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Author Topic: Tuning in CW stations with IC-718  (Read 4817 times)
NG3Z
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Posts: 4




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« on: August 31, 2007, 02:53:36 AM »

I'm back on the air after a long hiatus and bought an IC-718. I should know better but I don't understand how to tune in a station. Per the manual it seems like if I have the CW tone set at 600 hz then I tune in the calling station so the receiving tone matches my CW sidetone (which I suppose I could do by ear or make exact by zero beating it then turning up the VFO 600 hz). And it seems like I should go up in freq from the zero beat and not down. And then there's that CW reverse which I think I understand - it's what I said above except you'd tune down in freq from the zero beat (?).

Any thoughts on this topic would be helpful. Also how to tune in SSB properly. Thanks.
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KE3WD
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« Reply #1 on: August 31, 2007, 07:36:19 AM »

Just zero beat the received CW note to your sidetone.

The radio will then transmit the correct amount of shift.  

When you hit the CW reverse button, the amount of shift is moved to the other side of the center frequency.  

How CW offset works is not rocket science, if we were to tune to the exact center of the CW carrier, we would hear next to nothing, certainly not a tone.  

The tone you actually hear is the difference frequency between the carrier frequency and where the radio is tuned, because any two frequencies when mixed make two other frequencies, the sum of the two and the difference between the two.  

In CW mode the sum is filtered off, leaving that difference value.  Tuning to 600, 700, 800 Hz or so either side of the carrier freq. creates an audio spectrum tone of that frequency that we can hear.  

When you zero beat the sidetone, then, you are automatically set to come back to the other op right where your signal is supposed to be.  

Reversing the thing can sometimes help you deal with interference that is above or below by shifting your receiver's center point the amount of the sidetone difference.  


KE3WD
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KB9CRY
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« Reply #2 on: August 31, 2007, 02:34:14 PM »

Also how to tune in SSB properly.

Until they sound intelligible.
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NG3Z
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« Reply #3 on: September 01, 2007, 02:09:31 PM »

Thanks to KE3WD for the tuning primer. I now understand what is going on and I will assume that if I change the sidetone freq (as I can with the 718) that the offset freq changes along with it. I must admit I like the way my 15 year old century 22 tunes in freqs better.

I was worried that my 718 wasn't working but I think it's just bad band conditions and my crappy 20m attic dipole that is restricting me. I need to put up a better antenna soon. 73
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WQ3T
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« Reply #4 on: September 07, 2007, 11:55:04 AM »

To zero beat with the IC-718, you need to set BK-IN to OFF instead of SE or FL. This way you can hear both your sidetone and the incoming signal. A straight key or bug helps because you can lean on it or use the shorting bar to hold the key down. When you tune a signal while keying with BK-IN OFF, you will hear beats get slower the closer you get to matching the frequencies. This is a common method used to tune a mucial instrument to a frequency reference. After you zero-beat, you must change BK-IN to SE or FL so you can transmit a CW tone over the air. I bet your old TEN-TEC rig works the same way. My Kenwood TS-520S does; it has a VOX switch to switch from receiving a signal with sidetone (VOX OFF) to transmitting a CW tone over the air (VOX ON). A brand new ICOM IC-7800 zero-beats a CW signal the same way a 30 year old TS-520S does.
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NG3Z
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« Reply #5 on: September 07, 2007, 04:58:42 PM »

Thanks WQ3T,

This helps even more. I understand zero beating because I am a musician and use it all the time to tune. I was a bit confused about actually how to do it, i.e. produce a sidetone against the actual station tone. I'd love to use this techinque but it is a pain to switch back and forth between break-in methods (using the set button, etc). I'll try it and see how quickly I can go back and forth.

To tune my old C22 I used to get exactly on frequency (when the signal went to a whisper, tone of 0 hz) then I would use the offset dial to change the receive freq so I could hear a tone. I hope I was doing it right - no one complained to me about being off frequency. I do miss a lot of the old C22. The full break-in was amazingly good.
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K7KBN
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« Reply #6 on: September 07, 2007, 05:18:51 PM »

Back in the day of separate transmitters and receivers, "zero beating" was a bit more complex, depending on the specific equipment involved, yet whatever problems there were -- well, we just lived with them.  If we called CQ and someone answered, we just adjusted our receiver for best intelligibility and went from there.  SSB produced a hiccup or two, but with practice we all managed to be able to tune other stations in.

One feature that many newer hams don't seem to know about is the RIT, sometimes labeled "Delta Rx" or something similar.  If you call CQ and an answering station seems "off frequency", use the RIT, not the main tuning control, to improve copy to your liking.
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73
Pat K7KBN
CWO4 USNR Ret.
K9JH
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Posts: 49




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« Reply #7 on: April 24, 2008, 05:55:25 AM »

I also have a IC-718.

The fastest way to zero beat is to put the radio in sideband mode (USB/LSB) and then tune the radio so that the CW goes lower and lower in pitch until it becomes nothing.  Then your radio will be tuned to the CW.  Then put the radio in CW mode, and the radio will automatically offset the freq. so you can hear the CW at whatever audio freq you have chosen (Mine is set for 700hz).  

Hope that makes sense.

K9JH
JIM
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KB4MB
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Posts: 295




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« Reply #8 on: May 07, 2010, 12:52:09 PM »

I agree with Jim - it is easiest just to put it in SSB mode and tune the signal until it disappears then put it in CW... then you don't have to fool with menus ruining your break-in.  Couldn't be simpler.
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VA7CPC
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« Reply #9 on: May 07, 2010, 04:56:05 PM »

PMFJI --

Many rigs (not all) will generate a "spot" tone when a specific button is pressed.

The "spot" tone is generated at the sidetone frequency -- tune the incoming signal so it has the same pitch as the "spot" tone, and you're at zero-beat.

I'm surprised that the IC-718 doesn't have that feature.   Changing BK-IN to OFF, and holding the key, will have the same effect, but it's clumsy.

                Charles

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VA7CPC
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« Reply #10 on: May 07, 2010, 04:58:23 PM »

BTW --

If you tune to 14.070 USB, around noon, you should get a fair bit of PSK31 activity.  If there's nothing to hear, either:

. . . the rig is broken

. . . the antenna is _really bad_ (even an attic dipole should work OK in this test)

. . . band conditions are truly awful

. . . your local noise is very high (which could easily happen with an attic antenna).

             Charles
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K9ZMD
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Posts: 173




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« Reply #11 on: May 07, 2010, 09:10:03 PM »

Louis,

If you have a computer in your radio shack, you have the first ingredient needed to effortlessly zero beat any signal.  The second ingredient is any one of the free digimode programs available on the internet. The third ingredient is a patch cord with proper connectors at each end; plug one end into your computer's Line In jack, the other end to your receiver to pick off audio.   If you are already a digimode operator, you are already equipped and know where I am heading. 

When you key your rig with the digimode waterfall running, your sidetone will appear at a spot corresponding to your side tone frequency.   Make a note of that spot.

As you tune in a received CW signal, you'll see it on the waterfall; continue to tune until the signal is at your side tone frequency.  You are now perfectly tuned to that signal.  Effortlessly zero beat.   

If that doesn't give you the best tone to comfortably copy the received signal, then use your RIT to change the pitch.  That won't alter the zero beat setting because it is not changing your transmit frequency.  Just remember to clear the RIT offset on completion of the QSO.   Wink

As an added benefit, the waterfall display also helps you locate a clear frequency before calling CQ.  I've sometimes been able to see the tracing of CW signals that aren't even audible.  73

Gary, K9ZMD/6
Palmdale, CA
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AA4PB
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Posts: 12980




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« Reply #12 on: May 08, 2010, 12:22:39 PM »

There are plenty of circuits around for a simple PLL (phased locked loop) IC zero-beat indicator. Adjust it for the audio frequency you need for zero beat, hook it across your speaker and tune the signal until the LED flashes with the CW keying.
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NG0K
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Posts: 334




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« Reply #13 on: May 09, 2010, 06:13:15 AM »

If you have a narrow CW filter then just center the CW signal in the filter passband.  Close enough most of the time unless the bands are really busy.  A few Hz one way or another isn't going to matter much.   In time (unless physically unable) you will recognize the pitch to within a few Hz.

73, Doug
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73, Doug - NG0K
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