FT8 / Do I have to worry about Noise, when using only 50HZ for FT8

Discussion in 'Working Different Modes' started by NN2X, Apr 4, 2021.

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  1. NN2X

    NN2X Premium Subscriber QRZ Page

    Hello Ham community!

    Talk about noise!,

    My neighbor has a Solar Panels, other neighbor a Plasma TV, and about 20ft to my antenna are power lines..This equates to 20/9!.

    There is noise, and every where from every direction, my noise can be as high as 20/9, (Why wonder folks in the Suburbs lean toward digital, but I digress)

    Speaking of digital, I would assume, when using lets say FT8, the bandwidth is 50Hz all the other features like NR, tighter bandwidth (RF/IF or Audio) or adding Attenuation has negligible impact when using lets say FT8? (Due to the fact there is only 50 Hz of Bandwidth).

    (On a side note: I might later on create NR, specifically for the noise being generated, (Like Power Noise, Solar Panels, or Plasma TV), I would like to design Algorithms just for those RFI, but this for another plan! Have a few buttons labeled (Plasma, Solar Panel, or Power Lines). I have access to a ton of Phds that do this for a living, they probably can do this over the weekend! )

    I look forward to your response

    NN2X / Tom
     
  2. N3KE

    N3KE Ham Member QRZ Page

    The WSJT-X demod for FT8 is essentially doing its own noise blanking and narrowband filtering so indeed the bells and whistles on the receiver aren’t really going to help. That said you definitely want to make sure the receiver isn’t being overloaded which would make things much worse (so for example attenuation might help if that prevented overloading).
     
  3. NN2X

    NN2X Premium Subscriber QRZ Page


    Thanks for the response. I thought this was the case. Just double checking. About overload the receiver. I am good there the latest WSJt -X have a indicator for receiving so it is easy to monitor. Thanks again for clarifying. NN2X. Tom
     
  4. N3KE

    N3KE Ham Member QRZ Page

    Just be aware depending on the receiver design you can end up with the front end RF stage being overloaded even though the AF input at WSJT-X is not overloaded. For instance one could crank up the RF gain and even turn on a pre-amp causing bad overloading in the front end but then turn down the AF gain such that WSJT-X is showing green.
     
  5. NN2X

    NN2X Premium Subscriber QRZ Page

    Thanks for the input, I was not aware of this...I do add the attenuator to the input (This feature of the FT 450), I assume, it is about 10 or 20db, but I do it, to knock down the 20/9 noise! So maybe by default, (By accident), I am not overloading the front end!

    I have been having many QSOs on FT8 across the globe, it seems to be working. I think you nailed it, when you said the WSJT-X does all the work..!

    DE NN2X / Tom
     
  6. WA9FZB

    WA9FZB XML Subscriber QRZ Page

    In order to avoid receiver overload, I set the audio transfer levels from my computer and my rig's built-in sound card to a low to mid-level position, then manage it by adjusting the rig's RF Gain control up or down to attain about a 30 dB signal level on the receive bar graph when there are no signals. At times, contrary to popular advice, I do run one of my rig's digital Noise Reduction options with good results. At least I think I get good results, as I readily see decodes that report the incoming station down to -20 to -23 dB signal strength.

    On 40 meters, I do not use the RF Pre-Amp. Sometimes on 20, 15 or 10 meters I do. Simple antennas always take their toll.

    Another way I judge the (relative) quality of my receiving system is that I can always decode/receive more stations than I can contact. LPCA even applies in digital mode operation, I guess.
     
  7. KP4SX

    KP4SX Premium Subscriber QRZ Page

    You should keep all the gee-gaws like noise blanker and noise reduction turned off. You can actually see the distortion they cause on the waterfall.
     
  8. W9FL

    W9FL Ham Member QRZ Page

    You are free to operate your equipment however you choose, but running the preamp and/or noise reduction goes against all the knowledgeable advice on how to properly run FT8.
     
    KG5EYC likes this.
  9. WA9FZB

    WA9FZB XML Subscriber QRZ Page

    I've tried it with and without the preamp - I'm pretty sure my jockeying of the RF Gain just readjusts overall gain back to the level required by the WSJT-X receive level graph. Maybe it affects SNR, but not in any way I can see. Same with the noise reduction system. It doesn't affect what I see in decodes, but it does "clean up" some of the trash on the graph.
     
  10. NN2X

    NN2X Premium Subscriber QRZ Page

    Thanks for the information,...I have 20/9 noise! So Digital all the way, Having fun with JS8CALL, at least some QSO!

    NN2X Tom
     

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