On Thu, 14 Oct 2004 07:01:36 -0500, "Ken Bessler"
wrote:

|Take a dipole, cut for 3.922. Put it up as an inverted V
|with the apex at 30' and the ends at 10'. Feedline is 100'
|of 450 ohm ladder line/12t 5-1/4" coax balun/30' rg58.
|
|Antenna works nice, esp at night.
|
|Now take the same setup and feed it with an L network
|autotuner, say an LDG AT100 pro and run it on 1.825
|mhz. Feeding the antenna as a marconi is not an option
|due to lack of ground area for radials.
|
|Where does my 100w go? is it lost as heat in the tuner?
|(my guess) Is it lost in the feedline due to high SWR at
|the apex?

Using readily available tools, Multinec, XLZIZL.xls and TLDetails.exe,
all available at www.qsl.net/ac6la I computed the following.

Two wires, fed at the junction with a split source:

Wire 1 coordinates (ft):

End 1 End 2
X Y Z X Y Z
0.000 -55.285 10.000 0.000 0.000 33.000

Wire 2 coordinates:

0.000 0.000 33.000 0.000 55.285 10.000

Resonant at 3.922 over average ground. At 1.825 MHz the feedpoint Z =
12.53 -j 1366.

I copied these values to XLZIZL and defined a feed network that
(beginning at the antenna) consists of 100' of Wireman type 553, 35'
of RG-58A, a series capacitor = 1754 pF and a shunt inductor = 2.14
uH.

Now, I don't know whether the LDG tuner will configure itself this way
or not, but this is the optimum solution. The input Z of this mess =
49.19 +j 0.4. SWR = 1.02

XLZIZL gives the total network loss as: ~9.0 dB.

To see where the losses come from we can first look at the L network
and see that with the component Q's I used: Qc =500 Ql =200, the loss
is only 0.09 dB.

The best way to see the line losses is to go to TLDetails and first
select 100' of Wireman 553 and a load Z of 12.53 -j 1366.

The program shows that the total line loss is: 7.7 dB, most of it
attributable to SWR. The input impedance of this line section is 5.58
+j2.11.

If we use this value for the load Z and change the line to RG-58A with
length 35', we find that the loss is ~ 1.35 dB.

As a sanity check, we add the three losses 7.7 + 1.35 + .09 = 9.1 dB,
just as was determined earlier.

So most of the power is burned up in the "low loss" ladderline!