Indoor Counterpoise For Random Wire Antenna
Thanks Sal, Roger, and Bob as well as
the many others who have not yet replied
-- actually my mic is plastic.
I truly appreciate your assistance, but I think
I really need to explain my rationale somewhat.
The real intent of my questioning is to provide
a counterpoise system whereas the tuner does
not just have an unbalance by simply feeding
the random wire, but a balance achieved
whereby the counterpoise connected to the
tuner acts as the other (missing) half of the
unbalanced system, thereby balancing it just
as the ground image does with a quarter wave
antenna. Does this make sense? If not, wait till
you read further about MFJ and the push and
pull explanation.
I have two tuners at my disposal -- one is an
MFJ-949E Deluxe Versa Tuner II -- a common T
match configuration. The other is an MFJ-1625
Window/Balcony Mount Antenna which contains
matching circuitry and also a loading coil
for tuning the counterpoise wire or wires.
I hope to use the 949E, if I can resolve the
matter of knowing when the counterpoise
is properly adjusted. It is this matter that
I am trying to resolve to my satisfaction. I
could equally use the MFJ-1625 which is
just an MFJ-1623 with a 12 ft whip and
an 80m loading coil.
I'm fairly well read on antennas, but still my
knowledge of this monumental subject is very
limited i.e. to me a Smith Chart is something
belonging to a hospital patient named Smith.
I sort of understand the concept of the
counterpoise acting as the missing half of the
system, but have difficulty putting it into words.
MFJ, in the MFJ-1625 Manual say....
QUOTE
It is always important to have a good RF ground,
provided by the counterpoise, when using any
whip or long-wire antenna. This is because the
MFJ-1623 tuner needs something to "push"
against in order to force current into the antenna.
If a good RF ground is not available, RF will usually
find its way back into the power line (RFI),
transmitter audio circuits (RF feedback),
or the operator (RF burns). Water pipes provide
good dc and ac safety grounds, but they are
often inadequate for RF grounding because they
are long single conductors. RF grounds
require large "spread out" surfaces with direct
multiple connections to the equipment ground
point. Water pipes, heating ducts, or multiple
ground rods may work (especially if they are all
connected together with jumper wires), but the
best RF grounds are radial systems or
multi-wire counterpoises.
UNQUOTE
I have to admit that this explanation contains
terms like long-wire antenna used in what I think
might be confusing or ill-defined ways, but the
idea of push and pull of antenna current feels
right. If this is not already confusing, it is the
MFJ-1625 Manual, but the tuner is an MFJ-1623.
Many hams use the term MFJ as standing
for 'Mighty Fine Junk', and at times I agree, but
I do have good skills as a technicial and find that
a little resoldering and tightening of ground nuts
turns it into somewhat better than any of the
homebrew or modifications I have ever put on
the air. I no longer have a house, shack, workshop,
and tower, etc,etc,etc and am now working with
largely storebought items and limited space.
I have considered a cabin in the mountains where
I would not interfere with anyone around, but where
would I find one with built in housekeeping and
meals? Just the expense of the extension cord alone
makes me shudder.
I am not as concerned about a case of 'rf lip' as I am
about stray RF causing possible problems with the
neighbours on all sides of me, with all my electronic
toys such as computers, DVD players, the local
fire-alarm system and other such things. The last
thing I want to do is draw attention to the fact that I
am running a ham radio station from my suite until
I know I am not causing any problems.
Thusly, my goal is to provide myself with a first rate
RF ground system, entirely contained within my suite,
in order that I do not wake up at night with the fire
alarms set off and great numbers of disturbed
residents gathered around pointing at me and saying
'Ham! Ham! For Shame! For Shame!' and the Residents
Council having special meetings to decide how to deal
with me. They already think I'm crazy -- and I may be
somewhat, but I don't want to make matters worse!
So, having herein explained my rational, lets see what
help I can get in the way of producing the ideal indoor
low-cost non-radiating counterpoise radial system.
Actually, I have lots of wire for the radials, the
tuner contains a loading coil to assist in tuning
the counterpoise, and my big concern is how do
I determine when the counterpoise is operating
effectively. The metering system in the tuner should
reach a peak and subside on either side of the
correct counterpoise tuning point, and what I
really need to know is how to determine when the
stray RF is minimized if not eliminated.
I have to explain that I do all this in a somewhat
humorous manner, I find all my predicaments funny,
but then I brought myself into them and this is the
only way, short of outright denial, of dealing with them.
You have probably already noticed that I am a
man of few words!
Irv VE6BP
P.S. In a previous topic where the matter of electrons
escaping from the end of the antenna was hotly
debated, I have solved that problem by forming a
wee loop at the end of the antenna, thereby taking
any of those loose electrons and feeding them back
into the wire! I used the loop and a nylon cable tie
to fasten the end of theantenna into the tree which
supports most of it, thereby eliminating the cost of
a ceramic insulator and it's accompanying end effect.
I'm sure Tesla and Marconi could have used some of
my simple practical solutions like this one, and perhaps
negated the necessity of long discussions re electrons
escaping from antennas.
"Irv Finkleman" wrote in message
...
I am using a random wire antenna which runs outdoors through a hole in a
window frame.
I do not have access to any good RF grounding system and plan to use an
indoor
counterpoise wire from the ground connection on the tuner (MFJ-949E). I
have a
nice role of #18 wire, the end is connected to the tuner, and it is my
intention to
unroll it along the floor through my suite until such time as it is
properly tuned.
MY QUESTION IS - How can I tell when I have unrolled the right amount of
wire
for the frequency in use. I know it will not be 1/4 wave, and that it
should be less.
From what I understand, when it is adjusted properly I should not have any
hot
RF burning my lips from the mike. Checking it with my lips is not what I
call
a desireable means of testing, and being single I cannot call my wife to
test it
for me. I'd like to find a better way and hence my questions.
I believe (according to what theory I have learned) that the tuner chassis
would
be hot with RF, with the amount of RF becoming less and less as the
counterpoise
wire approaches the proper length. If this is true would a simple RF
sniffer tell me?
I can rig one up fairly easily.
OR - What would I be looking for using my MFJ-259B SWR Analyzer? I expect
what it would show readings similar to a dipole with resonance at the
operating
frequency and an impedance (resistive) of somewhere in the order of 60
ohms.
plus or minus -- is this a correct assumption?
OR -- does anyone on the group have any suggestions that will tell me when
the
system is properly adjusted -- the simpler the better!
Once I have found how to do this, I can put tape markings on the roll of
counterpoise wire to show the appropriate length for each band or narrow
band of frequencies in which I will be operating.
I have already tested the hole -- it is just a little less than 1/4 inch
diamater,
but that seems to be enough to let both sidebands through -- I carefully
tested
that using AM which proves that two sidebands can fit through the hole at
the
same time, which allows me to further assume that either the upper or
lower
sidebands should squeeze through easily! :-)
Thanks in advance for any assistance you can provide in this matter.
Irv VE6BP
On the air finally but afraid to get to close to the mike! I may have
to use rubber gloves and teflon lip gloss!
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