29-06-2012, 03:30 PM
Hi Al, when I build this thing properly I will incorporate a 1 Mhz osc that can be offset by 10 Khz or so and also incorporate a harmonic amp/generator stage, I am pretty sure this could be done in one valve envelope, I will also make provision for an external osc input, I am reasonably happy with the trial HG idea as it stands at the moment despite its limitations in its present form, those limitations being:
1) Harmonic selectivity reduces as frequency increases, obvious I know but I am mentioning it anyway.
2) Harmonic output falls the futher away from the fundamental you go.
A possible solution which I have yet to investigate is feed the output of the harmonic generator into a diode clipper to fix the amplitude of the harmonics then use that to excite another tuned tank which might or might not need another amp to feed it, if it does need another amp then this whole HG section could be contained in two valve envelopes which was the original brief, ganging two tank circuits should not present any major problems.
This might help compensate for the effects described in 1 & 2 above.
This whole HG idea has been a product of a little bit of theoretical thinking coupled with a lot of try it and see, and as mentioned in other posts I have received all continents bar one (SA) so far as amature transmissions go so I guess I musn't complain.
I will try and draw a circuit diagram of the latest offering as tested and get it posted on the forum.
Lawrence.
1) Harmonic selectivity reduces as frequency increases, obvious I know but I am mentioning it anyway.
2) Harmonic output falls the futher away from the fundamental you go.
A possible solution which I have yet to investigate is feed the output of the harmonic generator into a diode clipper to fix the amplitude of the harmonics then use that to excite another tuned tank which might or might not need another amp to feed it, if it does need another amp then this whole HG section could be contained in two valve envelopes which was the original brief, ganging two tank circuits should not present any major problems.
This might help compensate for the effects described in 1 & 2 above.
This whole HG idea has been a product of a little bit of theoretical thinking coupled with a lot of try it and see, and as mentioned in other posts I have received all continents bar one (SA) so far as amature transmissions go so I guess I musn't complain.
I will try and draw a circuit diagram of the latest offering as tested and get it posted on the forum.
Lawrence.
