With Varying Frequency - Amateur Radio Ponderings

I’ve been long interested in Antenna Modeling, and had started using EZNEC-ARRL as part of the ARRL CCE Antenna Modeling Course.

As I recently wrote about, I’ve also been using CocoaNEC on a Mac.

In both cases I have been approaching program limitations with some of the full-station modeling I have been trying.

EZNEC Version 5.0+ seemed to be the best fit for the modeling projects I am attempting and after discussion with Roy Lewallen W7EL I took the plunge & bought his latest version.

One must remember that NEC2 itself is limited and no “shell” surrounding the NEC2 core can overcome those minor limitations.

From Roy W7EL’s website:

The best way to get acquainted with EZNEC is to download the free demo program. It’s a complete EZNEC program except limited in the complexity of antenna it can analyze. With it, you’ll quickly learn what EZNEC can — and can’t — do for you.

Information About the Free EZNEC v. 5.0 demo version

ARRL has version 4.0-arrl included with the ARRL Antenna Book as well.

Now it is up to me to make good use of this tool!

73

Steve
K9ZW

One of the items that very much caught my attention at Dayton was the new VNA (Vector Network Analyzer) units available at “shack-friendly” prices.

I’m not going to cover the use of a VNA, as there are web write-ups that explain it better than I ever could.

Wiki is a first stop: Vector Network Analyzer (VNA) - Measures both amplitude and phase properties 

One of the advantages that struck me as most useful is the ability to “Move the Reference Plane.”  What this allows is through a number of techniques the test equipment - the VNA - is excluded from the circuit or antenna being tested.  This contrasts with usual metering techniques which tend in highly influence certain test results as part of the test process.

At least that is what was explained to me!

Two commercial products I have started looking at are: Array Solution’s VNA  and  TenTec’s VNA

Both are targeted price-wise decently and appear to be reasonably easy to use.

If you are using a VNA in addition or in replacement of an Antenna Analyzer, please tell me how it is working for you!

73

Steve
K9ZW

This is a repost of a February 2007 Article. Several of our local club members asked about WWV during a club shack session, prompting the return of this article.
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Did you know that the USA Government provides a free to use time reference that is as accurate as anything on the planet?

Perhaps you have heard the “beep beep beep at the Tone it is X:XX Universal Coordinate Time” on the air?

Perhaps you have an “Atomic Clock” or watch?

Perhaps you have even done sound-calibrations using the WWV radio signal and one of the digital mode software packages?

All use the WWV (and WWVH & WWVB) radio transmissions.

The National Institute of Standards and Technology is the US Government Agency charged with running the radio time beacons as part of its overall charter:

NIST’s mission is to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life.

NIST Radio Station WWV is the part of NIST that Radio Amateurs most use.

Located in Colorado, the site itself is not open to the public, and looks like this:

How accurate is WWV’s time keeping?

Less than 1 microsecond of Coordinated Universal Time (UTC) at the transmitter.

Of course the signal is delayed as it travels to your receiver.

This delay increases with distance, and also changes with Propagation as at various times the signal is bouncing between the earth and the ionosphere which effectively changes the distance. Usually in the USA the accuracy should be better than 10 milliseconds (1/100 of a second).

Over the telephone, acurracy drops, but WWV should still be accurate to less than 40 milliseconds (1/25 of a second).

The Broadcast Format

Is best explained by this NIST WWV Graphic:

WWV broadcasts much more than just the time. There is so much it is best to simply check the WWV Website for more information!

The Phone Option

WWV shortwave broadcast, can be heard by phone at (303) 499-7111 and for WWVH time announcements from Hawaii, call (808) 335-4363 WWVB does not have a number published

The Internet Option

You can synchronize your computer clock to NIST using either an Internet or a dial-up, and using simple software available at the WWV site.

Other Uses

Using WWV to calibrate radios or other gear is quite easy, but usually equipment specific. You will need to follow the directions for your specific gear.

WWV is a unique service. Though a few other countries have similar systems, no other has so much to offer on an open user basis.

Remember “It’s about Time” at WWV !!!

73

Steve
K9ZW

At Contest University 2008 the importance of this book was again stressed, and a discount coupon to buy a copy was part of the CU packet.  Here is my write-up & review of the book from 2007.  It is also being reposted as it was done before Tags and RSS feeds were implemented for this blog.

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At Dayton 2007’s Contest University one book on the important issue of station design for Multi Stations and SO2R (Single Operator Two Radios) Stations was mentioned by several of instructors.

Managing Interstation Interference by W2VJN

During the Dayton show I made a beeline to the INRAD booth to buy three copies - one for my local club, one for my Dayton traveling partner George W9EVT and one for my amateur radio library.

I found George W9EVT speaking with a long lost old time High-Speed CW contact who had worked Skeds for years between them. Imagine my surprise to find that with the books fresh in hand that this CW expert was none other than George W9JVN - Author of the Books!!

I mentioned how this book had received multiple mentions and recommendations during the Contest University and how I appreciated meeting the Author in person.

From the introduction of the book:

Whenever two or more transceivers are used in close proximity there is some level of interference involved. This level can vary from practically no problem to actually burning up components in the receiving radio. The purpose of this book is to identify and quantify the various parameters that create the interference and to show methods that will reduce or eliminate it.

My read of the book since Dayton has found that the CTU Profs understated the quality and usefulness of the information in this book. And that the book has not gone unnoticed by other experts:

ON4UN says:
“George [W9JVN] covers every imaginable
aspect of the interference
problem in this book…”

The actual stubs can either be designed and made by the amateur themselves, or one of George’s other businesses Top Ten Devices offers W2VJN’s Stubs as a commercial product:

Band Reject Coaxial Stubs
Every multi-transmitter environment suffers to some extent from harmonic interferences. In some cases, coupling due to closeness of antennas is sufficiently high that potentially damaging voltages may be present at the receiver terminals. Harmonics can be so strong that operation within 25 or 50 kHz is not possible due to receiver overload. Application of band reject coaxial stubs will reduce transmitted harmonics from the final amplifier and reduce fundamental pickup as well. This translates to fewer complaints from the operators, higher contest scores, and reduced risk of receiver front end damage.

Approximately 30 dB of harmonic attenuation can be expected from a single stub. Lumped constant filters can also provide the mentioned benefits, but none are available for amateur use unless they are home built. Top Ten Devices uses high quality RG-213 coax with a silver plated, teflon PL259 and heat shrink tubing on the shorted or open end. Rated ultra-conservatively at 1.5 kW continuous duty operation, these stubs will last a lifetime.

Stubs are manufactured to order and are individually trimmed with a Hewlett Packard network analyzer to +/-10kHz. When ordering, please specify CW or SSB, and the stub will be cut to plus 25 kHz from the sub band edge.

A single stub can be connected to the output of an amplifier with a UHF tee connector. For multi band operation, the stub(s) may be connected after the antenna switch. There is no requirement for a specific length of coax between the amplifier and the stub. Well shielded line should be used to prevent radiation of harmonics before they get to the stub. Two or more stubs for a given band may be used together. For example, a CS-4 and a CS-5 together will null 40,15 and 10. They would be connected with two UHF tee connectors close to the amplifier, if possible, to minimize pick up or radiation on the connecting lead. For stations where the amplifier is used on more than one band, automatic stub switching can be accomplished [and the] station antennas can be switched at the same time.

It is worth noting that not only has George W9VJN passed on what he has learned in his book, he is ensuring that his product knowledge & products remain available by passing the torch at INRAD. International Radio now in the very capable hands of new owners Trey, N5KO, and Mark, AG9A with George staying involved in the development of new products.

A recommended Book!

73

Steve
K9ZW

Mancorad W9DK has announced a summer 2008 Hamcram with VE session.

The pre-session orientation is June 2nd and the Hamcram & VE session Saturday June 21st.

Here is the PDF announcement:  hamcram-summer-2008-announcement-v2

W9DK has sponsored several Hamcrams (check this blog - search on Hamcram) and this is the second session where the Sheboygan Radio Club has offered to provide massive support for the VE session.  

73

Steve
K9ZW
 

Working at modeling the new Bruce Array for Washington Island

Here are PDF files of the various outputs from my first efforts in cocaoNEC:

40m-bruce-v2-geometry

40m-bruce-v2-elevation

40m-bruce-v2-azimuth

40m-bruce-v2-3d

73

Steve

K9ZW