Rog (K9AB) 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=-
I certainly won't disagree with you and I am also fortunate enough to not
require an antenna tuner on any band but 160 (didn't get the built in
antenna tuner in the Orion as I don't need it). Not all hams though are
lucky enough to have antennas or the space for antennas that will present a
descent match across all of the amateur bands, and an antenna tuner is the
only option.
My question to Rog is:
What type of antenna do you use on 160 mtrs that will allow descent coverage
of the band without a tuner? I would think that most 160 mtr antennas that
can be erected by the average ham would require a tuner.
Personally, I have two phased verticals that are 66 ft tall and linear
loaded. Each have 120 (+ or - a few) radials that are 135 ft in length.
My 2 to 1 bandwidth is 40kc with a resonant freq of 1840. A good ant
tuner is the only answer I know of short of putting remote tuned matching
networks at the base of each tower. Granted, there is some loss in the coax
as the antenna is used above or below 1840, but it is not something I can
not live with.
Dick K8ZTT
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|