William Clarke's Crystal Sets

William Clarke's crystal radio

William Clarke's crystal radio

William Clarke's crystal radio

William Clarke's crystal radio

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Hi Dave

I am sending this first radio "showcase", hoping that the files are not too large. I have included a table of some stations received (excel sheet) that shows this receiver has decent performance.

The coil is wound on an ABS coupler of 5" outer diameter. I used teflon coated wire. I placed a loopstick close by as a wavetrap. I tried a concentric position at first, but the tuning shifted when the trap was "on". The outside location works very well with minimum effect on the tuning.

I find the tuning is best when ground (earth) is coupled through the small oscillator section of the ganged cap. The audio transformer section is the Stanley/Bogen "Select to Match" Impedance Matching Circuit by Steve Bringhurst. I first became aware of this "sound powered phone thingy" while looking at your website last fall.

Thanks
William Clarke



William Clarke's crystal radio

William Clarke's crystal radio

William Clarke's crystal radio

William Clarke's crystal radio

Hi Dave
This radio is a loose coupled type. The same 5" tuning coil is fed by a 4" rotating primary. Between the detector taps and the center tapped primary, I can get any degree of selectivity I need. The front panel is a masonite clipboard and the bearings for the primary are a couple of eyebolts with grommets in them. The shaft is a 1/4" dowel rod. The audio transformer setup is the same as the other radio.



William Clarke's crystal radio

William Clarke's crystal radio

William Clarke's crystal radio

Here is a Telefunken type radio. The primary is moveable and the detector winding is close-coupled to the tuning circuit. I've also tried attaching the antenna and ground to different spots on all 3 windings (kind of like a "mystery set" configuration) - the conventional connections seem to give the best tuning range. I use an external transformer/SP phone with this one.



William Clarke's crystal radio

William Clarke's crystal radio

William Clarke's crystal radio

This is another loose coupled type. The primary is a large tapped coil which moves on a small wood track. The rest of the radio is similar to the others - detector taps and transformer for sound-powered phones. I get a lot of stations on this one as well. It has a velvet vernier for the tuning and a plastic front panel which shows fingerprints very well.


William Clarke's crystal radio

William Clarke's crystal radio

William Clarke's crystal radio

I just wired and tested this one. With the exception of the 3 switches going to the 12 taps, there's hardly anything to it. It's just a logical extension of the MRL #2 set.

I just gave the antenna and detector the same access to taps as the ground in the original plan. I used a calrad 45-700 in the "transformer thingy" - it works fabulously with the RCA phones. I will still need to do some testing, but the BCB performance is very sharp.

The wavetrap setup uses the 2 trimmers on the panel. I just set each one to a local station and use a 3 position switch. For the way a trap should be used, this makes more sense - just switch to the station you need to silence.