reduced power on SSB but not CW

Discussion in 'General Technical Questions and Answers' started by KA8ZAW, Jul 17, 2017.

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  1. KA8ZAW

    KA8ZAW Premium Subscriber QRZ Page

    I am operating a Kenwood 590SG into either a 144' loop ( using the internal antenna tuner ) or a Gap Eagle ( not using the tuner). I run the antennas into an antenna switch, thru an MFJ watt meter and into the radio. Today I noticed my SSB signal on the watt meter was only 40 watts. I checked the signals on both antennas on 40 and 17 with the same results. I dropped down to the CW portion of each band and the output hit 100 all around. The information on the radio indicates 100 watts out. What happened to my 60 lost watts on SSB? Thanks, Jeff KA8 ZAW
     
  2. WG7X

    WG7X Premium Subscriber QRZ Page

    Sounds about normal for the full carrier to SSB ratio's to me. Is this something that you just noticed?

    Did you have about 100 watts on your meters before? Does your meter read true PEP?

    I only ask because these kind of questions usually relate to e metering problem rather than an actual power drop.
     
    NN4RH likes this.
  3. KM3F

    KM3F Ham Member QRZ Page

    Talking on SSB mode, the power will be a low average since it is not a constant output.
    Only way to see the voice peaks is use a peak reading wattmeter.
    Have you considered this difference?
    Good luck.
     
    NN4RH likes this.
  4. KC8VWM

    KC8VWM Subscriber QRZ Page

    Peak reading meters are somewhat better in detecting this, but Oscilloscopes are always going to visually detect instantaneous rise time in the peak envelope of the waveform, and will display your maximum peak values far more accurately than any meter does.

    Generally speaking, when using an external meter, your full CW output meter reading is going to be your maximum PEP output on SSB. If you're visualizing 40 watt peaks on the meter on SSB from a 100 watt rig, I wouldn't really worry about it.

    You're probably just not seeing maximum peaks occuring on the external meter scale due to meter dampening effect and it has nothing to do with any low output power from the rig.
     
    Last edited: Jul 17, 2017
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    You should hook it to a dummy load and whistle it up. ;)
     
  6. KA8ZAW

    KA8ZAW Premium Subscriber QRZ Page

    Hello everyone:
    Thanks for all your advice. I'm going to obtain a dummy load and give that a try. It seems odd that the CW signal is 100 and the SSB is about 40. Every time I used SSB before it was always at 100 watts. But, that's what makes ham radio great, constant learning. Thanks again, 73, Jeff KA8ZAW
     
  7. K5DH

    K5DH Ham Member QRZ Page

    It's all about the duty cycle. CW is 100% duty cycle. A typical SSB signal has a duty cycle of 30% to 40%, higher if speech processing is employed. Your typical power meter reads average power. To read PEP, you need a peak-reading power meter. There are many of them on the market. In the mean time, KA9LJM's suggestion is a good one. Use a single tone into your mic and the SSB output will approximate a CW signal. If everything is working right, you will see something near 100 Watts output.
     
  8. G3YRO

    G3YRO Ham Member QRZ Page

    As posted on other threads, with transistor PAs you often find your output on SSB is limited by the time constants of the ALC !

    Roger G3YRO
     
  9. N5DMC

    N5DMC Ham Member QRZ Page

    Your ALC reading should always be 30 to 60% depending on how it's measured. I'm thinking it's your modulation strength, like the mic gain adjustment or possible connection.
     
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    It all depends on the final RF amp, Mode and the class that it runs.

    Sometimes any ALC indicates that distortion is being generated.

    Normally when I see a lot of ALC indication I back my mic gain down.

    It is best to use a scope, Then there is no need to guess what your radio is doing.
     

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