"gareth" wrote in message
...

Pictures of the tower and hat are at
http://www.oldradio.com/archives/warstories/640.htm
and scroll down most of the way.

Thanks, but I do not pursue URLS, my viewpoint being
that if there is something worthwhile to discuss, then
discuss it.

That's fine.

"Sal"

"Kafkaësque" wrote in message
...


The latter link is a series of photographs. Are you saying you need
somebody to describe them for you?


Please don't pursue this. I would feel terrible if my post inspired yet
another ****ing contest. Let it go, please.

"Sal"
(KD6VKW)

On 14/02/2014 19:07, Sal wrote:
"Kafkaësque" wrote in message
...


The latter link is a series of photographs. Are you saying you need
somebody to describe them for you?


Please don't pursue this. I would feel terrible if my post inspired yet
another ****ing contest. Let it go, please.

Of course. But thanks for posting it - fascinating that a circle of
relatively small diameter, plus a few feet of wire, could save 75 feet
of vertical tower.

It seems that nobody has pointed out the third advantage of capacity
hats; that they reduce the Q of the antenna, and therefore broaden the
bandwidth.

"Kafkaësque" wrote in message
...



It seems that nobody has pointed out the third advantage of capacity hats;
that they reduce the Q of the antenna, and therefore broaden the
bandwidth.

That makes sense when you say it but I wouldn't have thought it. I guess
such a bandwidth broadening affect is akin to spreading out the element(s),
as with a vertical cage or a fan-wire, but without adding full-lendth
elements.

Experiment time! (aka "play time")

"Sal"

On Friday, February 14, 2014 1:09:58 PM UTC-6, Kafkaësque wrote:
It seems that nobody has pointed out the third advantage of capacity
hats; that they reduce the Q of the antenna, and therefore broaden the
bandwidth.

If we define bandwidth in terms of 3:1 SWR(50), a capacitive hat tends to decrease the bandwidth since it reduces the feedpoint impedance. For instance, the 3:1 SWR(50) bandwidth of a 1/4WL vertical is about 1.2 MHz while the 3:1 SWR(50) bandwidth of a 1/8WL vertical with horizontal top hat is about 0.5 MHz according to EZNEC.
--
73, Cecil, w5dxp.com

It seems that nobody has pointed out the third advantage of capacity
hats; that they reduce the Q of the antenna, and therefore broaden the
bandwidth.

If we define bandwidth in terms of 3:1 SWR(50), a capacitive hat tends
to decrease the bandwidth since it reduces the feedpoint impedance. For
instance, the 3:1 SWR(50) bandwidth of a 1/4WL vertical is about 1.2 MHz
while the 3:1 SWR(50) bandwidth of a 1/8WL vertical with horizontal top
hat is about 0.5 MHz according to EZNEC.

What would be the 3:1 SWR(50) bandwidth of the same 1/8WL vertical,
with no horizontal top hat, under the same conditions?

Actually I guess there would be two sets of conditions:

- No base loading coil or matching network (in which case I'd guess
it's outside the 3:1 range anyhow)?

- A theoretical (but handy) zero-loss matching network at the base,
giving it a 50-ohm feedpoint impedance at the desired center
frequency?

I think the latter is what was being referred to by the original
poster.

On Friday, February 14, 2014 7:25:29 PM UTC-6, David Platt wrote:
I think the latter is what was being referred to by the original
poster.

Sorry, I was looking at it from another angle - starting with a full-sized resonant antenna and adding a top hat for the purpose of decreasing its height.
--
73, Cecil, w5dxp.com