If you had asked me what a Magnetic Loop antenna was a couple of years back my reply would have been "never heard of one"
Ask me how it works and my answer is: "
I don't have a clue"  If you want "Technical Jargon" this is the wrong place but you can find it all out there on the Internet.

I have become a bit fixated on the 60 meter band over the past couple of years and can boast a half decent dipole antenna at around 40 feet but after checking out the virtues of Mag-Loops on the web, I decided to see for myself how these mysterious devices performed.

There are a number of calculators to be found on the internet which will offer performance characteristics based on the inputted frequency and dimensions. I decided on a 2 meter loop diameter giving a ring circumference of 21 feet.
You will find an online loop calculator on this link: 
CALCULATOR

The next issue was the material for the loop, typically 22mm copper pipe would be the material of choice but some of the efforts to bend or form into to shape I had seen on the web looked real shabby and then there is the weight issue and high cost of the pipe and also resistivity problems if multiple soldered fittings are used, the tube alone would cost around £80.00.   
I had an idea about using lightweight plastic water pipe which could easily be formed into a loop and then shroud it in copper foil tape which is inexpensive and would handle 100W of power. The total cost of my Materials, less the Capacitor was £30.00.
It is suggested that a Vacuum Variable capacitor offers superior performance to a regular air tuning capacitor but at a typical cost of
£80 - £120 per unit it is not something that I will be trying anytime soon.
The present design is good for 80m - 60m - 40m being too large to tune the higher bands.

Advantages:  Lightweight (weighs 3lbs), flexible, rugged, durable, rotatable, low band noise, easy to store, unobtrusive.
Disadvantages: Narrow bandwidth, critical tuning, high voltages present near the capacitor. 
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Construction Details 
Materials
Click For A Larger Image

Click For A Larger Image

Blue Water Pipe 25mm x 8M

Blue Water Pipe 25mm x 8M

Pipe Cross Section 25mm OD

Pipe Cross Section 25mm OD

Copper Tape 50mm Wide

Copper Tape 50mm Wide

PVC Tape 50mm Wide

PVC Tape 50mm Wide

Barbed Pipe Connector 20mm Dia.

Barbed Pipe Connector 20mm Dia.

Loop Wrapped With Copper

Loop Wrapped With Copper

Loop With PVC Wrap

Loop With PVC Wrap

10mm x 490mm_copper_primary_loop_a

10mm x 490mm_copper_primary_loop_a

Tuning Capacitor 680pf 3KV

Tuning Capacitor 680pf 3KV

Tuning Connections

Tuning Connections

Primary Loop Position

Primary Loop Position

DC Motor Loop Tuning

DC Motor Loop Tuning

Simply join the plastic tube with the pipe connector. The copper foil is then  wrapped length-wise on the plastic pipe which is 21 feet long, two strips are needed to go round the circumference of the 25mm diameter pipe, so it is totally shrouded.  Then bond the two strips of copper in four places in the hoop by wrapping the foil round the hoop and soldering along the join. At the capacitor end a low loss connection from the loop to the capacitor is crucial, I used very thick silver plated copper wire wrapped around the tube ends and soldered to the copper tape.  Finally I spiral wrapped the tube with 2 inch wide pvc tape.
With the Loop just standing inside the Garage behind the metal door, I tuned the antenna capacitor using the Rigexpert Analyser on 5.3985Mhz achieving around 1.6-1 SWR, with careful positioning of the smaller Primary Loop it was possible to achieve a reading of 1.1-1.
The first couple of contacts were with Scottish stations around 400 miles to the north of me both reported 5.9 signals. Band conditions were not at all good. The next evening a CQ resulted in a LA/MM station off the Norwegian coast giving me 5.9 with the antenna still inside the garage!   
On moving the Loop to the garden, things seem even better. Right at ground level the reception is superb with residual band noise down from S5 to S2, the transmitted signal on 60m appears to be around 1.5 S-Points down against my dipole at 40 feet and QSB  is more apparent with the loop.

After fitting a reduction motor to drive the Capacitor and remotely tune the antenna, I tried the Loop on 80m with what appears to be a good result, typically S9+20 on a few contacts made around the UK.

I will update details on performance with time.
First Impression
SWR 0n 60m

SWR 0n 60m

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Click any image for a full size view
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