Re: K2 + ATU + Loop antenna in the attic

[stan levandowski]

On Mon, Apr 11, 2011 at 7:11 PM, Wayne Conrad wrote:


> I want to start out with an loop antenna in the attic, etc....

Wayne, you've already gotten some pretty good advice on this subject.
May I add my two cents' worth here?

First, you did not make it clear at all if your attic antenna is a
'must' due to  CC&Rs or simply your "choice".  Wayne, if you have any
choice in the matter, put the antenna outside. I have no choice due to
CC&Rs so my antenna has been in my attic for the past nine years since
we moved into this townhouse.

Second, lightning,'close strikes', and static build-up can wipe out your
investment in hardware just as easily in the attic as can happen
outside.  I happen to know this because a Hallicrafters SX-146
practically blew up in my face several years ago.  Take the necessary
precautions, please!

Third, how successful your attic installation will be largely depends
upon the particulars of YOUR situation.  Some issues can be mitigated;
some cannot.  Assess your attic environment and if the list of
"negatives" outweighs the "positives" then you might want to start
investigating some sort of outside 'stealth' setup.  In my case, I found
my attic to be quite RF friendly.  There is no metalized insulation up
there, the vents are all PVC, all wiring is below the attic floor, there
is no HVAC at all, tthe shingles are asphalt, the ice dam is
non-metallic, the gutter runs are extremely short (due to the
architecture) and the downspouts are 90 degrees off from my antenna
plane and much lower.  There were two runs of "slinky-like"  4" bathroom
vent hose.  I went up and chopped them up into small segments and then
put them back together again with duct tape.  These are a few things you
might want to check out in your attic.

Fourth, I run only QRP with my attic antenna.  Technically, I can meet
the MPE Uncontrolled limits at 100 watts but I prefer not to run higher
power.  Above a nominal 30 watts I turned on my neighbor's carbon
monoxide detector, put my CW signals into her telephone, and turned my
own DVD player on and off, on and off.  The CO problem was "unfixable"
and probably due to the unit's design.  The phone problem was solved
with the addition of a filter from KY Filters.  The DVD problem was
solved with a single Mix 43 toroid on the DVD player's line cord.

For  your information, the antenna I chose to install in my attic is a
homebrewed 62' doublet bent a couple times to fix the space available.
I avoided doubling it back on itself.  The center insulator is the
Delta-C surge supressor from Alpha-Delta. I fed it with 14 feet of 450
ohm ladder line directly to an SGC-237 autocoupler on a shelf near the
ceiling in a linen closet right below the feedpoint.  This keeps the
rather expensive autocoupler out of the winter's cold and the summer's
heat in the attic.  The run from the autocoupler to my station is about
25 feet of RG8X.  I have a copper cold water pipe behind my operating
desk and I confirmed that it is tied into the electrical panel as per
code here in NY.  The ground is *not required* in the sense that the
doublet is already balanced but it's good practice and I use it.  I'm
working "the world" on 5 watts, frequently much less, and having all the
fun I can handle.  I can load up 160 through 6 meters with the doublet.
My SWRs are all below 1.4:1 except for 40 meters where I am 1.8.  I may
need to shorten/lengthen the ladder line somewhat.

I guess the message is simply this - evaluate your environment, consider
the options, and then go for it.  Electromagnetic particles can't read
textbooks so they don't often realize that they are not supposed to
propagate themselves to the far corners of the world from a measly attic
antenna hi!

Good luck with your loop!  It may surprise you!

73, Stan WB2LQF
KX1 #2411    K1#2994    K2# 6980    K3#5244     K9 #1 (Cocoa the
Chihuahua)
Everything is QRP, even the dog.



You seem set on a loop.  They work and they work well.

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