Isn't she beautifull...
My Versa tower behind the house with a trapped Inverted-V,
My "Magnetic Loop" project. (Started in dec 2008)
Many hams are using a "magnetic loop" antenna. So I got curious and started collecting information about this antenna. The Internet is a great source.
After some calculations with "loopcalculator.xls" I decided to go for a 1.8 - 7 Mc loop capable to run 100 Watts. A loop with a diameter of 400 cm is the goal.
15 meter, 22mm copper tubing was ordered...
I want the copper tube to be a perfect loop so I made a simple tool:
Then I started with the motordrive, 4mm spindle to control the slide-potmeter and the end-switches.
Lucky I have a metal lathe..
Busy day today... may 29, 2009.....
Creating the +-joint was easy using a piece of Trespa and bending some aluminum strip. The white stuff in
the middle of the epoxy tubing is glue.
Here is the assembly....
The vacuum cap has to be 'all weather proof' ... here the 160 mm PVC enclosure with glued PVC support
to fit on the epoxy tube.
The wires for cap-motor and slide-potmeter are lead through the vertical tube of the +-joint. In some way this
feels better than leading them through the copper loop.
I can't get it out of my mind that leading the wires through the copper loop has some bad influence on the loop's
Another thing was keeping my mind busy. How to mount the cap-assembly into its enclosure without drilling
holes in it? Holes would make it less 'all weather proof'.
Well, after another cup of coffee and some serious 'number-crunching' I came up with this....
to be continued.....
11 june 2009 ..
This is the idea... turning the cable-tensioner will push the doorstop upwards and the base-plate downwards.
..and the other side..
Something wrong in the pictures?.......
Yes, the cap-assembly is upside-down. It was just for the pictures.
Okay, let's put it up...
Two high-tech equipment in one picture....
Grounding a Magnetic Loop..... 5 meters copper pipe pushed (by water) in the ground.
Loop and shield of steering cable are grounded.
View from the shack...... june 13, 2009.
Now I'm testing it... first rapports from PA-land on 80 and 160 where very good.
Designed with the loop-calculators on the web it should tune on 160, 80 and 40M.
But in practice the Loop has to be a little bit smaller in diameter to tune it on 40M.
Too much L in the circuit in this setup.
On 80M, tuned 1:1 with the vacuum cap, bandwidth is +/- 5.5 kc, swr 1.5:1
on 160M, "" "" +/- 1.1 kc, swr 1.5:1
The vacuum cap is a 5KV type so 100 watts is save.
In compare with my Inv-V on 80m there is little or no difference in send and received reports.
(Local European contacts.)
But the Loop is much more quiet and no splatter from nearby stations.
73's, Twan - PA0KV