FT8 + Linear ?

Discussion in 'Working Different Modes' started by KG7FIU, Sep 27, 2017.

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  1. KG7FIU

    KG7FIU Ham Member QRZ Page

    Heard someone else make the statement "Can work stateside contacts all day, but seem to have a problem working much DX" -- and it seems to be the same for me.

    Wondering if I should try a linear -- or will that result in excess splatter and interference?
     
  2. VA3VF

    VA3VF Guest

    The problem is where we are in the 11 years propagation cycle, low point. A linear will bring more contacts for sure, but not really necessary. Improve your antenna first, and learn to use the band and time of day propagation openings/enhancements.
     
    K2NCC likes this.
  3. NS8N

    NS8N Ham Member QRZ Page

    I agree with above. I've made a fair amount of DX contacts since starting with FT8 and whenever I look them up here in the Zed, they usually have an awesome antenna setup and usually transmitting fewer Watts than I. Better antenna will triumph over amplifier every single time.
     
    WU8Y likes this.
  4. KG7FIU

    KG7FIU Ham Member QRZ Page

    OK, thanks for the feedback, all. Yes would love an improved antenna, but got the dreaded HOA blues.
    Might try to optimize bands and time of day more--thanks for that suggestion.
     
  5. K7GQ

    K7GQ Subscriber QRZ Page

    It doesn't appear that your HOA blues are that severe from your antenna photos. I wonder what DX areas are difficult for you, and on which bands?
     
  6. VA3VF

    VA3VF Guest

    I have to agree. I thought it would be more restrictive. The antennas are better than the one I use. As already mentioned, focus on band and time of day propagation openings/enhancements.

    Nice picture on the top right corner of KG7FIU's page. My hometown. ;)
     
    Last edited by a moderator: Sep 28, 2017
  7. W4KJG

    W4KJG Subscriber QRZ Page

    Yeesh! Needing an amplifier for FT8?

    I guess "amplifier" has to be defined.

    About two hours ago (noon, EDT) I was doing some testing using a homebrew SSB exciter that was generating about 50 mW into a nearly invisible antenna. For several years, I've been developing and testing antennas, here on my farm, for use at my HOA-restricted snowbird home. Today's experiment was on 20 meters.

    Kind of as a joke to myself, I just wanted to see where my mighty 0.05 Watts of FT8 might be heard. So, I put out a CQ on 20 meter FT8. (Mostly I use WSPR for this.)

    The crazy thing is that I got a reply from someone about 25-30 miles away! Maybe NVIS -- but this was at 14.074 MHz. Not likely NVIS. More than likely it was ground wave.

    I'm not a DX hunter. For most of the last 50 years, I've seldom run more than 5 watts. My primary rig is an old Ten Tec Argonaut 505 with some modifications. I've never run anything more than about 100 watts at my own station, and that goes back to the old AM days of running things like DX-40s and DX-100s.

    The exciter I was testing today will eventually use a solid state "linear amplifier" -- but not in the sense of hundreds of watts. I have it built and operating, but I don't have the filters done. I will probably run it at about 20-25 watts CW/PEP, although the specs say I could run it as high as 75 watts. I presently use a 12BY7/6146 "tube linear". I use it to test small exciters with antennas, to put out about 25-35 watts.

    I have no problem making contacts. As I said, I'm not a DX hunter. I have no idea how many countries I've worked on AM, SSB, CW, RTTY, and the older/newer digital modes in the last five decades. But, I know I have QSL cards from a number of countries that no longer exist.

    It really pains me right now when I get on HF FT8, and there are signals 40-50 dB above the ambient noise floor in a 2.5 kHz bandwidth. Something is wrong. I'm pretty sure it isn't my receiving system, and I don't think it is the sunspot cycle.

    When the MUF is above the band you are operating on, ten watts should be more than adequate for FT8. One hundred watts is heading towards overkill, especially if you are using a high gain antenna. Running the full legal limit with high gain antennas acts just like jammers for everybody else trying to enjoy the hobby.

    All bets are off if you are running well above the MUF.

    Grumpy old Ken
    K8KJG
     
    N0NC, K4AGO, ND6M and 1 other person like this.
  8. KJ3N

    KJ3N Ham Member QRZ Page

    JMO, but...

    If you need a linear to work FT8 DX on any band (other than 160m), you should look into why your antenna sucks. :p

    Hell, this was done on a bit less than 100w on 160m...

    5t5ok-160m.jpg

    And, yes, it's confirmed in Club Log. https://secure.clublog.org/charts/?c=5T5OK
     
    W7UUU and W4KJG like this.
  9. W4KJG

    W4KJG Subscriber QRZ Page

    This is just an addition to the post above. It shows where my 0.05 watt FT8 signal was seen by PSK Reporter at about noon-time today on 20 meters.
    Increasing my power to 0.5 Watts/500 milliwatts would have brought those numbers up by 10 dB. Going to 50/100 watts would have brought those numbers up by 30/33 dB, which is still a pretty strong signal.

    Does anybody really need to be running signals more than 40 dB (or 50 dB with antenna gain) above that on the higher bands, like 20 and above? But, even on 40, 80 and 160 during the summer, it doesn't take much more than some expertise to work DX using narrowband signals like FT8, JT, PSK, CW, etc.,

    As a footnote I would like to add that although I am mostly a QRP non-voice operator, I still sure love to work AM on 160, 75, and 40. What a dichotomy.
    [​IMG]
     
    Last edited: Sep 28, 2017
  10. W4KJG

    W4KJG Subscriber QRZ Page


    Just think what you can do on some cold January night with that "bit less than 100w on 160m..." It could set the ionosphere on fire!:eek::D
     

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