Jara's Single 1T4 Radio

Jara's Single 1T4 Radio

Jara's Single 1T4 Radio

Jara's Single 1T4 Radio

Jara's Single 1T4 Radio

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Hi Dave,

You can see , that my receiver is very simple. I use rotating coil for positive feedback. (I found it also in my hamshack...)

Antenna coil is 2...3 turns for Low - Z antenna (coax cable) and cca 10 turns for Hi - Z antenna (cca 35m longwire) But you must test it!. There is no RC circuit to g1. I tested it and receiver work better without it (if you use low anode voltage: cca 9-18V. If you use higher voltage, you can use capacitor cca 330p to LC circuit and resistor 820k from g1 to ground).

I use two parallel J310 and two 1N4001 for heating voltage. (You must select two J310 for current cca 50...60mA!) It is better than if you need two other voltage for receiver. Heating voltage is 1,39V now. Other idea is 78L02 voltage regulator and a resistor.

Receiver does not have big selectivity or sensitivity (I think that 6F35 or 6F31 or one triode from ECC86 will be better also with low anode voltage but the filament current is not low) but it is good for nearby stations. Feedback with coil has big range and it is better than other systems (if you use low anode voltage).

But my tuning coil is not very good: it has tiny wire, and I think that sensitivity and selectivity will be better with good HF litz.

Jara


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