Status

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

Keeper: Iain Philipps, G0RDI

Information last updated: 06 November 1997

Coverage: See high resolution map

Location

2 KM South of Amersham, Buckinghamshire

National Grid Reference: SU 957955

IARU Locator: IO91QP

Antenna Configuration

Base of Tower: 165 m AMSL

Antenna height: 210 m AMSL (35 m AGL)

Antenna: End Fed Vertical Dipole ( 0 dBd gain)

Single Antenna working used

Radiation: Omnidirectional

Repeater Equipment

Transmitter: Modified Tait T336 + Microwave Modules Amplifier

Output Power: 12 dBW ERP (but licensed for 14 dBW ERP)

Receiver: Modified Tait T335

Sensitivity: Better than 0.15 uV / 12 dB SINAD

Logic: G0RDI, based on NHRC/2

Duplexer: Procom/Telewave 6 cavities (3 in RX leg, 3 in TX leg)

RX isolated by > 102 dB from TX,

TX isolated by > 102 dB from RX

Frequencies & Access Control

Input (repeater receiver) frequency: 51.340 MHz

Output (repeater transmitter) frequency: 50.840 MHz

Access by CTCSS 77.0 Hz (UK tone "C") at peak deviation 250 Hz

Continuous CTCSS tone needed for talk-through.

Controller Characteristics

Initial Access - transmit on input frequency with correct CTCSS tone

After initial successful access repeater sends Morse "K" at 18 WPM

If no further access made, repeater waits for 10 s and closes down.

End of user transmission over indicated by 100 mS "beep"

Wait for "beep" before reaccessing

Talkthrough time limit - 3 minutes

Timeout indication - inhibits talkthrough, sends "TO" in Morse and then disables repeater transmitter. Reaccess only allowed when input clear. Repeater sends Morse "TO" when input clear and reaccess possible.

Morse Ident "DE GB3AM" sent every 4 minutes at 875 Hz deviation

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:- 06 November 1997