The crystal detector is the ERLA brand, and is a semi-sealed unit with two screw-type connectors. I'm wondering how the crystal is electrically connected inside?
My crystal radio experience involved a cat's whisker that you had to play around with to get a good spot on the crystal. This one has no adjustment.
I removed the cover from the crystal unit. Yes, there is a tiny cat's whisker against a little crystal. The cat's whisker is a springy bronze-looking wire, maybe about 3/16" long, bent into an L-shape to contact the crystal, itself about 1/16" square. By jiggling the whisker, I could tell that the contact was touchy.
Discretion being the better part of valor, I decided to bend the cat's whisker away from the crystal, and bypass the whole thing with a 1N34A diode, which I happen to stock.
Onward and upward.
BTW... why do you happen to stock this item?...
The other day I went through every diode I have here and could not find a single germanium any where...
.. when I was 9 years old I was building crystal sets.. for myself and friends...
Those were the days 1951-54 that I'd stuff a crystal set into the tiny tool pouch that hung on the back of my bicycle seat. Then I'd run an antanna wire to an old car antenna that I had taped to my back fender support.
I must have looked rather weird as I rode around town...lol
I'd have a set of earphones on and ride around town all proud and excited that I could listen to music while on my bike... ( those were the days when people would ask me what I was doing.. and then they'd be totaly amazaed to hear radio on my headphones... and they'd think I was some kind of science genius or something..lol)
Ahh yes.. I think it was Mitch Miller's "The Yellow Rose of Texas" that was a big hit back then.
Anyway.. I quickly learned the frustration of a cat whisker crystal. And I can remember now rather vividly (1952) ..walking down to my local electronic store to buy a germaium diode for each set I'd build.
In fact... yes, I think it was a 1n34 diode.
http://semiconductormuseum.com/MuseumStore/MuseumStore_1N34_Index.htm
marv
:Yes Doug:
: I was going to suggest the use of a gremanium diode... but you got it.
:
:BTW... why do you happen to stock this item?...
:
:The other day I went through every diode I have here and could not find a single germanium any where...
:
:.. when I was 9 years old I was building crystal sets.. for myself and friends...
:Those were the days 1951-54 that I'd stuff a crystal set into the tiny tool pouch that hung on the back of my bicycle seat. Then I'd run an antanna wire to an old car antenna that I had taped to my back fender support.
:I must have looked rather weird as I rode around town...lol
:I'd have a set of earphones on and ride around town all proud and excited that I could listen to music while on my bike... ( those were the days when people would ask me what I was doing.. and then they'd be totaly amazaed to hear radio on my headphones... and they'd think I was some kind of science genius or something..lol)
:
:Ahh yes.. I think it was Mitch Miller's "The Yellow Rose of Texas" that was a big hit back then.
:
:Anyway.. I quickly learned the frustration of a cat whisker crystal. And I can remember now rather vividly (1952) ..walking down to my local electronic store to buy a germaium diode for each set I'd build.
:
:In fact... yes, I think it was a 1n34 diode.
:http://semiconductormuseum.com/MuseumStore/MuseumStore_1N34_Index.htm
:
:
HEY... I'm too young to be this old!
marv
:Ok Marv... ;-))
:.... Sorry but us ... (read ME)...old-timers do get to drifing off into yester-year now and then...
:huh? ....what year is it now??
:
:HEY... I'm too young to be this old!
Remember that ?? .. or was the mnemonic that you were taught just a bit more politically correct?
:Yes Doug:
: I was going to suggest the use of a gremanium diode... but you got it.
:
:BTW... why do you happen to stock this item?...
:
marv
:There are two stages of RF amplification ahead of the crystal detector, so I probably could have gotten by with a silicon diode rather than a germanium. But the lower forward voltage drop of the germanium diode helps.
I can only assume that the factory aligned the cat's whisker to a good spot, because the radio worked before working on it. I jiggled the whisker a little, and decided that if it was aligned on a hot spot in 1924, I had probably screwed it up, and decided to bypass it with a 1N34A for peace of mind. I left the original crystal package in place, and just bent up the whisker a tiny distance so it was no longer making contact with the crystal.
There are three "tuners" ahead of the detector. Two are variable caps for the RF stages. The third is a varicoupler which essentially tunes the antenna.
The audio output from the crystal detector goes through an audtio xfmr, and is fed back to the grid of the 2nd RF tube in a reflex manner. Then there is an AF amp stage.
Interesting circuit. Apparently, ERLA's reflex circuit did not require a license under Armstrong's regen patent. I guess the patent covered feeding back the RF signal, but not the audio signal?
The only schematic I've found is on p. 190 of Alan Douglas' "Radio Manufacturers of the 1920's," Vol 1.
:Doug,
:I'm curious about the cat whisker in the original pkg, and remember so many years ago searching for that 1 hot spot on a Galena crystal. I gather that a hot spot had been found prior to final packaging taking place, and was it indeed a small Galena crystal slice that you removed before the 1N34 install? The two RF stages are presumably tunable?
:
:marv
:
::There are two stages of RF amplification ahead of the crystal detector, so I probably could have gotten by with a silicon diode rather than a germanium. But the lower forward voltage drop of the germanium diode helps.