I just acquired a Wilson 1000 base-loaded mag-mount antenna. The whip
is 62" long and gives lowest SWR (1.2) at CB channel 1 (26.965 mHz).
So, to be a good CB antenna, the whip needs to be shortened to give
lowest SWR at 27.200 mHz -- roughly the middle of the CB band.

I want to also use this antenna for 10M. I don't want to bother with
a tuner. I originally was going to buy a second, even shorter, whip
for 10M and switch the whips for th eband I wanted at the moment.
Then I thought that maybe I could throw together a simple RLC circuit
to use at the radio for 10M.

How can I determine what I need? I think I have more than enough
sophisticated equipment, but not the practical experience to use it.

In particular, I just built the AmQRP Antenna Analyzer and can measure
the SWR, impedance and reactance at any frequency. I have a dip
meter. I have manual tuners that can bring the SWR down to 1.0 in the
middle of the 10M band.

How do I use these to design a simple RLC circuit that does what the
manual tuner does at the middle of 10M?

Ken KC2JDY

Ken
(to reply via email
remove "zz" from address)

How do I use these to design a simple RLC circuit that does what the
manual tuner does at the middle of 10M?

Hi Ken, If you have the equipment to determine the impedance of the antenna at
the middle of the 10M band, there are a number of ways to match it to 50 ohms.

First of all, you don't want an RLC circuit. Leave out the R cause that is
power lost as heat. You want everything to be radiated. An "L" network
consisting of an inductor and capacitor will match anything to anything.
What I usually do is determine the feedpoint impedance of the antenna at the
frequency of interest, and use the Smith Chart to determine the configuration
and values of an "L" network to get a match.
If you are not comfortable with the Chart, there are some programs on the net
that will design the network for you. Or, if you give me the complex impedance
and frequency, I will be glad to provide a network.
73 Gary N4AST

Hi Ken, If you have the equipment to determine the impedance of the
antenna at
the middle of the 10M band, there are a number of ways to match it to 50
ohms.

First of all, you don't want an RLC circuit. Leave out the R cause that
is
power lost as heat. You want everything to be radiated. An "L" network
consisting of an inductor and capacitor will match anything to anything.
What I usually do is determine the feedpoint impedance of the antenna at
the
frequency of interest, and use the Smith Chart to determine the
configuration
and values of an "L" network to get a match.
If you are not comfortable with the Chart, there are some programs on the
net
that will design the network for you. Or, if you give me the complex
impedance
and frequency, I will be glad to provide a network.
73 Gary N4AST

Ummmm wouldn't it be easier to just trim the whip? Years ago I trimmed a 4
ft "Ugly Stick" down for 10 meters it worked quite well. I used to easily
work Japan from my pickup in Portland Oregon with 25 watts, using just that
ugly stick.

Ummmm wouldn't it be easier to just trim the whip?

Yes, but this is not what Ken was asking. I gathered he wanted to leave the
whip at a length that would work in the CB band, and add a siple matching
network for operation in the 10M band.

I used to easily work Japan from my pickup in Portland Oregon with 25 watts,

When 10M is open you can work anywhere with just about anything. During a
recent 10M contest I worked all over the world using a 8' loaded dipole indoors
and 10 watts.

73 Gary N4AST