast about 10 feet below the receive, it's 2 cavities are tuned to
notch out the transmitters carrier on the receive channel.
 
Radios and Logic Control
There have been 4 XX repeaters at the same site XX-3 and XX-4 are still in use and we swap between
them to maintain continuous service.

XX-1 (up to 1995)

? A Yaesu FT 726 fitted with a Sat board to allow full duplex operation.
? For in-band operations, which is how it was used, two 70Cms Modules are required.
? Usually the 726 cannot usually have two of the same module fitted so the one used for transmit was modified
to appear to be tuned to 144.925 where it was actually on 434.925.
? The logic was the old original GB3US logic.
 
XX-2 (Main repeater 1995 – 1999, backup till 2001)

? The same FT 726 as XX-1
? The main processor for the Logic was an 80552 micro-controller programmed to be almost identical to the
old GB2US logic.
? The only addition was that CTCSS was added using a professional module CDS VM.
 
XX-3 (Main repeater 1999 – 2004, now the backup)

? Both the Transmitter and Receiver are Storno CQM 5663 with the channel selectors replaced by fixed links.
Both of these were donated by G8GVV. Thanks Phil.
? The logic is controlled by an OOPIC (www.oopic.com) programmed by G6EGO
? The software has a number of on-air configurable options including
o Ident after QSO On/Off
o Engineering Beacon mode On/Off
o Processor Diagnostic Messages (Morse)
o Remote Shutdown
o Send Locator after 6th Ident.
o Send ‘C’ or ‘T’ as the ‘over’ code to let people know how it was accessed Ctcss or Toneburst.
? The interface between the logic and the radios is home made by G6EGO.
? The circuits were developed using the CAD program ‘Windows Electronic Workbench’ from Interactive Image Technologies, donated by their local distributor.
? XX also has a new vented and Fan Cooled cabinet. The cabinet is mounted on legs that keep it three feet off the ground. This saves the engineering team sitting on the wet concrete while doing repairs. Built by G4SFB, Thanks Dave.
? The logic and interface circuit for XX-3 will be rebuilt next time it is out-of-service to make it plug-in swappable with the XX-4 logic.
 

XX-3

XX-4 (Jan 2004 onwards, now the main repeater)
? The radio part of the repeater is a professional Kyodo 450 donated by NorCall in Northampton.
Thanks to M1FJB, Sam for tuning it.
? The logic is another OOPIC design by G6EGO.
? The logic now runs on a ‘bus’ based system where other modules can be added, for example;
o Speech synthesis.
o Real time speaking clock.
o Cassette Tape Log control.
? The logic to Radio interface is mounted inside the radio.
 

XX-4

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