Well, I agree with Walt on this, except there is also a (usually small)
loss in the tuner. If you run Dean Straw's (N6BV, ARRL Antenna Book
Editor) excellent TLW, one of the s/w packages that comes with the ARRL
Antenna Book, it will calculate the loss in the transmission line as
well as calculate the antenna tuner loss for different configurations of
tuner.
73, Joel
Joel R. Hallas, W1ZR
Randy Russe3ll wrote:
Sounds to me like Maxwell needs to go back and read
the ARRL Antenna Handbook.
--- JOHN <ku3g@yahoo.com> wrote:
Thank You Scott finbally somebody has it correct.
73 john ku3g
ps interestinmg subject
Scott Harwood <scotth@hsc.edu> wrote:
Hey guys:
In his book, "Reflections", Maxwell states that all
power fed into the transmission line (minus line
loss) is absorbed by the load, regardless of the
mismatch. Secondly, with open-wire tuned feed lines,
we can ignore this mismatch at the junction of the
feed line and the antenna, and all matching can be
done at the transmitter itself. Put another way, if
an antenna tuner can properly match the impedance of
the input of the feed line, using open wire line we
can transfer just about all power to the antenna.
Thus, the case for open wire line and a tuner.
Scott K4VWK
---------- Original Message
----------------------------------
From: Randy Russe3ll
Reply-To: Discussion of Ten-Tec Equipment
Date: Wed, 18 Jan 2006 18:57:09 -0800 (PST)
Even if you have a finely tuned resonant dipole,
and
it is actually 50 ohms at your feedpoint heighth,
you're losing more db in 100 feet of coax than I am
on
a mismatched 4:1 swr. If you put your loading coils
on to "fool the transmitter" your using even more.
If
you try to use your coax on any kind of mismatch,
your
losses skyrocket. This includes feeding a 35 ohm or
say 80 ohm feedpoint with 50 ohm coax. Those are
both
Z's attained on dipoles between 20 feet in the air
and
a full wave high. The purpose of coax is
convienence
swapped for performance. A link coupled tuner is
more
of an Antenna impedance transformer. You've already
got a few of those in your rig anyway. I didn't see
anything supporting your theory about transmission
lines in the ARRL Antenna book. In fact, if you go
back and read it, you will understand what I'm
saying
about losses in coax, and the reasons for the
superiority of balanced feedlines. In a multi band
system, it's an absolute must. Oh, and resonance is
NOT a requirement for radiation efficiency. 73s
--- Roger Borowski wrote:
After more than 45 years of continual hamming on
all
bands and modes, I can
honestly say that I never have used an antenna
tuner
and never found any
system that will outperform a resonant antenna
fed
with coaxial cable, which
I've always used since the early 60's. If the
antenna isn't resonant on the
desired frequency of operation, many people think
an
antenna tuner is the
fix. While an antenna tuner will allow you to use
most anything metallic as
a radiator of RF, the most efficient power
transfer
is to a 50 ohm resonant
load via 50 ohm coaxial feedline. In all cases
where
an antenna tuner is
used with a coaxial fed antenna, all it does is
further complicate a system
with an added piece of equipment that only fools
the
transmitter into seeing
the match it is looking for, while creating
losses
in itself and further
losses in the coaxial feedline due to the
mismatch
that still remains
between the antenna tuner and the antenna.
Fortunately I've never been
forced to use anything other than resonant
antennas
fed with good quality 50
ohm coaxial cable. If you're bound and determined
to
use open wire feeders
to one of the many non-resonant antenna designs
of
yesteryear, that would
require an antenna tuner. Why anyone who
understands
antennas would want to
do that 50-60 years after coaxial cable became
common place is beyond my
comprehension. It's an easy chore to adjust
antenna
lengths for resonance
and where available space doesn't permit, it's
also
easy to use loading
coils or linear loading configurations on the
antenna. If you haven't a clue
as to what I'm saying, pick up a book on
antennas,
such as the ARRL Antenna
Book and read the entire section on the theory of
antennas. As a Ham, you
really need to know this. An antenna tuner is a
band
aid approach that
allows one to use an inefficient antenna,
whatever
it may actually be, with
some degree of success. You see 1:1 SWR on the
tuner
meter and you and your
rig are happy, but in actuality, put another SWR
meter after the antenna
tuner and you'll see the real mismatch, why you
are
generating RFI, and
experiencing far less performance, both
transmitting
and receiving, than you
could be.
73, -=Rog-K9RB=-
FCC First Class Commercial License first attained
in
1967, Ham Radio license
first attained 1961.
A-1 Operator Club, ARRL Life Member, DXCC #1
Honor
Roll (350) Mixed, Phone,
CW (since '92) and presently need 11 more on RTTY
for H.R. Need (4) more
zones on 160M. for all (9) HF band "Worked All
Zones". At present 160 Meter
DXCC - 211 + 36 zones. Former member NIDXA
No.Ill.DX
Assn., 9th area
incoming QSL bureau sorter for many years,
Charter
Member Metro DX Club,
Life member / former Trustee W9AA Hamfesters
ARC.,
CP-40 in 1963 at 14 years
of age, former ARRL OO, & NCS, active 160M
through
V.H.F. / U.H.F. for 45
years. 1st place CQWPX-CW 15M in 1981. 1st place
CQWW-CW 40M in both 1980 &
1988. (Ancient history now!) Also KG4RB -GTMO
Cuba,
Bio and photos available
at www.qrz.com Reply direct to; K9RB@arrl.net
----- Original Message -----
From: "Richard Williams"
To: "Discussion of Ten-Tec Equipment"
Sent: Wednesday, January 18, 2006 5:43 PM
Subject: Re: [TenTec] What makes the 238 good or
any
other tuner good?
Rich,
Quite a number of answers I see on the board. My
personal opinion is the
best tuner out there is the XMatch tuner
manufactured by Paul Schrader
(N4XM). This is pretty well backed up by the ARRL
when they did a review
of this one and three others back in Mar of 97.
You
can read it by signing
on to the ARRL home page and search for XMatch
tuner.
I don't think anything comes even close to it
specs
when operating on 160
Mtrs. I believe he still makes them as I see his
ads in EST..
=== message truncated ===
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|