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

Feedline is IN !!

Ok, for those of you who live in a house in a non-deed restricted neighborhood, or have your own acreage with flexibility to put up whatever type of wet dream antenna farm you desire, as high and as bold as you please, this may not seem like a big deal.

If you’re living in a large condominium complex that is very conscientious about uniform, consistent and aesthetically appealing appearance, just running a feedline external to the building (which is “common grounds”) is a very big deal!

So I’m very proud to say that after one additional round of lobbying with a few board members and neighbors to address a few remaining concerns, and after modifying my plan for the antenna feedline conduit run and intended antenna location up top one more time in order to make both even less conspicuous to the casual observer, we’ve just finished installing the conduit, feeding one run of RG-213 coax for my HF feedline, a three-conductor rotator control line and three jet lines.

The last term above was new to me, and maybe new to you, although the concept is clear to anyone who has ever needed to plan for running additional feedlines after the initial set-up (as backup, for a different band (e.g., VHF), to add RFI noise suppression beads IF necessary, etc.). These are additional “pull” lines run through the conduit with the feedline, and stand ready to pull additional lines or to extract an existing line to add beads, etc. What I learned today was a fascinating and simple way to get the initial jet line through a 28 foot conduit with one right angle turn and two 7 inch offsets.

But I’m getting ahead of myself.

Indulge me – the last three and a half hours of effort, just completed by the endorsed association craftsman for such installations, with my help as a runner and grunt extraordinaire, represent the culmination of over four years of planning, lobbying, presenting, cajoling, compromising and finally, implementing a long-held dream I’ve had to establish a ‘new’ QTH in my retirement home, one thing I’ve truly missed about living in my own standalone house “up north”. Down here (in Southwest Florida), I’ve only been able to operate mobile so far.

I learned a few very interesting tricks today that might also be new to you, so here we go!

Below, piece-parts assembled at oh-dark thirty this morning. Supposed to be ready to rock with Todd by 7am. I was fortunate to catch him at all before he leaves on vacation later today for an extended period, so I let him dictate the time. Note the (previously gray PVC) conduit is all painted to color match the exterior color of our condo building:

Todd arrives with his mobile workshop, along with his intimate knowledge of the structure of our steel-reinforced concrete building and the rather elaborate category four hurricane-certified roof system that we’ll be leveraging. By the time we’re done, my antenna mount will be compliant with category four standards (able to withstand winds up to 155 MPH. So it will NOT be the mount that lets loose!

Is this guy equipped, or what!

Much of the morning was spent perched on some very tall ladders (by he-who-must-be-insured) to insall the conduit from roof to apartment:

Cutting just the right size hole in the underside of the eaves for the two inch diameter conduit…

This oughta do it…

With the upper offset connected to the straight-run conduit by just two dabs of PVC glue (so as to stay put, but be easy to pull apart with an aggressive twiest), and affixed to the wall with wrap-around brackets and tap-cons (screws) into the concrete and stucco, this conduit shouldn’t be too difficult to uninstall if/when we decide to relocate…

Tip number one: barbeque your conduit to form custom shapes.

We needed to fabricate a custom offset through the use of that highly specialized pipe-bender called a propane barbeque grill. Be sure to turn frequently to ensure uniform softness around the circumference of the PVC pipe for the two feet or so necessary to create the two offsetting bends.

Once softened, lay on a flat surface with the section intended to remain straight along a railing or something straight so you can more precisely plan and execute the two offsetting bends. Then once there, cool and stabilize with a soaking wet towel.

Done!

The result. A bit of touching up the paint and put ‘er into play!

Looking up the vertical run from the top floor eaves and the interior of the mansard (more on this later when we move to the roof):

Transitioning to the horizontal run straight into the shack with a ‘sweep’ – a gentle curve which makes it easier to pull cables through and obviates the need for a bulkier LB fitting (elbow with a screw-on access plate). 

Todd drilled and punched through over a foot of concrete, trying to miss the steel rebars by offsetting a bit out from the corner. Took a few trial holes before hitting the sweet spot:

Hammer drilling and hammering through two layers of the tough stuff, and then the hole saw for the sheet rock inside:

After touching up the paint scratches on the conduit sections from teasing joints to fit (with a hammer), the twelve foot vertical run from the eves and the sixteen foot horizontal run into the radio room don’t look too bad, huh? Couldn’t have tucked them more neatly into vertical and horizontal corners! Good design, guys – thanks for the advice!

Unless you were specifically looking for it, probably not noticeable at all. Looks like it belongs…

Now on to the roof, requiring a ten foot (extension) ladder to get up there.

Todd popping the access panel to the innards of the mansard below.

Using a magnet, I determined that the vertical surfaces are galvanized steel, and the painted orange top and outer mansard roofing material is painted aluminum (non-magnetic). So much for using the top of the wall for a VHF ground plane!

 

Inside you can see TV cable & CAT-5 runs for some of the twelve units in our building:

The vertical aluminum box you see below is actually a structural brace to distribute load of the antenna to be mounted on the opposite side of this galvanized sheet metal wall below. The load, as you can see, gets distributed across several strong horizontal “top hat” beams. It also captures the stout double thick 3/4″ plywood backing plate (total 1.5″) between this dimensionally-stable brace and the outer galvanized steel sheathing…

Feedline and control line flaked (laid) out on the roof in preparation for pulling ’em through the conduit:

You see the white lines layed out diagonally in the pic above? They get pulled easily off the spool in the box below. Todd calls this “jet line’, since it comes out of the box at the speed of a jet, if pulled quickly. 

Tip number two: duct-tape a shop vac to the shack end of a cable conduit. In the roof end, insert the jet line tied to a bit of foam to give the end of the line some volume for sucking. Turn on the shop vac in the shack, and in about 8 or 9 seconds, the jet line will magically show up in the shack!

From there, its a snap to pull the cables through, with someone attending them on the roof end.

This little tip resulted in the following rat’s nest in the shack. I photographed this mess immediately after the heat of the moment. I was wildly pulling all the excess feedline down from the roof.

I had two hundred feet. Now I only have 150 remaining, so I now know where to cut and install connectors to another fifty feet of coax which will become the VHF feedline. After drawing that line through, I’ll add add shack-end connectors and noise suppression beads to both (mix 77 on HF, mix 43 on VHF).

One of the cosmetic compromises caused my feedlines to enter the shack a good ten feet from the equipment and near the ceiling instead of lower and closer to the gear. Longer RF gr0und runs from each piece of equipment to this entry point (to ensure all at the same potential in case of a direct or near lightening strike). Oh well. As long as I get on the air!

One the vagaries of a second floor shack in a three story condo building with prestressed concrete floors above and below is an earth ground that doesn’t radiate RFI or create other common mode current issues. I’m still evaluating the wisdom of an earth ground this far up (I’m almost exactly 1/2 worst case wavelength away from the earth on at least one of my intended operational frequencies).

I’ll trim the conduit later and install an entry (RF ground) plate, although I probably won’t pursue an earth ground at this time, just a good RF ground, being a good half wavelength or more on some HF frequencies from Mother Earth.  This post, after all, is about the feedline portion of our station.

 

Total feedline length from shack entrance point to antenna mast = 16′ horizontal run + 12 foot vertical run + 24′ inside mansard and through vent to mast (allows some slack for rotation and running around inside mansard) = 50 feet (rounded up from 48 feet). My entry point is then another twelve feet to the rigs, but I’ll probably install an RF ground connector plate at the point of entry with another set of connectors from there to the rigs.

Now the feedline and control line exit the mansard at one of the drip-proof vents on the mansard wall and will then drape to the base of the mast.

Here you see the mast securely strapped and bolted to the mount/backing plate inside the mansard (not visible in this pic) through a set of pre-treated wood spacer blocks to enable the mast to plumb vertical for appropriate radiation angle as intended by the design of the antenna.

As Todd said, “this baby ain’t goin’ nowhere!”

Kay and I are taking off in the boat for a few days this weekend, which means antenna assembly and testing will have to wait until next week (arghhhh!!). The remainder of this week will be spent getting the boat ready (which is also big fun). Check out the boat at www.oursojourn.wordpress.com.

73

de K0GKJ

dit dit

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