A Beginner's Guide to Four Metres
(c) Ross G6GVI

What's so special about 4m?

The fact that it is not in widespread use around the world (especially not in the USA and Japan) means that there is practically no commercially-built Amateur equipment for the band. Consequently, everyone using it uses either home-made or modified equipment. This means that 4m operators generally have more of an interest in the experimental aspects of the hobby than some of their counterparts on other VHF bands.
4m is also particularly good for mobile operating: the fading is not as severe as on 2m or 70cm, and the aerial efficiency is better than on 6m.
And finally, Four is known as "the friendly band": try it for yourself and find out why!

Getting on Four with ex-PMR gear

In the British Isles, a considerable amount of de-comissioned VHF low band (68-88MHz) PMR equipment has found its way into the hands of Amateurs and been converted for use on 4m. Since Autumn 2002, over one thousand Ascom SE550s have been "recycled" in this way.
Although modern PMR gear uses synthesized oscillators, there are still a number of crystal-controlled sets still in use - just two or three channels is all that is required to be effective on 4m FM.
70.450MHz is now widely used as the FM calling channel, with 70.475, 70.425 and 70.400 being the most popular working channels. More recent PMR gear has 12.5kHz channels, and these are starting to be used for FM operation too.
In some areas, there is still a little AM operation centered around 70.26MHz, but in Eire, FM is now becoming popular in this part of the band (due to their narrower allocation).

It should be remembered that mobile PMR transmitters were not intended for continuous transmissions of several minutes duration, so the long "overs" used by some stations may cause the sets to over-heat! Some sets have a built-in time-out which cuts off the transmission after a certain period. It is also worth considering modifying the transmitter to reduce the output power, or to have a switchable low-power setting to reduce over-heating.

It is not uncommon for PMR equipment to have a pre-set squelch circuit (rather than an externally variable control) and for this to be set at a level well above the receiver noise-floor. This may cause difficulty on the Amateur band, where signal levels are often weaker than in the PMR environment. It is thus possible for a receiver with a badly-adjusted squelch to miss signals which would be easily workable with the squelch defeated. A station using one of these transceivers would therefore miss answers to their "CQ" calls, and may unwittingly block the calling channel, or cause QRM to an existing QSO. It is therefore important to adjust the pre-set squelch to a suitable level, or use a squelch-defeat switch to listen for weaker signals.

Most stations on FM use simple vertical aerials, either a quarter-wave or half-wave.

Finding someone to talk to

The People Database contains a list of hundreds of stations known to be active on the band, and is searchable by QTH or locator: this is a good way to find who's on Four in your area. There is also a list of regional nets.
Not for nothing is Four known as "The Friendly Band". I find that I get many more CQ calls answered on 4m than on 2m or 70cm: perhaps the fact that there are fewer of us makes 4m operators more willing to come back to a call? Having said that, it may sometimes be a useful tactic to put out a call on 2m "looking for contacts on 4m" - this may catalyse some activity on the band.

One plea at this point: please don't block the calling channel with your QSO. If you have a synthesized rig, there really is no excuse for not QSY-ing. If a lack of crystals mean that you can't find a clear channel, then please be considerate if you stay on 70.45: keep the overs short, and listen carefully between them for other stations trying to call in.

For up-to-the-minute news of what's happening on the band, check out the forum and newsgroup for details. These can also be used to seek information, (such as how to alter the squelch setting on a particular set), and for sale or wanted items.

Building up activity

Here are a few suggestions on ways in which you may be able to increase 4m activity in your area (they worked for me):
Put out CQ calls on 70.45 at every opportunity, and monitor this channel whenever you can for other calls. If you hear a station call on Four while you're busy in QSO on another band, call them back to tell them you've heard them, and ask them if they can stand by until you're free;
Mention your activity on 4m in QSOs on other bands, and when you meet up with a new station who may be in range, ask them if they have any 4m capability. I sometimes make obvious use of 4m as a "talkback" channel when in a net on 2m;
If you can find another local 4m enthusiast, try to set up a regular sked, and encourage other stations you work to join in. Some clubs have a 4m activity night once a week, or once a fortnight.
As an example, I've seen a five-fold increase in 4m activity in the Bristol Channel area through 2003 (outstripping that of other VHF bands), most of which is down to the tireless efforts of two or three keen stations.

Further afield

As well as being a super "local natter" band, 4m can sometimes exhibit enhanced propagation: tropospheric ducting is not as common as on 2m or 70cm, but Sporadic-E can often be heard during the summer months. This used to be a nuisance, since it brought in loads of QRM from broadcast stations in Eastern Europe. However, in recent years, most of the broadcasters have moved into Band II, allowing Amateur operation to take over.
Slovenia was the first to appear on Four (back in 1996), and UK stations new to 4m FM were often astonished to hear strong signals from Ivan S51DI and his compatriots coming through from "the sunny side of the Alps"! Recently 4m allocations have also been made available to Amateurs in the Faroes, Denmark, Greenland and Croatia, so we can expect to hear a lot more DX on Four from now on.

As with the other VHF bands, greater range can be achieved by switching from omnidirectional vertical aerials to horizontal beams. Some stations seem to think that all FM operation must be vertically polarised, but there's no reason why this should be so!
Further improvements in range can be achieved by using narrowband modes, such as SSB, CW, PSK, etc. Most of the SSB and CW activity takes place on 4m on Sunday mornings, especially on days when the RSGB run a contest event. These contests on 4m are rather different to those on other VHF bands, with stations often exchanging conversation as well as the obligatory numbers, and since the events are all-mode, FM stations can join in too.

Try it for yourself

I've had an immense amount of enjoyment from 4m since 1992, and made well over two thousand contacts on the band (nearly eight hundred of them during 2003!). But don't take my word for it, try it out for yourself...