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PostPosted: 14 Feb 2017, 16:17 
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Joined: 31 Dec 2008, 15:34
Posts: 441
Location: Denmark
finally i made a crystal set which actually can hold the stations. :wizard: most people can make a crystal radio, but those who have tried to make one knows how it drifts almost immediately when a station is found. i'm using a loop antenna made of four broken fishingrods, to make a rectangular frame ( 4,5 ft x 5 ft ). on the frame i've added a twin pair of telephonewire ( blue/red type ).

the crystal set is very simple. i've added a twin pair of adjustable capacitors 365 pF ( see the pictures ). there's three seperate coils 20T/40T/10T on a ferrit rod and the last one works as a kind of booster coil ( as i see it ). then the fun starts ....it's the small critter which has something to do with holding the stations ( weird but true ). it's a kind of both cap and coil in one. also is the loop antenna weird, because it's not connected in one end. i'm able to reach 3 stations and 'HOLD' them by adjusting the capacitor ...which is a big thing for me. if i move one of the loop antenna wires ( make them parallel + adjusting the ferritrod ), it gives me 2 new stations + keeping 1 of those who where there before. success today ...and i needed this succes, because it has been two days with a lot of frustrations.

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PostPosted: 16 Feb 2017, 17:39 
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Critter is a good name for it. I just recently built a kit that uses the same concept to couple the antenna, but they called it a "gimmick" capacitor - magnet wire twisted together.

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PostPosted: 17 Feb 2017, 06:46 
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nice, i'll add 'gimmmick' to my vocabulary Image. now i've got critter, gimmick, gizmo, thingy and n.e.e.d ( non explainable electronic device ). all this can be chained together with words like weird, wicked, magical, mysterious to make it even more attractive. :wizard:

anyway the shown critter is nothing more than a kind of combined filter of L, R, C in a very small scale. when i tried to stretch the wires out, which was the same as removing the critter ( houdini style: now it's there, now it's not ), then i began to hear mixing of different channels, so it had a purpose of focusing on one channel. unfortunately i was not lucky, when trying to make a working critter again. :down:

gio, i guess you're refering to the ozark, where the gimmick is inserted. this one must be seen as a cap and only a cap, because both ends of wires are not connected ...or is it (?) because it could also act as a sort of small antenna. it's not encapsulated.

the critter is connected an must be seen as both a coil, cap and resistor combination, as i see it.



update: right now i'm working on a better loop antenna build on a wooden frame, instead of the broken fishingrods.


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PostPosted: 17 Feb 2017, 21:39 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi, The term from my amateur radio days was a "gimmic" . Most were a pair of twisted together wires. About 3-5 turns about 1/2 inch long. Most common use was to keep transmitter tubes from putting out excessive harmonics. Basically a very small capacitor and inductance. I suspect they operated as sort of an LC trap. Could be wrong there as that was about 50 years ago when I built such transmitters. Without the gimmic some were able to wipe out TVs for blocks around. With it, zilch. The worst offender tubes were the ones we were (because of cost) forced to use....horizontal output tubes for TVs. In class C operation some would deliver over 50 watts to the antenna. You can imagine what that would do to nearby TVs that used antennas as well back then if there was no gimmic.

Good listening
Bruce

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PostPosted: 17 Feb 2017, 23:41 
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KrammeAcoustics wrote:
this one must be seen as a cap and only a cap, because both ends of wires are not connected ...or is it (?) because it could also act as a sort of small antenna. it's not encapsulated.

Correct, it is not connected, I thought of it as a capacitor, but there is also a inductive component as Bruce suggested. Who knows how it all works. With the regen receiver I assumed it was to lightly couple to the antenna so not to overload the receiver.

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