GB3LES is a 13cm Microwave Beacon.

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Tx Freq
10w (erp)
Alford slot radiating at 160 degrees
Geoff G3TQF
Off Air


This is a 2watt transmitter, F2 modulated with callsign and QRA locator; ZM24J.

The NBFM transmitter comprises a 0.5watt Wood & Douglas source on 386.826 MHz which is filtered and then amplified to an output of approximately 10watts. A retuned Microwave Modules 1296 Varactor multiplier is then used to triple the input and after filtering drives a varactor doubler.

The doubler, which is a VHF Comms design by DF7QF, produces, after further filtering, a final output power of approximately 2watts. A 25m length of FHJ50-2 coaxial cable is used to feed the RF to the antenna which is an Alford slot, the performance details of which may found in the Microwave Handbook chapters 14.29, 15.26.

The antenna is contained in a 'radome' fashioned from 50mm diameter of gray plastic drainpipe.

The transmitter and keyer were built by G4LRT. The Alford slot was built by G3JVL and G3WDG.


#1 M0VSE 2022-11-03 10:59
GB3LES was taken off-air on 6th October 2022 as it was found to be operating at significantly reduced power. Once the fault is located and fixed, it will be returned to service