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50 watts out only SSB,450D?

Discussion in 'General Technical Questions and Answers' started by KF7WMM, May 29, 2018.

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  1. VK4XJB

    VK4XJB Ham Member QRZ Page

    From that line I am wondering if the question is regards the single tone from a morse code practice oscillator/key combination with the radio set to a ssb mode and not from ssb voice. If that is the case then with a single tone driving the radio I would be concerned with why if I noticed any changes in power level.

    If that is wrong I am blaming it being too close to midnight and I should be asleep.
  2. G3YRO

    G3YRO Ham Member QRZ Page

    In terms of the CHANGE the OP is describing . . .

    Maybe he IS using a Peak-Reading Wattmeter . . . and maybe he's just not getting enough Drive on SSB any more (due to a faulty Microphone with low output . . . or the mic gain suddenly being set much lower)

    Whether or not you have enough Drive on SSB will be demostrated by monitoring the ALC on the rig's Meter . . . is it moving OK? (and the same as before?)

    Roger G3YRO
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    The OP has not came back.

    This is a sign of operator error recognized.

    Short between headset possibly. o_O
    KS4W likes this.
  4. KD2ACO

    KD2ACO Platinum Subscriber Life Member Platinum Subscriber QRZ Page

    ... but that won't stop us from commenting on it for another year or two! :p
    G0GSR, KI7QVR and KA9JLM like this.
  5. KI7QVR

    KI7QVR XML Subscriber QRZ Page

    On my radio, when I have the mic compression on and the mic gain at 100%, when I modulate, the radio will peak at 100w every now and then but obviously not continuously. However, FT8 uses USB. When I'm on FT8 and transmitting on USB, it shows 100w.
  6. K9STH

    K9STH Ham Member Volunteer Moderator QRZ Page


    You had better be making short transmissions because the final amplifier is not designed for 100-watts continuous power! Running data, with an SSB transmitter, you really should not run more than about 25% to 30% of the rated PEAK output for SSB. Otherwise, you can definitely start having problems with the final amplifier stage.

    Also, running at that level can definitely result in spurious emissions which, in turn, will cause undue interference to others operating on the same band and that includes modes other than the FT8 crowd.

    Glen, K9STH
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    No problem.

    QRZ has technicians available to help you change parts.

    TSOI (Trouble Shoot Over Internet) is the berries.
  8. G0GSR

    G0GSR Ham Member QRZ Page

    No they are not but no mode has a duty cycle greater than 50% over any significant time period so there is no problem.

    This advice is for those using the PSK31 mode (only) where the peak to mean ration is 4:1, Average power shouldn't exceed 25W for a PEP of 100W.
    It's becasue of linearity, not PA dissipation.

    Last edited: Jun 14, 2018
  9. K9STH

    K9STH Ham Member Volunteer Moderator QRZ Page


    If FT8 is like most data emissions, and if he is running 100-watts output, that will definitely stress the final amplifier stage if the transmissions are very long. Most amateur radio transceivers are designed for SSB operation with a peak of 100-watts output which is really more like an average of 25-watts to 30-watts. If the transmissions are short, with time for the transistors to "cool down", then not so much a problem. But, if the transmissions take very long, then there is a definite chance of premature failure of the final amplifier transistors.

    Glen, K9STH
  10. AA7EJ

    AA7EJ Ham Member QRZ Page

    From the onset of this thread it seems that "general public" - both OM and new OM have very little understanding of RF modulation.
    Perhaps it is not in test? Or just result of no CW requirement?
    ( Continuous wave AKA FULL power. )

    Why would "100W" on FM make a news?
    Why "30W" on AM is surprising?
    USB (upper sideband) and LSB have different RF outputs ?

    And then we have this "ALC" and build-in the SS (! hollow state ) rig SWR monitor shutting down the TX ( any modulation) when over 3:1?

    73 Shirley

    With all do respect to Glen - thermo protected solid state is an ancient technology , heat sinks and small fans work fine too - my 857 has TWO!
    Last edited: Jun 14, 2018
    K3KIC likes this.

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