"Aiming" the dipoles

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N1VAU, Apr 11, 2012.

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: L-MFJ
ad: Subscribe
ad: abrind-2
ad: Left-3
  1. N1VAU

    N1VAU XML Subscriber QRZ Page

    In my usual "Ham Style" I try to think things through (aka over complicate).

    I ran one of the "beam heading" programs and came up with 60 degrees (plus 15 declination) is "aimed" at Madrid Spain.

    This is the direction I set up the broad side of my 20/40 2 wire dipole @ ~40' up in the air.

    I have more trees and wire (80m +160m) to string. Looking at the other trees there isn't anymore "perfect pairs" and the next antennas may be more randomly "aimed".

    This distresses me a bit.

    Am I worrying too much and I should just get'r done?

    ~N1VAU
     
  2. N4OGW

    N4OGW Ham Member QRZ Page

    Don't worry- at 40 feet up, 80m and 160m dipoles will be pretty much omnidirectional.

    Tor
    N4OGW
     
  3. WA8UEG

    WA8UEG XML Subscriber QRZ Page

    just get er done :)
     
  4. KJ3N

    KJ3N Ham Member QRZ Page

    You're being anal.

    What they said.
     
  5. K7KBN

    K7KBN Ham Member QRZ Page

    For determining the best path to a distant point, it's much easier to use True North, rather than Magnetic North. (Your mention of "declination" tells me you were working with MN.) Google "great circle map" and you should find any number of maps you can print, showing your location in the center and everywhere else in their short-path directions. Couldn't be easier.

    But, as several others have said, if you have a 40 meter dipole at 40 feet high, you basically have an omnidirectional antenna. You'll be able to use it with good results, and you'll make as many contacts off the ends as you will broadside.
     
  6. KO6WB

    KO6WB Premium Subscriber QRZ Page

    Quit over thinking and get something up and get on the air. Tune them for low SWR and you're done. Putting up antennas can be fun. Sometimes you make improvements other times, well, back to the chalk board.
    73
    Gary
     
  7. G3TXQ

    G3TXQ Ham Member QRZ Page

    Unless you are trying to work stations beyond about 1000 miles, in which case there's a 6dB to 7dB difference between broadside and end on. The difference would be close to 10dB for a 40m dipole at 40ft.

    Steve G3TXQ
     
  8. K1DNR

    K1DNR Ham Member QRZ Page

    If you are chasing DX it matters but you have to do with what you've got.

    Don't think of antenna patterns in 2 dimensions. That will hold you back if you really start to get into this.

    Its a 3 dimensional problem. Pictures say more than words:

    Here are 3 dimensional plots at 40 feet for the 20m, 40m, and 80m dipoles. There is vertical polarization off the ends, which is not really shown here - many times you'll find yourself able to work DX off the ends. Propagation changes, polarization shifts with propagated signals, etc...

    I wouldn't say "forget about it". But, I would say measure it (here you have some data you can sink your teeth into). Open the images up so you can see what the colors mean. The polarization is horizontal broadside, and vertical on the ends.

    You have to think in terms of elevation angle as well - something Steve alluded to. Maybe you have the archetypal "dipole pattern" at 30 degrees, but at 50 degrees it is quite omnidirectional, etc...

    Its more complicated than saying a dipole only works on the broadside, etc...

    I also attached a great circle map centered on your grid square. You can download GCMWin by SM3GSJ http://www.qsl.net/sm3gsj/index.htm and make your own.
     

    Attached Files:

  9. K1DNR

    K1DNR Ham Member QRZ Page

    Here's a better one:

    And an example of an experiment I did overlaying the azimuthal patterns on my own QTH, the problem with the projection on my QTH is that it only shows the azimuth pattern at one elevation! The yellow line is a full wave dipole on 20m at ~40 feet feed with open wire feed (tuned). I use a tuner on 17,15 and 10.

    I still work DX over the pole on 20m, even though it appears to be 10's of db down.

    I don't *often* work DX where the null is - and if I were to put up another dipole, or rotate it, I would be working those directions more frequently.

    Now, go ahead and put up your antennas and enjoy them.
     

    Attached Files:

    Last edited: Apr 11, 2012
  10. G0GQK

    G0GQK Ham Member QRZ Page

    Maybe you have set the dipoles at the correct angle to reach Spain, but the most important thing which we have very little of is good propagation. you're not going to get out of the US unless there's some good numbers and the SFI is 93 and the K is about 8 which is not good, and there's some decent east west propagation. All the complications about Db's and azimuth patterns are just a side show, blokes were pulling in stations from all around the world with 10 watts in the 1960's and they knew diddly squat about radio science
     
Thread Status:
Not open for further replies.

Share This Page

ad: ARR