Eddystone Edometer 902, Wavemeter 696/1 & Modulation Meter 678

Eddystone Test Accessories

Eddystone made a number of small items of test gear for the amateur radio community which are quite hard to find these days. This page describes the units that I have as there is little on the net about them apart from some summary information on the excellent Eddystone User Group web site. Those appearing at auction seem to be snapped up quickly. I would be interested in copies of the instruction leaflets for the 678 and 696, though neither really requires them.

Edometer Model 902

These units are seldom seen and there is little on the internet about them. My Edometer dip oscillator was made in December 1969 according to the serial number LU0950. It is a nice transistor based unit with a trademark Eddystone dial. It operates from a 9V battery and covers from 370Kcs to 115Mcs in 7 ranges with the usual plug in coils. They were supplied in a nice wooden case complete with manual.

It makes a handy source of low power RF for testing vintage equipment, though obviously accuracy is not high. They are quite collectable with Eddystone enthusiasts, but rarely come onto the market. Mine was purchased some years ago at a swapmeet.

A copy of the specification leaflet and manual is available from the BAMA website.

Absorption Wavemeter Model 696/1

This unit is a good deal older than the GDO as its serial number ED0249 dates it to May 1952. It is extremely simple consisting of a meter, a tuning capacitor and diode. It comes in a crackle painted steel case, with a set of 9 plug-in coils and is in working order. It is in good condition apart from is a bit of corrosion on the top and handle.

The unit is the opposite of a GDO in that it measures RF radiation and requires no power supply. Its use is to indicate the approximate frequency of a transmitter and identify any harmonics.

I have found little mention of these units on the net and have no instruction leaflet or frequency charts for each range. These wavemeters are quite rare and again would be of interest mainly to collectors.

Modulation Meter Model 678/S33

This unit is in mint condition and in working order, though the telescopic aerial is a replacement and is missing its original leaflet, though a copy has been obtained. It measures the modulation percentage of an AM transmission and can check for harmonics. It has a set of 6 coils, covering the HF amateur bands of its time (1948-1956). Oddly, the instructions and coil holder only allow for 5 coils, with that for 21MHz omitted. It may have been added later after this band became available. The unit requires no power source and has two germanium diodes. The meter is first set up by turning the rear switch to SET and aligning the needle to the red SET position by varying the power level through changing location or fine tuning the aerial length. Once this is done, the switch is turned to % MOD and the percentage read off. Allowance is made for monitoring the audio quality with phones.

This unit has its original box. The meter is marked AA886 signifying that it was made in Jan 1949 and also Model S33 while the box quotes the hand written stock number as 678. The appearance is similar to that of the 669 S-meter.

These meters are of little practical use today, but are an attractive collector item.

Count since 28/6/07.
Page maintained by Simon Buxton VK2UA . Created: 8/01/06 Updated: 28/4/2011