Mystery Wireless Set SSF Mk. II

SSF Mk. II

An example of Wireless Set SSF Mk. II was discovered some years ago. At the time nobody could identify the set and its function, and up to now it remained to be a mystery set. Having strong resemblance with Wireless Set No. 18 of which indeed many parts were used, it seems that Wireless Set SSF Mk. II was produced in a small quantity, the nameplate on the transmitter front panel indicates serial number 52. (Go to the Wireless Set No. 18  page for the front panel view of the No. 18 Set)

With the exception of the original No. 18 Set receiver unit, the mechanical and electrical construction and quality of the set has a rather low standard, and it is not surprising that some people consider this set a fake. Still a number of details reveal that the set might have been build in a small series. The manufacturer was M.I.C.O. Co. Ltd in London, investigation to trace this company had no results. Its original function is still not very clear and the model or type name "SSF" does not give anything away.

• The SSF Mk. II is a self contained set, comprising separate receiver, transmitter and mains/vibratory supply unit.
• The set is enclosed in a plywood case, the 30ft wire aerial and accessories stowed in the lid.
• Frequency range 6-9 MHz.
• RF output not known, estimated about 1-2 Watts.
• Two valves are used, an EF50 as crystal oscillator and a 6V6GT RF power amplifier.
• The transmitter is crystal controlled using two switchable type FT-243 crystals.
• System used is CW only, the Morse key is fixed mounted on the front panel.
• Power supply 100-250 V AC mains or 6 V DC.

Detailed internal views of Wireless Set SSF Mk. II

Chassis layout of SSF Mk. II. Note that the receiver section (top) is a virtually unmodified receiver section from Wireless Set No. 18, still having its original 2 V battery valves. Both receiver and transmitter units are fixed to a main front panel on which also the power supply unit is mounted. The transmitter uses the RF tank coil and ancillary parts from a No. 18 Set transmitter unit. A new transmitter chassis and front panel is constructed having similar dimensions as the original No. 18 Set transmitter unit.

	Detailed picture of receiver unit. Apart from the power cable which is connected internally, there are no apparent changes.		Detailed picture of transmitter unit and mains/vibratory power unit front panel section.
	View of mains/vibratory power unit. Note that this unit is constructed from various parts with a few modern components later added.		View of transmitter unit showing  EF50 crystal oscillator (left), 6V6GT RF power amplifier (centre) and original No. 18 Set tank coil (right).

The SSF MK. II set is now in the collection of the Dutch Amateur Radio Museum "Jan Corver". Anyone who may be able to provide more details on this set is kindly asked to contact either myself ( louis@wftw.nl ) or the museum curator Cor Moerman PA0VYL ( ws19@iea.nl ).