Microwave Amateur Radio Station, Waterbeach. 8km North Of Cambridge JO02cg

To Contact me:

Skype johng4bao

ON4KST Microwave Chat

E-mail john at g4bao dot com



About me 

My Equipment 


Related links

Downloads and Bodger's Guides





GB3CAM 24GHz beacon

Allocated Frequency - 24048.870MHz GPSDO locked

 Keying sequence is:
Even numbered minutes. "GB3CAM IO92WI" in JT4G followed by "GB3CAM" in Morse 

Odd numbered minutes. Unmodulated carrier until (minute +32 sec) then "GB3CAM" in Morse.

Carrier                          24048.8700000MHz
Keyup tone for CW       24048.8696000MHz

JT4 tones
Tone 0 24048.8697980MHz
Tone 1  24048.8701130MHz
Tone 2  24048.8704280MHz
Tone 3  24048.8707430MHz

Output power - 250mW

Location - West Cambridgeshire,   IO92wi,   33m ASL

Antenna - Horizontally polarised slotted waveguide at 31m AGL clover leaf pattern

QTF approx 10dBi to SE/NW, 6 dBi SW/NW.    


The idea for adding a 24GHz beacon to GB3CAM came out of some musings on the success of the 10GHz beacon. Mainly while cycling to work, in August 2007 and in a subsequent series of emails betwen myself, Bernie G4HJW and Sam G4DDK. 

The idea came together very quickly as I already had a 12GHz multiplier, and Chris GW4DGU was keen to try out his design for a new ultra- stable  oscillator known as the "DISTAW". (pron. dish-tau) . Apparently distaw is a Welsh adjective meaning quiet or silent.

So from concept to on air took just 13 months. It would have been 10 months if I'd not blown up two PAs in the process, but that's another story!

The upgrade in May 2010 with GPS locking made it the first 24GHz beacon in the world to run JT4G (unless you know better)


GB3CAM Supporters
G4HJW - GB3CAM concept. Design, build and test of 3cm beacon.

John,  G4BAO  -  24GHz beacon design build and test.

Chris, GW4DGU - 24GHz beacon reference oscillator.

Paul, G4AJE - Beacon site


John G8ACE, Brian G4NNS, Andy G4JNT, - the Reverse DDS team   

Ian, G8KQW, Brian G4NNS - 24GHz antenna build and test

Phil, G8MLA - 24GHz PA

Murray, G6JYB - Ofcom Liaison.

Tom, G4TWJ - original 24GHz PA

Sam, G4DDK - second 24GHz PA and moral support when things began to fail!

Alan G3NYP -Connectors

Dave WW2R/G4FRE  - original keyer  

Ian G4AKD - Trial site for 3cm beacon

The UK Microwave Group for financial support.

The shutdown operators. G4HJW, G4BAO, G4BEL, M0BXT


































































This Web Page Created with PageBreeze Free Website Builder