Hi Yall,
There is not much reason to be guessing about tuner losses. Of
course it is possible to design a pathologically poor tuner. And
it is possible to misapply a well designed unit. But a correctly
designed, applied, and adjusted tuner should typically show
losses in the one to five percent range. This corresponds to a
loss of from 0.05 to 0.3 dB approximately. For more detailed
information see <http://www.cebik.com/delta.html> on this subject.
Now I'm sure that there are examples of tuners currently
available that use marginal or worse components whose tuning
range of component values is also marginal or worse. However,
since there are several others available which are properly
designed and use high quality components, lets just decide not to
use one of the poorly implemented units.
I'm also sure that there are operators who do not take the
trouble to learn how to properly apply whatever tuner that they
have. But if tuner loss really _is_ the issue why not assume
that the op will take the trouble to learn how to minimize it?
For the purpose of discussing the merits of a tuner / open-wire
transmission line system, why can't we agree to use the worst
case end of reasonable for the tuner loss asumption rather than
the worst case end of every conceivable parameter potentially
associated with a tuner? If we do that, the merits of the open
line for some applications (even relatively short runs) become
more obvious.
For example:
1. Dipole cut for 3.795 MHz, operated on 1.84 MHz, feedline
length 100 feet.
Total tuner plus 450 ohm ladder line loss: 0.65 dB. Start
out with 100 watts, radiate 86 watts.
Total tuner plus RG-213 50 ohm coax loss: 7.84 dB. Start
with 100 watts, radiate 16.4 watts.
2. Same dipole operated on 7.03 MHz, same feedline length.
Total tuner plus 450 ohm ladder line loss: 0.35 dB Start
with 100 watts, radiate 92.3 watts.
Total tuner plus RG-213 50 ohm coax loss: 2.87 dB. Start
with 100 watts, radiate 51.6 watts.
Notice that all of this fits on a 100 by 100 lot.
73, Eric N7CL
>From: "Gary McDuffie, Sr." <mcduffie@scottsbluff.net>
To: <towertalk@contesting.com>
>Date: Tue, 16 Nov 1999 14:16:52 -0700
>
>On Tue, 16 Nov 1999 13:57:46 -0500, Guy Olinger, K2AV wrote:
>
>> A 30% tuner loss is huge and would be dissipating 500W of a
>> 1500 watt input in a closed space. That wouldn't take long to
>> set it on fire internally, and would quickly make it too hot
>> to touch.
>
>I have a friend who peeled the paint on one of the Dentron
>tuners a few years ago, and he only had a FL2100 at the time for
>an amp.
>
>Gary
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