"Henry Kolesnik" wrote in message
...
In the Feb. 2004 QST there's an article by AD5X for a mobile antenna using
a
Hamstick or Bugcatcher with shunt capacitor feed or an L match. Can
someone
please explain, including the math, on how a ~500pf capacitor transforms
10
ohms to 50 ohms for 40 meters? I get no understand from reading either my
ARRL Handbook or ARRL Antenna Handbook. There are no stupid questions,
only
stupid people asking!
tnx
hank wd5jfr


Hi, Hank -

If you have a low value resistor and you want to make it appear to your
source to be a higher value resistor, you can add a series resistor or
reactance. If you add a resistor, it will use up some of the available power
which you intended for the original resistor. So, you use a series reactance
instead. The only problem is that you now have some (usually) undesirable
reactance to contend with. But, you can get rid of the series reactance by
adding a shunt reactance of the opposite type. That is, if you added a
series capacitor, you can put in a shunt inductor to compensate. Note that
you could have added a series inductor and compensated with a shunt
capacitor. Which one you use is a matter of convenience sometimes.

Before I go into the math, I should ask if you are comfortable with complex
variables. You know, complex conjugate, R+jX and all that stuff? Besides,
the delay will give someone else an opportunity to put in something I've
missed or messed up. There are a lot of very knowledgeable guys on this
group, you know.

John