10-05-2012, 11:30 AM
Just trying out my new laptop:
As previously stated the work on the anode feedback regen det stage has more or less come to an end, so time for a go at a Hartley regen det (cathode tap) for this I used a 6SH7 pentode which I had spare, regen is controled by a screen grid pot, the same coupling arrangement from the mixer was used and remained unchanged (choke/capacitor coupling) After removing the previous windings I wound another coil on that same 1.5" former winding 20 turns over a distance of approx 1.5" (approx 10 uh) this spacing enables enough room select and solder on the cathode tap, the best results were obtained at a tap 1 turn from the chassis end.
It tunes the designed 3 to 3.5 mhz frequency range ok, at the maximum frequency the capacitive element of the tuned circuit is approx 170 pf so the L/C ratio is still quite low which is part of the design requirement.
Regeneration is very smooth throught it's advancement, when in full oscillation there is no pulling when tuning the RF in to the mixer and virtually none when advancing the regen control from the onset of oscillation to the point of full oscillation, when the regen control is further advanced there is a small pulling effect which I guesstimate is around 200 to 400 cycles (based on listening to a CW & SSBtransmissions) and a drop in gain which is to be expected.
All in all a good result, out of the two methods the Hartley one has the edge for me.
It is to be noted though that all regen designs suffer from overload when presented with a very strong signal, to that end the final design will have a simple flick switch attenuator in the aerial input circuit.
I gave it a good test on 40 and 20 meters last night and it works very well. (Copied a Ham from Boston US)
If I can get my new laptop to communicate with the scanner/printer etc I will post up a couple of diagrams of the story so far.
Lawrence.
As previously stated the work on the anode feedback regen det stage has more or less come to an end, so time for a go at a Hartley regen det (cathode tap) for this I used a 6SH7 pentode which I had spare, regen is controled by a screen grid pot, the same coupling arrangement from the mixer was used and remained unchanged (choke/capacitor coupling) After removing the previous windings I wound another coil on that same 1.5" former winding 20 turns over a distance of approx 1.5" (approx 10 uh) this spacing enables enough room select and solder on the cathode tap, the best results were obtained at a tap 1 turn from the chassis end.
It tunes the designed 3 to 3.5 mhz frequency range ok, at the maximum frequency the capacitive element of the tuned circuit is approx 170 pf so the L/C ratio is still quite low which is part of the design requirement.
Regeneration is very smooth throught it's advancement, when in full oscillation there is no pulling when tuning the RF in to the mixer and virtually none when advancing the regen control from the onset of oscillation to the point of full oscillation, when the regen control is further advanced there is a small pulling effect which I guesstimate is around 200 to 400 cycles (based on listening to a CW & SSBtransmissions) and a drop in gain which is to be expected.
All in all a good result, out of the two methods the Hartley one has the edge for me.
It is to be noted though that all regen designs suffer from overload when presented with a very strong signal, to that end the final design will have a simple flick switch attenuator in the aerial input circuit.
I gave it a good test on 40 and 20 meters last night and it works very well. (Copied a Ham from Boston US)
If I can get my new laptop to communicate with the scanner/printer etc I will post up a couple of diagrams of the story so far.
Lawrence.
