impedance: how to
 

Greetings,

I built my antenna with the help of this newsgroup and other articles
from the net. thanks to all. Now, the only problem is i am a little bit
confuse about impedance. (but still studying for it). how will i know
the impedance of my antenna so that i can buy a transformer or balun
that will match the ... feedline(is it the right term?). Is there a
standard formula for calculating impedance of a home-made antenna?

thanks in advance,

ian

there are programs that will calculate it, but usually not very accurately.
it is best to measure it and either adjust it to match the feedline or add a
matching network to get it to match the feedline. how closely it must match
the feedline depends on what it is being used for, which you haven't said.

"yhan" wrote in message
oups.com...
Greetings,

I built my antenna with the help of this newsgroup and other articles
from the net. thanks to all. Now, the only problem is i am a little bit
confuse about impedance. (but still studying for it). how will i know
the impedance of my antenna so that i can buy a transformer or balun
that will match the ... feedline(is it the right term?). Is there a
standard formula for calculating impedance of a home-made antenna?

thanks in advance,

ian

yhan wrote:

Greetings,

I built my antenna with the help of this newsgroup and other articles
from the net. thanks to all. Now, the only problem is i am a little bit
confuse about impedance. (but still studying for it). how will i know
the impedance of my antenna so that i can buy a transformer or balun
that will match the ... feedline(is it the right term?). Is there a
standard formula for calculating impedance of a home-made antenna?

thanks in advance,

ian

Impedance is very complex. As mentioned in another reply the easiest way
is to measure it. But, that post did not give advice on how to measure it.

Contact a Ham [amateur] radio operator/station in your area. Once found,
ask if [s]he knows someone who has an antenna analyzer. Most Antenna
analyzer owners, they cost about $200 to $300 USD, are willing to make
the measurement for you. Most Ham clubs have several people who own such
instruments.

What kind of antenna did you build? If it is a 'standard' type we can
give you a fair estimate right here on r.r.a.a.

Ham Op

There are more formulas than there are types of antenna.
Please describe in little detail the type of antenna you are
interested in.

But in general, you will be unable to use a formula because you will
not know the basic data to put into it.

However, given more information, somebody may be able to provide you
with a sufficiently accurate numerical value.
----
Reg.

yhan wrote:
I built my antenna with the help of this newsgroup and other articles
from the net. thanks to all. Now, the only problem is i am a little bit
confuse about impedance. (but still studying for it). how will i know
the impedance of my antenna so that i can buy a transformer or balun
that will match the ... feedline(is it the right term?). Is there a
standard formula for calculating impedance of a home-made antenna?

If you describe it, some kind soul may be able to tell you.
Is it single frequency or multi-band? Sometimes a 1:1 choke
is the logical choice for a "balun".

What a lot of us do is model our antennas to get an estimate
of the feedpoint impedance. A free version of EZNEC can be
downloaded from http://www.eznec.com.

Other free software available from:
http://www.btinternet.com/~g4fgq.regp
--
73, Cecil http://www.qsl.net/w5dxp

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Ham op wrote:
Impedance is very complex.

:-) sometimes yes, sometimes no. :-)
--
73, Cecil http://www.qsl.net/w5dxp

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Cecil Moore wrote:

Ham op wrote:

Impedance is very complex.


:-) sometimes yes, sometimes no. :-)

NOTE: CECIL is very complex!! Sometimes Yes, sometimes No :-)