[Milsurplus] FT-241 surplus LF crystals chan - freq list ?

[WA5CAB at cs.com]

Hue,

This isn't going to Tetrode.  You may repeat it over there if you wish.

I wouldn't describe it as moss.  It wasn't shiny but had a relatively 
smooth surface.

I used the BC-604 or BC-684 that they were for.  And a TEK 2335 on the 
output of the first multiplier.  The fundamental was still in there but well 
down in amplitude from the higher frequency or possibly two or more higher 
ones.  With the multiplier detuned, it was quite a weird looking wave form.  I 
only actually opened and looked at two of them.  And concluded that before I 
opened up any more, I need to fabricate a jig to break them open because 
upon opening the first one, I broke the crystal.  But I examined the wave form 
of several.  Some were just dead.  But some worked well enough to give 
reasonable output but on the wrong frequencies.  That was what prompted me to 
open up the two.

And one other thing - I mispoke when I said at 3X the nominal frequency.  
What I should have said was that they gave output at around 3X the marked 
channel numbers.  Or maybe it was actually more like 2X to 4X for channels 
between 10 and 20 or 25.  Above that, I had no trouble finding good ones.  This 
was in either 2002 or 2008.  And I have had no feedback as to whether either 
radio still works.

In a message dated 11/13/2017 00:11:42 AM Central Standard Time, 
Kargo_cult at msn.com writes: 
> Very interesting. My information about the failure modes was based on 
> reports from members of the Glowbugs list. Some years back, in what is now
> 
>  recalled as "The Great Crystal Caper", a stash of forgotten surplus LF 
> crystals was found. The stash was apportioned into lots and sold off to all 
> comers.
> 
>  The sad reports of high failure rates followed. Some people opened them 
> up to do a post mortems. 
> 
> I have never heard of the moss phenomenon. I did read somewhere about 
> cleaning the crystal. I don't mean scrubbing the wax off, as with the 915 kHz
> 
>  rock in the BC-348, or using an etchant solution. I'll try to note that 
> advice when I find it again. Maybe in some article on crystal grinding. 
> 
> The LF crystals where the plated on lead has popped off, I wonder if it 
> would work, to remove the other side's contact too, then grind the surfaces 
> slightly
> 
>  to restore the smooth plane, and then repackage in another holder?
> 
>   
> 
>  Robert, what kind of test oscillator circuit did you use for checking 
> these?
> 
>  -Hue 
> 
> 
> Subject: Re: [Milsurplus] FT-241 surplus LF crystals chan - freq list ?
> 
>   
> 
>  From examining two or three about 10 or 15 years ago, I concluded that 
> the failure (or actually the failure to remain resonant at the original 
> frequency because I found several that oscillated reliably in the range of about 
> 3X the original frequency) was caused by a buildup of something green on 
> both sides of the blank.  A magic potion that could dissolve the green 
> without effecting the original constituents would be a possible solution.
> 
> Robert Downs - Houston
> 
> 
> 
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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