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With the loss of my preferred frequent flyer status, airlines tightening their checked luggage allowances, and the addition of another traveler to the family, I’ve been contemplating a new portable antenna that is easier to pack than my usual DK9SQ mast and dipoles.  I don’t do high-priced reduced-size antennas if at all possible since portable installations usually have other efficiency-reducing problems.  Multi-element antennas take up additional space and have feeding and installation complications that are unnecessary for the casual DX operator.  So, that leaves us to choose between a vertical and a dipole.

A few words about efficiency:  Dipoles have a distinct efficiency advantage over verticals in almost every practical installation for 40 meters and up, except when the vertical is physically placed in or over salt water.  Radiation efficiency tends to be dominated by near-field conditions, pattern is dominated by stuff that’s farther away.  This is why vertical dipoles work so well for long-haul DX when placed within a few wavelengths of salt water.  They don’t need the near-field efficiency enhancement as much as base-fed verticals, but they still leverage salt water for developing their far-field radiation pattern, especially at low angles required for long-haul communication.

I’m a casual DX operator, not a DXpeditioner, so I never operate on 160 or 80 meters.   That is, considering the discussion above, why I have been using dipoles with the DK9SQ.  But, verticals have a distinct advantage over dipoles in the sense that they are self-supporting.  I decided to build a vertical because: 1) my next DX trip would include time near a beach and 2) I wanted to be able to bring my own support as I had with the DK9SQ.

My remaining requirements were now simple:

1. A vertical antenna that requires no additional supports.  Guying is OK.
2. The antenna must be full-size (quarter wavelength) on 40 meters and above.
3. Experience has shown that multi-band operation is desirable, but instant band switching is not necessary.
4. The longest piece must fit inside my suitcase (20 in / 50.8 cm maximum length).
5. Field assembly and repair with only a Leatherman tool.
6. Minimum cost, minimum weight, minimum volume, minimum installation time.

And this is what I came up with:

There are 21 aluminum sections, most with a “swaged” (actually, a poor-man’s swage to be described in a moment) end and a slit end.  They are shown here bundled perfectly inside a section of cardboard shipping tube.  An 18 x 2.5 x 0.125-inch aluminum plate serves as the base.  I used DX Engineering resin support blocks to insulate vertical from the base.  A point could be fashioned on the bottom of the base and a foot plate attached to push into soft soil, but that has not been done.

Most sections fit together using overlapping joiner pieces that I previously referred to as “poor-man’s swaging.”  I’m not sure that it’s actually a savings over paying a local shop to swage the ends for you when time is considered in addition to material, but I cut telescoping pieces six inches long and fastened them three inches deep in one end of a 17-inch section of tubing with two offset and orthogonally-placed aluminum pop rivets for a total length of 20 inches.  This geometry not only fits in my suitcase, but results in a very small amount of wasted material as well.

The other end of each piece is slit about 2 inches and they mate with an all-stainless steel hose clamp.  The first 10 feet of the antenna are 0.75-inch 6063-T832 tubing followed by telescoping sizes down to 0.375-inch at the very top.  The transition pieces are a full 20 inches long and are slit on both ends.  The full-size antenna will stand in a light breeze, but guying is a good idea.  Guy rings are fashioned out of flat washers drilled in three places.

Tune-up is easy…the more radials you use, the less critical their length.  After about 8 or 10, you’re in the clear here.  I never attached enough to prevent them from affecting the tuning.  If you only plan to have a couple of radials, go ahead and cut them to 1/4 wavelength (even though ground proximity will detune them).  Then, set the length of the antenna using the required number of 17-inch sections (the 234/f formula is surprisingly close) with the last section being a variable length for fine tuning.

I’ve intentionally left out most of the details of the antenna itself because I don’t expect anyone duplicate it exactly.  But, here are a few notes for anyone considering building one themselves:

1. There are lots of parts vendors out there.  McMaster-Carr and DX Engineering will get you there in one order from each.  There is a surprising amount of overlap in their inventories.  Get the hose clamps from McMaster…even if you get stainless-stainless (stainless band, stainless screw), they are about 1/3 of the DXE price.  On the other hand, the resin support blocks are cheaper from DXE.
2. I carry a compact antenna analyzer (Autek Research VA-1) with me.  Field tune-up is a snap and it runs on a single transistor battery.  It’s about 1/4 the size and weight of an MFJ-259 and good enough for amateur work.  Oh, and I bought mine used for a fraction of the MFJ.
3. A tubing cutter is fine if you only have a half-dozen or so cuts.  But, if you have a chop saw or need an excuse to buy a chop saw, it will make cutting the tubing far easier.  My hands were raw for a few days after cutting the tubing by hand.  I’m sure the antenna performs better on account of it, though.
4. Find a friend with a metal-cutting bandsaw to slit the ends of your tubes.  I went through a half pack (McMaster mega-size pack) of cut-off wheels for my rotary tool doing my slits.
5. McMaster only sells the aluminum plate in 36-inch pieces.  If you don’t have the aforementioned chop saw, an angle grinder with a cut-off disk does a surprisingly good job.
6. I pack a combination-screwdriver that has hex drivers that fit the hose clamps and #6 nuts.  Even though the antenna can be erected with only a Leatherman tool doesn’t mean it has to be.
7. The small parts box shown in the top picture holds all of the parts for the antenna—it was 2 USD at Home Depot.
8. The final and most critical component is a clip-lead that can be used to attach various nearby metal structures to your ground plane.  I have used it to make a temporary radial out of excess tubing sections on 12 meters as well.

That’s it.  The antenna goes up in a few minutes, especially if not used at full length.  I used it successfully last week as OA5/K8GU, which will be detailed in a future post.

In this episode of Linux in the Ham Shack, our intrepid hosts put aside idle banter, childish meandering and silly stories in favor of true content, both ham radio and Linux related. All right, that doesn’t happen even a little bit. Instead, Richard has a lot of fun telling you all the trouble he has with Linux Mint Debian Edition, all the while mentioning a bunch of other operating systems he’s tried recently including Ubuntu, Kubuntu, Crunchbang among others–letting you know what’s wrong with all of them.

Then there’s some discussion of svxlink, an Echolink client and server application for native Linux environments, Allstar Link, Open Media Vault, contest loggers and a whole bunch of other stuff besides. Ahh, perhaps there is some content here after all. Hope everyone enjoys this episode and can perhaps contribute a dollar or two towards the Hamvention fund. It’s coming up soon and we hope to see you all there.

73 de The LHS Guys

A few days ago, I was chatting to a friend on the repeater about the Baofeng UV-3R and what a useful radio it was. He was interested in getting one, but explained he didn’t use eBay. Rather than have him pay £50 in the UK, I said I would order him one.

It arrived today. I had ordered a UV-3R Plus, rather than my Mark 1 model. What are the differences?

The Plus has dual band display. In practice, I don’t think this is a big deal.

The Plus came with a dual band antenna rather than two mono band antennas

The Plus comes with a drop in charger. The charger tray can be powered from the USB style charger that comes with the rig, although I plugged the lead to an iPhone charger.

Although it is entirely adequate, I feel the build quality on the Plus is not quite as good as the Mark 1. What do I expect for £32.90?

Although I have not had any QSOs – it is my friend’s rig, after all, performance of the rig seems as good as the Mark 1. I was able to blip up GB3TD and GB3UK from inside the house.

The Plus came with two earpiece/ microphones – the standard one and an added bonus.

I hope my friend will be pleased with it!

My online ARRL course, “Introduction to Emergency Communication,” is in full swing. I’m happy to say that it is pretty demanding. Not that the material itself has been especially difficult (yet), but the essay-assignments do require some thought — and other assignments are pushing me to do some new things on the air, like listening to several nets, critiquing an NCS (Net Control Station), and checking into a net (okay, I probably have checked into a net or two over the years, but it’s been so long that I hardly remember doing it).

Today I reaped some unexpected benefits from one of these assignments. Having been assigned to check into a formal net, I checked into the PICONET this morning. This was no small feat, since it was on 75 meters. My New Carolina Windom is only cut for 40 meters, and the automatic tuner on my Kenwood TS-440S has never been able to match it — the SWR is terrible! But using my old Drake MN-7 Matching Network, I was able to match it surprisingly well. So now I’m on 80/75 meters! I even made a CW contact with a fellow in Wisconsin, and got a decent signal report.

Lyle Koehler, KØLR, with Katharine Lord, KØTHY (photo copied from the PICONET website)

And after checking in this morning, I visited the PICONET website — and learned that Lyle Koehler, KØLR, would be the NCS for the PICONET this afternoon! Wow! Lyle is the ham who gave me my Novice code test back in 1978. I was only 10 years old, but I remember it like it was yesterday. I’ll never forget how I shook like a leaf on the couch in his living room while he sat beside me and tapped out 5 wpm code with a straight key and oscillator. When he told me I passed, I couldn’t wipe the grin off my face for the rest of the day!

So the thought of talking with Lyle again after all these years was enough to make me watch the clock, eager for the PICONET to open again at 1500 CDT. And sure enough, at the appointed hour I heard Lyle’s voice as he opened the net! I was his first check-in, and I took advantage of the net’s slow start to explain that he had given me my Novice code test over three decades ago. He remembered me!

What a pleasure to meet this fellow on the air after all these years.

I’ve mentioned similar courses in the past, but here’s a new twist….. you’re not just watching videos of lectures, you can actually participate.

Here is a description of the purpose of the MITx program, from MIT:

“MITx will offer a portfolio of MIT courses for free to a virtual community of learners around the world. It will also enhance the educational experience of its on-campus students, offering them online tools that supplement and enrich their classroom and laboratory experiences.The first MITx course, 6.002x (Circuits and Electronics), will be launched in an experimental prototype form.

Watch this space for further upcoming courses, which will become available in Fall 2012.”

The Circuits and Electronics course has already started.  Though I can’t participate at this time, I did notice I could still click on the link and enroll.

If you have the time, check it out.  Maybe come back and give us some feedback on the experience.  The link to the course is:

Lately I’ve been fascinated by the capabilities of mesh networks. The ability to quickly create ad-hock computer networks could be an invaluable resource for amateur radio operators in general and particularly for emergency communications (EMCOM)

The particular device and software I have been experimenting with is the Linksys WRT54G router and HSMM-MESH firmware from http://hsmm-mesh.org/.

Installing the HSMM-MESH firmware changes the way the Linksys router functions and allows it to automatically connect to other HSMM routers in a mesh network. No special configuration is required after setting your callsign. All TCP/IP configuration is pre-configured, even down to automatically assigning addresses to connecting clients.

Mesh networks are highly fault tolerant. Every router in the network is aware of every other router and has the ability to move network packets through from one unit to another provided there is a link, or chain of linked routers, between them.
In the diagram to the right each router is represented by a numbered circle. If router number 6 were to fail then network packets that needed to move between router 1 and 7 would travel through routers 2 & 3 or 5 & 10 until 6 was repaired. All this happens automatically and quickly enough so that there is no disruption to the traffic.

Anything you can access on a normal computer network can be made to work on a mesh network. Some of the services that have been demonstrated include email, voice over IP (VOIP), video conferencing, file sharing, web servers & groupware applications.

With simple modified antennas the modest output power from the WRT54G (100 to 200mW) can be used to reach distances of many miles or tens of miles with directional antennas. Mounting the router on a mast in a sealed enclosure can reduce losses from long cable runs while running off 12V power makes them compatible with ham radio power sources including solar and wind power.

The example to the left is from NG5V located on hsmm-mesh.org and consists of an omni-directional external antenna and a lawn sprinkler controller box from a popular home improvement store.

Did you know that … Frequencies used by channels one through six of 802.11b and 802.11g fall within the 2.4 GHz amateur radio band. Licensed amateur radio operators may operate 802.11b/g devices under Part 97 of the FCC Rules and Regulations, allowing increased power output but not commercial content or encryption.

I hope to acquire a few more WRT54G routers and put together a mesh network in the Katy TX area as a resource for experimentation and education in an area not normally touched upon by regular amateur radio operators. Who knows what the future holds & it behooves us to investigate this technology and bend it to our own needs.

The Amateur is Progressive … He keeps his station abreast of science. It is well built and efficient. His operating practice is above reproach.