HIGH Q LOADS AND PROTECTION TRIPS OF THE TRANSMITTER

    N2DTS said: ↑

        1.4 to 1 will trip it out.
        Tight bandwidth (High Q) will trip it out on the high frequency audio sometimes.

AB2RA said:    

    Correct.
    It also is unhappy with arcing, rubbing on tree branches, intermittent bad connectors, etc.

    For an experiment on high Q antennas. or antennas fed with a high Q antenna tuner, try this.
    Adjust the tuner as you would normally, for lowest SWR on the carrier frequency.
    Then lower the power and mute the audio.
    Gradually lower the carrier frequency until it is at the predicted carrier minus the audio band width. Measure the SWR there.
    Then do the same, except above the carrier frequency.

    This demonstrates why the protection is complaining on modulation peaks on a high Q load.
    The DYY doesn't like more than 1:1
    Some people back down the power to 250 or 200 watts, which really will not move the other guy's S meter noticeably.

    The same K7DYY rig works fine on a dummy load without trips.
    The problem isn't the rig, its the antenna system.
    Many solid state linears do not like such antennas either.

    People who insist on old school open wire feeders will probably find that the K7DYY rig is not for them.
    Especially when wind or rain or ice can cause variations.

    I use coax fed fan dipoles fed directly with quality 50 ohm coax and teflon connectors, and a seriously overbuilt tuner which will not arc.
    I have gone over 5 years continuously without a single protecton trip.
    I run 300 watts output with +120% audio peaks from a MAX processor, which is about 1500 PEP.
    I was involved with the Beta test of the 80/40 and made suggestions which solved the problem of frequent FET failures.
    Tamper with the internal adjustments, and plan on replacing a lot of FETs.
    Bruce knew what he was doing, and if you know better than him, have at it.

    I also migrated from an Inovonics 223 to a MAX audio processor.
    Inferior or misadjusted audio systems which do not guarantee precise control of peaks, especially negative peaks, can and will cause protection trips.

    The K7DYY D104 board uses a 2167 compressor (many other systems use the same chip) which does not have a fast enough attack time.
    It was a cheap way to get on the air, and many found it good enough for their needs.
    The slow attack time causes the "first syllable" problem, when a quiet period is followed by a voice peak, especially P, T, F, S etc.
    Many ham AM processors use the same 2167 chip, and some of the music store systems do not have a hard limiter either.
    The solution for the D104 processor is to ignore the scope and back the output level down until the trips stop.
    Yeah, the average modulation on a scope or an accurate modulation monitor will show a lower level.
    If you cannot accept that, you need to spend more than $80 for a better modulation audio system like the MAX, which is not that much more, and solves a lot of other problems like excessive bandwidth in one easy to adjust box.
    The MAX uses a compressor circuit made from discrete components and is pure genius.