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An Indoor Reduced Size Rectangular Loop

by Yukon John, KL7JR

Be sure to see updates for March, April, May and September 2011 below.

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?

I am on an end apartment on the top floor of a 14 story apartment building. This concrete building withstood the Alaska Earthquake of 1964, so it no doubt has a lot of rebar in it.

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 did not even solder the splices or feed point connection (photo 2- the flower vase keeps my cat away!) which was one foot up from a lower corner

I may install a balun later if I get tvi complaints.
Using the loop formula (1005 divided by frequency in MHz) I was just short of three-quarters WL on 20 meters. It would either work or not I thought.

I spent the first weekend testing the antenna which was actually quieter than I thought it would be with noise levels of S1-S2 when VE6FI answered my first call and gave me a 5x8 report. Then I worked VA7TT, JA7FTR, KH6LC, VE3EJ and several others on 20 meters and a few east coast stations on 17 meters as well.

With an ATU the loop works 10-20 meters and perhaps 40 meters as well! By the second weekend of casual DXing (early November 2009) with improving band conditions, I racked up 6 countries and 18 states. If I could hear them I could usually work them and the sent and received reports were the same 75% of the time.

I think I will leave the loop up awhile! The moral of the story:
Indoor antennas do work, and sometimes very well!

Further experimentation update:
40 thru 10 meters like a charm!

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,
experiment and have fun. 73, John KL7JR

Photo 1- showing speaker wire thumb tacked to wall near ceiling

Photo 2- Feed point connection with flower vase standing guard...keep away Kitty!

Photo 3-  Showing the Slinky coils in one of the vertical sections. 
2 are required, one
 for each vertical section.

Update February 2010

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!

Not recommended for high power indoors for safety reasons!

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!

Vertical Loop from Balcony
My New "DX" Window Antenna Farm!

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. 

Top is at 22 feet and bottom at about 12 feet off ground.  Once we move upstairs to our condo,  I'll be able to add 12 feet to both measurements!

See world maps with contacts made with vertical loop below!
Note, these are large files and will take some time to load with dialup connections! Close window to return to this page.
World Map with contacts made with vertical loop March, 2011
Click Here for map...close window to return here.

Click Here for April and May, 2011 using about 63 feet total loop in length.
Close window to return here.

September 2011 Update


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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