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zero beating?

Discussion in 'Ham Radio Discussions' started by W8RNO, Nov 19, 2011.

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  1. G4OTU

    G4OTU Ham Member QRZ Page

    I think some of you are scaring the socks of W8RNO.

    It is so simple , spend a few minutes getting used to the sound of your sidetone then go on tha air and look for a CQer.

    Try to tune so that he sounds something like your sidetone was. Then call him. Either he'll hear you or he won't - in which case just find another.

    After a few QSOs you'll wonder what all the fuss was about.

    Good luck- enjoy CW ,...hope we'll work someday soon.
     
  2. WA3VJB

    WA3VJB Ham Member QRZ Page

    Zero Beating for AM

    Another part of the hobby where zero beating is important among stations in a QSO is for those of us who prefer AM on HF.

    There are several reasons to align the gathered stations all to the same frequency. One is that during congested band conditions people often pinch down the selectivity of their receivers. When stations are more than a couple Kc away from that spot on the dial, there's a constant need to fine tune to keep stations in the passband and sounding good. Also, some contemporary transceivers have an AM center frequency that is different than when the radio is using other, incompatible modes. If you're told that "you're a couple Kc off," it's worth the time to use your receiver incremental tuning at a given value, so that your carrier frequency matches other stations you're talking with.

    Another good reason to zero-beat is that it benefits those AM stations using synchronous detectors on their receivers. The Sherwood recently improved its design to allow a certain amount of variance, so that this external sync detector can track and "lock" to the variety of AM stations around (but not quite on) a given frequency. Earlier designs and other models (such as the Sony 2010) lacking this ability would lose lock on the next station if they're a little off frequency, and the receiver would need to be fine tuned to restore this improved method of receiving a wholesome AM signal.

    Most recently, as the sunspots return, AM activity on 10 meters has really gone up. It's helpful for the stations (typically two per QSO because of propagation) to dial right to one another's frequency so that others who cannot hear the other side of the conversation are able to find their own clear spot on the dial to establish another QSO.

    Here's an example of a well-tuned AM QSO on 10 meters, with synchronous detection activated.

    http://www.youtube.com/watch?v=Vn-d63EEpNo
     
  3. W5SMD

    W5SMD Ham Member QRZ Page

    My Yaesu ft-857 has an LED on top that turns blue when you are in CW mode and are at the same frequency as an incoming signal. Makes zero beating really easy.
     
  4. K4PP

    K4PP Ham Member QRZ Page

    I've gotten pretty good at adjusting to match my side tone but sometimes I'll swap back and forth between the other side of the signal with the CW/CW-R button to make sure the tone is the same.

    K4PP
     
  5. K0RGR

    K0RGR XML Subscriber QRZ Page

    With the transceivers mentioned, there shouldn't be a big challenge. I do find that I've become slightly tone deaf, so I rely on narrow filters to help get me close. I also use a low sidetone frequency, which makes it easier to compare. Usually, if the signal is tuned in correctly with a 500 or 300 Hz filter, I'm close enough.

    If they are using a direct conversion receiver, or any receiver that is not 'single signal', you will hear the CW signals on both sides of zero beat, and you can easily be quite a ways off frequency. I recently had an issue with my IC-7000 where it was behaving like a DC receiver, and indeed, I fooled myself several times and called people quite a ways off their frequency. I'm still not sure what the problem was, but a change to the PBT corrected it. The problem only happened in CW mode - not in USB or LSB.
     
  6. NI7I

    NI7I Guest

    Zero is about the number of beatings I care to have.
     
  7. WA7PRC

    WA7PRC Ham Member QRZ Page

    Nope. That's not what you need to do. Read below.

    Exactly. Further, your rig may be able to key the sidetone while in the receive mode, and the sidetone frequency should be the same as the T/R offset (typically 800 Hz). Hold the key down while the other station is sending. As you tune close to the other station's frequency, you'll hear two tones beat against each other. The difference between the two frequencies is the "beat note". When they are on the same frequency, the beat note will be zero.

    Sounds like a phase/frequency detector. Nifty!
    Da-dum!
     
  8. KY5U

    KY5U Subscriber QRZ Page

    If you hit an Occupy Wall Street protester in the head, is that zero beating?
     
  9. 2E0OZI

    2E0OZI Ham Member QRZ Page

    Fascinating thread - I hope to be on CW in a couple of months for the first time. I know about 15 characters at the moment, so theres a bit of a way to go!
     
  10. KA5S

    KA5S Premium Subscriber QRZ Page

    When we say "zero beat" nowadays we usually mean "exactly on frequency". The beat note -- in radio, the difference between frequency of an oscillator used to "beat" the desired signal down to audio, is DC, meaning there isn't any difference.

    In the (hah) "good old days", if you were using a separate VFO, you could turn the VFO on and adjust for the same pitch the other guy had, but before there were narrow, "single signal" receivers, you might be on the other side of him -- the same beat note occurring above and below a CW signal -- the wrong sideband . So the only way to be SURE was to retune the receiver so it had a his "beat note" was at a very low frequency, then adjust your VFO so it had a very low frequency tone as well. After that, you could tune the receiver (only!) for a comfortable sound.

    A modern rig of current vintage usually sends CW that is offset by the same amount as its sidetone, and has good opposite sideband rejection. This means, if you tune the other guy to your sidetone frequency, you are ON frequency. Some don't, usually slightly older ones; the IC-765 I'm repairing now (for example) has its adjustable sidetone pitch, but does not change the transmit frequency to match if you adjust it.

    Here's VK1OD's quite clear explanation.

    Cortland
    KA5S
     
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