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
|