| Author |
Message |
Reg Edwards
Guest
|
 Posted:
Wed Mar 02, 2005 4:08 pm Post subject:
Re: Using non-overtone crystal in overtone mode? |
|
|
A solid slab of crystal naturally oscillates at frequencies at which one of
its three dimensions, length, breadth and thickness, is a mechanical
1/2-wavelength. It can easily be induced to oscillate at harmonics of the
fundamental.
It can also oscillate in one of several mechanical modes, eg., longitudinal,
breadth-wise or in torsion. And in shunt or series-resonant electrical
modes.
The circuit it is embedded in can encourage a preferred frequency. It is
easy to select harmonics. Self-preference is also given to the frequency
which has the highest Q, ie., the least mechanical loss. This is usually the
fundamental.
It does not oscillate EXACTLY at multiples simply because it has three
dimensions and Length, Breadth and Thickness slightly 'interfere' with each
other.
A poorly cut crystal, eg., lack of parallelism, at which there may be no
strong preference may jump erratically between two non-harmonically related
frequencies.
Frequency versus temperature curves depend on oscillation mode and on the
angle at which the slab is cut relative to the direction of the individual
crystals in the bulk material lattice as found by optical means. Cubic
curves are best because they contain a flat horizontal portion.
|
|
| Back to top |
|
 |
John Fields
Guest
|
| Posted:
Wed Mar 02, 2005 7:02 pm Post subject:
Re: Using non-overtone crystal in overtone mode? |
|
|
On Wed, 2 Mar 2005 01:41:06 +0000 (UTC), don@manx.misty.com (Don
Klipstein) wrote:
| Quote: | In article <ts6921d632jtuabnv9d0n9b0hv5mlb573i@4ax.com>, John Fields wrote:
On Tue, 1 Mar 2005 08:12:48 -0800, "RST Engineering \(jw\)"
jim@rstengineering.com> wrote:
Sorry, dude, 50 years of designing with crystals, right from when I ground
my first surplus WWII rock on a piece of glass with toothpaste as the
abrasive says that what the original poster asked is correct.
Will the harmonic be precise? No. Will it be "close", which is what the
original poster asked? You bet. Depending on the oscillator circuit, can
it be "pulled" on frequency? Perhaps.
But to say that the crystal doesn't resonate anywhere near the harmonic is,
as I said, bullpuckey.
---
Sorry, dude, no matter how much time you've got in, if you go back
and read my post, you'll find that I wrote:
"You can use a fundamental mode crystal as an overtone oscillator, but
even if you can get it to oscillate, it won't be generating an
overtone at 100MHz, since overtone modes of oscillation aren't
harmonically related to the fundamental."
and that you replied with:
"That is total and absolute bullpuckey."
Notice that I didn't say "near", I said "at".
If you can find fault with anything I wrote in that post, I'd
appreciate specific criticism instead of that broad brush you painted
with.
Now suppose someone makes a crystal oscillate in some overtone mode that
the crystal manufacturer recommends against and is predicted to be
"inharmonic" but turns out to be only a few hundred or even sometimes a
few 10's of KHz from a multiple of a frequency that results from being
used as directed?
|
---
If it's not an integer multiple of the fundamental then it won't be a
harmonic.
---
| Quote: | As I said in different words in a different post - correctly predicting
that $#!+ (AKA "slop") will spatter does not necessarily that much will
spatter nor that any will spatter far, and maybe in many cases it is
doubtful that both much will spatter and that much will spatter far.
|
---
If the prediction came true, then it came true.
--
John Fields |
|
| Back to top |
|
|
J M Noeding
Guest
|
| Posted:
Mon Mar 07, 2005 2:13 pm Post subject:
70MHz Imagerejection mixer with 2x SA602 (?) |
|
|
Hi
have been examining some surplus mobile telephone base station
equipment and discovered that the 70MHz to 455kHz mixers consists of
2x SA602. Since I've never seen an application using two such items,
my guess it for an image rejection type mixer.
Could somebody please guide me into some notes describing such mixer,
possibly using 2x SA602 (and a crystal osc)
Jan-Martin
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm
|
|
| Back to top |
|
|
Highland Ham
Guest
|
| Posted:
Mon Mar 07, 2005 5:13 pm Post subject:
Re: 70MHz Imagerejection mixer with 2x SA602 (?) |
|
|
| Quote: | have been examining some surplus mobile telephone base station
equipment and discovered that the 70MHz to 455kHz mixers consists of
2x SA602. Since I've never seen an application using two such items,
my guess it for an image rejection type mixer.
Could somebody please guide me into some notes describing such mixer,
possibly using 2x SA602 (and a crystal osc)
======================================= |
Jan-Martin , With 2xSA602 ,are you sure there isn't a 10.7 MHz
'intermediate' IF as well ?
Frank GM0CSZ / KN6WH |
|
| Back to top |
|
|
Andrew Holme
Guest
|
| Posted:
Mon Mar 07, 2005 6:32 pm Post subject:
Re: 70MHz Imagerejection mixer with 2x SA602 (?) |
|
|
J M Noeding wrote:
| Quote: | have been examining some surplus mobile telephone base station
equipment and discovered that the 70MHz to 455kHz mixers consists of
2x SA602. Since I've never seen an application using two such items,
my guess it for an image rejection type mixer.
|
An image rejecting mixer requires quadrature inputs (both signal and
LO), two mixers, and summation of the outputs i.e.
sin(A+B) = sin(A)cos(B) + cos(A)sin(B)
Also - you're unlikely to have image problems at the second mixer. |
|
| Back to top |
|
|
J M Noeding
Guest
|
| Posted:
Tue Mar 08, 2005 4:02 am Post subject:
Re: 70MHz Imagerejection mixer with 2x SA602 (?) |
|
|
On Mon, 07 Mar 2005 11:13:33 GMT, "Highland Ham"
<abcgm0csz.kn6whxyz@abcntlworldxyz.com> wrote:
| Quote: | have been examining some surplus mobile telephone base station
equipment and discovered that the 70MHz to 455kHz mixers consists of
2x SA602. Since I've never seen an application using two such items,
my guess it for an image rejection type mixer.
Could somebody please guide me into some notes describing such mixer,
possibly using 2x SA602 (and a crystal osc)
=======================================
Jan-Martin , With 2xSA602 ,are you sure there isn't a 10.7 MHz
'intermediate' IF as well ?
Frank GM0CSZ / KN6WH
Nope, it is shown as |
http://www.noding.com/la8ak/12345/images/bd34-rx.jpg
This for NMT450, while earlier NOKIA NMT900 mobile phone BS used
21.4Mz IF as well as 455kHz, while modern 900mc GSM handsets now are
direct conversion. In the actual rig there is a 70MHz xtal filter as
well as 455kHz ceramic filters
The complete page (in Norwegian) is at
http://home.online.no/~la8ak/d28.htm
73, Jan-Martin LA8AK (ex GW5BFV)
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm |
|
| Back to top |
|
|
|
|
|
|
FAQ
Memberlist
Register
Profile
Log in to check your private messages
Log in