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Author Topic: Question on zero beat  (Read 676 times)
AB5ON
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Posts: 36




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« on: September 18, 2005, 07:56:20 PM »

Not being critcal, just curious.  

I notice quite a few CW stations responding to CQ's that are as much as 800 Hz off the calling station frequency.  I run a audio spectrum analyzer in the shack and can measure the frequency difference.  I know if I have my DSP filter on I would never hear them respond to me.  I watched a pile up on one DX station that had a dozen stations spread out over about 1.4K.  Looked like baby chicks surrounding the hen all chirping at different frequencies. :-)

Just wondering why most operators don't zero beat the sending station a little closer.

Any thoughts?

Rick
AB5ON
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KA3RFE
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Posts: 185




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« Reply #1 on: September 18, 2005, 09:09:29 PM »

dhat's a good question. I don't know an answer, though. In fact, I may be doing zero beat incorrectly myself. I'm almost compoletely deaf but I can sense the short and long noises and discriminate tones. What i do is tune back and forth slowly until the sidetone and received signal seems to be at the same auido freq. Not hearing two tones, just one.

But sometimes I have stations saying I'm not on frequency, so I duuno what's going on.

73
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NI0C
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Posts: 2436




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« Reply #2 on: September 19, 2005, 07:56:52 AM »

If you are part of a DX pileup, you want to call on a clear frequency-- not on the same frequency a couple hundred others are using.  That's why virtually all modern HF transceivers have either a T-F button or dual-receive capability.

73,
Chuck  NI0C
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WB2WIK
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Posts: 20666




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« Reply #3 on: September 19, 2005, 08:27:52 AM »

That's exactly right.  When we call rare DX, we spread out from his frequency on purpose, to help the DX station copy one signal at a time.  If everybody called zero-beat, the DX station would never hear anybody.

WB2WIK/6
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K7UNZ
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Posts: 691




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« Reply #4 on: September 19, 2005, 08:46:21 AM »

It also helps to allow the DX station to be heard when a bunch of guys are calling him.  What you don't need is to have him covered up by a bunch of guys all calling at different intervals, mostly NOT hearing the DX stations replies.

It does get a little ruff when the DX just says "up" to indicate where they are listening, 'cos "up" could be anything.

Jim/k7unz
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AB5ON
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Posts: 36




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« Reply #5 on: September 19, 2005, 11:36:01 AM »

(Light bulb on)  Ah ha!  The DX pile up makes sense to me.  I don't work DX pile ups on CW, I have a hard enough time with one clean signal.  :-)

Thanks for the enlightenment.

Still puzzled by the single stations so far off.

Rick
AB5ON
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KC0SOG
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Posts: 68




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« Reply #6 on: September 19, 2005, 01:26:03 PM »

I notice this too.  I have yet to work CW dx cuz I hear the pileups but can't hear the DX. My copy skills aren't good enough yet, but I'll keep trying.

73, kc0sog
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NI0C
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Posts: 2436




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« Reply #7 on: September 19, 2005, 03:11:18 PM »

"Still puzzled by the single stations so far off."

There are a number of reasons for this, including using wide SSB filters to tune CW signals, lack of familiarity with gear (especially "boat-anchor" gear), misaligned radios, and carelessness. A couple of weeks ago, I worked a QRP station whose frequency drifted about 500 Hz during the course of his transmission.  I had to follow him with the RIT control to keep from walking across the band myself.

73,
Chuck  NI0C
   
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AC0H
Member

Posts: 16




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« Reply #8 on: September 22, 2005, 10:45:53 AM »

Another possibility is that they are using "Sound Card CW", an audio tone simunlating CW sent to the mic jack in SSB mode. If they don't factor in the CW  offset when setting up they can be high or low by that offset amount.

If you're going to use the computer to send CW, hard key the rig in CW mode through a simple serial port interface.
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