Practical Wireless August 1964, Transistor Tuner/Converter

 Practical Wireless Transistor Tuner/Converter

 

The Transistor Tuner/Converter described in the August 1964 issue was a one, two or up to five transistor frequency converter

It was in effect the front end of a normal radio set, with a traditional Denco Blue coil front end RF tuned circuit , tuned by VC1 

This fed a to the Base of the first OC171 (Tr1) and amplified and the signal appeared at the collector

and tuned again the the Denco Yellow coil with VC2

the output of this yellow coil is fed to base of the next OC171 (Tr2)

If you note Tr2 is also wired with a third Denco coil this time a white oscillator wired in a Self oscillating mixer circuit

Here's a clue, instead if changing the base current to make the transistor oscillate, The Output from the collector is fed back to the emitter to change that 

This mixer oscillator OC171 (Tr2) runs at 1.6 Mhz and the base of this transistor is fed with the received signal the frequency the converter is tuned to, the two mix and hey presto the out put appears

this can be fed directly to a Medium wave radio tuned to the converters output

As with all mixers a number of other mix frequencies appear at the out put car has to be used to tune the Medium wave radio to the correct one 

One set back of this set is the coils fitted were 3T range about 1.6Mhz to 5.5Mhz to cover the Long wave all the way to 10 mtrs the builder needed to purchase 5 ranges of coils and it cost a lot of money.

N.B

Denco made two types of Oscillator a White 1.6Mhs +- and Red 465Khz to run with each coil set

except there was no specifically made 1.6 Mhz Osc coil for the lower 1T range 

Denco made a range of IF transformers again for 1.6Mhs +- and 465Khz 

yes after changing a OC171 (leaky ) to a spare AF116 I had it works well 

now part of my collection