# crystals



## charles henry (May 18, 2008)

Maybe I'm showing my age again but anyone out there had to grind a crystal to get to a frequency of an hf station that had an oddball listenting freq. I had to do it once to get hold of a Japanese station. 

You require a flat (Preferably glass base) and use a household scouring powder (Vim, Commet etc). You grind it using a circular motion and reversing sides often. If you "overshoot" your frequency you can lower it by making pencil marks on the sides.

A difficult and lengthy procedure and you lose a lot of your fingernails doing it. I had first learned this using military surplus crystals and getting them to fit frequencies for the ham bands.

Ah memories de chas


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## Naytikos (Oct 20, 2008)

Not exactly but I did repair one once. Somehow it had cracked into two pieces and the wire from one side had broken off. I used a miniscule trace of epoxy and had to hold the edges together until it began to cure. I then polished it with toothpaste to get rid of the excess adhesive and soldered a bit of 1 amp fusewire to the gold flashing to remake the connection. It was about half a Kc off at fundamental frequency but held together until I was able to get a new one.


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## wireless man (Jun 16, 2008)

Slightly off topic but the word crystal made me think about the crystal sets I used to make. Anybody else remember these


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## mikeg (Aug 24, 2006)

wireless man said:


> Slightly off topic but the word crystal made me think about the crystal sets I used to make. Anybody else remember these


Yes, fiddling around with the cats whisker trying to get the best reception.
Coils wrapped around toilet roll centres and home made tuning condensors (no one called them capacitors in those days). Needed a long aerial and good earth to work best but I found out that bed springs worked well. Used to listen to programmes like Jack Hulbert and Cicely Courtneidge under the bedclothes.
Good nostalgia


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## Naytikos (Oct 20, 2008)

Snap!
Mine was only supposed to tune the MW band, but by connecting the earth lead to the antenna screw, as well as the antenna wire itself, it would pick up Droitwich 1500m no matter what setting the condenser was at.


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## 5TT (May 3, 2008)

Ahhh the old crystal set. I cheated and used a OA something, point contact diode and the standard toilet roll coil former, and pretty much all I could receive was the BBC Home Service. I woke up many a time during the night with my eyes popping out of my head, as the headphone cable had coiled itself around my neck a few times !!
I progressed to a HAC single valve regen set after that, with the green Denco octal based coil, was probably better than a Marconi Monitor on H/F too once the reaction capacitor was peaked up, but I still had the same problem with the headphones at night.
= Adrian +


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