Ameritron al 80 a on 160 meters.....

Discussion in 'Amateur Radio Amplifiers' started by KB4MNG, Jun 25, 2019.

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  1. KB4MNG

    KB4MNG Ham Member QRZ Page

    That was my next question, would you be ok with operating into a 3 swr for and extended amount of time? If not, what would be the max you would operate at. The antenna i am using is very narrow in swr width.

  2. N8FVJ

    N8FVJ Ham Member QRZ Page

    The max SWR I use with a tube amp is 2 to 1 SWR.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I doubt "time" (duration) makes any real difference. If the amp can be tuned for a plate dip (which is also the tuning point for a grid current peak), the LOAD control operates within its range (not pointing to "0" or to "10") and the amp produces normal power into your load, it should be fine.

    I've operated several hours at a time in the ARRL 160m contest several times (it's in early December) loading my AL-80B into a 3:1 or worse VSWR and doing a lot of transmitting and it was fine with that. I don't recall the difference in the AL-80A circuitry.
  4. G3YRO

    G3YRO Ham Member QRZ Page

    As stated above, as long as the Amp can be loaded correctly, the actual SWR is irrelevant with a Valve Amp (or PA for that matter) . . .

    As long as it's within the range of the Load capacitor, and it's not flashing over (due to excessively high impedance) then there shouldn't be a problem . . . I've used lots of Valve PAs into SWRs as high as 5:1 . . . this is the advantage of having a Pi-Tank, it can usually match a fairly wide range of impedances without having to use an ATU.

    Of course on 160m, any antenna will only have a fairly narrow bandwidth, so you will often have an SWR of 3:1 or more if you're operating away from the resonant frequency. (so the best amps for 160m will have a large value Load variable, rather than relying on big padder capacitors)

    Roger G3YRO
    W1BR likes this.
  5. KB4MNG

    KB4MNG Ham Member QRZ Page


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