Driver to drive?

[Joerg]

Tim Williams wrote:

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:L%AZl.18986$jZ1.14237@flpi144.ffdc.sbc.com...
Yeah but, less gusto -> more heat. One the design I am doing right now
25nsec more transition time makes all the difference between a relatively
cool FET versus one that solders itself off the board with an evil hiss.

Ahh, but I have a heatsink, so that doesn't matter to me. ...

Oh no. Now you've attracted the wrath of the warmingists

... 100-200mA is
plenty of drive for this application. What's more, I need about that much
to drive the GDT at the lowest frequency. I don't think I can get more than
1A peak through the GDT without a lot of interleaving anyway. Mere '3904s
are fine, but alas, take an annoying amount of space to wire up.

And another thing- a pair of TC4420 is as expensive as one of the IGBTs.

Well, you could get one of those Japanese transistor arrays if you want
to pinch the last penny and still make it small.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Tim Wescott]

On Tue, 16 Jun 2009 09:35:41 -0700, John Larkin wrote:

On Tue, 16 Jun 2009 11:28:58 -0500, Tim Wescott <tim@seemywebsite.com
wrote:

On Tue, 16 Jun 2009 08:38:49 -0700, John Larkin wrote:

On Mon, 15 Jun 2009 21:11:36 -0700 (PDT), MooseFET
kensmith@rahul.net> wrote:

On Jun 16, 12:03 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Suppose I really want a crystal oscillator at, say, 122.167958 MHz.
And I'd like to have the option of phase locking it to some standard
reference, 5 or 10 MHz maybe. And I'd like cheap ones for low-end
products, and TCXO or OCXO stability for better versions.

Is 122.167958 the real number?

It's actually 2^40/9000.

We want to make a multi-channel DDS synthesizer that has precisely 1
mHz resolution, and a clock in the ballpark of 125 MHz.

If you do it the obvious way, phase accum lsb = 0.001 Hz, the clock
has to be 2^N/1000, candidates being 137.438... and 68.719... MHz,
neither acceptable. So some brilliant engineer observed that the phase
accum input need not be "1" at 1 mHz, it could be any small integer. A
bit of poking came up with "9", which resulted in the target
frequency.

So the problem became how to generate that weird clock without
grinding custom quartz (for, potentially, both cheap XOs and optional
OCXOs) and how to lock it *precisely* to an external 10 MHz reference.

So if we use the SiLabs VCXO, we can have a nominal osc frequency
close on-target. Then we can build a ninth DDS channel, program it to
make 10 MHz, and close a loop on that, against an external input or a
local 10 MHz OCXO. Since the extra channel is programmed to and locked
to 10 MHz, obviously (as pointed out by a different brilliant
engineer) any other channel can be programmed to make precisely 10 MHz
too, and all are settable to exactly 1 mHz resolution, namely DDS
settings that are multiples of 9.

It's one of those things that starts complicated and simplifies itself
later on. Practically everything winds up inside the FPGA where it
belongs.

John

Why didn't you _say_ so?

If you use a 128MHz time base, and implement each adder as a mod 5^9
stage (or nine mod 5 stages) followed by a mod 2^18 stage, then you'll
have plenty of binary bits to feed your lookup table, and you'll be able
to divide the clock down with nice even numbers of mHz.

(not to mention a fun job building the adder so that it meets timing --
that's left as an exercise to the reader).

We already have a pipelined bidirectional 40-bit DDS design, and it's
really tempting to leave it alone.



Figuring the increment will be odd, but that's what software is for.


But I don't like being assaulted by FPGA designers who are younger and
bigger than I am.

If you're only going to use nine bits into your look up table, you can
have 9 digits of BCD with nine bits of straight binary on top, which
might make the adder easier.

You're talking torches and pitchforks now.

If they're younger they should have more flexibility of mind than you.
Feel free to point this out .

If they're bigger they shouldn't need the torches and pitchforks.

So what are they, FPGA designers or readers of cookbooks?

Were it me I'd assess the differences in development time and performance
for the two approaches, then jigger the numbers to what I wante -- I mean
I'd let the best approach win.

--
www.wescottdesign.com

 

[Tim Williams]

<langwadt@fonz.dk> wrote in message
news:2c0a090f-e986-4dbb-a89e-3aabb559c02e@f19g2000yqh.googlegroups.com...

thought about trying something like ir2153?

Hmmmmmm, weird. A 555 stacked with a half bridge driver. Constant duty
cycle output (i.e., fixed dead time), so it's no good for a forward
converter. Resonant apps I guess. Thing is, you need a variable resistor
to control frequency. A pair of current mirrors on Ct, with diode steering
from Rt or whatever, would be a fine substitute. Mismatched currents will
PWM the output (unbalanced PWM), which would be great for a class D power
amplifier, but not good for a resonant switcher. Matched current mirrors
would do okay.

Thing is, I'm not sure I want fixed duty cycle. I may still want to vary
power output by varying duty cycle (ala forward converter, TL494 et al.)
rather than frequency. That's impossible with this chip.

Besides, I want my control circuit grounded to ground. None of the IRxxxx
chips I've seen can accommodate that, at least without a big stinking
isolation transformer supplying the HV side.

Come to think of it, I have a few IR2101s that I could just run at 0V as
dual drivers for my immediate goal. That might work out. Still not an
ideal solution, a weak dual TC4420 is really what I want, but I happen to
have some of these on hand.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

 

[langwadt@fonz.dk]

On 16 Jun., 17:35, "Tim Williams" <tmoran...@charter.net> wrote:

Think I'm going to do it like this.  That inductor kind of bothers me
though.

http://webpages.charter.net/dawill/Images/Small_2.gif

Tim

--

thought about trying something like ir2153?

-Lasse

 

[Dave Platt]

In article <JRPZl.21707$8_3.4217@flpi147.ffdc.sbc.com>,
Joerg <notthisjoergsch@removethispacbell.net> wrote:

Back in Germany I've used another outfit that had better pricing. I
believe it was located in the little village of Daun (Eifel Region). But
that was very long ago, always under 20 Deutschmarks. Then some outfits
in the Netherlands with sometimes even better prices, well under 20
Dutch Guilders back then. 1980's.

For super top notch crystals where price was not an objective we used
KVG (Neckarbischoffsheim?).

Here in the U.S. I'd suggest checking with Cal Crystal Lab / Comclok.
They claim that "Custom frequencies - our specialty", they have no
minimum order quantities, and on the one occasion I dealt with them I
found them to be quite friendly to the small-shop developer. I've
heard similar good things about them from some other folks who have
used their services.

--
Dave Platt <dplatt@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

 

[Jon Kirwan]

On Tue, 16 Jun 2009 08:42:27 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Tue, 16 Jun 2009 04:13:42 GMT, Jon Kirwan
jonk@infinitefactors.org> wrote:

On Mon, 15 Jun 2009 16:40:30 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:

On Mon, 15 Jun 2009 15:17:23 -0500, James Waldby <no@no.no> wrote:

On Mon, 15 Jun 2009 13:56:50 -0400, Phil Hobbs wrote:
Tim Wescott wrote:
On Mon, 15 Jun 2009 13:05:24 -0400, Phil Hobbs wrote:
Tim Wescott wrote:
...
4: Find some pair of integers whose ratio is close enough to
12.2167958 to be well within your tolerance budget, and use them for
your two dividers. You can usually get astonishingly close with just
the right pair of integers -- for example, 88303 / 7228 gets you to
less than 1PPB error with a 1kHz reference -- and you aren't going to
achieve 1PPB with your 10MHz reference unless it's way more expensive
than a VXCO.
That's a good trick--like the approximation pi ~ 355/113.

Anytime you need to approximate some precise number it's a good trick.
I don't know of any way to find a "good" pair of numbers other than an
exhaustive search, but with today's tools that search is pretty easy.

Yes, one would be unlikely to want to go beyond, say, 10**5, and it's
only a 1-D search. Even searching up to 10**10 would probably be faster
than coding a more efficient algorithm.

88303 / 7228 is the 9th continued-fraction rational approximation to
12.2167958, much as 355/113 is the 4th such for pi. Continued-fraction
rational approximations take a few microseconds to compute. See eg
http://en.wikipedia.org/wiki/Continued_fraction#Best_rational_approximations

Here is some bc code that shows the first 14 c-f-r-a's of 12.2167958:
(Eg, the 6th c-f-r-a of 12.2167958 is 6255/512)

define trunc(x) { auto s, t; s=scale; scale=0; t=x*1/1; scale=s; return t;}
t=h=12.2167958;m=0;n=1;c=1;d=0;for (i=0;i<15;++i){
k=trunc(t); if(k>10^10)break;
v=m;m=n;n=v+k*n; v=c;c=d;d=v+k*d;
print n,"/",d,"\t",n/d-h,"\n"; t=1/(t-k);}

For us non-programmers, can you reduce that to understandable
algorithmic steps?

First, you may want to read this paper:

http://www.math.hmc.edu/~benjamin/papers/ccf.pdf

On the last page they define two recurrences, P and Q, which are
mimicked in the code as 'n' and 'd'. The difference is that the above
authors permit a value other than 1 for the series b, while the
code assumes that b=1 for all n.

The code includes two basic parts. One to calculate successive
continued fraction terms. The other is to follow the recurrences
mentioned in the above paper in order to produce a continued fraction
from the terms as they are generated in succession.

The first part is very easy to follow. Take your value, get the
integer part of it, write that down as the next entry in a list of
integers, then divide 1 by just the fractional part and replace the
current number with that. Repeat as long as you like. For example,
the value 2.45; write down 2 as the first value in the list, then
divide 1 by .45 getting 2.2222222..., then write down 2 as the second
entry in the list and divide 1 by .22222.... getting 4.5, then write
down 4 as the third entry in the list, then divide 1 by .5 getting 2.
Write down 2. That's it. The continued fraction is [2;2,4,2], which
means 2+(1/(2+1/(4+1/2))), or 2.45.

The second part of the code keeps track of P and Q, such that at
any n the resulting fraction is P/Q. From the cited paper, you
find that the two recurrences are P=a*P(n-1)+b*P(n-2) and
Q=a*Q(n-1)+b*Q(n-2), where P(0)=a(0), P(1)=a(1)*a(0)+b(1),
Q(0)=1, and Q(1)=a(1). The recurrences are the same except for the
starting point values.

In the program, b=1 for all n, so keep that in mind. Also, they
don't want two starting conditions that depend on already knowing some
of the continued fraction terms (for each recurrence.) They prefer to
take one step further back and define things this way: P(-2)=0,
P(-1)=1, allowing the general recurrence of P=a*P(n-1)+P(n-2) to
yield the P(0)=a(0) and P(1)=a(1)*a(0)+1 that the paper discusses from
those prior values. Similarly, Q(-2)=1, Q(-1)=0, allowing then the
general recurrence of Q=a*Q(n-1)+Q(n-2) to yield the Q(0)=1 and
Q(1)=a(1) that the paper discusses.

The code "says:"

1: m=0; ' P(-2)
2: n=1; ' P(-1)
3: c=1; ' Q(-2)
4: d=0; ' Q(-1)
5: for (i=0;i<15;++i) { ' Perform a loop until useful digits expire
6: a = trunc(t) ' generate a
7: if (k>10^10) break;
8: v=m; ' P(n-2)= P(n-1)
9: m=n; ' P(n-1)= P
10: n=v+k*n; ' P = P(n-2) + a * P(n-1)
11: v=c; ' Q(n-2)= Q(n-1)
12: c=d; ' Q(n-1)= Q
13: d=v+k*d; ' Q = Q(n-2) + a * Q(n-1)
14: print n,"/",d,"\t",n/d-h,"\n";
15: t=1/(t-k) ' next iteration with t=1/(t-a)
16: }

Lines 6 and 15 are the two lines generating a and belong to the
first part of the algorithm I described. Lines 8 to 13 belong to the
second part of the algorithm, as discussed in the paper, and depends
on the generation of successive a values by the first part of the
algorithm. Obviously, line 14 is for displaying the fraction and, it
appears, an error value ('h' holds the actual number, forever.)

Good numerical methods experience should include a solid grounding in
recurrences and generating functions. I'd heartily recommend
"Concrete Mathematics" as an excellent segue.

I hadn't ever seen this application of recurrences to continued
fractions before, but seeing the code it was obvious that a recurrence
relation was being applied and it was then not difficult to find a
paper discussing it. It's application to understanding the code was
then instantly obvious.

Jon

Cool, but sometimes it's easier to write a brute-force Basic program
with a few intelligent constraints, and run it for a few minutes or
hours. Most real problems won't have to run for days or centuries.

Oh, in this case, I agree. It's not hard to simply work out a problem
like this by hand -- done it many times, myself. An efficient program
using recurrences is more a demonstration of mathematical education
than outright utility.

In this program's case, it illustrates to me that the author was
somehow exposed to this recurrence method -- probably some reading at
some point -- and wanted to embody it in an algorithm. Sadly, the
author was not _also_ exposed to better numerical methods for actually
computing the terms using a design by someone crafting around the
limitations of floating point computations on computers. The line
used to compute the next term, line 15, is very very poorly designed.
It's straight out of "the book," so to speak. It's the very first way
one learns to do it. But it is obvious the author was NOT exposed to
good methods for computing terms. People like Bill Gosper know how to
do this well, by the way, to drop a singularly important name in this
area. The program author obviously hadn't much education on that side
of the mathematical road.

So it is a case of selective education and showing off one side,
without knowing much on another.

My point about a thorough grounding in recurrences and generating
functions remains, though. And given this program's lack of skill in
getting the most out of floating point, I'd recommend a good text on
numerical methods, as well. One that deals with theory, not practice
so much. One needs to learn to fish for themselves, not eat fish
others catch for them.

Jon

 

[RST Engineering - JIm]

Jan Crystals, Ft. Myers FL. Google for the web page.

Jim
WX6RST


"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:tOzZl.20427$D32.4813@flpi146.ffdc.sbc.com...

Back in the day, you used to be able to get specific crystal frequencies
reasonably inexpensively in small quantities--can you still?


Yes. Best to ask a ham radio operator who still builds stuff (before they
are extinct ...) for some good hints where to buy.

 

[RST Engineering - JIm]

Toothpaste on window glass. Grind it a little too far you could bring it
back up with a few lines of pencil lead (graphite).

Jim

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2009.06.16.00.04.29.98644@example.net...

Decades ago, I read an article on lapping your own crystals, but they
were the ones in the box that you could open and just lift the crystal
out (keeping track of the springs and electrodes, of course. ;-) ).

Cheers!
Rich

 

[RST Engineering - JIm]

And, oh, yes, I remember CometT... the good old days when crystals
were in holders with screws ;-)

FT-243

Jim

 

[John Larkin]

On Tue, 16 Jun 2009 11:47:13 -0500, Tim Wescott <tim@seemywebsite.com>
wrote:

On Tue, 16 Jun 2009 09:35:41 -0700, John Larkin wrote:

On Tue, 16 Jun 2009 11:28:58 -0500, Tim Wescott <tim@seemywebsite.com
wrote:

On Tue, 16 Jun 2009 08:38:49 -0700, John Larkin wrote:

On Mon, 15 Jun 2009 21:11:36 -0700 (PDT), MooseFET
kensmith@rahul.net> wrote:

On Jun 16, 12:03 am, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
Suppose I really want a crystal oscillator at, say, 122.167958 MHz.
And I'd like to have the option of phase locking it to some standard
reference, 5 or 10 MHz maybe. And I'd like cheap ones for low-end
products, and TCXO or OCXO stability for better versions.

Is 122.167958 the real number?

It's actually 2^40/9000.

We want to make a multi-channel DDS synthesizer that has precisely 1
mHz resolution, and a clock in the ballpark of 125 MHz.

If you do it the obvious way, phase accum lsb = 0.001 Hz, the clock
has to be 2^N/1000, candidates being 137.438... and 68.719... MHz,
neither acceptable. So some brilliant engineer observed that the phase
accum input need not be "1" at 1 mHz, it could be any small integer. A
bit of poking came up with "9", which resulted in the target
frequency.

So the problem became how to generate that weird clock without
grinding custom quartz (for, potentially, both cheap XOs and optional
OCXOs) and how to lock it *precisely* to an external 10 MHz reference.

So if we use the SiLabs VCXO, we can have a nominal osc frequency
close on-target. Then we can build a ninth DDS channel, program it to
make 10 MHz, and close a loop on that, against an external input or a
local 10 MHz OCXO. Since the extra channel is programmed to and locked
to 10 MHz, obviously (as pointed out by a different brilliant
engineer) any other channel can be programmed to make precisely 10 MHz
too, and all are settable to exactly 1 mHz resolution, namely DDS
settings that are multiples of 9.

It's one of those things that starts complicated and simplifies itself
later on. Practically everything winds up inside the FPGA where it
belongs.

John

Why didn't you _say_ so?

If you use a 128MHz time base, and implement each adder as a mod 5^9
stage (or nine mod 5 stages) followed by a mod 2^18 stage, then you'll
have plenty of binary bits to feed your lookup table, and you'll be able
to divide the clock down with nice even numbers of mHz.

(not to mention a fun job building the adder so that it meets timing --
that's left as an exercise to the reader).

We already have a pipelined bidirectional 40-bit DDS design, and it's
really tempting to leave it alone.



Figuring the increment will be odd, but that's what software is for.


But I don't like being assaulted by FPGA designers who are younger and
bigger than I am.

If you're only going to use nine bits into your look up table, you can
have 9 digits of BCD with nine bits of straight binary on top, which
might make the adder easier.

You're talking torches and pitchforks now.

If they're younger they should have more flexibility of mind than you.
Feel free to point this out .

If they're bigger they shouldn't need the torches and pitchforks.

So what are they, FPGA designers or readers of cookbooks?

Were it me I'd assess the differences in development time and performance
for the two approaches, then jigger the numbers to what I wante -- I mean
I'd let the best approach win.

Another thing we like to do is to run DDSs backwards, at negative
frequencies. You can do stuff like simulate quadrature encoders, or
make polyphase motors run in either direction. That's easy in binary.

John

 

[David L. Jones]

John Larkin wrote:

Suppose I really want a crystal oscillator at, say, 122.167958 MHz.
And I'd like to have the option of phase locking it to some standard
reference, 5 or 10 MHz maybe. And I'd like cheap ones for low-end
products, and TCXO or OCXO stability for better versions.

I can have custom XOs and TCXOs and OCXOs made at great expense. Or I
can lock a VCO to a standard, stock 10 MHz rock.

So what's a good way to do the frequency shift? If we start with a VCO
that's in the 122... ballpark, we could build a DDS that generates 10
MHz from it, sinewave lookup, dac, lowpass filter, and phase detect
the nominal 10 MHz result against the reference 10M and close that
loop. That should work, but is a bit of a hassle.

If we sart to leave out parts, I assume phase noise and such will pile
up.

Any ideas or recommended references?

What's wrong with the likes of the Fox XpressO service?
http://www.foxonline.com/xpressomain.htm

Dave.

--
---------------------------------------------
Check out my Electronics Engineering Video Blog & Podcast:
http://www.alternatezone.com/eevblog/

 

[Joerg]

Dave Platt wrote:

In article <JRPZl.21707$8_3.4217@flpi147.ffdc.sbc.com>,
Joerg <notthisjoergsch@removethispacbell.net> wrote:

Back in Germany I've used another outfit that had better pricing. I
believe it was located in the little village of Daun (Eifel Region). But
that was very long ago, always under 20 Deutschmarks. Then some outfits
in the Netherlands with sometimes even better prices, well under 20
Dutch Guilders back then. 1980's.

For super top notch crystals where price was not an objective we used
KVG (Neckarbischoffsheim?).

Here in the U.S. I'd suggest checking with Cal Crystal Lab / Comclok.
They claim that "Custom frequencies - our specialty", they have no
minimum order quantities, and on the one occasion I dealt with them I
found them to be quite friendly to the small-shop developer. I've
heard similar good things about them from some other folks who have
used their services.

Nice! Thanks. And right here in Kahlifohniah, cool. For John and others
who may be interested:

http://www.calcrystal.com/

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[RoyLFuchs]

On Tue, 16 Jun 2009 18:39:45 +1000, Bob Larter <bobbylarter@gmail.com>
The biggest retard in Usenet wrote:

RoyLFuchs wrote:
On Tue, 16 Jun 2009 17:35:30 +1000, Bob Larter <bobbylarter@gmail.com
wrote:

Ayup, that's our DimBulb.


You're an idiot, Larter.

Go fuck yourself.

Hahahah! The immature little retarded bastard can't handle the truth.

Not your anything, dumbfucktard.

 

[Rich Grise]

On Mon, 15 Jun 2009 22:19:02 -0400, Spehro Pefhany wrote:
....

They had a big lapping machine about the size of a high school
"birdbath" as well as hard vac deposition equipment.

"High school 'birdbath'"?

???
Rich

 

[BobW]

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2009.06.17.02.04.53.991633@example.net...

On Mon, 15 Jun 2009 22:19:02 -0400, Spehro Pefhany wrote:
...
They had a big lapping machine about the size of a high school
"birdbath" as well as hard vac deposition equipment.

"High school 'birdbath'"?

???
Rich

Yeah, that's an odd expression. Maybe he's from England?

Bob
--
== All google group posts are automatically deleted due to spam ==

 

[Spehro Pefhany]

On Tue, 16 Jun 2009 18:47:17 -0700, the renowned "BobW"
<nimby_GIMME_SOME_SPAM@roadrunner.com> wrote:

"Rich Grise" <richgrise@example.net> wrote in message
newsan.2009.06.17.02.04.53.991633@example.net...
On Mon, 15 Jun 2009 22:19:02 -0400, Spehro Pefhany wrote:
...
They had a big lapping machine about the size of a high school
"birdbath" as well as hard vac deposition equipment.

"High school 'birdbath'"?

???
Rich


Yeah, that's an odd expression. Maybe he's from England?

Bob

What did you guys call these things? Or do you recognize them)

http://news.thomasnet.com/images/large/521/521350.jpg
http://www.bradleycorp.com/images/products/fixtures/wf2808_highres.jpg



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[BobW]

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:malg3552516a8b4qii1f1fnnbpqithi43n@4ax.com...

On Tue, 16 Jun 2009 18:47:17 -0700, the renowned "BobW"
nimby_GIMME_SOME_SPAM@roadrunner.com> wrote:


"Rich Grise" <richgrise@example.net> wrote in message
newsan.2009.06.17.02.04.53.991633@example.net...
On Mon, 15 Jun 2009 22:19:02 -0400, Spehro Pefhany wrote:
...
They had a big lapping machine about the size of a high school
"birdbath" as well as hard vac deposition equipment.

"High school 'birdbath'"?

???
Rich


Yeah, that's an odd expression. Maybe he's from England?

Bob

What did you guys call these things? Or do you recognize them)

http://news.thomasnet.com/images/large/521/521350.jpg
http://www.bradleycorp.com/images/products/fixtures/wf2808_highres.jpg



Best regards,
Spehro Pefhany

Hmmm. Maybe it's a birdbath. Or, it could be a cotton candy machine.

I don't recall seeing any birdbaths in high school. A lot of birds (aka
girls), but they wouldn't let us watch them take their baths in high school.

Bob
--
== All google group posts are automatically deleted due to spam ==

 

[John Larkin]

On Tue, 16 Jun 2009 12:56:06 -0700, "RST Engineering - JIm"
<jweir43@gmail.com> wrote:

Jan Crystals, Ft. Myers FL. Google for the web page.

Jim
WX6RST


"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:tOzZl.20427$D32.4813@flpi146.ffdc.sbc.com...


Back in the day, you used to be able to get specific crystal frequencies
reasonably inexpensively in small quantities--can you still?


Yes. Best to ask a ham radio operator who still builds stuff (before they
are extinct ...) for some good hints where to buy.

This

ftp://jjlarkin.lmi.net/Lap-Tech.JPG

is a 40 MHz oven-type vacuum-sealed glass AT-cut crystal that is made
for us by Lap-Tech in Ontario. They mark the turning-point temperature
on each one. These are superb crystals... high Q, low aging. They look
like little pieces of jewelry.

John

 

[Richard Cranium]

On Tue, 16 Jun 2009 17:32:18 -0700, RoyLFuchs
<RoyLFuchs@urfargingicehole.org> wrote:

On Tue, 16 Jun 2009 18:39:45 +1000, Bob Larter <bobbylarter@gmail.com
The biggest retard in Usenet wrote:

RoyLFuchs wrote:
On Tue, 16 Jun 2009 17:35:30 +1000, Bob Larter <bobbylarter@gmail.com
wrote:

Ayup, that's our DimBulb.


You're an idiot, Larter.

Go fuck yourself.


Hahahah! The immature little retarded bastard can't handle the truth.

Not your anything, dumbfucktard.

Hi Archie:

Still avoiding the puzzle challenge?
Still refusing to explain your admission of celibacy?

You're a douchebag!

 

[Tim Williams]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:mqng35hj14adg979gbicfid4km737vjghi@4ax.com...

ftp://jjlarkin.lmi.net/Lap-Tech.JPG

is a 40 MHz oven-type vacuum-sealed glass AT-cut crystal that is made
for us by Lap-Tech in Ontario. They mark the turning-point temperature
on each one. These are superb crystals... high Q, low aging. They look
like little pieces of jewelry.

Neet.

Glass? It would be much more poetic to use pure fused quartz. And a
sintered quartz plug for the white part.

And, uh... non-stoichiometric SiO2 for the leads I guess???...

Oh well.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms