If I wanted to measure the radial and feedline AC current, not having any
RF ammeters, I might just take a #47 lamp or other small pilot lamp and
stick it in series with the radial and transmit into it. 40 mA will make a
#47 lamp glow very dimly. Is this a good thing to check on?
Probably not with series lamps, unless the radial impedance is pretty high.
The measuring device or system must not significantly change the series
impedance of the path or it will alter the results.
If I find that some radials don't carry enough current to light up the
lamp... is that a sign that the low current radial is not needed?
Usually, but it also depends. Radials can have standing waves. What we
measure at one point might not be what is happening 1/10th wave away.
If other radials are carrying way more than average current... is this a
sign I need more radials in that direction? Or is it the other way
around? Or is this all academic and I just need another few thousand feet
of copper wire? :-)
I use one of these:
http://www.mfjenterprises.com/Product.php?productid=MFJ-854
I designed that device to measure very low current levels, and (if they
calibrate it correctly and still build it the same) to be accurate. It also
does not change the circuit much.
It's really a handy device for measuring current, it has a very wide dynamic
range.
I'm just not sure if, for what you are doing, it is necessary. I'd just use
as many radials as I could as straight and long as possible, but not over a
quarter wave or more than 30-40. I think sometimes we make too much worry or
magic over things. :-)
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Topband reflector - topband@contesting.com
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