wrote in message
...
On Mon, 4 Oct 2004 15:19:41 -0500, "John Smith"
wrote:

Okay, then, I will present data measured this day for this antenna:

http://www.sophisticatedsolutions.us...d%20Dipole.jpg

This is shown in "Antennas for All Applications" on page 820, figure 23-17
(a).

Just an off the cuff remark and a possible clue.

It's not clear from the picture or explanation if the center
conductor is continious from the right half of the antenna to the
left. I understand the center conductor does not connect to the
right half at the T.

The center conductor in the right half is not used at all. The right half
should actually be a piece of coax with the center conductor removed.

For the case that it does continue:
Looking that the picture, if the right side were parallel to the left
I'd call that a 1/4 wave 1:1 balun with a shorted load connected
rather than an antenna. That would result in a significant reactance
or a short depending on frequency. The sorted load would be the
continued centor conductor in the right half.

For the case that it does Not continue:
I'd call that a 1/4 wave 1:1 balun with an open load connected rather
than an antenna. That would result in a significant reactance again.

There is a third case:
A connect dot is missing at the junction of the center conductor where
it meets the shield of the right loop (top center). If the lengths
were ~1/4 wave for each side then the impedence at the center would
be high for the left center conductor and the right shield and that
would likely be a tuneable folded dipole.

Did I miss something about the antenna design?


The center conductor of the left side is connected to the shield of the
right side. The shield of the left side is not connected at the top center.


As drawn it looks like an attempt to take a parallel line balun (coax
with a 1/4wave 1:1 balun) and make it serve as a radiator. There is
detail missing one possible dimensions and other connections.

FYI: if you used one of those cheap eithernet Tees to create the
junction, I've found them to be very poor at UHF. Use a good quality
one with TFE insulation and test it seperately first.

Allison

I wound up not using a T. I simply soldered all connections to a BNC
connector at the bottom center of the figure.

John