Radio Frequency (RF) & Wireless Design

Thank you for posting this Steve. I was unaware of these resources on the ARRL website.

David Dohm

David ; Yes they are but please be aware that you get what you pay for ! Also these are used in conjunction with the ARRL Antenna Book which also has examples and other resources that you get when you purchase the book. - Steven

I completely understand the concept of freeware (or stripped down demo software), and accept it for what it is.

I haven't looked at a copy of the ARRL Antenna book in years, so it might be well worth it for me to pick one up.

I recently purchased one of the inexpensive VNAs and have been experimenting with 915 Mhz antennas.

I'm also planning on acquiring an HF SSB transceiver and getting back on the air (i've been off for about 30 years after having all my HF and UHF equipment stolen in a burglary). I'll have to learn to be creative with antennae, as I live in a complex with a particularly grumpy HOA. I'm considering a vertical loop up next to a tall fence or DDRR antenna around the eves of my home to keep it out of sight.

Thanks for the reply and suggestion,

David

David ;

This is a good link for indoor and apartment antennas from ARRL :

http://www.arrl.org/limited-space-and-indoor-antennas

Here's a good site for stealth antennas :

https://www.dxzone.com/catalog/Antennas/Stealth/

This is a good book on stealth antennas :

http://www.arrl.org/shop/Small-Antennas-for-Small-Spaces-2nd-Edition/

This is a source for commercial ones :

https://www.dxengineering.com/search/part-type/hf-portable-stealth-antennas

Try these out. - Steven

David ;

Also at 915 MHz

A full wavelength = (300E6 m/s) / (915E6 MHz) = 327.64 mm

A 1/4 wavelength = 81.91 mm = 8.191 cm or about 3.25"

So i wouldn't worry too much about this antenna for stealthiness.

Typically when you get into VHF you can get away with most antennas even when mounted outdoors, but for HF antennas they take up a lot of room. For 30 MHz (10m band) an antenna is 2.5 m for 1/4 wavelength which is about 8 feet and definitely noticeable.

The slinky antennas are a great choice since they are very cheap and compact as well as can be put up in most attics very quickly. The problem is the coil-to-coil capacitance that loads the antenna so that tuning them is harder.

They also have a circular polarization across a linear line which means that the side coils will receive better than the top coils.

All antennas have their peculiar characteristics, so it may take some experimenting to find your best choice.

Steve,

The size issue comment I made related to my hope to get an HF SSB station set up.

My experimentation for 915 antennas has been focused on yagi and vertical collinear constructions, which at that frequency are relatively small and somewhat easily hidden.

The small "rubber ducky" antennas furnished with some of the Espressif development kits perform reasonably well, but I am attempting to push the effective CLOS range beyond that with the stock antennas using LoRa modulation with a spread factor of 12.

Thanks Again for your comments,

David

Thank you Steve, I appreciate your sharing these resources.

David

Very lucid and insight full writing. May I request you to write on "increasing the gain of antennas in terms of multiplicity of dimensions" in non mathematical literature and give out essence behind the concept for few famous antenna types.

Regards

Umesh ;

First off, thank for the compliment on my perspicaciousness writing style. I try to be transpicuous.

However, just increasing gain without a target from a RF Signal budget is meaningless since you can improve antenna designs infinitely.

Perhaps its the mathematical model that you are pursuing, but as engineer I am always focused on the practical applications in regard to cost, size, efficiency, RF link budgets, and down to material costs.

So if you are simply looking for the highest gain, I can tell you they are directional antennas. That may seem simplistic, but its logical too. Depending on the frequency, they can be yagi arrays or for millimeter bands they are parabolic dishes for narrow band, or log-periodic or spiral for broadband.

For extremely high sensitivity please see my article on the Very Large Array (VLA). The giant parabolic dishes of the world (e.g. Arecibo Observatory in Puerto Rico) and others offer the highest gains for their size.

When studying Electro-Magnetics you will find that the surface area of the antenna matters, so larger surface areas are better. But are they affordable or practical ? So again even though you might 'think up' an antenna, it may not be viable as a solution; especially when considering marketplaces and business models.

-Steven

Umesh ;

I found this paper for you titled "Effect of Antenna Size on Gain, Bandwidth, and Efficiency" :

https://nvlpubs.nist.gov/nistpubs/jres/64D/jresv64Dn1p1_A1b.pdf

It is very heavy in math but if you focus on the ideas more I think that you will come to similar conclusions that I stated.

This is another article but has better examples for you :

https://arxiv.org/pdf/1812.07058.pdf

This would also apply to antennas like yagi-uda types wherein increasing the number of directors likewise increases directional gain.

Steven

I was browsing thru the latest 2021 Amateur Handbook for Radio Communications and there is an entire chapter 6 devoted to simulations.

This covers what I described earlier for various methods and also calls out many types of simulation tools.

So if you are interested in learning more about RF and also want to know more about simulations, its probably a good idea to get this book since its hot off the press !

In (6) volumes :

http://www.arrl.org/shop/ARRL-Handbook-2021-Six-Volume-Book-Set

or as I prefer in one book :

http://www.arrl.org/shop/ARRL-Handbook-2021-Softcover

Here's another listing of antenna EM simulators as well :

https://www.microwavejournal.com/articles/29437-antenna-design-analysis-and-simulation