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Right; I think that's how a lot of tcxo's are done nowadays; muchOn Tue, 22 Mar 2005 07:41:47 -0800, John Larkin
jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX> wrote:
On Tue, 22 Mar 2005 13:34:47 +0000, John Woodgate
jmw@jmwa.demon.contraspam.yuk> wrote:
I read in sci.electronics.design that Fred Bartoli
fred._canxxxel_this_bartoli@RemoveThatAlso_free.fr_AndThisToo> wrote
(in <4240112b$0$2080$636a15ce@news.free.fr>about 'an electronish
puzzle', on Tue, 22 Mar 2005:
"John Woodgate" <jmw@jmwa.demon.contraspam.yuk> a écrit dans le message de
news:UhnOqPT9YAQCFwz5@jmwa.demon.co.uk...
I read in sci.electronics.design that Fred Bartoli
fred._canxxxel_this_bartoli@RemoveThatAlso_free.fr_AndThisToo> wrote
(in <423fe4ea$0$2048$636a15ce@news.free.fr>
puzzle', on Tue, 22 Mar 2005:
Maybe you can buy a tin of violet paint?
Violet is N750. OK, making 1/3 of the capacitance N750 and the rest
NP0/COG would do. But yellow paint gets you N220. (;-)
So he has to get the missing 30ppm by carefully hand selecting NPO?
What a paint in the arse...
Actually, he still needs a sniff of N750 to *increase* the overall TC.
But yes, it was a PITA correcting drift this way, especially as you had
to wait at least an hour to see the results of any change.
"Pain in the arse" is a good assessment. The current product uses a
varicap driven by an LM45 temp sensor, a couple of opamps, and a
trimpot. Even without soldering, adjusting the tc is a huge, tedious
nuisance. Now I want to make a really tiny version, so an NTC cap
would be ideal. There's a huge matrix of possibilities combining fixed
caps and NTCs; NTCs are theoretically available from N220 to N5600.
Disc NTC caps are still somewhat available, but it's hard to get
surface-mounts unless you want to buy a million, which makes
experimenting problematical.
If I could get the TC down from -125 to, say, +-40 maybe, it would
solve my problem.
John
Years ago I designed a scheme that tested an oven-less crystal
oscillator over several days.
A DAC was used to adjust the varicap voltage to bring the oscillator
frequency dead-on.
Data was stored in a ROM that was addressed dependent on temperature.
Oven performance without oven. <http://saunders-assoc.com/index.html
...Jim Thompson
Yes. I have a long-record, digitizing o'scope, so I
about 'an electronish Who ever said that LB was nice? But try y = k*exp(ln(x)) + c. (;-)
Well- why haven't you? You said it has been some 30 years. Guess you're
A "long-record" scope, and an "expectable response"-hmmm- sounds like
Well- well, well, well- nobody should hold their breath waiting for your
about 'an So I also have read. He took the prism out of the 'spectrometer'.
Great story. Robert Wood was a physicist and humorist; he wrote "How
Please do. It's great stuff.
Ah, but then you haven't seen my collection of colorful little
Well, he's civil and has manners. Could be worse (hint, hint.)I read in sci.electronics.design that John Larkin
jjlarkin@highNOTlandTHIStechnologyPART.com> wrote (in
lkm041dujd0erjhiok06jv0jk9jt6fkue2@4ax.com>
puzzle', on Tue, 22 Mar 2005:
Well, you are implying that I can't tell a straight line from an
exponential. That's not very nice, you know.
Who ever said that LB was nice?
Don't be silly. Nothing can go faster than c.
Knock it off, John! You have me laughing so much my stomach hurts ;-)
480)460-2350 | |480)460-2142 | Brass Rat |Well, Fred keeps tossing these wonderful setups. I should really try
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Typical queen response....
No he's not- he's a little dodging slanderer and bullsh_t artist puke-
Oh reeeeeeally? And do you flip your wrist while you write that? You're