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Proper power for XXXX mode !

Discussion in 'Working Different Modes' started by AG3Y, Jul 28, 2010.

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  1. AG3Y

    AG3Y Guest

    I notice a lot of different threads here about how much power is proper for this mode, or that mode. I have a general rule of thumb to stress concerning ALL the soundcard generated digital modes. It has been mentioned in other threads, but seems to be overlooked, or perhaps different operators think that it should be different depending on what mode one is attempting to operate.

    If your digital signal is being generated by your soundcard, and you are using the audio stages of your rig to create the RF suite of frequencies that will be turned back into tones and decoded by the software at the other end, is is always BEST to adjust the power of your rig for MOST LINEAR output, with NO ALC action being generated in the radio ! ! !

    This is almost a CARDINAL RULE for digital transmissions.

    If you are using a commercial interface, adjust the gain controls on it to somewhere around the 1/2 to 3/4 position, but not fully on. Turn the RF level up full ( except in a few rare cases with some specific radios ), and advance the soundcard gain until you barely see SOME ALC, and then back it off just the slightest amount.

    This should give you a fairly high level of RF output, and everything should be operating in the linear region. You shouldn't see any problems, and the receiving station should see a pure signal on his/her waterfall!

    I repeat, this should apply no matter WHAT soundcard signal you are attempting to transmit, PSK, Olivia, Baudot even keyboard generated CW, DRM and the "analog" types of SSTV.

    Hope this helps!
     
  2. AF6LJ

    AF6LJ Ham Member QRZ Page

    "More is better" is human nature. The more we learn the less this axiom feels right. It's always best for new hams to ask questions and for those who know to educate as apposed to dispensing a blanket answer. Knowledge is the foundation for more knowledge and son on.......

    Your answer provides enough education that the new ham can see the general relationship between signal quality and power output.

    For you new hams out there......
    The more ALC you transmitter's ALC meter is showing the more compressed and distorted your output signal will be as a general rule.

    Think of your ALC meter like the Engine light on your dashboard, it's telling you something is wrong and you should move to correct it.
     
  3. K4RKY

    K4RKY Ham Member QRZ Page

    To quote you Sue... "Think of your ALC meter like the Engine light on your dashboard, it's telling you something is wrong and you should move to correct it."
    And for the newer hams, you do NOT need 100 watts to have fun. 10 to 30 watts depending on conditions is all you need... Take your foot off the gas! :)
     
  4. M0WAN

    M0WAN Ham Member QRZ Page

    ...and enjoy the much extended life of your rig!
     
  5. AI3V

    AI3V Ham Member QRZ Page

    There is a funny scene in the movie "This is Spinal Tap" about knobs that go to 11 instead of 10.

    For your viewing pleasure...

    These go to 11"

    :rolleyes:

    Rege
     
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    Knob inflation. :D
     
  7. WB3BEL

    WB3BEL Ham Member QRZ Page

    I agree that soundcard generated digimode operators should adjust their audio and RF power levels to avoid creating distortion. Distortion is counter productive and may lead to signal reception problems for the receiving station. Or it may result is excess bandwidth usage which could create problems for other users on a crowded band.

    But I do NOT agree that a "One size fits All" lowest power mentality is right either. To be clear, you should read the actual language of the FCC reg CFR 47 part 97.313 as it is almost always misquoted on QRZ threads.

    An amateur station must use the minimum transmitter power necessary to carry out the desired communications.

    http://www.gpo.gov/fdsys/pkg/CFR-2009-title47-vol5/pdf/CFR-2009-title47-vol5-part97.pdf

    If I desire to be heard on the opposite side of the earth under poor or seldom existent propagation conditions it is legal and perhaps good practice to run high power.

    I have operated a lot of QRP probably 10,000 QSOs in almost 300 DXCC. So don't get me wrong. I know what is possible. The achievement is mainly due to the receiving station operator skill. It can be fun. But its not for everyone or for every situation.

    I run high power when I want (desire) to. It is my freedom to do so. I will not be intimidated by those whose OCD behavior wish to restrict my freedoms. Some modes/conditions require high power, some do not. And the situation is not black and white.

    No one gave any amateur station a grant to interference free operation. Use good judgment and be courteous but also be flexible and open minded. There are a lot of different things going on in amateur radio and there is room for us all.
     
  8. G0GQK

    G0GQK Ham Member QRZ Page

    Absolutely correct, no ALC should be seen and transmit between 25 and 30 watts of PSK. Using more isn't better, and its like these people who wind up power in contests with the processer wide open, strong and thick with no clarity. Same on PSK strong signal, very thick, dirty transmission and often without clarity.

    G0GQK
     
  9. KE5FRF

    KE5FRF Ham Member QRZ Page

    Or an even better analogy. Think of your ALC as the tachometer, and realize that the engine has a range of efficiency for each gear...outside of that range and the engine is not working as designed!
     
  10. AG3Y

    AG3Y Guest

    BEL, I NEVER said that you had to restrict your power. In fact, my exact words were, "This should give you a fairly high level of RF output, and everything should be operating in the linear region."

    Some people believe that the only way to get a clean signal is to turn everything DOWN and operate with only a few watts of RF output. I am NOT advocating that at all ! If you can operate a legal full gallon and still keep your signal as clean as can be, then "more power to you!" ( pun intended ) And those who would complain that someone's signal is stronger than anybody elses on the "band", need to learn how to adjust their receiver so that it only picks up the desired station, and not a whole wide swath of RF at the same time.

    I know that there are several programs out there that will pick up 3.5Khz of psk signals at a time, and demodulate them in several rows of scrolling text. That may be an OK way to operate during contests, and just to see what is happening on the band. But if a strong station comes on the air, and the operator's receiver adjusts to that one signal level, and elminates all the others in that 3.5Khz window, it is up to the operator doing the listening to make the necessary adjustments. It should NOT be the transmitting operator's responsibility to adjust his signal strength to match everyone else on the band. How would he actually DO that ?
     
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