G7NPL,

Much as I really dislike even the thought of modding Eddystone sets these days (especially non-reversible mods that hack the chassis etc), many years ago in my youthful enthusiasm I undertook an ‘extreme’ modding exercise on my unfortunate EC10mk1.  Mods included: xtal calibrator, NBFM detector (Foster Seeley disc), noise squelch, ‘Burns’ 2-Metre converter (using 4 to 6 MHz tuneable IF), fine tuning (including external fine tuning), S-Meter with amp, stabilized psu, AF239 RF (TR1), FET mixer stage (2N3819 circuit in place of TR2), Q-multiplier (with peak/null, and variable notch depth & bandwidth), pump-diode fast/slow amplified AGC, external muting, and a product detector (the latter may be of interest to you).  I hunted down the circuit for the product detector and a few other of these mods and have attached a pdf compilation of these – apologies for the poor quality but these scraps of paper were found stuffed into my original 1964 EC10mk1 manual, complete with all my circuit board layouts etc.  I recall that the product detector was one of the first mods I did to the set and it worked very well, making SSB resolution much better.  If you don’t mind further modding, I would suggest that switchable fast/slow AGC is also added as well as fine tuning is you have a mk1 set to further improve SSB signal handling.  Also, improved stabilisation of the psu improves frequency stability quite a bit – needed for receiving SSB at higher frequencies.

The product detector (page 1 of attached) can be added with relatively little modification to the original circuitry (see page 3 of attached) and could be easily reversed if you ever want to revert the set back to original condition.  It used a couple of matched  ‘period’ OC44 PNP germanium transistors (though type is probably not too critical) and was constructed on veroboard (this was before I started to etch my own boards, so was likely constructed around 1973).  I would have taken some photos for you, but the set is in my mother-in-law’s garage in the UK (I live in Canada) – probably the best place for it poor thing..…. RIP.  Maybe one day I will rescue it and reverse as many mods as I can.

Hope this helps a bit.

73’s

Gerry G8GUH

Hi the eddystone ec10 has bfo that is ok for cw but it is very hard
the use on ssb dos eney member know how to modifi the bfo for ssb.has
eney member don this mod thanks qaxbgb g7npl.