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Zero Beat -off frequency

Discussion in 'On-Air Operations - Q&A' started by KD2RON, Oct 5, 2017.

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  1. KD2RON

    KD2RON Ham Member QRZ Page

    I use an audio scope when I run qrp cw to zero beat. I noticed that quite often QSO's are not on the same freq. by maybe less than a tenth of a khz. When I answer a cq I try to call the exact freq. even when its just a little off a more commonly used one (eg 7050). I was wondering in a transciever if the trans is off is the rec off the same? In other words if for example you have your transciever set to 7050.000 and you are really trns on 7049.95 do you rec on 7049.95 ? Obviously if you have vintage rig with separate trns and recv they would be different but do modern transvievers use the same freq control for both trans and recv. Just don't want to waste my little 5 watts of signal answering on the wrong freq the caller is listening on. I am not talking about DX up or down.
     
  2. VK3YE

    VK3YE Ham Member QRZ Page

    Unless you're using a very narrow filter, 100Hz off frequency is no big deal.

    Assuming a quiet band it's good practice for stations calling CQ to use a wider filter setting so they can hear those a little off.

    Transceivers may come with a 700 - 800 Hz offset preset.

    The offset it so that signals on receive provide an audible beat note without you having to adjust the transceiver's tuning.

    The rig's offset should be set to your favourite pitch for receiving CW (all but very old rigs allow you to vary the offset).

    Eg the ear is most sensitive at a somewhat higher frequency but if the note is lower it's easier to pick out the signal if others are close by.

    The person replying to your call may prefer a different note to the offset.

    This can be catered for in the rig but it's possibly a menu setting that many operators don't bother with.

    Here I discuss CW offsets with particular reference to basic homebrew gear.

     
    KO4LZ likes this.
  3. N8AFT

    N8AFT Subscriber QRZ Page

    Where's the big deal???
    I'm on MY frequency. Unless we're talking about 60m we are NOT channelized. RIT serves a purpose on your RX.
    You fail to realize perhaps that there are still some of us CW ops who frequently / usually
    run tube and XTAL gear. XTALs are not guaranteed to be accurate.
    I'll tune in whoever needs to be tuned in and not complain about it, it's part of operating CW on HF OM.
     
    VK4HAT likes this.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Using a scope to zero-beat anyone is kind of over the edge.

    CW contacts are usually within about 200 Hz of each other, which is more than close enough 99.9% of the time; any offset has nothing to do with whether a transceiver really RX and TX's on the same frequency -- it has much more to do with "I tune you in to a pleasing pitch for me and then transmit."

    In DXpedition pileups or contests where a station might be working 180 Q's an hour, think anyone bothers to actually zero-beat? No time for that. Tune 'em in and when it's time to call, call.
     
    WA7PRC and K7GQ like this.
  5. KD2RON

    KD2RON Ham Member QRZ Page

    I operated a DX20 until recently, I wonder what makes us so arrogant.
     
    WR2E likes this.
  6. AI3V

    AI3V Ham Member QRZ Page

    What kind of scope are you using?

    The usual procedure is to tune the other station in so you hear whatever tone sounds best to you.

    You transmit back as close to his frequency as you can.

    If he needs to fine tune your tone, he should only adjust his receiver frequency (rit-receiver incremental tuning). Unless he has reasons to believe his transmitter has changed frequency (drifted) since the start of the qso, he should leave it alone.

    Likewise, you should only change your receiver frequency, usually to change the tone because you are tired of listening to it.

    Rege

    P.S. I allways transmit on an exact frequency, I'm exactly where I am.:cool:
     
    WA7PRC likes this.
  7. G3YRO

    G3YRO Ham Member QRZ Page

    So are you saying that if I was transmitting on, say 7083.25, you wouldn't reply on my frequency?!

    I'm amazed that a lot of stations DON'T reply on your frequency, mainly on SSB . . . as if the HF bands are somehow channelised !!

    In terms of CW, you shouldn't need a 'scope to net on the other station's frquency . . . your ear should be able to judge the pitch and get you within 20 Hz.

    I have a 250Hz CW Filter in both my transceivers . . . so if you called me 200 Hz off frequency, I wouldn't hear you ! (unless I tuned about)

    Roger G3YRO
     
    Last edited: Oct 9, 2017
  8. WR2E

    WR2E Ham Member QRZ Page

    Not all are musicians with perfect pitch Roger!

    I think he's probably talking about an audio spectrum analyzer app on a computer. Easy way to learn the pitch and set the rcvr to that... Then you should be by close to zero beat.
     
  9. N8AFT

    N8AFT Subscriber QRZ Page

    Zero Beating a CW signal is /should /used to be one of the very first things a new CW op needs to master.
    I zero beat my transceiver's TX signal to my digi readout equipped RX so I know where is the exact frequency off-set.
    Also a pro quality frequency counter is sniffing on my RF output line.
    I think digi readouts are a great advancement in TX and RX accuracy but we tend to maybe get a tad carried away with them.
    Just my two cents.... VY 72 / 73
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Setting your transmitter frequency to some specific frequency, whether that indication is 100.000000% accurate or not, actually doesn't matter much.

    If you tune in a station to a pleasing pitch for your ears, that's the frequency you should be tuned to. If the "other" station finds that pitch objectionable, he can use RIT to change the pitch to whatever sounds good to him.

    Who cares what the actual frequency is? I only care that I'm "in the band.":p
     
    K3UJ and W4POT like this.

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