I got a question about analyzing antennas with traps and loading.
If you're familiar with the book "The Short Vertical Antenna and Ground
Radial" by Sevick, I simulated one of the antennas he wrote about in an
NEC2 system and I think I got it right, but the way that you put traps
and loading coils and such into NEC is not well described anywhere that
I could find, nor are there many examples with simple antennas that have
any loading coils. If you're not familiar with the book, or you're
interested in which antenna, Sevick describes a 40m antenna that's right
at 6 feet tall with a cap hat on the top and a loading coil in the
middle. The way I modeled this is by having a single wire from near the
ground to the top of the antenna and then one wire for each of the eight
spreaders in the cap hat and a wire between each of the ends of the
spreader. I arranged the elements such that the coil is near the center
of one of the segments in the vertical wire and I put a lumped
inductance on that segment. It seems to work, in that I got SWR curves
that are similar to what's in the book, but is that how you're supposed
to do it?
Similarly, with a trap dipole, I just have one wire and put an
appropriate capacitor and inductor in parallel at the center of the
desired segments.
On 12/1/2020 8:35 PM, Rick Hiller via BVARC wrote:
Comments on your suggestions: Sorry for the length.
*MiniNEC, EZNEC, 4NEC2, MMANA-GA*L are all based on the NEC
computation engine. What differs is the interface to you, the user.
I prefer EZNEC but then I have been using it for about 20 years.
Cost for the Ham Radio level versions: EZNEC DEMO is free but with
severe limitations for all but very simple antennas. $99 gets you to a
quite useable version. 4NEC2 is totally free. MiniNEC is $29.
MMANA-GAL is 139 Euro's, There are PRO versions and interface
add-ons from various 3rd parties for most of the modeling engines.
Just like my comment about the Nano VNA, in that it's gonna take some
time to understand its' use and even more time to study antenna
systems to understand what you are doing and why and how -- same goes
for modeling software. But....certainly all in good fun and ham
education and well worth the journey.
*Folded dipoles a*re simply a way to get a match to 300 ohm TL. No
advantage in gain , etc. Maybe slightly quieter on receive...maybe.
TTFD is a different fish.
*Books: *ARRL Antenna Handbook is certainly the antenna builders/users
bible. You can however buy the Kindle version of each of the
separated set books, so you don't have to spend the $60. Most of the
theory is the same in these new editions versus going back to the 70's
and before. The practical side of antennas with new materials, etc.
is what gets upgraded with each new edition. Old versions of the ARRL
antenna manual can be had for $10 typically. You can't go wrong
buying any older version.
If I had to steer you to books to read to get you up to speed about
your total antenna system -- ATU, TL, tools, and grounding, I would
tell you to get the following ARRL Joel Hallas and Ward Silver books:
The Care and Feeding of Transmission Lines -- Hallas
Understanding your Antenna Analyzer -- Hallas
ARRL Guide to Antenna Tuners -- Hallas
Grounding and Bonding for the Radio Amateur -- Silver
I'd tell you to read and understand these before jumping into a
NanoVNA, of which there is also a small book on the use of the
NanoVNA. Kindle version available for $4 or thereabouts.
Sorry for the bandwidth, but I don't agree with just buying something
just because it is suggested. There is alot to learn in Amateur
Radio and it is certainly fun to have a continual information influx
throughout the life of your Ham Radio journey. But watching the $'s
helps you buy bigger toys later on.
GL ES 73....Rick -- W5RH
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On Tue, Dec 1, 2020 at 1:16 PM KJ Anderson via BVARC <[email protected]
<mailto:[email protected]>> wrote:
* MiniNEC pro analyzer
o
http://www.blackcatsystems.com/software/mininec-antenna-analysis-modeling-software.html
<http://www.blackcatsystems.com/software/mininec-antenna-analysis-modeling-software.html>
* DX Commander
o https://www.m0mcx.co.uk/ <https://www.m0mcx.co.uk/>
* Folded dipoles (couldn’t google a site reference other than
the actual antenna form)
* EZNEC
o https://www.eznec.com/ <https://www.eznec.com/>
o There’s a free version
* ARRL Antenna Physics
o
http://www.arrl.org/shop/Antenna-Physics-An-Introduction-2nd-Edition/
<http://www.arrl.org/shop/Antenna-Physics-An-Introduction-2nd-Edition/>
o http://www.arrl.org/shop/ARRL-Antenna-Book-Boxed-Set/
<http://www.arrl.org/shop/ARRL-Antenna-Book-Boxed-Set/>
*-------------------------------------------------*
*KJ Anderson*
253-380-2636
www.linkedin.com/in/scrumnerd <http://www.linkedin.com/in/scrumnerd>
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--
Rick Hiller
*/e-mail: [email protected] <mailto:[email protected]>/*
*/Cell: 832-474-3713/*
*/Physical: 9031 Troulon Drive/*
*/ Houston, TX 77036/*
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