YAESU FT-902 DM - Problems in CW

Discussion in 'General Technical Questions and Answers' started by F8BDX, Nov 25, 2019.

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  1. F8BDX

    F8BDX Ham Member QRZ Page

    in contest, the first character of my call sign (F) is deformed by the corespondant which includes N or R.
    in slow speed, no problem.
    if I send in CW (DE F8BDX), no problem.
    or search?
    Thank you
  2. K9STH

    K9STH Ham Member QRZ Page

    Unfortunately, VERY common problem!

    It is caused by the delay of the VOX circuitry in getting the transceiver in the CW transmitter mode. That is one of the reasons that I use the PTT function to place the transmitter in operation before I start keying. I use a foot switch for this and having done so for almost 5-decades.

    Glen, K9STH
    K7TRF likes this.
  3. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Does this happen only when you use an amplifier or does this happen with the rig used alone?

    The issue one way or another is how quickly the rig and possible external amplifier are keyed into transmit mode vs the timing of that first dit of your callsign. It's a common problem with external amplifiers that lack QSK keying loops. Some hams run a foot switch to put the rig into transmit mode and others use external keying sequencers that key the rig's PTT line and any external amplifier prior to delivering the first CW character.

    If this happens with just the rig running barefoot then it's possible you have a bit of excessive time delay in your CW VOX circuitry that you might try to resolve by adjusting VOX parameters but if it happens when running an external amplifier then the problem requires some kind of sequencer or non VOX keying like a foot switch.
  4. F8BDX

    F8BDX Ham Member QRZ Page

    thank you both for the quick response HI.
    problem with the amplifier, and not amplifier
    the internal curtis of 902, and also with the MJ-492 HI
    thank you - Jose
  5. F8BDX

    F8BDX Ham Member QRZ Page

    with the ELECRAFT K2 no problems.
    a very good Transceiver for the CW HI
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Yes, it's not the keyer itself whether internal or external. It's how the rig's VOX switches into transmit mode when it senses the first CW character. The Elecraft K2 has more sophisticated CW keying vs rig T/R switching delay that avoids this problem as do many modern rigs. Modern CW oriented rigs delay the sending of the CW signals a small amount as in 25 to 50 milliseconds relative to switching the rig into transmit mode to avoid problems like you're seeing. It also helps by reducing the chances of hot keying an external linear amplifier where transmit power from the rig arrives at the amplifier input before the amp has fully switched into transmit mode.

    Your best bet is either to run an external keying sequencer with the FT-902DM or run a foot switch to switch the rig into transmit mode prior to your first CW character. One option is to run a K1EL external keyer that has a small time delay CW sequencer built in and has a rig PTT output keying line in addition to the normal key output line. In other words the K1EL buffers and very slightly delays the CW data relative to keying the rig via the PTT line.
  7. F8BDX

    F8BDX Ham Member QRZ Page

    ok thanks for everything.
    73 QRO

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