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Author Topic: Zero beating a CW signal  (Read 3469 times)
WZ7I
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Posts: 22




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« on: May 15, 2004, 03:16:44 PM »

For 15 years I have struggled to learn how to quickly tune my transceiver to the same frequency as a CQ call.  The best solution I have found requires a computer: I run a tiny window on my screen with UA9OSV’s CwGet program which has a very nice spectrogram display with a vertical line set to your offset frequency.  It works well.

But, it requires a computer and it certainly isn’t appropriate for mobile or portable operation.  In May’s QST, page 69, an article was published suggesting the use of a small musical instrument tuner for zero beating.  I tried it and it works very well.  I bought a Korg CA-30 ($20 + $5 shipping on the web), hooked it directly to the line audio output on my Paragon, and tune the radio till the other guy is an F sharp!  It works as slick as you could wish.

I commend the article to your reading.
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K7KBN
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Posts: 2801




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« Reply #1 on: May 17, 2004, 04:24:49 PM »

I'm not quite sure what the fuss is over "zero-beating" a CW signal.  Certainly for SSB, the stations in QSO must be on the same frequency within a very narrow bandpass or you will have mutual unintelligibility (heck of a word!)

For CW, I hear a station calling CQ and decide to answer him.  I tune his signal in for the best and clearest sound and call.  So what if I'm a couple hundred hertz off?  (If he's got a super narrow filter in line, he's likely not to hear me or any other station anyway).

I'm usually pretty close, however.  By using my transceiver's sidetone note and tuning the other station to where it sounds at the same pitch, I have essentially zero-beat him.
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73
Pat K7KBN
CWO4 USNR Ret.
AE4RV
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Posts: 952


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« Reply #2 on: May 19, 2004, 02:58:55 PM »

"So what if I'm a couple hundred hertz off? (If he's got a super narrow filter in line, he's likely not to hear me or any other station anyway)."

EXACTLY!  He might not hear you.  Also, between the two of you, you will be using more bandwidth than necessary.  (It's true that a super narrow filter should not be used when calling CQ, unless in a contest, but this is mainly because not everyone knows how to zero-beat a CW sig).


"By using my transceiver's sidetone note and tuning the other station to where it sounds at the same pitch, I have essentially zero-beat him."

Yep.  That's what I do.  A musical background helps.  I am to the point where I can usually do it by ear because I have essentially "memorized" my sidetone pitch (abt 640hz).  When I need a reference, I just turn my break-in off, and play the sidetone, kinda like a pitchfork.

I am glad there are cheap tuners out there to help those with "tin" ears...no offense intended...

Also, I have discovered that a lot of hams don't understand the side-tone relationship and the zero-beat thing.  Adjusting your side-tone will also adjust the pitch of received CW signals.  Get your side-tone where you want it, then adjust your VFO to where the CW signal you wish to talk to sounds the same (same pitch), and THEN you are on the same freq.  Some people don't know that....I used to be one of 'em!
 
73
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K7KBN
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Posts: 2801




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« Reply #3 on: May 20, 2004, 05:33:54 PM »

"...like a pitchfork."

I assume you're referring to a tuning fork.  A pitchfork might be dangerous outside the hayloft (chuckle!)

In over 50 years of CW operating I've never taken any great pains to "zero beat", unless it was on a net where the NCS requires "QNZ".  And that has been exactly twice, in my recollection.  There's really no extra bandwidth being used unless both you and the other station (separated by a couple hundred hertz) are transmitting at the same time.

And what about DX stations that tell calling stations "UP5" -- or worse, just "UP".  There might be hundreds of stations calling, and the spectrum between the DX and the pack will be crammed full, but each individual station is probably in full compliance with the spectral purity requirements.

I respectfully maintain that precisely zero-beating another station for a simple CW QSO is unnecessary.
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73
Pat K7KBN
CWO4 USNR Ret.
WB2WIK
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Posts: 20595




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« Reply #4 on: May 20, 2004, 06:54:27 PM »

Here's another way, that works with *most* modern HF transceivers:

Switch MODE from CW to TUNE.  Tune station into actual "zero beat," a la the way we used to do it in the olden days.  Real zero beat = no tone, but you can still hear the AGC pumping.

Return switch to CW mode.  You should be right there.

Works perfectly with about 9 out of 10 modern HF transceivers, which use no offset in the TUNE mode.  

With a musical ear, you can tune a station in to match your sidetone note, and that usually does work very well; however with a horrible ear, you can still tune to a zero beat.

WB2WIK/6
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AE4RV
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Posts: 952


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« Reply #5 on: May 22, 2004, 06:43:37 PM »

"...like a pitchfork."

hehe, yes, I stand corrected...

Thanks, and also thanks to WB2WIK for enlightening me to the origins of the term zero-beat.  I assumed it refered to the 'interference pattern' generated when two similar-but-not-exatcly-equal tones play at the same time.  Now I know better.
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KENNETH
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Posts: 27




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« Reply #6 on: March 03, 2005, 10:43:36 AM »

newbie here, would this also be zero beating? Using an ultra narrow 50 Hertz DSP filter and turning the tuning knob until it reaches peak on your S meter?
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EC8AYR
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Posts: 1




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« Reply #7 on: May 11, 2005, 04:20:53 AM »

Hello Kenneth,

yes, you could zero beat in that way, though the zero beating would be a little tricky, because I think 50Hz it's too narrow (maybe ~150Hz).

un saludo.

---
72 de EC8AYR, Baltasar.
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