[R-390] Re: 200 KHz crystals again

[Perry Sandeen]

Gentlemen,

Wrote: > First you'd have to put three 455 crystals together and somehow fuse them so that they
became one crystal. Then you could grind off material to raise the frequency.

Asked: > Is it possible to disassemble an HC-6 crystal and grind it to a different frequency?

Wrote: > You could grind a 100K to 200K with some good lapidary equipment.

Wrote: >why not just come up with a little drop in to generate a 200 KHz square wave off of a cell
phone TCXO?

I would respectfully offer that these cures are far worse that than the disease

IIRC I posted this a while back but I’m re-posting it as I believe this is the path of least
resistance to solving the 200 KHz problem.

First though the true source of the problem.  The oven runs at 85C.  This will always be a
problem.  Finding a way to lower it to say 45C would go orders of magnitude to keep both crystals
running for probably an indefinite time.  The cure for this is another rant.  Contact me off list
if you want a simple heater ckt.

A  Simple Solution.  (Purists close your eyes so you won’t be contaminated)

1.  Obtain a copy of the ARRL handbook 2004 to 2006 , which are the only copies I have.

 2.  Go to section 25.15 (2006 manual).  There is circuit called "A Marker Generator With
Selectable  Output".

3.  Buy the PC board, 5 IC’s, a few miscellaneous parts and an aluminum box. If you don’t want to
buy the board RatShack has dual IC boards that can be used.  Build unit. One can obtain 1 or 10
Mhz TXTO’s very reasonably for a  master oscillator.  A side benefit to using a TXTO is that one
can slave the 17Mhz oscillator. Or one can use either a 1, 2, or 4 MHz crystal on the marker
generator board.

4.  Set jumpers to any desired sub-multiple of  your choice. Inject the cal signal into Pin 5 of
205.  The harmonics are probably strong enough that you won’t need any amplification. If not
increase the 20 pf cap to .001 mfd  or larger.  Then V205 and V206 become redundant.

 Regards,

Perrier



       
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