Eznec Question

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K5WZI, Jul 23, 2019.

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  1. SPEEDSKATER

    SPEEDSKATER QRZ Member

    Where are these help files located?
     
  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    I just click on the "help" tab in the program. A printable version is here.
     
    W1VT likes this.
  3. UA3TW

    UA3TW Ham Member QRZ Page

    I began studying transformers and made a simple model consisting of one source and one dummy 50 Ohm load connected with a transformer between them. I expected unity SWR as a result but got severe warning instead.
    What is wrong in the model, help me please?
     

    Attached Files:

  4. AC6LA

    AC6LA Ham Member QRZ Page

    Unless you are using a NEC-4 engine, a wire segment can be no shorter than 0.001 (1/1000) WL. Each of your two wires has 3 segments so each wire must be least 3*0.001 WL long. At 3.65 MHz that's ~247 mm.

    An easier way to play with various insertion objects such as transformers and transmission lines is to use virtual segments. Put the source on V1, put a load with Ext Conn = Par on V2, and place a transformer between V1 and V2. (If you try to put a load on a virtual segment using Ext Conn = Ser you'll get an error so set the Ext Conn field first and then set the "Specified Pos[ition]" to V2.)

    You still need at least one wire in the model but that wire can be anywhere in space and need not have anything connected to it. Even if not used the wire must still meet the minimum segment length criteria.

    Like so, to test a 1:4 transformer:

    InsObjs.png

    Actually the transformer impedance ratio should be expressed as 50:200 rather than 1:4 although in this case it doesn't make any difference. See the EZNEC Help on Transformers.

    Be sure you are using the double precision NEC-2D engine, not the mixed precision NEC-2 engine. Try both and you'll see the difference.

    Dan, AC6LA
     
    UA3TW likes this.
  5. UA3TW

    UA3TW Ham Member QRZ Page

    Thank you, Dan. It was the "Ext conn" column that mattered most in my model - there were no such column in EZNEC v.4
    Will move futher to the hybrid coupler now.
     
  6. UA3TW

    UA3TW Ham Member QRZ Page

    Tryed to open 4SQ 160m EZNEC model with hybrid coupler in 4nec2 and got a strange result. Is it natural?
     

    Attached Files:

  7. AC6LA

    AC6LA Ham Member QRZ Page

    When reading *.ez files, 4nec2 does not recognize any of the new features added as of EZNEC v. 5.0. So in your case all the Ext Conn = Par loads are treated as normal NEC loads in series with anything else on the same segment, and the transformer connecting wire 5 to wire 7 is completely ignored.

    One other very minor point: You may want to change the "Title" field. :)

    Title.png

    Dan, AC6LA
     
    Last edited: Aug 30, 2019
    UA3TW and KX4O like this.
  8. AC6LA

    AC6LA Ham Member QRZ Page

    Just guessing here, but if the intent was to be able to see a 4nec2 3D plot of the EZNEC model you can do that using the free XLGTa - Antenna Gain/Temperature and Other 3D Metrics workbook (requires Excel). First follow the steps in the "Creating ... With EZNEC" section, then see the "Showing 3D plots" section.

    So you can start with below left and end up with below right:

    Nick3D.png

    Dan, AC6LA
     
    UA3TW likes this.
  9. UA3TW

    UA3TW Ham Member QRZ Page

    Thank you very much again, Dan. My intension was very small hope that 4nec2 is upgraded enough now as to meet the new features of EZNEC and I would be able to present my models to those who do not have EZNECv5.
    Still it is possible to build a hybrid coupler out of two 1/8 W pieces of coax and two capacitors, without transformer
    Both models are giving similar results.
    Even in MMANA is possible to make a complete calculation of 4SQ and the like using some
    tricks.
     
    Last edited: Aug 31, 2019
  10. AC6LA

    AC6LA Ham Member QRZ Page

    That sounds pretty interesting. Would you mind posting your equivalent 4nec2 and MMANA models?

    Dan, AC6LA
     

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