Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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You think YOU have problems. I have a very hard time typing Gary!! :-)
All crystals change with age. There are many factors, but a few are
adsorbing (or releasing) contaminants that were trapped at manufacture,
different coefficients of mounting materials, possibly even flaking off
particles of quartz, stress relief in mounting structures, and on and
on...... Aging is akin to drift, in that both result in the frequency
of oscillation changing over time. Like drift, it can go in either
direction.
Aside from all the handwaving, I think the biggest source is lack of
cleanliness in manufacturing. Obviously cleanliness costs money, and
the "bargain" crystal makers seem to cut that expense first. Probably
because it doesn't show up for years, and is therefore "not their
problem". :-)
You'll find band crystals in Drake (AND Collins) equipment that are
several kHz off frequency after 20 -30 years. Even with the best of
manufacturing processes crystals still age, just at a slower rate.
Typical aging for quality crystals can still be in the range of 5-10
ppm/year (5 -10 Hz per year) which is plenty good enough for our uses.
Anyway, when the 4-8 crystals in a crystal filter start changing
frequency at random, all sorts of bad things happen to the passband.
Usually excessive ripple in the passband is the first to suffer.
Insertion loss goes up (think of multiple IF stages that are tuned to
different frequencies rather than all on the same frequency), etc. In
severe cases (say a chunk of flux finally breaks off of a crystal
element!) a big notch or peak can show up in or outside of the passband....
73, Garey - K4OAH
Glen Allen, VA
Chuck Grandgent wrote:
Garey (OK, I just recently picked up that we have both a Garey and a
Gary here, I'm pretty slow :),
HOW do the crystals age ? Is it the mechanicals inside or just what ?
Chuck, K1OM
On Jan 1, 2008 3:52 PM, Garey Barrell <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
Garey Barrell <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>
made an utterance to the drakelist gang
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Wade -
The Drake filters are generally fine, and if you can save some money
while getting GOOD Drake filters, they should cost about half of what
the Inrad filters cost. The vast majority of the Drake filters still
meet their specifications.
That said, the Inrads are better filters. They had the benefit of 25
years of technology improvement, and much more powerful computers,
resulting in smoother passband among other things.
Obviously they are also 25 years "younger", and crystals DO age
over time.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com <http://www.k4oah.com>>
wmacleod wrote:
>
> Hello Drakelist:
>
> Does anyone know how the INRAD selection of 5695 KHz 2^nd IF filters
> for the R4C compare against the original Piezo Technology filters
> offered by Drake? Would I be better off obtaining original Drake
> filters or going with the INRADs.
>
> regards
>
> Wade
>
>
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