K0GKJ – Just Another Ham
The New QTH – A Floating Shack

Antenna Construction

Hi kids!

Well, the base station here in SW Florida is still under construction (condo rules – now have approval for antenna on roof, so progress!). Also relocating the shack from our guest bedroom (one of only two in this apartment) to a large (6×16) walk-in closet where the XYL will allow me more “artistic freedom” for “all that radio stuff” ūüôā Gotta be stealthy, outside AND inside! No problem. It’s a very nice closet with lights, power, internet access port, lots of wall space for desk and shelves for the good stuff, and an exterior wall for the antenna feedlines (although the walls are a hurricane resistant 16 inches of concrete block and steel rebar (can you spell “Farraday Cage”?!). Again, no problem – they make nice long masonry bits for my hammer drill.

By the way, the pitch to our home owner’s board focused on disaster preparedness and recovery, offering my shack as a command post & communication station should a hurricane knock down landlines and cell towers in the area like Hurricane Charley did in 2004. They thought this was a good idea, as long as I stayed very stealthy.¬† I’ll upload the presentation (PowerPoint) as soon as I figure an efficient way to post it (or in PDF format, etc.). You might find interesting what worked in this situation.

J-pole called a copper tube “slim jim” that took all of about an hour to build with about $12 of copper and miscellaneous hardware, taken from the hamuniverse site. Yet to be tested on the air… meanwhile, running 2M and 40M mobile…

boat and tenna 019

For HF ops in the shack, I chose an antenna called the broadband hexbeam from K4KIO for several reasons: directional (good gain and front-to-back ratio) with¬†relatively small turning radius (<11 ft.), reportedly very quiet on the air, low¬†vertical profile (42 inches),¬†low¬†and ¬†symmetrical wind load (< 6 sq. ft.), unusual appearance (shouldn’t be a critic magnet if spotted, stealthy, single feedline for all bands, a time-proven design, and well supported by vendors and users including a very popular hexbeam group on Yahoo). This is my first experience with a beam (directional) antenna, so I took the time to do the research, and hopefully, I’ve found the right antenna for my covenant-restricted QTH.

Now setting up the antenna rotator in anticipation of raising the hex beam antenna soon (more info on this antenna bel0w if interested). The rotator is an RCA VH126N that was less than $100, has twelve memory locations with a remote, and should be heavy-duty enough for this light and relatively small antenna:

boat and tenna 020

The bottom of the center plate of my new 4 band hex beam antenna (appropriately camoflaged to blend in with the Florida sky, of course):

boat and tenna 022

Rotator, with antenna stub installed (1.25″ schedule 40 PVC) necessary to connect the antenna hub to the rotator:

boat and tenna 024

The center post that extends above the hubto which all antenna elements connect (just wires):

boat and tenna 027

The whole affair precariously perched on a temp stand in the garage. When assembled (not until ready to place on the roof of the condo building), the six fiberglass spreaders (see below) radiate out from the center base plate and curve up to a maximum height of about forty-two inches, and then the antenna wires are strung around this frame. The whole thing will look like an upside-down umbrella frame (if you can even see it as it’s almost invisible from a distance, and will be essentially obscured by the building itself). Cool, huh?

boat and tenna 028

By the way, here are pics of my antenna mast and components as received (from K4KIO, a.k.a., Leo Shoemaker,¬†in kit form – nice job of kitting, Leo!) before application of my own three-tone design for “sky camo” (using Krylon Fusion paint, made to stick to plastic and fiberglass – you can get it at Wally World for less than seven bucks a can)

Before the application of “sky camo”:

Below are four foot fiberglass poles (surplus military camoflage screen support poles picked up at a hamfest). These interlocking poles will comprise my antenna mast, and will bolt to my vertical mansard roof wall (see below):

hexbeam etc 004

I have five (twenty feet worth) left over to use as my field day mast. I’ll use one four-footer for assembling and testing the antenna after assembly…

The spreaders to the left and centerpost to the right opened up to show internal coax cable harness:

hexbeam etc 004A

The rotator motor “au naturale”:

hexbeam etc 009

The hub “naked” (notice that Leo even conveniently included an allen wrench to tighten the mast and center post to the center brackets! What a guy!

hexbeam etc 014

And the RF Choke kit from Ron at http://www.hexkit.com/rfchoke.html. This will slide over the RG-213 feedline just below the hub plate above and ostensibly prevent common-mode current traveling down the outside of the feedline coax shield, potentially injecting nasty RFI into the air and worse, into the shack. Thanks for kitting these and making them available, Ron:

hexbeam etc 005

For those of you not familiar with the broadbeam hex beam, this antenna will naturally resonate (without a tuner) across the 20, 17, 15 and 10 meter bands (I chose not to install the 12 meter band as money was limited, plus it is said to impede the performance of the 10M band, which I’m looking forward to using as the next solar cycle heats up!). This should exhibit some good gain as well as a very respectable front to back ratio (see Steve Hunt’s excellent hexbeam site for more technical info).

It’s also said to be an extremely quiet antenna which minimizes background noise on both received and transmitted signals.

The trick in this installation will be to get the antenna high enough above the metal roof of our three story building to avoid undesirable coupling between antenna and roof,¬†but not so high as to be very visible from the ground (a no-no around here).¬†The antenna mast will be mounted inside the vertical mansard wall below (silver), i.e., NOT on the horizontal roof per my board’s approval, and protrude above the roof as little as possible. My initial attempt will be to get the bottom of the antenna eight feet above the top of the wall:

roof pic antenna

Well, that’s it for now. I’m also in the midst of a major restoration of my forty foot motorsailer call “Sojourn” (fifty-one feet length overall), and that is dividing my time big time! I’ve repeated the highlights of this antenna installation over on that blog for my non-ham boating friends, so sorry for a little duplication if you follow the link above to check it out. If any of you are interested in what’s entailed in a lengthy and costly yacht restoration, have a look. If any of you are considering the insanity of restoring a thirty year old yacht, go get your head examined. Remember, the purchase price is simply the first tiny drop in the bucket!

‘Nuf for now.¬†

73 de gene k0gkj dit dit

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