I presently have 5 dipoles in parallel with one 50 ohm coax and a tri-band
beam.
Bruce
> 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@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@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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