On Tue, 28 Sep 2004 22:54:22 GMT, "John Smith"
wrote:
I think you misunderstand, but that is most likely because I have a hard
time conveying what's in my mind. Especially in print and expecially at my
age. I didn't used to have that problem...

Hi John,

I understood you, the illustration is sufficient.

I take a half-wave (at 1.0 velocity factor) length of RG58 with a BNC
connector on one end and make a hairpin loop. This is the left side of the
folded dipole. The BNC connector is at the bottom center. I take another
half-wave piece of RG58 with a BNC connector connected to the shield only,
and make a hairpin loop for the right side of the folded dipole. Now I
install a T at the bottom between the left and right sides. As for the upper
element, I attach the center wire of the left half to the shield of the
right half. I repeat, the center conductor of the coax on the right side is
not used.

This is as it should be - for a folded halfwave dipole. However,
there is some question that this is intention of the design expressed
with great paucity of facts by Kraus. More on this below.

Now I have an antenna completely constructed with a feedpoint at the bottom
center via the T. What is the impedance at the T?

It will be the transform of that load found at the opposite side where
the signal is developed by the connection of the inner conductor to
the outer shield. More on this below.

Almost mute, yes. The only discussion for this particular arrangement is
beneath the figure where it says "(a) A folded dipole has zero potential at
the midpoint of the lower dipole half at all frequencies. Thus, this point
is ideal to attache a coaxial cable."

More useful is it can be attached to a metal support without
interfering.

I recently got some of the instruments I now have. Owning them, however,
does not mean I know what I'm doing with them. This is my first foray into
UHF and the instruments and techniques are new to me. Yes, I can handle
complex arithmetic, but that doesn't mean I know how to set up a test
properly at 440 MHz.

You need to add a directional coupler to separate out the forward and
reverse components is all.

Resolve this in an evening? I first have to learn how to make the
measurements with some accuracy and repeatability before I can get
meaningful results. At this frequency, I've learned, even getting a true
short circuit takes care.

Do you have a manual? I've been trying to find a link to HP manuals
that was offered in this group in the last couple of months. The "App
Notes" written during the 60s offer a complete education without
requiring a double-E to understand.

Also, I have nobody to work with me as I try all this new stuff. This group
is the only resource I have with people who are knowledgeable enough to
answer such questions.

I'm doing the best I can.

You'll get there, by and by.

73's
Richard Clark, KB7QHC