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Reasonable power output for PSK-31

Discussion in 'Working Different Modes' started by KB1JCY, Jul 23, 2010.

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  1. AC0FP

    AC0FP Ham Member QRZ Page

    What type of radio do you have? Many popular radios are rated at 100 watts PEP output power. If you were to have one of these radios the maximum PSK31 power you could run, as measured on a "average" reading watt meter (the most common type), would be 50 watts and still remain linear!


    fp :)
  2. K6OK

    K6OK Ham Member QRZ Page

    Warning to Kids and Small Animals: Rant Follows! :eek:

    Use any power you want. The whole "low power only" on PSK is a myth and it's wrong! KR2D is spot-on with his post.

    Splattering and waterfall blanking are two different things.

    Splatter on PSK happens when the transmitting station has their audio input set too high. Audio should always be set so that is just below the cutoff for ALC. It doesn't matter if a station is using 1 watt, 100 watts or 1000 watts, if the modulating audio is too high, it will splatter.

    Waterfall blanking occurs because the receiving station leaves the IF setting on wide and a strong signal anywhere on the waterfall causes the AGC to kick in and reduce RF gain. PSK operators are the only people who expect to view 3000 Hz of bandwidth without strong signals! I think PSKers could learn a few things about filtering from the CW folks. They never complain about strong adjacent signals, they just filter them out.

    FCC regs say you should reduce power to the minimum needed to make the QSO. If you need 100 watts or more for the other station to get 100% copy from you, then feel free to run the power. Just make sure your "audio in" is not set too high.

    OK, rant over! :D -- Jim
  3. K7JBQ

    K7JBQ Moderator Volunteer Moderator QRZ Page


    I completely agree with you, with one caveat.

    If you have a 100 watt rig, sans amp, do not attempt to run 100 watts on PSK. Your rig will not like it, nor will the rest of the folks on the band. As stated earlier, 50 watts is about all you can run in that situation without going "off-linear" and splattering.

    If you "run out of print," due to propagation, may I suggest a switch in mid-QSO to Olivia.

  4. K6OK

    K6OK Ham Member QRZ Page

    Good point Bill. PSK has a duty cycle of about 90 percent, and so only those 100 watt rigs rated 100 watts at 100 percent duty cycle should run PSK at full power.
  5. G0JKZ

    G0JKZ Ham Member QRZ Page

    which is why I use a linear for the main pa work.... keep the radio linear, below alc level and drive the valve amp at a level that will get through without melting the valves.

    In my case, the linear can peak at 800w on ssb but full duty use I would never let it run more than 300-400w without thinking about the valves melting.
  6. WS2L

    WS2L Guest

    I normally run 40-50 watts to make up for my crappy antenna.

    Anything above 50 watts is a bit much for this mode and 90 watts is way to much.
  7. G0JKZ

    G0JKZ Ham Member QRZ Page

    of course... the fact that I can run 400w doesn't mean I always do, it is there if I want to. Most of the time 50w is plenty.
  8. K7JBQ

    K7JBQ Moderator Volunteer Moderator QRZ Page


    The duty cycle is one thing; linearity is another.

    Even those rigs with a 100% duty cycle should be run at no more than "half power" to preserve a clean PSK signal.

    If you must run 100 watts, use an amp.


  9. AC0FP

    AC0FP Ham Member QRZ Page

    You had better add one more qualifier to that statement (assuming you wish to remain transmitting a linear signal): The transmitter that runs PSK at 100 watts should be rated at 200 watts PEP minimum! :eek: The PEP power rating indicates the peak/peak power a SSB 2-tone signal can have without clipping on the top half of the waveform.


    fp :)
  10. N0WYO

    N0WYO XML Subscriber QRZ Page

    That's an important point. PSK-31, along with most of the other modes requires a %100 duty cycle during TX. Not only will you distort your signal at 100 watts, but you can also fry some finals in the process.

    50 watts is the max rating for most radios, but in the case of most digital modes, less is more. The purer the signal, the more likely it is to be heard/decoded properly.

    Proper set up and power output is everything on SSTV. Otherwise the station you're working will only see fuzz.
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