Status

Brought into service at 16:00 GMT, 1st May 1997

Keeper: Bill Rothwell, G0VDE

Information last updated: 12th May 1997

Coverage: See high resolution map

Location

BT Laboratories Radio Tower, Martlesham Heath, Near Ipswich, Suffolk, IP5 7RE.

National Grid Reference: TM 250447

IARU Locator: JO02PB

Antenna Configuration

Base of Tower: 30 m AMSL

Antenna height: 80 m AMSL (50 m AGL)

Antenna: Vertical Dipole ( 0 dBd gain)

Single Antenna working used

Radiation: Omnidirectional

Repeater Equipment

Transmitter: Kenwood TS60S

Output Power: 12 dBW ERP

Receiver: Kenwood TS60S

Sensitivity: Better than 0.2 uV / 12 dB SINAD

Logic: G8CUL

Duplexer: Procom/Telewave 5 cavities (3 in RX leg, 2 in TX leg)

RX isolated by >108 dB from TX,

TX isolated by > 88 dB from RX

Frequencies & Access Control

Input (repeater receiver) frequency: 51.220 MHz

Output (repeater transmitter) frequency: 50.720 MHz

Access by CTCSS 110.9 Hz (UK tone "H") at peak deviation 250 Hz

Continuous CTCSS tone needed for talk-through.

Controller Characteristics

Initial Access - 2 seconds audio (and CTCSS of course!!)

After initial successful access repeater sends K.

If no further access made, repeater sends its callsign "GB3EF" after a 10 s pause and closes down.

End of user transmission over indicated by Morse "K"

Wait until K has finished before reaccessing

Talkthrough time limit - 4 minutes

Timeout indication - inhibits talkthrough, sends 10 'pips' at 1 second intervals and closes. Reaccess only allowed when input clear. Repeater sends Morse "OK" when input clear and reaccess possible.

Morse Ident "GB3EF" sent every 4 minutes at 1.1 kHz deviation

Morse Ident "GB3EF" sent every 4 minutes during talkthrough at 400 Hz deviation

Locator details and location 'BT Labs' given in morse every 12th Ident

If incorrect (or no) CTCSS supplied, no access allowed

If CTCSS drops out or changes during talkthrough, talkthrough audio is inhibited and the repeater closedown process is invoked


Places to go from here:
Back to the GB3AM Home Page; Latest available information about UK 6M repeaters from my update page; Some pictures taken on site at GB3AM; An insight into the hardware in use at GB3AM; the history of GB3AM.

Disclaimer: This page is the way it is. There's nothing you can do about it

Webmaster: Iain Philipps - G0RDI

Note: This page is Copyright (c) 1997 Iain Philipps. If you must copy information from it, you are free to do so PROVIDED you acknowledge the source. A much better thing to do is provide a link to it!

Last updated:- 12 May 1997