[TenTec] Rog K9RB Antenna Tuners

Randy Russe3ll lord_russell53 at yahoo.com
Thu Jan 19 13:40:04 EST 2006


Fascinating Bruce.  I would love for you to share a
desciption of your antenna farm with us, being new to
Ham radio I'm confused and would like to learn more.
First, how many resonant antennas do you have?. I
simply don't have room for a 3501 Mhz, dipole, a 3502
dipole, a 3503 dipole,etc. Well, I guess that would
take 500 dipoles to cover the 80-75 meter band with
resonant antennas. I would need miles of coax to space
all those dipoles out enough to have zero interaction
(losses). What would my losses be at 1db at 100ft@ 1:1
swr? for that many miles of coax. At what SWR do you
shut down and stop operating on any given antenna? Do
you never operate into anything higher than a 1:1 swr
with coax? Do you accept a range of 1.5:! Do you
happen to know the loss of your coax at 2:1? Also,
when you say only resonant antennas, what do you do
when using a full wave or multiple wave antenna,
trimmed to an exact frequency (resonant)? Since it's
impedance wouldn't match the arbitrary number of(50
ohms) manufacturers have set for coaxial cable? Is a
1/2wave 40m dipole, set at a low height, (so that it
matches coax impedance w/out lossy tunning
network)going to give me a superior signal than a 264
foot dipole at say, 120 feet in the air?  What if I
install my 40 M dipole at one wave high and it's
impedance soars to the theoretical 72 ohms.?  Ok, I
could swith to 75 ohm coax, but now I have a mismatch
between line and transmitter of 1.5:1!   Sheeesh, this
is a lot more complicated than I thought radio was
going to be. One thing I will agree on is:  There are
comprimise antennas, and there are comprimise
feedlines. Coax is a comprimise feedline and far from
efficient. The SOLE reason to choose coax, as I see it
is convienance.  (well, it is suited for buried
applications.)If you do use coax with a feedpoint
mismatch of, say 2:1, the damage is already done. (of
course, this would have zero affect to balanced line) 
The tuner doesn't change that in coax applications.
Ideally you place your "lossy" tuner at the feed
point. But what possibly could be the advantage of
using coax, over balanced feedline, or running
antennas at 50 ohm impedance, just to suit the
material you are using?   Now, about them " Old Days".
 What did you guys do in the Old Days?  Did you run
your plate current straight into resonant HI-Z
antennas? (OR) Did the old rigs have a multiple "L"
tuners in series, between the plate and the antenna
system?  I guess you would call that a pi-network. Do
modern transmitters still have L or pi-networks at
their outputs?  Are these no-loss tuner circuits? What
is the loss difference adding one more L? I'm
confused, since I've been using  a 1953 tuner and
balanced, open wire Line, the performance has shot up
dramatically.  It replaced a dipole I pruned for my
favorite operating freq. and fed with a short run of
coax. Both receiving and transmitting have undergone 
a huge boost with the balanced system.  Quieter, too.
Should I junk it and get some coax and start over? 
I'm assuming lossy baluns are never used by 
experienced hams on their beam, verical, and dipole,
resonant 50 ohm superior systems.  Of course the
losses associated with these do not concern balanced
line users, as these devices are not needed. I guess I
better go back and read the antenna book again, as Rog
suggested, if I want to be a Real Ham.  Not trying to
be a wise guy, I have only had my license about 8
months, just want to learn from the experienced Hams.
It's just that inquiring minds want to know.  I guess
I've gotthe science all wrong.  Illuminate me.   
Thanks guys es 73s  

--- Bruce Lanning <blanning at acadia.net> wrote:

> 
> Thoroughly enjoyed your recent article on antennas
> and antenna tuners. You 
> are right on the mark. I have been a licensed ham
> since 1949 an have never 
> used an antenna tuner. Nothing but losses. Have
> always used resonant 
> antennas with coax. Thanks for the very fine
> disertation.
> Bruce W1GBS 
> 
> 
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> 


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