24-06-2012, 08:48 PM
Had another go at this today, first thing was to tidy it all up a bit to reduce all the stray C, that turned out ok.
It is clear that the signal from the donor Xtal marker in the B4O D does not have enough output so what's to do...
I switched the B40 to band one and pulled the mixer valve removed the screening plate covering the acsess to the turret tuner, I then slid a 100pf between contacts 2 and 3 on the oscillator section and screwed the osc coil down to 1 Mhz for use as a fundemental frequency generator, this was then fed from pin 3 of the mixer valve socket in the B40 into a harmonic amp and the anode tank was duly tuned, with the 10th harmonic tuned and fed to the mixer of the regenerodyne the reception on 40 meters was very good so I changed the tank coil and re tuned for the 17th harmonic to test the reception on 20 meters, the good news is that there was a contest on so plenty of transmissions and also I had plenty of output from the tank on the 17th harmonic to drive the mixer, reception was very good.
The bad news is the Q of the harmonic selector tank starts to fall off somewhat at the 17th and when tuning the tunable regen det, products of one of the lower harmonics were coming through even though the tank was tuned to the 17th, bit of a blow but kind of expected, back on a positive note, feeding the sig gen into the harmonic amp and tuning the harmonic selector tank to increase the sig gens output produced very good results. It might be posssible to have a double tuned tank to increase the overall tank selectivity for the harmonic selection, next time I have a spare day I might give that a go.
Lawrence.
It is clear that the signal from the donor Xtal marker in the B4O D does not have enough output so what's to do...
I switched the B40 to band one and pulled the mixer valve removed the screening plate covering the acsess to the turret tuner, I then slid a 100pf between contacts 2 and 3 on the oscillator section and screwed the osc coil down to 1 Mhz for use as a fundemental frequency generator, this was then fed from pin 3 of the mixer valve socket in the B40 into a harmonic amp and the anode tank was duly tuned, with the 10th harmonic tuned and fed to the mixer of the regenerodyne the reception on 40 meters was very good so I changed the tank coil and re tuned for the 17th harmonic to test the reception on 20 meters, the good news is that there was a contest on so plenty of transmissions and also I had plenty of output from the tank on the 17th harmonic to drive the mixer, reception was very good.
The bad news is the Q of the harmonic selector tank starts to fall off somewhat at the 17th and when tuning the tunable regen det, products of one of the lower harmonics were coming through even though the tank was tuned to the 17th, bit of a blow but kind of expected, back on a positive note, feeding the sig gen into the harmonic amp and tuning the harmonic selector tank to increase the sig gens output produced very good results. It might be posssible to have a double tuned tank to increase the overall tank selectivity for the harmonic selection, next time I have a spare day I might give that a go.
Lawrence.
