Question: AL-80B/3-500Z Driving Power

Discussion in 'Amateur Radio Amplifiers' started by KJ4BJ, May 16, 2019.

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  1. K0OKS

    K0OKS Premium Subscriber QRZ Page

    Just use the nice ALC circuit in the AL-80B and adjust it per the manual.
     
  2. KM3F

    KM3F Ham Member QRZ Page

    I use a 50% duty cycle 30 wpm speed dot drive from the radio's internal keyer to tune the amplifier and the antenna Tuner via Peak reading power meters in both the AL80B and the Tuner, as well as the radio's SWR indicator..
    I peak the Plate and Load first, then the Antenna Tuner for both a flat match out and the radio to a flat match as it reflects back through the tube to the input circuit.
    The Load is then advanced to drop the output by some 10 watts for a hopeful improvement in IMD reduction, then add some ALC for just a perceptual power drop and Amplifier ALC meter kick on peaks to be sure the amplifier cannot be over driven on voice peaks.
    Using this procedure, my signal as observed on receiving ends many times has never shown tendency to splatter by just audio or on band scopes on modern radios or be wider than the 3k I run from a stock unmodified radio.
    The outboard audio is being highly processed and compressed. Audio reported as notable to sum up all the different comments.
    All the matches from the radio through the amplifier input to the output and Antenna are satisfied in one tune process.
    I see 800 to 850 watts on power peaks with 90 watts of drive.
    The 90 watt drive level even if perceived a small bit excessive is taken care of with ALC feedback. When the ALC meter just kicks on voice peaks, it's working as it is designed to do.
    Most don't go to these lengths, but I do, and get the results that work for me.
    The AL 80B is about 25 years old, purchased used and has had tubes replaced a number of times before I got it.
    The last owner abused it running RTTY as I found out after firing it up the first time about 5 years ago.
    I tend to use equipment to the limits just to learn, but not intentionally to destruction but max fine operation.
    I have an AL 1500 waiting to be put back together, being bought as a basket case from the last jerk who owned it.
     

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