ALC high on the FT-450D

Discussion in 'Radio Circuits, Repair & Performance' started by N1QWI, Nov 19, 2018.

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  1. N1QWI

    N1QWI Ham Member QRZ Page

    Hi and thanks for reading,

    I recently put up a new antenna and have been testing it out and realize that although my tuner can get the antenna to a 1.5: 1 SWR when I am operating 30 m CW, for some reason the ALC runs a little bit high. Please see attached photo. Any help would be greatly appreciated as I can’t seem to figure out how to turn down the level control on the radio.
     
  2. N1QWI

    N1QWI Ham Member QRZ Page

  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    Do you have a operator manual ?

    You need to set the power level in a menu.

    Maybe a external tuner would be best to use, If you have a large antenna mismatch. ;)

    Good Luck.
     
  4. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Interesting - I checked mine as well and regardless of power setting, when sending CQ via the internal keyer - my ALC goes all the way up as well - perhaps that is what it was designed to do?
     
  5. PA1ZP

    PA1ZP Ham Member QRZ Page

    Hi

    ALC might be a bit of and high due to SWR being not 1 , test the ALC level on a dummyload.
    Your in CW continious wave, it doesn't have ALC, its a unmodulated carrier ON or OFF, that is all.
    If the internal tuner can not get the SWR down , use larger impedance reach external tuner or improve the antenna.

    73 Jos
     
  6. 2E0LPL

    2E0LPL Ham Member QRZ Page

    My brand new 450d is the same on the ALC...goes even higher than the OP does...in fact it goes 4 bars higher than the max mark....this is only on CW or FM.

    I have stopped using CW till I can get an answer to see if its going to damage the PA if I use it like this....

    I dont do any digi modes.

    On voice SSB its fine...I can adjust it with the mic gain setting...the middle setting seems to keep it below max unless I shout.

    Noticed the right-hand side of the radio toward the front gets quite warm very quickly with a voice contact of only a few mins...with a near perfect SWR.

    I get the same over-reading ALC even if I run into my dummy load.

    There is nothing in the manual about this and next to nothing about the ALC.

    Can anybody help please.
     
  7. K7TRF

    K7TRF Premium Subscriber QRZ Page

    ALC is meaningless when operating in CW mode. All it tells you is that the rig is hitting maximum transmit power when keying in CW as it should. You could reduce the Carrier level to see less ALC meter response but in CW it doesn't mean signal distortion or splatter the way it does in SSB mode.
    You will not damage the PA in your rig when you have high ALC response in CW mode.
     
  8. K7TRF

    K7TRF Premium Subscriber QRZ Page

    ALC is just a negative feedback loop that keeps the transmit power from hard clipping as you reach the maximum power. When you see a high ALC response it just means the rig is very near, or at maximum transmit power and the ALC loop is functioning correctly. When transmitting an SSB signal you should only come close to or actually hit that maximum transmit power on your louder voice peaks and ALC metering should only jump high on those same voice peaks.

    In CW mode or FM mode or other constant carrier modes the ALC meter will jump high every time you transmit at the rig's rated power. You can reduce that power, at least in CW mode by reducing the Carrier level but it's not harmful for the rig to transmit at maximum power and the ALC meter is just doing what it is supposed to do which is show a high reading as you hit maximum power. The fact that the ALC meter jumps high in CW mode does NOT indicate excessive stress on the finals, it actually means the ALC loop is applying relatively large amounts of negative feedback to the overall drive chain but that's fine when operating in a constant carrier mode at full transmit power.

    I thought we had this discussion a couple of weeks ago. ALC metering and setting mic gain to only hit the top of the ALC range on voice peaks only applies to linear modulation modes like SSB. In CW, FM or other constant carrier modes a high ALC response just tells you that your rig is hitting maximum transmit power which will happen every time you key the rig unless you've backed off the Carrier level and aren't actually transmitting at the rig's full rated power level.
     
  9. 2E0LPL

    2E0LPL Ham Member QRZ Page

    K7TRF when you say reduce carrier level...the only thing I have to adjust that has any bearing on the ALC is the mic gain and mic equalizer...its a quite basic radio....RF power out as low as 5w and its still high on the ALC.

    Is there another adjustment your thinking of.

    Its a warranty replacement radio...as the PA failed twice on the old radio...the ALC read over on that one as well....I am very apprehensive using it as it is...it seems to heat the right side case quite quickly in SSB voice use...not using CW at all till I feel confident with it.

    SSB voice has the ALC hitting between 70 and 90% on the ALC scale.
     
  10. K7TRF

    K7TRF Premium Subscriber QRZ Page

    You're right, Yaesu left off a Carrier setting control on the FT-450d which is a bit unusual for a CW rig. You could see if varying the output power described on page 37 of the manual allows you to also reduce power on CW.

    But either way, high ALC meter readings in CW DOES NOT mean over driving the final amplifier or risking in finals damage. It means the rig is hitting full transmit power and the ALC is doing exactly what it is supposed to do which is applying a fair amount of negative feedback and actually limiting overdriving.

    Yes, I remember you had finals trouble but high ALC readings in CW mode was not the cause of those troubles as high ALC readings actually mean drive power into the finals is being limited specifically to avoid driving the finals too hard.
     

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