19-05-2012, 06:10 PM
Did a bit more on this today, pinched a 6SA7 pentagrid from my beloved Hallicrafters SX28 and tried it out in the regen as the mixer, works very well, signal to G3 and Sig. Gen to G1, it needs the full output from the Sig. Gen. though (200 mv) Also used the other half of the 6SC7 double triode (other half is used as an audio amp) I plumbed in this spare half as a crude RF amp, tuned grid input & choke with capacitor output coupled to the mixer tuned grid input circuit by a few turns over the cold end of it's tuning coil.
Amazingly this RF amp lash up works up to 15 mhz but from then on it becomes a transmitter......No doubt due to all the long wires I used to connect it up with.
Managed to gang the two RF tuned coils I and got them to track ok.
Changed the mixer to regen coupling from coil to choke/capacitor, this gives a lot more gain, a relatively large value coupling capacitor can be used (200 pf) as there is only the anode capacitance and the choke self capacitance to take into account at the mixer output, I will do some listening tests tonight and tommorow if the band conditions are favorable.
Lawrence.
Amazingly this RF amp lash up works up to 15 mhz but from then on it becomes a transmitter......No doubt due to all the long wires I used to connect it up with.
Managed to gang the two RF tuned coils I and got them to track ok.
Changed the mixer to regen coupling from coil to choke/capacitor, this gives a lot more gain, a relatively large value coupling capacitor can be used (200 pf) as there is only the anode capacitance and the choke self capacitance to take into account at the mixer output, I will do some listening tests tonight and tommorow if the band conditions are favorable.
Lawrence.
