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Yet another antenna question

Discussion in 'General Technical Questions and Answers' started by KI4DAC, Mar 26, 2009.

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  1. W9JEF

    W9JEF Platinum Subscriber Platinum Subscriber QRZ Page

    Antenna height does matter

    Steve,

    Your FB article in May '09 QST is a 'must read' for any ham (especially a newcomer).

    The Higher the Better is a myth
    in need of debunking.

    What would be the optimum height for an NVIS on 80?

    BTW, other than a possible connector difference, do you know if a telephone designed here in "the Colonies" work in the London phone system?


    73,

    Jim
     
  2. G3TXQ

    G3TXQ Ham Member QRZ Page

    Jim,

    Thanks for the kind comments about the QST article.

    I'm no expert on NVIS, but if I model an 80m half-wave dipole over average ground, and look at its "overhead" performance at various heights, I see:

    1) High ground losses at very low heights (below 20ft)
    2) Steadily improving performance as it is raised from 20ft to 50ft because of decreasing ground losses.
    3) Steadily decreasing performance above 50ft as the elevation pattern begins to develop more low-angle at the cost of the overhead.

    So on that evidence I'd have to say somewhere around 50ft was optimum. Improving the ground conductivity reduced the losses, but the optimum height remained at around 50ft.

    Telephones: Sorry, I know nothing about them :)

    Steve
     
  3. KI4DAC

    KI4DAC Ham Member QRZ Page

    Ok, sorry it took so long to get back to everyone here. I work 60-100 hours a week between my 2 jobs so getting my antenna up took much longer than I anticipated. I ended up not having enough room to put up the dipole as the tree I was using to support it was closer to the house than I originaly estimated. I ended up putting up a delta loop cut for mid band on 80 meters. I ended up using 14 gauge galvanized electric fence wire (I know I'm going to catch quite a bit of flak for this). It is supported by three trees in my yard and is approximately 25-30 off of the ground. I fed it from one corner using rg-6 coax to my tuner. I have only had it tuned on 80 meters for the 3.980 tennessee phone net and so far but it seems to be working great. I am hoping to have a chance to tune around on it some more later this week when I am off of work. I have attached a picture so you can see how it is run.

    73 and thanks to everyone for your input. :)
     
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