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 by Neal McEwen, K5RW


by Colin Waters, G3TSS

Extracts from "Morsum Magnificat"

Copyright © Morsum Magnificat

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The Eddystone S689 Bug Key holds a unique position. It is, with one small but notable exception (the Autoplex of 1932), the only Morse key of semi-automatic design manufactured in Great Britain and sold in significant numbers. Sadly, the key was never to attain a high degree of popularity, but its construction and appearance are enough to give it a great deal of character.


By the late 1940's, the Birmingham based Stratton and Company Ltd, later to become known as Eddystone Radio, had built up a fine reputation for the manufacture of high class communication receivers and accessories. But it was not until late 1947 that initial work was begun on the development of a semi-automatic Morse key.

Mechanically, it was to follow the by then well proven principle of Martin's 1904 Vibroplex Original design, but in a style in keeping with the traditional Eddystone use of die castings. After careful testing of shapes and materials for the various components, a number of pre-production models were assembled and evaluated by the radio amateurs working for the company, one of these pre-production models being displayed at the Amateur Radio Exhibition in November 1947.

The first production run was made in early 1948, when a batch of 250 keys was assembled. Unfortunately, sales proved poor although a second production run, again of 250, was planned for late 1948. It is almost certain, however, that only 100 or so of this batch were actually assembled.

Although the S689 was undoubtedly liked by many users, sales of the key continued to be poor. Eventually the company, foreseeing no future improvement in its popularity, decided to offer the remaining assembled keys, and some unassembled components, as a job lot to Birmingham's Chas. H. Young Amateur Radio Company, who placed the S689 on special offer and continued selling them until stocks were exhausted.


The key is almost entirely constructed of untreated brass and die cast aluminum, the base and cover being finished in the then almost obligatory black crackle or wrinkle paint. Despite the base and cover being aluminum, the weight of 2 lb. 14 oz. (1.304 kg) is adequate for most operators, although fixing holes are provided in the base.

The majority of adjustments are carried out in a similar manner to most other conventional single lever semi-automatic keys. The exception to this is the dot return coil spring, the tension of which is not independently adjustable. This spring is held by the left-hand control arm stop screw and the tension can only be varied to a small degree by setting of both the left-hand and the right-hand stop screws.

The main pivot pin bearings consist of a single ball for each bearing, only the lower of which is adjustable. Two speed weights are provided, one large and one small, and use of either or both can give a wide variation in dot speed. The arm is damped in the rest position by a rubber grommet on the back stop. This is remarkably effective in use, although the rubber does become brittle with age.

Unlike the majority of American designs, where the lever arm, lever rod, and main spring are riveted together, the control arm of the S689 can be completely dismantled down to individual components.


Why the Eddystone S689 proved to be so unpopular is unclear. Whilst admitting that the general feel of the key does fall somewhat short of the many excellent American high speed semi-automatics, the key does not suffer from any major defect in design. The combination of a number of its shortcomings may, however, have been a contributory factor to its unpopularity.

The exact number of S689s produced is unknown, but it seems clear that the figure did not exceed 500. No serial plates were fitted to the keys. A number is stamped on a connecting strip on the underside of the base, the keys in the author's possession being numbered AG1995 and EZ0829.

Unfortunately, records do not exist concerning the sequence of these numbers, and the author has been unable to contact anyone who knows their significance. He would like to receive correspondence (Address: 1 Chantry Estate, Corbridge, Northumberland, NE45 5JH) from any readers of MM who have used, or still use, the Eddystone S689.


The author is grateful for the help given by the following in the preparation of this article: Chris Pettit, Managing Director of Eddystone Radio Ltd., Chas. H. Young., Bill Cooke, former Chief Engineer and Managing Director of Eddystone Radio Ltd, now retired after 50 years with the company, who provided all the dates and figures of production.

(From Morsum Magnificat #13, Autumn 1989)


Since my article on the Eddystone Bug appeared in MM13, a number of readers have been in touch with me passing on impressions, histories and serial numbers of their own S689's. What has emerged is that there are more keys without a number on the underside connecting strip than was first realized. It is possible these keys form part of the remainder of the second production run which was eventually assembled for the deal with Chas. H. Young.

Recent correspondence with Cliff Hartles, who was employed by Stratton & Co. at the time, suggests the total number of S689's specifically assembled under this deal, together with the 100 or so distributed normally, may have finally completed the second batch of 250 keys. Cliff Hartles also confirms that the number stamped on the underside connecting strip was, in fact, a month/year code and production number of the type used on all major Eddystone products of that period. After further correspondence with Bill Cooke the sequence of this date code has finally been resolved.

Space does not permit a description of the date code used but I will be pleased to provide the date for other readers' S689's if they send me the numbers on their keys. (Send s.a.e. Ed.)

Colin Waters G3TSS, 1 Chantry Estate, Corbridge, Northumberland, NE45 5JH, England.

(From Morsum Magnificat #15, Spring 1990) 

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Neal McEwen,