An FT8 question...

Discussion in 'Working Different Modes' started by W8HK, Dec 2, 2021.

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  1. W8HK

    W8HK Ham Member QRZ Page

    When using FT8, what is the operating frequency?
    On 14 meters, for instance, the WSJT-X program places me at 14.074, but the strongest signals are at 14.076.
    This goes for all bands I have run FT8; 0.002 higher.
    I'm guessing that the program listens on a broader bandwidth, yes?
    So should I stay centered on 14.074?
     
  2. KP4SX

    KP4SX Premium Subscriber QRZ Page

    The radio is set to 14.074 for 20 meters. The individual signals are on the upper side roughly +200 to +2500 Hz.
    eg - 14.074200 to 14.076500.
    Yes, the program is copying that entire range. Each signal is about 50Hz wide.
     
    N3RYB and VE2GCE like this.
  3. N3RYB

    N3RYB Premium Subscriber QRZ Page

    One factor to consider when operating, is where to place your own signal in that spectrum. Depending on the receiver of the remote station, the SSB filter may cut off at different points. If you put your signal up too high(around 2600 or so for example) some receivers might not be able to hear you as you'll get cut off. Same thing at the bottom end. Occasionally I'll hear a DX station that is down around 200hz or so in the passband and my SSB Filter is cutting them off, in those cases, I will go ahead and move the VFO down a little bit :)
     
  4. KM8V

    KM8V Premium Subscriber QRZ Page

    Set your dial to 14.074 and your radio's filter as wide as possible. Mine is 3.6k
     
  5. NG1H

    NG1H XML Subscriber QRZ Page

    It is an USB signal. So the range will be the base frequency (14.074Mhz for your example) + your passband (usually 2.5Khz - 3.0Khz). So the range will be 14.074 - 14.0765/14.070.

    Due to *reasons* a lot of people avoid audio frequencies below 0.5Khz and above 2.5Khz. So the bulk of the signals in your example would be in the 14.0745 - 14.0765 range.

    You used the phrase "centered" but that is misleading. Your dial frequency would normally be the lowest end of the range (14.074 in your example). The actual individual signals are the dial frequency plus their/your audio frequency. Most of the time you just want to use the default frequency for the band. If you start changing the frequency for no reason other than mentioned below you are lowering the number of signals that can be potentially decoded.

    There is one case where you may want to change the frequency. If you have a radio that has attenuation near the ends of the passband (one of the *reasons* mentioned above) then you could consider starting to play around with the dial frequency. Here's how that works:

    Let's say someone is on 14.074 sending a FT-8 signal that starts at a 200Hhz audio frequency. So the actual transmission at 14.074200 (14.074 dial + .0002 audio).
    But your radio does not receive as well near the bottom of the passband.
    To help with this problem tune your radio to 14.073000. Now that 14.074200 signal starts at .001200 (1.2Khz) in your receiver, no longer at the bottom of the passband.

    But you need to remember to change the frequency back to the default after you have done this.
     
  6. KY1K

    KY1K Ham Member QRZ Page

    Another reason to move off the default frequency is if it's full. Especially on 20&40, the signals can reach from .074 to .080 into the default (and otherwise empty) JT65+JT9 area.
    This isn't CB. There are no set channels. Don't be afraid to move the dial slightly!
     
    N3RYB likes this.
  7. W4HWD

    W4HWD Premium Subscriber QRZ Page

    You don't have to leave your dial on 14.074; you can move up to 14.076 if you like. Same for all other bands as well, and working DXpeditions that leave the "window" to put themselves "in the clear" away from the shouting match so more stations can have a chance to work them. They'll go to something like 14.090, 7.090, etc...if the frequency window turns red on JT-X it means you left the normal subband for that mode - but you can still use that frequency.
     
    Last edited: Dec 4, 2021
  8. W8HK

    W8HK Ham Member QRZ Page

    Thanks so much for the info!!
     

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