|www.hamelectronicsmagazine.com (mirror site: www.earlandrews.com
(on the web since 2005)
by Earl Andrews Amateur Radio Station VE3AB (on the airwaves since
|JULY 15 2015
Now Earl VE3AB is trying a
Small Transmitting Loop in
his backyard. -- I borrowed
this antenna (I did not build
|Initial findings at day 1 of my testing - is that this antenna receives the signals on 40
meters about the same as the LNR Precision Modified Quad Band end fed Antenna. NOTE:
background noise level with the loop is significantly lower that the wire antenna
|First of all.. Here is the existing antenna at VE3AB - an LNR Precision Quad band antenna (end fed wire half wave on 40-20-10) .. My Quad
band antenna is really only a 3 band antenna. To see more about the LNR antenna you can visit this LINK HERE. Not visible in the picture is
the loading coil which is at the 33 foot mark (approximately). Then there is about 4 feet of wire beyond that. It is about a 41 foot end fed wire.
Works quite well but it does pick up noise in my noisy location. Many hams around Elliot Lake have high noise levels on 80 and 40 meters.
|Here is the 6 foot diameter loop. It was built by a fellow ham operator here in town
(Elliot Lake, ON.). Made from 1/2 inch copper pipe and 45 degree elbows that are
silver soldered - I borrowed this loop for a month or so while he was out of town and if
I like the loop.. I will build one up myself.
I had one qso on it today on 40 meters to southern USA and I got an S9 report.
Conditons were good between him and I but he was in the middle of a large
roundtable and didnt spend much time with me.
ONE THING I'm particularly aiming for is to reduce the noise level I receive here
especially on the lower bands ie 20, 40, 80 and possibly I might try 160 with a loop like
My initial testing on 40 meters (where the loop is pretty efficient) seems to indicate a
noise reduction of about (at least 4 S Units).
With the wire antenna -- the noise is a constant frying egg kind of noise about S 7 and
with the loop it drops down to less than about S2 to 3 or so. Hard to tell with the
summer static but this is just my first impression. Also hard to tell because the IC718
does not have an S meter per say but has a display that shows an S meter on it and I
dont know how accurate it is.
|The tuning capacitor is housed in what
looks like to me an upside down small
plastic trash container.
First situation I encountered with the
loop was: on 40 meters -- I could not
get the SWR down below 2 to 1.
I played around with the shape of the
small coupling loop. I squished it down
towards the ground and taped it in
place and the low SWR then was about
1.2 to 1. Good enough! Im going to
leave it at this and now begin
experimenting with comparisons
between the loop and my wire antenna
up the tower.
I used my MFJ SWR analyser to get
the antenna set up.
|The coupling loop shown above was not the right shape to get
me low SWR. I played around and squashed the loop downwards
towards the ground and that seemed to work much better. SWR
was low point of 1.2 to 1 at the frequency that the loop was
|Here is the controller which is from an old
MFJ loop that had a burned out motor and
was used as a parts source for this loop.
The wall wart is sufficient to run the motor
which turns a butterfly capacitor. The
butterfly capacitor is from the old MFJ loop.
|Pictured right is the lower part of the antenna. It is only about
maybe 22 inches off the surface of the ground. The 4 by 4
wooden post (painted grey) was previously used to support my
33 foot vertical antenna. The coax line (RG8) runs underground
in a protective hose to the shack basement window.
The power for the motor is fed using the coax and radio
chokes and by pass capacitors are used to permit DC and RF
operation with the coax.
|There is the top of the antenna in
the picture to the left.
There are a couple of copper
straps that run down the sides of
the plastic enclosure which allow
one to solder on a fixed capacitor
in order to pad up the capacitance
so that 80 meters can be tuned by
I plan to use an SO230 connector
on the straps so I can add on a
chunk of coax later in my
evaluation of this antenna.
I might even try to get this thing to
load up on 160 as an experiment.
I suspect the loop is a little small
to operate on 160 however.
This is only DAY 1 with this
antenna in my backyard. I live in a
small city lot (60 by 120 foot)
..which may actually be a wee bit
bigger than many city lots.
The results make me think that this
is the kind of antenna I should
have tried back in the late 1970s
and early 80s when I was in an
apartment building. I could have
tried something like this from my
Pictured left is the MFJ 249
What a valuable tool this is !
Tuning is quite sharp with the
loop. That can be an advantage for
city dwellers or apartment
dwellers. The loop will not radiate
harmonics very efficiently.
|this article is under
July 15th and for the
next month or so.
I will be writing much
more about this
antenna and the
experiments I will be
I did up load a short
movie clip on YOU
TUBE showing the
TS440s and the noise
levels on both
here is the link/url
CLICK HERE MOVIE
73 earl ve3ab