An adequate and not too expensive vector analyzer is the VA1 by Autek
Research. It reads resistance and reactance (including its sign)
directly and also has a function that automatically calculates the Z
at your antenna even though you are measuring at the rig end of your
transmission line. It is tiny and and battery operated and hence can
be used on balanced lines without unbalancing things very much.
I have no connection with the company, just a satisfied customer. Use
google to find them.
--Oliver Johns
W6ODJ
On 17 Sep 2008, at 3:52 PM, Bill W5WVO wrote:
I should add that you CAN adjust an antenna for minimum SWR at the
transmitter, but when you do that, you are in all likehood
including some non-zero feedpoint reactance in the net impedance,
and this is being observed through the length of your transmission
line, which then becomes part of the overall load the transmitter
sees. If you subsequently change the length of the transmission
line, you will no longer have Z=50 ohms at the transmitter. If you
tune the antenna for TRUE resonance (zero reactance, R=50), then
you can put any length of transmission line on it that you want
to, and it will behave just the same.
I know we all got along without the MFJ-259B for years, just going
by guess and by gosh (or sweating over Smith charts), but now that
we can actually tell what is happening in an antenna so easily,
it's crazy not to use one. Beg, borrow, steal, or if necessary buy
one, and learn how to use it. You won't regret it! Greatest thing
since CW killed King Spark. :-)
Bill W5WVO
----- Original Message -----
From: "Bill W5WVO" <[EMAIL PROTECTED]>
To: "Cranz Nichols" <[EMAIL PROTECTED]>; "LIST - elecraft"
<elecraft@mailman.qth.net>
Sent: Wednesday, September 17, 2008 4:39 PM
Subject: Re: [Elecraft] K3 - Numeric SWR Display
Actually, looking at transmission line SWR at the transmitter is
a
poor way to adjust an antenna. To get it right, you need to use
a
complex impedance analyzer like the now-ubiquitous MFJ-259B (or
equivalant instrument), and put it as close to the antenna
feedpoint as possible. Adjust as close as you can get for Xc=0,
Xl=0, R=50. You can't do that with an SWR bridge! :-)
Bill W5WVO
----- Original Message -----
From: "Cranz Nichols" <[EMAIL PROTECTED]>
To: "LIST - elecraft" <elecraft@mailman.qth.net>
Sent: Wednesday, September 17, 2008 3:53 PM
Subject: [Elecraft] K3 - Numeric SWR Display
I need to adjust the gamma matches on my 10/15M delta loop.
Is there a way to bypass the internal ATU and have the K3
display the SWR it
sees numerically?
Should dig out my old SWR bridge?
cln
WB5BKL
K3 #231
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