The UK Six Metre Repeater Network
Iain Philipps - May 1997
Go to for further details.


The GB3AM 50MHz TeleWave / ProComm DuplexerThe GB3AM 50MHz TeleWave / ProComm Duplexer

Doubtless many readers will be aware that proposals from a number of groups have been ‘in the pipeline’ for a long while now to introduce FM voice repeaters as a facility within the UK It is now expected that the first of these will be licensed and available for use during May 1997.

Hopefully these devices will generate a lot more interest in six metre operating among those who are not fortunate enough to live on a mountain top and sport a vast antenna farm. As you all know, when the conditions are right, a couple of Watts into a dipole (even indoors) can bring remarkable results. As we also know, here at the very trough of the current cycle, it can be exceedingly difficult to get an answer to plaintive ‘CQ’ calls, even running quite high power. And what of the Novice licensee, restricted to a very modest effective radiated power under all circumstances?

Well, the humble FM repeater - ancient technology by today’s standards, I’ll grant you - may just be the answer. There is no doubt about it, a well-designed and operated repeater station provides a focal point on any band. Being new to the UK, it was uncertain for a few years whether the authorities would ever agree to them for six metres. Thankfully (in my humble opinion, at least) common sense has prevailed. And rather than just slipping into the same ‘40 kHz per repeater’ utilisation of bandwidth, the six metre repeater groups now have the opportunity to demonstrate that - at the very least - only 50% of the bandwidth normally occupied by a repeater can work effectively, with the TX and RX channels being compressed to 10kHz each.

So the UK now has an IARU agreed band plan for repeaters on Six which is incompatible with the rest of the region. Or is it? Firstly, the allocated frequencies are as follows:

Channel Input Output
R50-1 51.220 50.720
R50-3 51.240 50.740
R50-5 51.260 50.760
R50-6 51.270 50.770
R50-7 51.280 50.780
R50-8 51.290 50.790
R50-9 51.300 50.800
R50-10 51.310 50.810
R50-11 51.320 50.820
R50-12 51.330 50.830
R50-13 51.340 50.840
R50-14 51.350 50.850
R50-15 51.360 50.860
R50-16 51.370 50.870
R50-17 51.380 50.880

Note that this is overlaid on the Region 1 band plan, which allocates 51.210 MHz - 51.390 MHz as repeater inputs. The "missing" frequencies are designed to avoid those currently allocated to packet radio in the UK

The current applications are for the following systems:

Call Chan. CTCSS QTH
GB3AE R50-1 94.8 IO71OQ
GB3AM R50-13 77.0 IO91QP
GB3EF R50-1 110.9 JO02PB
GB3FX R50-10 82.5 IO91OF
GB3HX R50-9 82.5 IO93BP
GB3UM R50-3 77.0 IO92IQ
GB3PD R50-14 71.9 IO90KT
GB3PX R50-7 77.0 IO92XA
GB3RR R50-11 71.9 IO93JA
GB3SX R50-8 103.5 IO83WA
GB3UK R50-6 82.5 IO83RO
GB3WX R50-12 77.0 IO80VX

As a matter of policy, all UK six metre repeaters use omni-directional vertical polarisation, and are accessible only to those with the correct CTCSS (sub audible) tone. Unlike repeaters on other bands, the tone is not used simply as an initial access method; in order to have your input signal relayed, you must transmit the correct CTCSS tone continuously.

It is important to note that with the 10 kHz spacing system employed, you must set your deviation to a maximum of 2.5 kHz, otherwise your transmitted audio will be "chopped" on speech peaks. For IC706 users, a reasonable stab at setting up for 10 kHz repeater operation is to select the "FM Narrow" setting, and adjust the microphone gain to "2".

For those with receivers expecting 20 kHz signals, the recovered audio will be at a lower level than would otherwise be expected. You must either replace the IF filters with narrow ones, or increase the AF gain - nothing else will work.

A few of the listed repeaters are currently built, tested and working, and these are the systems that are expected to be operational during May. They are GB3AM, GB3EF, GB3PX and GB3RR. It is also possible that GB3PD and GB3WX can be brought into service around the beginning of June, with a projected time scale for all of the others being brought into service by the end of August.

Early indications are that under ‘flat band’ conditions, the range for mobile stations is around 10% larger than that for similarly equipped stations on two metres - due mainly to the reduced ‘flutter’. Recent tests between the GB3AM site and G0VDE (JO02PF) have shown that signals are of reasonable quality over that 145 km path. The distant station, however, is sited in a "quiet" RF location, so it is expected that this will be the exception, rather than the norm.

Building and configuring a 50MHz repeater has been (for me) a rather interesting technical challenge, requiring significant investment in both time and money, but it is just possible that this will pay immense dividends in attracting new blood to the band.

Clearly the topic of six metre repeaters is more diverse than can be done justice in a couple of pages; if there is sufficient demand (requests to the Editor, please), then there is a great deal more to be said. Other than that, you may contact the author for further details.

To return to the archives page click here