No1PC: Antenna References and Measurements

A Growing Collection of Antenna Data
Some Reality Beyond the Myths and Legends

23 Dec 16

On this page are links to additional on-site and off-site references providing some theory, practical, and data results from a variety of HF, VHF, UHF homebrew and commercial, base and mobile antennas.

Introduction

Do not let this be any more mysterious than it has to be...

Antennas may seem magical, but they are not magic. There are basic foundation antennas like the half-wave dipole and quarter-wave ground-plane that are about as simple as can be - start there!

There are multi-wire antennas and complex multi-element directional rotating antennas, and there are dozens of compromises of any of these.

Basic performance requires a quarter-wave radiator and counterpoise. Gain requires a larger radiator and accompanying matching/compensation. Shorter/small = less efficient = less effective - PERIOD.

Antennas follow the same basic electrical theories as AC and DC circuits, voltage applied, current flow is induced, current must flow back. Cheat that and you cheat good RF!

Improperly terminated, improperly radiated RF is a bitch. At low-power levels like QRP with very compromised antenna constructs the issues are minor. At high-power levels improperly treated RF will make your station and operations miserables - perhaps your family and neighbors too.

It is easier and better to get this right than it is to cheat, cheap, screw this up and fight to apply band-aids to a gas tank leaking toward a flame.

Search, read, study, consider...

Antenna Basics - Types, Gain, Myths...

Antenna Basics from Larsen

Detailed Antenna Primer from K5QHD

A Casual Discussion of Antenna Gain Myths

Antennas 101 - Basics - de Ward Silver NĜAX

5/8-wave Antenna Design per CAI Networks

Simple 5/8-wave Antenna - de W9WQ

Antenna Info - Basics - de Walt Fari W5ALT

Simple Antenna Drawings via Buxcomm
(J-Pole addicts note the direct feed versions with choke! Still begs for radials!)

1:1 Balun Demonstration - YouTube de IZ2UUF
Note only baluns but current chokes are of benefit here.

End-fed v Dipole: Effects of Common-mode Currents - YouTube de IZ2UUF
"Zepps", j-poles, anything without a proper counterpoise can cause this serious problem.

NO1PC: Antenna and Counterpoise Basics
After you watch the YouTube demos above, you'll want to see RF circuits visualized.

NO1PC: Foolproof $50 Dual-Band Base Antenna
A simple base-mount kit and either of two proven dual-band mobile antennas
is one of THE most reliable ways to get a legit dual-band antenna with adequate gain.
A Tram 1465 or 1470 base kit ($25) and your choice of 'whip' are no-brainer get
up quick for home or portable use.

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Antenna Height - Most Relevant to HF

Antenna Height Article from Mike Banz, AA3RL, on QSL.net

VOA References - Illustrated

Extensive Paper from ARRL

How High Should It Be / How Far is LOS - Horizon Calculator

SWR

My goodness how this topic is mis-understood and abused...must read!

ARRL Article about SWR (may require member login)
ARRL Article about SWR
ARRL Article about SWR (may require member login)
- don't get lost in the Smith charts, the text covers things pretty well!

Generic Antenna Info

This is where you get help unravelling all the myths and hey-Bubba non-sense...

Antenna Myths? Or basic observations and findings.
- Myths is not the way I would have presented this, but some good generic info.

A LOT of info and basic observations to consider.
- Information to consider here, albeit in a rambling fashion without a lot of validation.

Mag mounts.
- Would not consider mag mounts performers, but here's why they aren't...

MORE antenna information...
Detail and reference links...

G5RV Reference Points

A very good antenna, if you know how to put it up and use it...

The G5RV is a much mis-understood but highly popular multi-band HF antenna. The antenna MUST be hung high enough to allow the ladder-line/twin-lead section to be completely off the ground and free of surrounding objects as it is a radiating element and important factor in the antenna's function.

In my opinion, having hung and used two variants of it, this antenna is not for everyone given the height and length dimensions and requirements. Yes, it can work on many bands, with a good antenna tuner. As with all antennas and feedlines, especially in mixed/multiple antenna and band of operation environments, the feedline must be protected from becoming an incidental radiator of RF from outside to inside the shack. Well-grounded entrance panels and where prudent, current chokes at feedpoints are highly recommended.

Luxorion Pages about G5RV - author unclear

W8JI - G5RV Facts

W0BTU G5RV Info

Wikipedia Brief


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J-Pole Reference Points

I don't tolerate junk science, unproven 'facts' and outright lies

Don't make me call this the junk-pole or slim-junk

Special Notice:After over a year of social media banter and subsequent inspired research I've compiled a LOT of test and reference information about the genre of J-antennas. The research is not my own, but the need to do the research from personal and related experiences is. I had tough questions and got some rough, unqualified answers to start, and in the absence of ANY better feedback, suggestions or hard data decided to dig much further.

"The results are in" - good, bad or indifferent - but compiled and freely available. The data is out there. The data appears to be valid, consistent, robust and comprehensive. Feel free to cross-check and provide equally legit data.

What I've Learned About the J-Antenna Genre

Returning to original rhetoric...

While the j-pole is a 'cute' or 'quaint' antenna it is one of if not THE most mis-understood antenna hams love to brag about. Even the proponents submit reference information with conflicting non-data and techniques - so it is impossible to tell which lie they are supporting. Have a look at a few quite similar descriptions and realities about this simple but not whole antenna construct in the links below.

Q: I submit and question - if this type of antenna is SO 'great' then why haven't Comet, Diamond or others provided their own cheaply reproduced version of them and made millions on the sensation? Why haven't the professional communications companies adopted them?

A: Most likely because:

  • the antenna is quite simply NOT what it is reputed to be
  • NO original designer has stepped forward to claim it
  • there is NO predictive modelling or antenna test range data available
  • has severe stray-RF/common-mode issues
  • conflicting 'expert' information on choking or not choking the feedline
  • conflicting information about whether or not the base can, cannot, must or must not be grounded
  • most of 'expert' web pages supporting it are merely copy cats of others' work and cannot provide ANY proof of performance, gain, pattern, etc.

Quite simply there is NO available valid scientific or engineering basis for this antenna. It appears to be an 'experiment' that no one is willing to take credit for but everyone got sucked into.

The j-pole is quite simply an end-fed antenna with an impedance matching coupling point, or points. The nature of the feedpoint does NOT create a counterpoise or remove the need for one. The short-stub at the bottom you connect across does NOT leave a 1/4 wave or adequate counterpoise - it's just a matching stub. ALL antennas need a counterpoise or whatever you want to call "the other side" that supports proper and necessary antenna physics. PERIOD.

Aside from studying and rationalizing the physics and basics of ALL antennas, there is measured and anecdotal evidence that this antenna is not self-contained. The claims that it does not need a counterpoise are ignorant antenna modeling and testing facts. Not always realizing that the antenna NEEDS a counterpoise (as most antennas do - dipoles have them, ground planes have them...) and that in most circumstances the feedline is the counterpoise. That is often discovered to be problematic, but not for the reasons people assume. The solution most often applied (feedline choking) might fix the problem(s) encountered (common-mode, incidental radiator, etc.) but then deprive the antenna of its needed counterpoise.

Does choking the feedline improve the performance of the antenna? NO!!!!! It merely deprives it of a necessary half of the RF wave equation. Choking the feedline probably makes it WORSE - the RF field needs someplace to return to... where??? The answer is probably NO WHERE, so you end up with a very awkward unresolved impedance, SWR, radiation pattern mess.

As people experience the j-pole, especially in multi-radio (ARES deployment) environments they discover that there is a LOT of RF cross-talk between stations. Of course the first-guess is to choke the feedline. Since the feedline IS the counterpoise, choking it to fix common-mode stray RF problems immediately deprives the antenna of the only counterpoise it has. This logic escapes everyone.

J-Pole - The Obvious Solution

THE solution is simply to include/provide radials in the design and construction. This is described in at least one of the analysis references below. If you're already soldering a bunch of pipe together, how hard can it be to add a couple of radials - seriously? Make them out of #14 or #12 solid wire. Portable use? Fold them up to store/transport, fold them down to deploy. The added 30-seconds is certainly not life-critical to be technically correct and effective. PVC+twin-lead j-pole? No problem - a copper or brass washer with a 5/8-inch hole with radials soldered to it, a suitable nut to secure onto the SO-239 at the bottom... instant radial kit, instant PROPER end-fed antenna.

For all that - why bother? The j-pole is huge, provides NO appreciable gain, and presents stray-RF vs a simpler, smaller 1/4-wave ground plane. For real gain a base-loaded 5/8-wave (for VHF) is equally simple and much more effective.

The last point to consider if nothing else... there are NO, ZERO, ZIP, ZILCH, NADDA, UH-UH, NEVER GOING TO HAPPEN commercial/public safety/military variations of the j-pole/slim-jim. That is NOT because the likes of GE, Ericson, Motorola, Phelps-Dodge, Decibal Product, Tx/Rx, Telewave, et al are ignorant, stupid, clueless or missing out.

It is specifically because the concept, design, manufacture, implementation, deployment and use are so complex, unreliable, uneconomical and ultimately UNNECESSARY as to be non-viable, inferior, WORTHLESS.

There is NO way to reliably, consistently, commercially or technically make this contraption effective versus KNOWN GOOD RELIABLE CONSISTENT designs.

Hack away. Play. Experiment. Contemplate. Make unqualified claims of greatness. Snark. Troll, etc. There is NO WAY this antenna is viable other than a cheap ARES (whatever that is) gimmick. It's along the lines of the same junk design and construction of cheap Chinese portables without properly engineered chassis systems to provide adequate RF platform for rubber-ducky attenuators. This is indeed as much junk-science in proven RF fields as anything you can imagine. Enjoy your stray RF and pointless choking.

W8JI End-Fed Details
One of two pages explaining counterpoise else common-mode RF issues.

W8JI End-Fed Details
Second of two pages explaining counterpoise versus common-mode RF issues.

AA5TB End-Fed Details = Needs Counterpoise
More evidence that a counterpoise is needed else common-mode RF on feedline.

AA1ZB J-Pole Data with very telling modeling
More evidence that a counterpoise is needed else common-mode RF on feedline.

A More-Correct J-Pole
A correct way to do the off-center-fed-dipole thing people claim/think a stub-tuned j-pole is.


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Dual-Band Mobile Antenna Reference Points

This is where the great vs. sucks antenna review and performance stuff starts. There is no such thing as a great multi-band mobile antenna, nor mag-mount. Not physically possible.

The Mini-Mag

Out of my own curiosity and further inspired by the many claims about this or that antenna being 'GREAT!' or 'better' or 'outperforms' some other "piece of junk" I've taken on some basic measurements of typical VHF and UHF ham antennas, starting with the oh-so-cute mini-mag mount dual-bander - and I'll just lay it out there - it IS junk for a ham antenna, but see the measurements in the pics. How is this even a ham antenna??

Mini-Magmount Mystery

The VHF Quarterwave on 440

Next up was the claim that a 1/4-wave VHF ground-plane makes a GREAT 3/4-wave on UHF, especially becuase VHF and UHF ham bands have a 3X relationship. Well, sort of, depending on where you want to operate - 144/432, OK. 145/445, not so much. As usual SWR does not tell the entire story... SWR does NOT provide ANY indication of impedance match which is the critical thing for your transmitter - a "gooder SWR" can still impose undo mis-match on the final PA, waste watts in coax, etc. Again, measurements and some dialog in the album.

VHF Quarterwave on 440

VHF/UHF Dual-Bander

Sampled here is a Tram 1180 - probably the best built and most consistent VHF/UHF dual-bander I've owned. I can't find my quarter-wave V/U dual-band pigtail so that album will have to wait.

These antennas follow-through the same measurement/resonance/operating range characteristics of the previous tests. The basic take-away is that no such antennas are ideal on both bands. The math and thus the construction do not have the same relationships as many multi-band antennas on HF (the 3.5, 7, 14, 21, 28 Mhz allocations) which are now confounded by allocations at 5, 10, 12, 18 and 24 MHz challenging 'easy' multi-band implementations.

The Ubiquitous Dual-Bander
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© 2015, 2016 de Jim Aspinwall, No1PC
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