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|John Bruce McCreath||Posted - 18 October 2013 13:41 |
I've just completed a major update to my web site, where in addition to my xtal radios, you can find some of my other electrical interests. Here's the link
73, J.B., VE3EAR
|krystallo||Posted - 25 October 2013 23:4 |
Cool stuff !
|Garry Nichols||Posted - 28 October 2013 17:49 |
I took a look too. Very nice! Thank you.
|Garry Nichols||Posted - 31 October 2013 8:7 |
Do you happen to have a circuit diagram for the bandpass set and the Tuggle tuner with variometer?
How is the variometer used in the Tuggle? I guess that that would provide two means of adjusting the coupling to the antenna/ground (vs. one with only a dual variable)?
|John Bruce McCreath||Posted - 31 October 2013 15:54 |
|John Bruce McCreath||Posted - 31 October 2013 16:9 |
I don't have schematics for any of my radios, as they tend to evolve over weeks or months as I try out ideas of my own and/or I "borrow" ideas I get here on Rap 'n Tap or from TheRadioBoard. Lots of clip leads are used until I finally get a set that's working as best as I can make it, then I build up a tidier finished version.
The Bandpass Radio is loosely based on Steve's TK-2 set with a pair of contra-wound tank coils for the Antenna and Detector sections. I use a small toroid transformer in the cold leads of the tanks to loosely couple them. The high-low switch selects a parallel or series connection of the tank coils with a 100 kHz. overlap around 1100 kHz.
The Tuggle set is simply that....one section of the varicap is paralleled with the two stator windings of the variocoupler, while the other section is in the ground lead. The moving coil is untuned and it allows for varying the coupling of the detector circuit as required by conditions.
All of my radios use an external audio module which is based on Ben Tongue's BT-Ultimatch circuit, using Hammond and Bogen transformers.
73, J.B., VE3EAR
|Garry Nichols||Posted - 1 November 2013 10:34 |
OK, J.B., thanks! I had been thinking that the variocoupler was involved with antenna coupling. I did not think of detector coupling.
The Tuggle single stage set is quite a good performer and I have used one quite a few times. But it often suffers from SW interference for me. I always tap the diode onto the coil about 1/3 up from ground or lower.
I was always going to juggle my antenna length around to see if I could escape the SW sigs, but never quite got around to it !
If we have a listening event in January I think that I will try Al Klase's Faraday shielded single tuned set to see if I can escape the SW:
|W0XI||Posted - 17 November 2013 17:6 |
Did you try a low-pass filter to remove
some of the shortwave at the front of the set?
Unc Phil, w0xi
|Garry Nichols||Posted - 17 November 2013 18:21 |
I would have to figure out how to make one! My initial thought is that the input and output impedances would have to be fixed in order to design it. But they would be constantly changing for a crystal set wouldn't they (as it is tuned across the band)?
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