Zero beating

Just starting out or wanting to learn about something new. Need help setting up your first station. Want to meet others just starting out. This category is for you.

Moderators: W5ALT, AC2C

Zero beating

Postby kd8ufc » Fri May 24, 2013 9:46 pm

Hi,
I'm a new member here. Name's Bob. I'm not exactly a new ham, but I just got re-licensed after 40 years. I have an IC-7200 xcvr and I'm confused about
the frequency readout.
Long ago, when I answered a CW station, I tuned up or down a little to find the null, or "center" of that signal. Then I set my xmtr to that frequency. It's what I
used to think of as "zero-ing" a signal.
With this IC-7200, everything's different. The manual and everyone else talks about a 'receiver offset'. Advice about "zero-beating" is complicated enough to be a lab
project in a physics class. And then there's the "split-VFO".

Question:
So, how do I find the exact frequency of the that CW signal (or SSB sig, for that matter)? It definitely helps to know this in a DX pileup. And yes, I have "RTFM" so please
don't suggest that. I could suggest that they "WTFM", too. Then we could understand it.

The manual does have the option of changing the "CW tone pitch" - default being 600 Hz. ??? It's this the receiver offset? The pitch changes with the tuned frequency, anyway.
THANK YOU MUCH!
Bob
kd8ufc
Member
 
Posts: 2
Joined: Fri May 17, 2013 4:29 am

Re: Zero beating

Postby W5ALT » Sun May 26, 2013 11:41 pm

Hi Bob, and welcome back!

Yes, the 600 Hz should be the RX offset. I'm not sure about your T/RX but my Icoms also set the sidetone to the same frequency. (Some older rigs had a fixed sidetone.) If yours is the same as mine, then you should tune for the same tone as your CW side tone. Now personally, I'm pretty tone deaf, so that doesn't work very well for me. As an alternative, you can turn off the BK-IN so you key only the side tone and not the rig, hold down the key to hear the RX and the side tone, then tune so the station beats with the side tone note and you'll also be on the same frequency.
73,
Walt, W5ALT
W5ALT
Member
 
Posts: 177
Joined: Tue Jan 31, 2006 2:11 am
Location: Houston/Austin, Texas

Re: Zero beating

Postby kd8ufc » Mon May 27, 2013 9:26 am

Thanks, Walt!

Thank you so much for your explanation. I believe I understand, now. The more I had thought about it, the more mixed up I
was. Now, it makes some sense.

The only thing, especially in a contest weekend, is that there isn't enough to do all of that zero-beating, accessing menus, etc.
But this is a little simpler...
I tune DOWNWARD in frequency until the signal nulls out. (Sometimes I hear a dull 'thumping' sound.) Then I tune UPWARD again, adding 600 KHz. That seems to do it. Most of the time, the other station answers me immediately, so I assume I'm right on frequency. And the voice quality seems normal at that point. No "duck".

Now to figure out how to do this with an SSB signal. There must be more than a 600 Hz offset. From the null, it seems to require about 1500 KHz to get back to a normal sounding voice. But it also varies with different signals. Especially the loudest ones. I guess that's because they have wider sidebands.

Anyway, Walt, thank you for ending my frustration! Hope to meet you on the air. I'm on 20 meters, most of the time. And the Facebook SKCC group.
kd8ufc
Member
 
Posts: 2
Joined: Fri May 17, 2013 4:29 am

Re: Zero beating

Postby W5ALT » Mon May 27, 2013 11:49 pm

Yes, Bob, your method will work as well.

Actually, I rarely worry about zero-beating. I just tune for a comfortable tone, then call. If you deal with pile-ups, most ops don't use real narrow filters, because it's a mess and the tone that is a little bit off of the rest is the one that gets through. For casual operating I don't use narrow filters, either, so a few Hertz plus or minus doesn't make too much difference.

In my opinion, zero beating is something that many people worry too much about. But that's just my opinion; others may disagree.
73,
Walt, W5ALT
W5ALT
Member
 
Posts: 177
Joined: Tue Jan 31, 2006 2:11 am
Location: Houston/Austin, Texas

Re: Zero beating

Postby k8jd » Thu Jun 20, 2013 6:31 pm

WHY "ZERO BEAT' ?
First off, Zero beating is a term left over from the old days of separate AM transmitter VFO and recievers back in the tube days. You would listen to an AM signal and to get on freq you turned on the VFO or "Spot" on the transmitter and tuned the VFO dial near the receiver freq and heard the hetrodyne beat tones go from High pitch and down to the ZERO, when you got to the right frequency.
When conditions are crowded, the way they can be in evenings and weekends when everyone gets on the air, it is important to be on the same freq as the station you are chatting with.
If you answer a CQ with no idea of "Zero Beating" him first, you may be so far off that you are on top of another QSO and causing QRM. This is more of a problem if you have only a wide SSB filter in your receiver or select the widest filter, because it is "easier to tune with".
One way to be sure you are close to the signal you want to call is using the narrowest CW filter you have and just tune for the strongest S-meter reading. If you are centered in the bandpass you are probably closest to the signal when you transmit.
Once you are tuned to the signal you want to call DO NOT mess with the VFO dial again. Ignore the freq display (only check if you are within your privelages band), just call.
MAKE SURE the R.I.T. or X.I.T settings are OFF or Zeroed before you start operating, they only apply to special conditions and you don't have to mess with them.
Hope this gives you some background and insight and helps you operate.
73 from K8JD, SKCC 1395, Centurion 18, Tribune 12, Band Endorsements; 160, 80, 60, 40, 30M, 20, 17, and 10M

Ham radio is real Radio, CW is real Hamming!
k8jd
Member
 
Posts: 380
Joined: Fri Feb 24, 2006 5:15 pm
Location: Commerce, MI


Return to Beginners Corner

Who is online

Users browsing this forum: No registered users and 2 guests