19-04-2012, 07:07 PM
http://www.qsl.net/wd4nka/TEXTS/REGENf~1.HTM
Hello again Al, above and below is a link to the design I want to base my Regenerodyne project on, within that link you can access the circuit and other relavent info. I must stress that the circuit is only a basis for what I have in mind ie: I will not be following it to the letter and probably will be using different valves.
The idea is to build a little SW Receiver that isn't a full blown comms. set but is better than the average one or two valve Regen. I have set a valve count to 4 or 5 envelopes max for the receiver, solid state signal diodes are allowed, the power supply will be a seperate unit all together. So that's the brief.
As can be seen from the circuit in the link the RF stage tunes from 7 to 14.5 mhz and there are three switched xtals in the osc. these could be chosen for say 7, 10 & 14 mhz coverage of the receiver (3 amature bands) taking into account that the xtal frequencies are chosen to give a center IF frequency in the receiver of approx 3.25 mhz relative to the band selected, note that in the circuit only the secondary of the IF transformer is tuned, the approx range of the tuned secondary is +/- 250 khz centered on 3.25 mhz.
My idea is to expand on the stability of using a xtal osc. but at the same time reduce the number of xtals needed for different bands, so I was thinking maybe just one xtal (maybe two) in the osc. but the osc. producing good harmonics, as it would say in a well designed xtal marker circuit.
I have not yet worked out the frequency of the xtal needed but to take an instance, if it was 1 mhz and the osc. circuit it was used in produced good usable harmonics up to say 33 mhz (the harmonic generator), then it might be possible to cover all the SW band with the one xtal. The idea would be to have another variable tuned circuit in the output from the osc (before it goes to the mixer) this tuned circuit would be able to "peak" the harmonic chosen for a particular part of the band that you would want to receive ie: if using a 1 mhz xtal the osc. the osc. feed to the mixer can be increased in i mhz increments, you could maybe go one stage further and have 2 selectable xtals in the osc. one 500 khz above the other, the harmonic "peak" tuned circuit as previously mentioned would still probably cover the new set of frequencies introduduced by adding the other xtal, the added advantage of a second (offset) xtal is that you can then have the IF either above or below Fs thus giving more options and control in reducing a particular strong station image problem. So in the above Idea...3 to 4 switched tunable RF ranges to cover say 1 to 30 mhz, 3 to 4 switched ranges to tune the harmonic required from the osc.
one tunable IF control, regen control, vol. control and maybe a 2 position xtal switch.
Can you see where I am coming from with this? I will try and do a block diagram and post it up tonight.
http://www.qsl.net/wd4nka/TEXTS/REGENf~1.HTM
Lawrence.
Hello again Al, above and below is a link to the design I want to base my Regenerodyne project on, within that link you can access the circuit and other relavent info. I must stress that the circuit is only a basis for what I have in mind ie: I will not be following it to the letter and probably will be using different valves.
The idea is to build a little SW Receiver that isn't a full blown comms. set but is better than the average one or two valve Regen. I have set a valve count to 4 or 5 envelopes max for the receiver, solid state signal diodes are allowed, the power supply will be a seperate unit all together. So that's the brief.
As can be seen from the circuit in the link the RF stage tunes from 7 to 14.5 mhz and there are three switched xtals in the osc. these could be chosen for say 7, 10 & 14 mhz coverage of the receiver (3 amature bands) taking into account that the xtal frequencies are chosen to give a center IF frequency in the receiver of approx 3.25 mhz relative to the band selected, note that in the circuit only the secondary of the IF transformer is tuned, the approx range of the tuned secondary is +/- 250 khz centered on 3.25 mhz.
My idea is to expand on the stability of using a xtal osc. but at the same time reduce the number of xtals needed for different bands, so I was thinking maybe just one xtal (maybe two) in the osc. but the osc. producing good harmonics, as it would say in a well designed xtal marker circuit.
I have not yet worked out the frequency of the xtal needed but to take an instance, if it was 1 mhz and the osc. circuit it was used in produced good usable harmonics up to say 33 mhz (the harmonic generator), then it might be possible to cover all the SW band with the one xtal. The idea would be to have another variable tuned circuit in the output from the osc (before it goes to the mixer) this tuned circuit would be able to "peak" the harmonic chosen for a particular part of the band that you would want to receive ie: if using a 1 mhz xtal the osc. the osc. feed to the mixer can be increased in i mhz increments, you could maybe go one stage further and have 2 selectable xtals in the osc. one 500 khz above the other, the harmonic "peak" tuned circuit as previously mentioned would still probably cover the new set of frequencies introduduced by adding the other xtal, the added advantage of a second (offset) xtal is that you can then have the IF either above or below Fs thus giving more options and control in reducing a particular strong station image problem. So in the above Idea...3 to 4 switched tunable RF ranges to cover say 1 to 30 mhz, 3 to 4 switched ranges to tune the harmonic required from the osc.
one tunable IF control, regen control, vol. control and maybe a 2 position xtal switch.
Can you see where I am coming from with this? I will try and do a block diagram and post it up tonight.
http://www.qsl.net/wd4nka/TEXTS/REGENf~1.HTM
Lawrence.
