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An Indoor Reduced Size Rectangular Loop by Yukon John,
KL7JR Ever hear of anyone adding coils to
loops?
Sometimes indoor antennas are our only means of
staying active with Amateur Radio. From the very first time I used an
indoor loop, I liked the performance. Would I like one again?
Rebar would cause a lot of interference I thought. Right? There is only one way to find out. I spliced together some
scrap speaker wire (photo 1 below) that I had to fit my living room wall
19 feet long by about 6 feet wide (just staying about a foot above the
floor) and thumb tacked the wire to the sheet rock wall. I may install a balun later if I get tvi complaints.
Further
experimentation update: It didn't load on 15 before the coils were added but does now.
Using a suggestion by VE8MN, I added the coils (Photo 3 below) to each vertical section of the loop.
It easily tunes on 15m now. The coil is about a foot long compressed and when stretched out measures 10-12 feet long.
I cut up a Slinky and added about 10-12 feet to each vertical section of my indoor vertical loop;
Voila- it worked! I'm loading 10-40m now.
Don't forget to use a tuner,
I removed the coils, added an air
choke "ugly balun" (see picture below)
and extended the horizontal sections of the antenna by about 3 feet each (yes, I punched two holes in the living room wall and extended the antenna to the bedroom!) making the antenna 3/4 WL on 20m. It rocks on 20 and 17 meters, and loads 10-40m easily. No propagation above 17m to date so I can't comment. Here's what I've worked on 17 and 20m the past two months on a casual basis from Anchorage: VE7, VE6, VE5, VE4, VE3, VE1, KL7, KH6 (many), JA (many, all areas), UA0 (many) and SJ2 plus 40 some states! Who said indoor antennas don't work- hi hi! Can you imagine what this simple antenna would do installed outdoors? I love loops! Update: March 27, 2010
I've added XE1, 2, PY5, LP1, PR2,5 and I now have
45 states in my 20
meter log including baseball legend Joe Rudi NK7U and
W1AW.
Still nothing heard above 17m when I check.
No doubt I am enjoying vertical polarization at it's finest. I
will try this antenna "outdoors" in
the near future!
I know I'm amazed, but
then.......
I love loops! KL7JR
Update March 28, 2011 - Now Operating from Dominican Republic!
My vertical loop is now outdoors at 53 ft long and
tunes 6-40m but doesn't like 15m. I'm amazed at what I'm doing with
this simple antenna. I have modified it from the one earlier in this
article......No balun. No coils. Just direct coax
connected. Click Here for map...close window to return here.
Click Here for April and
May, 2011 using about 63 feet total loop in
length. September
2011 Update ADDING COILS TO
LOOPS
I read somewhere if you use coils to make your
antenna seem longer, do not exceed 30% of
the antenna length for the coil length. Following that simple rule
has worked for me in the past. I
usually try to stay around 20% to be
safe.
I decided to challenge that rule with my 15'
square loop by adding 2 coils at about 7 feet long
to each vertical leg, making it now a
rectangular loop 15 ft x 22 ft, or an increase of about 50%
of the loops vertical "leg" length for the coils (I did
this to achieve 1WL on 20m).
It was a big mistake! Both my receive and
transmit were degraded severely, and my
omni-directional antenna was then very limited to bI-directional
only with some bands 10-40m produced a very high SWR. I
highly recommend you not exceed 20% should you decide to use coils in our
next antenna build.
(I now have the same set up but my coils are 2
feet long and I'm satisfied with a .75 WL 20m
loop which works 6-20m!).
73....KL7JR
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