An Indoor Reduced Size Rectangular Loop
by Yukon John,
Ever hear of anyone adding coils to
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.
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!
Here for April and May, 2011 using about 63 feet total loop in
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