[ARC5] [Glowbugs] "Using Defective Crystals" 1937

[hwhall at compuserve.com]

Nevermind, I needed to reread the comment before replying.

Wayne

-----Original Message-----
To: kv6lee at gmail.com <kv6lee at gmail.com>; k1lky68 at gmail.com <k1lky68 at gmail.com>
Cc: arc5 at mailman.qth.net <arc5 at mailman.qth.net>
Sent: Sun, Jun 21, 2020 11:46 pm
Subject: Re: [ARC5] [Glowbugs] "Using Defective Crystals" 1937

>From my physics days, I don't recall that quartz crystals reacted to magnetic fields, just electric ones.

WayneWB4OGM

-----Original Message-----
From: Bart Lee <kv6lee at gmail.com>
To: Roy Morgan <k1lky68 at gmail.com>
Cc: ARC-5 List <arc5 at mailman.qth.net>
Sent: Sun, Jun 21, 2020 10:27 pm
Subject: Re: [ARC5] [Glowbugs] "Using Defective Crystals" 1937


Some crystals are affected by electric fields (but not magnetic fields -- or so says the wiki). So my guess is that 
1) the coil puts some electromagnetic force at the desired frequency of oscillation into the crystal structure, 
2) to which it responds mechanically at its characteristic frequency of vibration at or near the desired frequency of oscillation, 
3) as a result of the electric part of the electromagnetic field. 
In effect, the coil "jump-starts" the crystal which then stabilizes the circuit's frequency of oscillation. A wild-assed guess?
73 de Bart, K6VK ##
-- -- 
Bart Lee, K6VK, CHRS, AWA, ARRL
Texts only to: 415 902 7168 

www.bartlee.com 
{KV6LEE(at)gmail(dot)com} ##



On Sun, Jun 21, 2020 at 8:33 PM Roy Morgan <k1lky68 at gmail.com> wrote:

Ken,

I am thinking you are right.  The FT-243 crystal blanks do get frequency from thickness - I ground some up in frequency years ago.  Based on what I have read, the behavior of quartz crystals is pretty complicated.

I used to own one of the type shown in the article.  If I do discover it, I likely will not crack the blank to see what happens !

I have also owned one of the crystal filter crystal units from early Hammarlund HRO receivers.  The quartz piece in them actually moves around enough so it can rattle when you shake the thing.

Roy

> On Jun 21, 2020, at 11:11 PM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:
> 
> On 21 Jun 2020 at 22:59, Roy Morgan wrote:
> 
>> Hue,
>> 
>> This is an interesting article.  I have had one of the round crystal holders shown, but never took it apart.
>> 
>> The business about
>> 
>> "If it (the crystal) has been cracked ... possible to get several good
>> crystals from an inch square plate ... all of which will oscillate on
>> the original frequency."
>> 
>> is pure baloney, based on all I have learned about quartz crystals and
>> how they operate.
>> 
> 
> You are probably correct, BUT, the frequency at which some cuts of crystal oscillates is
> primarily determined by its THICKNESS.
> 
> Ken W7EKB

Roy Morgan
K1LKY since 1958
k1lky68 at gmail.com




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