A Full-Blown 1/2 Wave Dipole?

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by WA2FXM, Nov 27, 2017.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: L-MFJ
ad: Left-2
ad: MessiPaoloni-1
ad: Subscribe
  1. W9XMT

    W9XMT Ham Member QRZ Page

    Below is a NEC4.2 plot of the elevation pattern fields at an h-distance of 1 mile from the base of a monopole, based on the same model parameters as in my original post above. A comparison is shown for that sector for the fields at 2 miles, also. These calculations include the surface wave, which is necessary to calculate/plot this scenario accurately.

    Z = elevation in meters above a flat Earth, and E = field intensity in mV/m

    Note that the two fields shown there have a ~1/r relationship, which is characteristic of a space wave. That relationship will be maintained for very low, but not zero-angle propagation paths reaching to, and reflected by the ionosphere.
    _____

    As a workaound, a Ø can be included in posts here by entering Alt+Ø216 using the number keypad.


    [​IMG]
     
  2. K8JD

    K8JD Ham Member QRZ Page

    Does this mean that the closer you get the stronger the field is ?
    What is the size of the monopole ? By "T" that seems to mean it's less than a QW tall vertical with a two wire capacity hat ?
    Not much info on the physical side of the antenna !
    I want to build a real antenna.
     
  3. W9XMT

    W9XMT Ham Member QRZ Page

    The T antenna dimensions are shown in the Comments section on the left side of the graphic in my original post about it.
     
  4. W5DFN

    W5DFN Ham Member QRZ Page

    Okay, an update to the above post. About the time I posted this, we sold our home and moved to the property where we own and operate a private gun club. On October 10, Hurricane Michael paid us a visit setting back getting back on the air. This week I got my HF/VHF antennas back up and today I put up half of my 1/2 wave 630 meter horizontal dipole. Running the "live" leg was fairly easy. Take out four damaged oaks, and lay it out in a zigzag. The shield leg came straight down from the 20' feed point and is grounded to the tower base. Guess what it works!
     
  5. AF7XT

    AF7XT Ham Member QRZ Page

  6. AF7XT

    AF7XT Ham Member QRZ Page

    shunt feed ...
    [​IMG]
     
    WA7PRC likes this.
  7. WA7PRC

    WA7PRC Ham Member QRZ Page

    The Wikipedia article leaves a lot of detail out. I toured NLK in the late 70s. Nominal output is around 1MW but, we were told they've had it cranked up to 2MW. When they do, Jim Creek is 1° warmer downstream. When we toured, the output current was 1296A. Into ZLOAD = 0.456Ω, that's "only" 766 kW. It made the broadcast xmtr (16 kW RFOUT) I worked on look like a QRP rig. :cool:
     

Share This Page