
The
PW Sudden
is an NE602 based direct conversion receiver published in the Practical Wireless
of March 1991. It uses Toko KANKseries coils, which are not that easy to get, so I
got hold of some surplus transformers which I managed to characterise and rewind.
Basically, I measured the inductance and then counted the windings, did the math. 30.5 turns gave an inductance of 8uH, and since #turns = 100 * sqrt(L/Al), that gives Al = 86uH/100T. The original part number is TLK680661 which is a Panasonic part used in TVs, apparently. I originally used both halves of the variable capacitor, but that gives a very wide coverage. I ended up using one section as well as a 50pF padding capacitor. Tuning is from just under 14.000 to around 14.430 MHz. 
hits since 20150227. 
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