QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/digital/940202.txt

Internet Message Format | 1994-11-13 | 12KB

Date: Mon, 20 Jun 94 04:30:23 PDT
From: Ham-Digital Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Digital Digest V94 #202
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Ham-Digital Digest          Mon, 20 Jun 94       Volume 94 : Issue  202

Today's Topics:
                       AEA DSP2232 Mailing List
                         DISTRIBUTION STATUS
                 finding the freq of an xtal (3 msgs)
                   GTOR evaluation/update? (2 msgs)
                    Railroad track as an antenna?

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policies or positions of any party.  Your mileage may vary.  So there.
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Date: 20 Jun 1994 00:01:03 +0200
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Subject: AEA DSP2232 Mailing List
To: [e-mail]

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AEA DSP 2232 - Digital Signal Processing Multi-Mode Data Controller

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Date: 19 Jun 94 16:54:16 GMT
From: [e-mail]
Subject: DISTRIBUTION STATUS
To: [e-mail]

SMTPGATE.HAMDIGI2     DISTRIBUTION STATUS INFORMATION      06/19/94 16:
53:00
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Date: 19 Jun 1994 13:12:22 -0400
From: news1.digex.net!access.digex.net![e-mail]
Subject: finding the freq of an xtal
To: [e-mail]

In article <2u0mk4$[e-mail]>, Acsys Inc. wrote:
>
> I have a xtal of unknown value (~8.7mhz) that I need to find the exact
> frequency of.  What is the best way to do this?  I do have a frequency
> counter, sho should I build a xtal osc and use the coutner?  How bout
> a simple osc made out of cmos parts like the 4011?  If so what would
> be a good schematic to use to do this?  I need to be quite accurate.
>
> thanx,
>
> mycal
>
The freq counter should be accurate enough, you have to find a buffered
point to pick off the signal, otherwise you'll pad the crystal oscillator
and throw it off frequency a bit if you go directly to it.

Andy N3LCW

------------------------------

Date: 19 Jun 1994 12:51:01 -0400
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!news.ans.net!newstf01.cr1.aol.com!search01.news.aol.com![e-mail]
Subject: finding the freq of an xtal
To: [e-mail]

In article <2u0mk4$[e-mail]>, [e-mail] (Acsys Inc.)
writes:


I have a xtal of unknown value (~8.7mhz) that I need to find the
exact
frequency of.  What is the best way to do this?  I do have a
frequency
counter, sho should I build a xtal osc and use the coutner?  How bout
a simple osc made out of cmos parts like the 4011?  If so what would
be a good schematic to use to do this?  I need to be quite accurate.

thanx,

mycal

Obviously an oscillator would be a fantastic way to check your
crystal.  In factr, given the circumstances, if you dont have really
good test equipment, it is probably the best way.  Another way you
could test the crystal would be a with a sweep generator that is
capable of going up to well beyond the frequency of the crystal, and
by using a spectrum analoyzer and a generator, you should be able to
sweep through the frequencies, look for the peak output and then
determine the center frequency.

Build the oscillator though... simplier... :)

Prof RickD, N0NJY

------------------------------

Date: 20 Jun 94 07:44:45 GMT
From: ihnp4.ucsd.edu!sdd.hp.com!nigel.msen.com!yale.edu!noc.near.net!news.delphi.com!BIX.com![e-mail]
Subject: finding the freq of an xtal
To: [e-mail]

[e-mail] (Andy Domonkos) writes:

>In article <2u0mk4$[e-mail]>, Acsys Inc. wrote:
>>
>> I have a xtal of unknown value (~8.7mhz) that I need to find the exact
>> frequency of.  What is the best way to do this?  I do have a frequency
>> counter, sho should I build a xtal osc and use the coutner?  How bout
>> a simple osc made out of cmos parts like the 4011?  If so what would
>> be a good schematic to use to do this?  I need to be quite accurate.
>>
>> thanx,
>>
>> mycal
>>
>The freq counter should be accurate enough, you have to find a buffered
>point to pick off the signal, otherwise you'll pad the crystal oscillator
>and throw it off frequency a bit if you go directly to it.

>Andy N3LCW



Well, sorta. You have to know whether the crystal is cut for a parallel
resonant mode (if so what parallel capacitance) or a series mode. Then you
build a leetle oscillator that is appropriate to the crystal's mode and
measure it. That tells you a little bit about the crystal. Howsosomeever,
crystals are sensitive to the amount of drive you place on them, temperature
(of course), pressure, etc etc. Um, just how acurate must it be? If a couple
hundred parts per million are enough then a rude-crude CMOS or TTL oscillator
should do. If you need it characterized to the nitties and gritties you have
a whole nuther ball of fish to fry. (Hm, could I mix that metaphore worse?)

An ideal way is a VERY stable network analyzer. Place the crystal in a well
calibrated fixture in shunt with the line. Slowly sweep til you see a small
dip. Note the frequency and the amplitude. Then place it in series. Note the
peak and dip as you tune. Then build an equivalent circuit from the results.
Repeat it with higher drive levels until you see the crystal frequency change
noticeably. Do not drive it within 10dB of that level if you want REAL
stability. Of course, if you need this level of accuracy you're playing serious
engineer and know how to do the math. Yer on yer own here. It is too long since
I limped through some of this for characterising some VXO crystals. (It DOES
work. The resultant VXOs very closely matched predictions, right down to when
the spurious resonances would kick in and become a PITA. Your measurement WILL
see them if you do it VERY patiently.)
{^_^}

------------------------------

Date: Sun, 19 Jun 94 08:36:53 MST
From: ihnp4.ucsd.edu!swrinde!cs.utexas.edu!asuvax!ennews!stat![e-mail]
Subject: GTOR evaluation/update?
To: [e-mail]

[e-mail] (Roger Buffington) writes:

> But would sure like to hear from actual GTOR users who have had the
> chance to really determine how it compares to Amtor and Pactor.

I have one of the new KAMPlus with both.  I really haven't seen much of
a difference between GTOR and Pactor, but I've only tried it on two
contacts so far, and only in conversation mode.  I haven't had the time
to transfer some medium size binary files to see it works any better.

david

---
Editor, HICNet Medical Newsletter
Internet: [e-mail]                 FAX: [phone]
Bitnet  : ATW1H@ASUACAD

------------------------------

Date: Sun, 19 Jun 1994 21:56:01 GMT
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!usenet.ins.cwru.edu!news.csuohio.edu![e-mail]
Subject: GTOR evaluation/update?
To: [e-mail]



Having tested both Pactor and GTOR over a number of environments, it is plain
that although GTOR offers superior performance, Pactor is more reliable.

We do quite a bit of camping.  When camping, we connect back home through a
number of BBS ports that support Pactor and GTOR.  In two systems, two KAMs
were placed in parallel with one on GTOR and one on Pactor.  A number of
weeks have been spent then getting back to the systems from remote locations.

On an eighty meters 200 mile path, GTOR was fantastic when the band was in
good to excellent condition.  We typically had to stay at the terminal to
read the data that was flowing through.  The rate of data flow was high
enough to be at the limit of reading it as it came in.  However, over that
same path, Pactor was found to be more reliable.  When the band was opening
or closing, GTOR would just not link or would do so only on stations that
were not scanning.  Pactor would link fairly quickly and the link would hold.
Data flow once linked would show Pactor throughput to be higher than GTOR.
As much of our operation is on 80 meters as the band opens and closes, Pactor
is the mode of choice for those limited to one TNC.

73,
Steve
        NO8M@NO8M.#NEOH.OH.USA.NA   <<< this works best
        [e-mail] <<< this works better
        the above address           <<< will not work at all

------------------------------

Date: 19 Jun 1994 21:33:14 -0400
From: ihnp4.ucsd.edu!sdd.hp.com!col.hp.com!csn!jabba.cybernetics.net![e-mail]
Subject: Railroad track as an antenna?
To: [e-mail]

STORM JAMES ([e-mail]) wrote:
: I have heard a legend that a college radio station (either at MIT, Tufts,
: or Swarthmore) welded antenna to railroad tracks, and peeved the FCC by
: broadcasting nationwide.  Is this true?  If anyone knows, please email me
: (or post here)  If you do know, could you please direct me to some
: documentation regarding this legend if you can.
:

I don't think that this would be useful for the frequencies used for
comericial radio, but the Pensylvania RR did use inductive train phones
that used low frequency signal passed through the rail.  The antennas
looked like hand rails on top of the cars and locos.  This worked very
well for the trains, but the equipment was not at all portable, and
propigation away from the tracks was very poor.


--
Tim Rumph                   Concord, NC
[e-mail] (PSE sent mail here, not to uncc.edu-ALL DONE!)
kd4ows@wb4kdf.#gas.nc.usa.na   (non-hams: don't try to use this on the
                                Internet)

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End of Ham-Digital Digest V94 #202
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