The making off a re-gen receiver
After building a number off double conversion receivers, I decided to build a re-gen three band receiver.
On the bands 20 40 80 meters.
The output transformer is suitable for the valve 6V6 5600 ohms to 2000 ohms headphone.
I used the valve EC92 instead I had to make a adaptor, because originally I wanted to to use 6J5 but has less amplification, the valve 6J5 will work.
As detector I used KTW61, this valve came out R1155 receiver and works well.
The end stage is 6V6.
Amplification and sensitivity is excellent but selectivity could be improved.
Again I was not impressed, I was not happy with the noise level from KTW61, I had a feeling it could be improved upon.
So I made an other design with different valves.
I didn't have to change much.( see Schematic)
One 100pF capacitor on the other side off L2 keeps the HF out off the grid from 6V6.
R3 is changed to 150k.
Also I placed a resistor from 22k to R2 and R3, this brings the voltage down to 43 volts on the connection R3 R1.
And change C6 to 0,022uF plus C3 to 56pF.
To avoid on the PA peak voltage, I added a switch in the high voltage to protect the capacitors C7 and C8.
Now you can turn the radio on without causing damage, and now you have a standby switch to operate.
It took some experimenting with resistors and capacitors to get it absolutely right.
The noise level is now acceptable, weak signals you can hear them clearly.
The receiver now, performs very well, and is very stable.
Constructing power transformer and output transformer.
The parts and coils 20 40 80 meters.
I used pill boxes 30mm to wind the coils.
Coil data:
80M 33uH 34 turns tap on 11 turns 0.4mm.
40M 10 uH 18.5 turns tap on 7 turns 1mm.
20M 4.5 uH 13 turns tap on 4 turns 1mm.
To get the frequency desired on the 20M you have to adjust the spacing off the coil.
You can use other forms to make the coils.
provided that they have the same diameter.
I constructed the receiver with a switch, you can work with coils that you can plug in.
Fitting valve sockets the capacitor and reduction drive.
The potentiometers.
The band switch tuning capacitors and coils.
Fitting the output transformer and soldering parts together.
Fitting the tuning scale
Mounting the tuning capacitors and coils, and the power transformer
View from the top
I fitted the KWT61 to front behind the screen to avoid hum from the power transformer.
All the wiring done on top and bottom.
The schematics.
The end result.