At 06:50 PM 2/7/02 -0500, Tom Rauch wrote:
> In an earlier message, Tom warned against this problem and suggested
>> modeling the voltage across a small load placed at the top of the
>> tower as a check on the voltages to be expected.
>
>You can either place a very *high* resistance load there, or a
>current source set to *zero* amperes.
Sorry, I wasn't thinking clearly. That makes perfect sense. I must have
crossed the two ideas from your earlier post.
Just for fun, I ran my whole-tower model with a zero-current source at the
junction between the top 40m yagi's reflector and boom. At 200w input to
the shunt feed (2A @ 50 ohms, if I did it right) the model shows 580v
there, vs only 68 volts across a similar point on the tribander 7 feet
below it. If the model is reasonably accurate in this respect, it looks as
if I probably only need to ground the 40m yagi elements for 160 meter RF,
and that not until I start to run high power on 160.
73, Pete N4ZR
Sometimes a tower is
just a tower
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