A fascinating arrangement of coils: their inter-connections and their inductance values.
At first I suspected the usual TRF arrangement: aerial coupling, reaction and two coils in series, the greater inductance value coil being short-circuited for M.W.; both in series for L.W. But the inter-connections of the three coils rules that out - and so does the inductance values. To tune the whole of the L.W. broadcast band with a 500 pF variable condenser requires either a coil with a lot more inductance than is available in total on that coil, or a very large parallel capacitor - which will make the tuning horribly non-linear.
However, if the inductance values are temporarily discounted for now, the inter-connections of the three coils looks very much like the Reinartz circuit arrangement was intended - but I'm not sure where the single 220 µH winding features in this coil's particular use - possibly for band-switching, since it is stated as a dual-range coil. And that's all very good and clever, etc., but it still doesn't change the fact that the inductance values simply still 'don't fit' M.W. and L.W. broadcast bands when used with a standard 500 pF variable.
Perhaps it was intended for M.W. and S.W.
All said - must go - boxes to unpack & a new workshop to build.
Al. / Jan. 18, '15 //
Edited Jan. 19, '15 by Al. //
At first I suspected the usual TRF arrangement: aerial coupling, reaction and two coils in series, the greater inductance value coil being short-circuited for M.W.; both in series for L.W. But the inter-connections of the three coils rules that out - and so does the inductance values. To tune the whole of the L.W. broadcast band with a 500 pF variable condenser requires either a coil with a lot more inductance than is available in total on that coil, or a very large parallel capacitor - which will make the tuning horribly non-linear.
However, if the inductance values are temporarily discounted for now, the inter-connections of the three coils looks very much like the Reinartz circuit arrangement was intended - but I'm not sure where the single 220 µH winding features in this coil's particular use - possibly for band-switching, since it is stated as a dual-range coil. And that's all very good and clever, etc., but it still doesn't change the fact that the inductance values simply still 'don't fit' M.W. and L.W. broadcast bands when used with a standard 500 pF variable.
Perhaps it was intended for M.W. and S.W.
All said - must go - boxes to unpack & a new workshop to build.
Al. / Jan. 18, '15 //
Edited Jan. 19, '15 by Al. //
