Photos
of the construction of my magnetic loop.
Click
on images to enlarge.
The
loop itself is constructed of 15mm copper pipe into a Octagonal shape
using
soldered 45 deg elbow joints.
The
circumference is approx 6M and the diameter approx 1.85M.
The
heart of the loop, a vacuum variable capacitor 10KV 20-1000pf, approx 290mm X
190mm.
Making
the clamps for the capacitor.
The
outer braid from a piece of RG213 coax acts as a connecting shell
to
the 8mm threaded rod which will be bolted to the copper loop.
First
mounting of the capacitor on the backboard.
Next
mounting and lining up of the remote control motor from a
14V
DC cordless drill.
Remote
control motor connected to the capacitor via a fibre glass tube so the
Capacitor
is isolated from the motor to prevent RF from burning out the motor.
Framework
to carry the loop, capacitor & remote tuning motor.
The
ends of the loop are bolted to the ends of the 8mm threaded rod
which
in turn are connected to the capacitor via the RG213 braid.
Starting
to take shape and now the first coat of green fence paint applied.
First
mounting of the capacitor and the remote control motor.
Powering
the motor to turn the capacitor.
The
Feed loop is made up from H100 coax.
After
adjusting the shape of the feed loop SWR on all bands is 1.3 or less
First
reception with the loop tuned to the UK 5MHz Channel FC
A
signal of 59+ is received from the beacon GB3RAL.
Loop
now moved to the end of the garden under the shadow of
my
MFJ1786 loop mounted horizontally at 3.5M AGL.
Cover
constructed to protect the capacitor & the DC motor from the WX.
Final
photo, my home built magnetic loop at ground level
next
to the MFJ1786 loop mounted at 3.5M AGL .
The
pole supporting the MFJ loop does not seem to have any
effect
on the tuning of my loop.
I
now have 80-10M coverage using my loop and the MFJ-1786, I suppose to
complete
my station I’ll have to build one for 6M ;-)
The
first QSO using my loop was on 40M resulting in a 59+10
report
from central France.
On
80M, I had a prolonged QSO with Cliff G0WKK/P who was
on
holiday on the south Coast of the UK. Despite a bit of QSB
&
static crashes from a nearby weather system the loop performs
well.
Cliff signal to me was up to 59+10 and he reported that my
signal
was up to 59. During the QSB Cliff’s signal faded to 52,
but
with magnetic loop being quiet I was able to still hear him
comfortably.
73’s
de Mike G1ZRN