Modeling coil-loaded dipoles in CocoaNEC 2.0

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KH6AN, Dec 13, 2018.

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  1. KC8VWM

    KC8VWM Ham Member QRZ Page

    I see. Do you have any other electrical data for this coil design for the calculator?

    For example, can you indicate what is the intended inductance as expressed in microhenries supposed to be for this particular coil in this portable antenna design?
    Last edited: Dec 13, 2018
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Do you have a link to the design or can you list the pertinent parameters including:
    - Total wire length end to end
    - Wire length of inner segments from center insulator to loading coils
    - Wire length from loading coils to end insulators
    - Intended frequency of operation

    From that it's not too hard to reverse engineer the appropriate value of the loading coils.

    IOW, in CocoaNEC build the model on the dimensions above, do a wideband SWR sweep and find out where the antenna hits resonance (and or best match). Add the loading inductors as series RLCs with a swag for starting value (e.g. R = 0.5 ohms, L=10 uH, C=0pf), repeat the SWR sweep to see where the antenna tunes. Change the L value as necessary (more loading equals lower tuned frequency) until the antenna tunes in the band of interest. Then look at feed point impedance, SWR bandwidth and other antenna characteristics of interest.
    KH6AN likes this.
  3. AL6O

    AL6O Ham Member QRZ Page

    David- I'm on Maui looking for any 2 meter activity and have found none so far. Do you have a 2m rig? If so, I'd love to chat with someone. Almost feel like my radio isn't working it's so quiet here. AL6O Charlie
  4. N5ST

    N5ST XML Subscriber QRZ Page

    Aloha, Former Maui resisdent here. (I ran the USAF observatory for a few years)

    If you are going to run QRP are you planning on voice? Voice is tough QRP. What does the attic of our condo look like? What is the longest straight run you can get? I am assuming composite roof? If the diminsions work, I have a G5RV jr dipole I would send you to get it out of my way.
  5. PA1ZP

    PA1ZP Ham Member QRZ Page


    I am using MMANA-GAL basic for simulating purposes, for over 10 yrs now.
    I find it real easy to model lots of antennas in this free software.
    However the problem with different V-factors in different insulations and thickness in wires will be there in every moddeling software.
    And MMANA-GAl basic also has the possibility to model even real easy trapped antennas, it even has a lovely inductance calculating tool etc.

    73 Jos

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