new 630 meter band

Discussion in 'General Announcements' started by W5KUB, Sep 24, 2017.

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  1. NO3M

    NO3M Ham Member QRZ Page

    5W EIRP
    AF7XT likes this.
  2. N6QIC

    N6QIC Premium Subscriber QRZ Page

    You will need to upgrade your license first to talk on the 630 meter band.
    AF7XT likes this.
  3. QRZFAN2

    QRZFAN2 QRZ Member

  4. AF7XT

    AF7XT Ham Member QRZ Page

    I figure it as maybe 1.1 ohm RL for my wire in the tree, realistically I'd be lucky to get it up past .8 ohm . That's with significant "hat" in the form of three wires near 40ft long.
    If I'm reading this right I'm somewhere north of 1400w in for 5w EIRP out ...
    W7UUU likes this.
  5. NO3M

    NO3M Ham Member QRZ Page

    Depends, you didn't mention several other factors that are important to figuring out the EIRP. The formula is:

    P(EIRP) = P(TPO) * n * G(a), where:

    P(TPO) is transmitter power output in watts
    n is efficiency, generally calculated as R(rad) / R(feed). R(rad) is the modeled radiation resistance. R(feed) is the actual measured resistance.
    G(a) is antenna gain factor, which is calculated as 10 ^ (G(dBi) / 10). G(dBi) is peak modeled gain. For a top loaded vertical, typically 2.2 - 3 dBi.

    Unless you have terrible ground loss or using a very lossy, low Q loading inductor, I doubt you need anywhere near 1.4kW TPO to reach 5W EIRP.
  6. AF7XT

    AF7XT Ham Member QRZ Page

    R(feed) (RL) is barely an ohm. Even with top loading peak modeled gain is barely over unity.
    Hence a bundle of watts in for 5 watts EIRP . Unless I need another cup of coffee...

    @NO3M Thanks for the explanation. I did have it nearly right
  7. NO3M

    NO3M Ham Member QRZ Page

    If you get the losses down to a tolerable level, say 50-75 ohms, it'll only take a little over 200W to get to 5W EIRP. Getting there includes radials, ground screens, whatever you can tie into to lower ground loss and constructing your loading coil for high Q, ie. "fat", low resistance conductor, optimal form factor, away from other objects to reduce leakage paths, etc. As a general guide... anything above 100 ohms combined losses for 630M is pretty bad, 50-100 tolerable, 30-50 good, 20-30 very good, 10-20 excellent, <10 exceptional.
  8. AF7XT

    AF7XT Ham Member QRZ Page

    so base loaded with
    ...wound around the 110' tall 4' around the base, Douglas Fir tree out back, say 10-15 turns , tapped up from ground, extensive ground radials, couple of vacuum caps, feed it from the house with the 7/8" hard line, strip one of my commercial inverters for the active devices ...

  9. KK5JY

    KK5JY Ham Member QRZ Page

    I want to see pictures of the tree after that exercise. ;)

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