Maidenhead Locator Squares

By John Desmond, EI7GL

What is a Locator Square?
If you are new to radio or the VHF bands, you may not be familiar with locator squares. The Earths surface is divided into 324 "fields", each one is 20 degrees (longtitude) by 10 degrees (latitude). eg. AA to RR.
Ireland and most of the UK is in the "IO" field (See Map below). Each field is divided into 100 "Locator Squares", each one is 2 degrees (longtitude) by 1 degree (latitude). For example, all of Ireland is made up of the following squares, IO41,42,43,44, IO51,52,53,54,55, IO61,62,63,64,65, IO74,75.
Each of these "Locator Squares" can be further divided into 576 "Sub-squares". Here in Ireland, these "Sub-Squares" are about 3.5 miles by 3 miles in size (5.5km x 5km). Typical examples of locator squares are IO63TH in Dublin, IO51SV in Cork, IO52QQ in Limerick, etc.

How do I work it out?
Well, if you are not sure about your locator square, the best solution is probably to ask one of the locals. If they live close by, there is a good chance that you are in the same square. Failing that, you need to get a good local map and work out your exact latitude and longtitude.
There are programs available for PC's which will convert your latitude and longtitude into a locator square. If you are on packet, this can be done on your local BBS.

Do I really need to know my locator square?
If you make any sort of long distance contacts on the VHF bands, especially on SSB, you'll probably be asked for your locator square. During all major contests and Sporadic-E openings, locator squares are exchanged.

Historical Background
Back in the 1950's, there was a need among Central European VHF and UHF amateurs for a short way of giving positions in contests. Because the scoring system was based on distance, normally 1 point per kilometre, the QRA locator system was introduced. The system became very popular and amateurs started to use it in all types of contacts, not only in contests.
The problem with this system however was that the locators were repeated. For example, a station in Norway and Sicily could have the same locator. With the advent of Satellite operation, increased 50 MHz usage and longer distances being worked on 2 metres, this started to cause problems.

In April 1980, a meeting of European VHF Managers was held in Maidenhead near London, where it was felt that the time had come to try and find a better system. It was found that the best system was the one proposed by G4ANB, with the modification that the starting point should be shifted to the principal dateline.
In 1982, the Maidenhead Locator system was adopted by IARU Region 3, in 1993 by IARU Region 2 and in April 1984 by IARU Region 1 with a start date of Jan 1st, 1985.

Why do people collect them?
Just as on HF, people chase DXCC Countries, on VHF/UHF, people chase locator squares. As you can imagine, its usually not too hard to work some of the more local squares. As you get more and more however, it gets harder and harder to find new ones and thats the real challenge!!

Just like on HF where people go on expeditions to activate rare DXCC Countries and Islands, on VHF, people go on expeditions to activate rare squares. In the past, groups from the UK, Germany, France, etc have come to Ireland to activate some of the rare EI squares such as IO41, IO42, IO43, IO44, IO55 and IO61. Some Europeans would probably argue that all the squares in EI are rare!!!

This article was first printed in the IRTS Newsletter, Oct 1997.

Back to the index page

The URL of this page is Last Modified : 13th Jan 2001