FT8 Power, how much ????

Discussion in 'Working Different Modes' started by K4EM, Nov 12, 2017.

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  1. N3RYB

    N3RYB Premium Subscriber QRZ Page

    I use enough power to get the QSO done with without a large number of retransmissions. Using less power but needing to repeat the transmission 5 times increases the S/N ratio for everyone. I've got no problems with throwing out 400W on 160m on FT8. Now if I get a report back that is +30dB or something, sure I'm going to turn it down, but often at higher power levels, I'm getting a nearly matching report back as a result. (Also I try really hard to make sure I'm not stomping on someone).
     
  2. KZ1O

    KZ1O Ham Member QRZ Page

    You may be confusing "duty cycle" with "average power". The term inherently refers to the "cycle" of transmitting and receiving, such as FT8 does (and CW, for that matter).
     
  3. W6UV

    W6UV Premium Subscriber QRZ Page

    I was referring to the duty cycle while the transmitter is keyed. By that definition, FT8 is a 100% duty cycle mode.
     
  4. ND6M

    ND6M Ham Member QRZ Page

    if you only count the RTX part of the cycle, then by definition there is no "cycle".

    BTW, another poster incorrectly said the "cycle" was 15 seconds on and 15 off, that is incorrect, the cycle is 13 seconds Tx on and 17 seconds off.


    13/17 is not 100% either
     
  5. N3DT

    N3DT Ham Member QRZ Page

    How much? I worked 9V1YC a few days ago on 20M. He was +2 but it took me 900W to get -13.
     
    K2TY, WD4ELG, W2VW and 1 other person like this.
  6. VA3VF

    VA3VF Ham Member QRZ Page

    I've been mostly on 160M these past few months. My 80W power feels like QRPp.:(
     
  7. AJ4GQ

    AJ4GQ XML Subscriber QRZ Page

    His calculated legal maximum ERP is over 6 kW.
     
  8. W6UV

    W6UV Premium Subscriber QRZ Page

    WSJT-X signal strengths are really signal-to-noise ratios. If you both were using the exact same power levels and the same antenna, but his noise floor was higher than yours, that could account for the 15 dB difference. In fact, he could have been using much less power than you even with a +2 SNR on your end and -13 on his.

    And that's assuming propagation is reciprocal, which it's often not.
     
    WD4ELG likes this.
  9. N3DT

    N3DT Ham Member QRZ Page

    Ah, the great flying spaghetti monster man again. I sent that book to my wife's cousin who believes the earth is the center of the universe along with his wife. And this guy has a PHD in Psychology and his wife was a vascular surgeon. But then they live in Wisconsin.

    Yes, I notice propagation is often not reciprocal, sometimes on 15M in the morning here, I can hardly be heard in EU when I hear them fine. Then other days I get equivalent reports with 50W. I don't know if it ever works the other way around, I'd have to be there to tell.
     
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  10. WA7FLY

    WA7FLY Ham Member QRZ Page

    It's nice to see that after 3 to 4 years, we still cannot agree on "Duty Cycle". o_O And, yes, I'm also here because I'm looking for an official answer and explanation that makes sense and is understandable.

    The source of the spirited discussions on duty cycle seems to boil down to a debate over the transmission Time/Period definition for duty cycle. No one is necessarily right or wrong in their opinions, it's just much harder to find an accurate and available definition regarding the "Time" or "Period". Just try an internet search ... it's not very clear or well-defined. At least not to the average kid who went to public school.

    One source that may help understand the definition says, "Duty cycle is the fraction of time that a system is in an “active” state. In particular, it is used in the following contexts: Duty cycle is the proportion of time during which a component, device, or system is operated." (www.radartutorial.eu/01.basics/Duty%20cycle.en.html - this source was referencing radar, but I think it is still relevant)

    Now, like everything else, that again is open to interpretation. But, I think it may help shed some light on what the dudes meant when they came up with "Duty Cycle". Or, not. :D

    -Tom
     

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