16-06-2012, 02:43 PM
Just a quick post re: regarding the tunable regen detector coil design,
I used the inductance calculator below as a guide to winding the the prototype coil:
http://www.66pacific.com/calculators/coil_calc.aspx
I think the above is based on the Wheeler formula.
And the nomograph below to work out the tuning range etc:
http://antiqueradios.com/albums/Misc/nomograph.jpg
The min to max tuning capacitance swing in circuit with the tuning coil disconected is 220 pf to 593 pf so I would say that the tuning capacitor has a nominal max value of 375 pf, in the circuit diagrams I have posted I gave the value as 300 pf, this was only a guesstimate as I did not have a capacitance bridge to hand then, the same goes for the twin gang RF tuning cap, when I have time I will check its value on the bridge.
So to re cap the tunable regen detector coil as it stands is 20 turns of .5 mm enamelled copper wire wound over a distance of 36 mm on a 36 mm diam. former tapped at 4 turns from the earthy end, the coupling winding from the mixer anode is 15 turns of .5 mm enamelled copper wire interwound with the tuning coil starting at the hot end of said coil, this and the above stated capacitances tunes from just over 3 Mhz to just below 2 Mhz bearing in mind that it is all still in the lashup stage and there is a fair amount of stray C kicking around. The inductance value of the tuning winding of the coil as measured out of circuit is 12.5 uH it is possible that the coupling winding might be contributing to this figure, the coil turns are not precisely spaced at this stage!
Note: Because of the relatively low L/C ratio of the tank circuit the total capacitance of 590 pf is not represented on the nomograph in the link, that only goes up to 500 pf, however if you extend the capacitance section of the nomograph in the same non linear fashion then all the figures more or less tie up allowing for tolerances wonky windings etc.
The next stage is to order up the three valves that Racal use in their harmonic generator and some valve bases and give the harmonic generator idea a crack. The Regenerodyne receiver as it stands is still in regular use on 40 and 20 meters.
Lawrence.
I used the inductance calculator below as a guide to winding the the prototype coil:
http://www.66pacific.com/calculators/coil_calc.aspx
I think the above is based on the Wheeler formula.
And the nomograph below to work out the tuning range etc:
http://antiqueradios.com/albums/Misc/nomograph.jpg
The min to max tuning capacitance swing in circuit with the tuning coil disconected is 220 pf to 593 pf so I would say that the tuning capacitor has a nominal max value of 375 pf, in the circuit diagrams I have posted I gave the value as 300 pf, this was only a guesstimate as I did not have a capacitance bridge to hand then, the same goes for the twin gang RF tuning cap, when I have time I will check its value on the bridge.
So to re cap the tunable regen detector coil as it stands is 20 turns of .5 mm enamelled copper wire wound over a distance of 36 mm on a 36 mm diam. former tapped at 4 turns from the earthy end, the coupling winding from the mixer anode is 15 turns of .5 mm enamelled copper wire interwound with the tuning coil starting at the hot end of said coil, this and the above stated capacitances tunes from just over 3 Mhz to just below 2 Mhz bearing in mind that it is all still in the lashup stage and there is a fair amount of stray C kicking around. The inductance value of the tuning winding of the coil as measured out of circuit is 12.5 uH it is possible that the coupling winding might be contributing to this figure, the coil turns are not precisely spaced at this stage!
Note: Because of the relatively low L/C ratio of the tank circuit the total capacitance of 590 pf is not represented on the nomograph in the link, that only goes up to 500 pf, however if you extend the capacitance section of the nomograph in the same non linear fashion then all the figures more or less tie up allowing for tolerances wonky windings etc.
The next stage is to order up the three valves that Racal use in their harmonic generator and some valve bases and give the harmonic generator idea a crack. The Regenerodyne receiver as it stands is still in regular use on 40 and 20 meters.
Lawrence.
