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GB3LD 2m Voice repeater located at the Langthwaite Farm transmitter site situated 2 miles SE of Lancaster.  QRA IO84OA, 470ft ASL.  East of the M6. (Coverage map)

The current version of GB3LD (MkIII) uses a Nokia BSR-150L/N PMR repeater that was originally used in a public utilities communication.

The earlier repeaters that use 2 Pye MX294's, (1 used as a transmitter, 1 as a receiver) have been retained as emergency spares with each one being self contained in their own case.

Output is approx. 12dBW/16W ERP via a Wacom WP641 duplexer and a J-Beam dipole type 7051. The receiver has a DCI-145-2H , 2 Mhz wide bandpass filter in the antenna feed to keep out local pager transmitters.

A three section AFL notch filter has been added to minimize interaction from a PMR VHF high band base station located at the same site.

Repeater control logic is by a custom built PIC circuit with GB3LD specific firmware written by GD4HOZ

Operation

The logic comprises of a custom PIC with software written by GD4HOZ.

For initial access it requires a 1750Hz toneburst of approx. 400msec duration and then the carrier continued for at least 3.5secs to latch the repeater into operation, or a 110.9Hz CTCSS sub audible tone (tone H) on the repeater input frequency of 145.075MHz.

The repeater output frequency is 145.675MHz (R3/RV54). After access the repeater will relay the FM signal for 215secs (4.25m), after which time if the transmission continues it will time out and close down. A pip tone follows dropping of the carrier where the TOT (Time Out Timer) is reset. A second pip follows, but is just for courtesy if stations want to allow extra time for other users calling in. Stations failing to wait for the first pip tone will only have what time was left by the previous station before handing over. Once the repeater is open access can be by carrier only.

The repeater identifies itself at high deviation every 5 minutes during quiet periods including an H suffix for the CTCSS frequency and at low deviation during busy periods. A longer ID with repeater location is given every 25mins when quiet.

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