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21 Nov Appendix B – NEC User Manual Installation. 4NEC2 is a NEC based antenna modeler and optimizer developed by Arie Voors. This is a 3rd. 22 Aug Hello! Does anyone know where I can find some good tutorial/guide to get a basics of how to use 4nec2. I am total beginner. I was able to find. 14 Sep 4NEC2 is a freeware antenna simulation software program. The guide already shows what the main windows of 4NEC2 do, and shows you If you mean operating instructions, I will redo the manual soon and upload it in a.

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Fill in your details below tutlrial click an icon to log in: How can I tune that? Much better is just a simple solenoid made from the coax feed line itself.

Figuring out the self capacitance of the choke coil took a little research. Note that the capacitance is almost entirely just a function of the coil diameter. If you have a tall tree, there seems to be little reason to spend too much time burying radials in the lawn! By continuing to use this website, you agree to their use. If I use 75 ohm coax, how long should the transmission line be?

This simple antenna system is a great sandbox for learning the tricks of the NEC codes and some of the basic principles of antenna design, and to find all the pitfalls of this nice idea.

Antenna Simulation Tutorials using 4nec2

RF current magnitude in green. Initial tests look pretty good.

Reflections from the ends of the cable will tend to cancel each other out with this special length cable. Remember, toothat you do not want a design that is sensitive to small parameter variations.

To drive this antenna several questions come up. The optimizer can converge to either solution depending upon starting conditions. Rasing the antenna higher improves the elevated vertical dipole. How high up should I pull this antenna?

A Simple Pull-up Mono-Band Verticle Dipole Antenna Design – and 4NEC2 Tutorial – Squash Practice

I just pulled this up in the tree today. What will be the SWR? View all posts by Gary Rondeau. A choke near the feed tutoriaal for a normal dipole is trying to choke off the RF compared to the drive impedance at that point — which may be only a 50 to ohms.

This is probably the main downfall to this antenna design because it depends so strongly on getting this choke right. You are commenting using your WordPress.

One way to get a handle on this is to compare signal levels against an isotropic antenna. Notice in the model figures that the feed point is substantially below the mid-point. The important thing to do is to define the end of that radiating segment for RF, so there we place a choke.

The choke both defines the length of the lower section of radiator, which is the coax cable shield, and also keeps the RF from traveling down the feed line back to the radio. Notify me of new posts via email. Feedline current with mistuned choke. Longer radials help a little for the conventional ground-based antenna. Attempts at direct measurement of capacitance are confounded by parasitic capacitance of scope probes and by resonances with the physical length of coil wires and connections themselves, so that the measured resonances do not reflect the desired stray capacitance of the coil but rather the length of wires.

To find out more, including how to control cookies, see here: Optimizer window shows rapid convergence on correct length L1 to minimize SWR. Choose only one variable at a time to begin with. Vertical dipole tip at 55 feet, green; 75 feet, pink; and 95 feet, brown. Leave a Reply Cancel reply Enter your tutorjal here You are commenting using your Facebook account.

The outside of the coax is part of the antenna system itself, and tutorixl the RF choke that defines the lower driven element of the antenna.

I have tall trees. Email required Address never made public.

Antenna Simulation Tutorials using 4nec2 – KW4FB

I spent an afternoon with a few ferrite cores, some coax cable, signal generator and oscilloscope and can report that even good ferrite is not very suitable for this application.

I try to express the dimensions as functions of things I might like turorial change, for example the height of the top of the antenna. For the resonant feed line antenna, the choke is located at the end of the radiating element where the local impedance is very high — voltage maximum tutorrial current approaching zero.

The optimizer is a nice tool, but not magic! Vertical antenna radiation patterns.