[Antennas] Isotron antenna <was> Re: 40m mobileantennae.r.p.compared

[Sam Morgan]

On Sun, 01 May 2005 09:24:27 -0700
Bob Nielsen <nielsen at oz.net> wrote:

> > 
> > yes, thats which one would expect, any large bandwith shows either
> > poor concept or poor components when comparing antennas of same
> > physical lenght
> > 
the phrase to good to be true? comes to mind??

> > I never tried an Isotron either, but was answering the comment that
> > its bandwith was wider then a normal vertical which would proof
> > poor efficiency
> > 
> > a good mobile antenna 2,50m long with high-Q base loading coil
> > has a bandwith for SWR=2 of about 30KHz on 80m
> 
> Looking at the Isotron web site there is nothing to indicate bandwidth.
> It says 3.5-4.0, 7.0-7.3, but I'm pretty sure that is not the
> instantaneous bandwidth and the antenna must be tuned for each operating
> frequency.
>
------
Perhaps I mis-stated, what's new, huh?
I said 7.0-7.3 and 3.5-4.0 then mentioned broadbanded
I should have said freq. range for above figures

then 

in a seperate comment mentioned the broadbanded comment
and referenced it as a *relative term* short vertical to isotron
------
isotrons:
40m model review said 
1.1:1 center 3:1 edge = 150kc bw
http://www.isotronantennas.com/isorv40.pdf

80m model review said
1.4:1 center 2:1 edge - 50kc bw
http://www.isotronantennas.com/isorv80.pdf

---
verticals:
hamstick 
2:1 edges for 40m=60kc  ..  80m=10kc
http://www.hamstick.com/9106.htm

But I'm under the impression one of the *tweaked to max* verticals I was
speaking of building would have a bandwidth more like the hamstick than
the isotron. Also the verticals will have a very low resistance
feedpoint .. in the range of 3 to 15 ohms and the rest reactive
components ... if I have read things correctly. I'm sure I'm saying that
wrong. Help me out here folks, please.

Where as the isotron will have 50 ohm feedpoint ....
meaning more actual power to and then radiated from the antenna??

I'll stop there before I mis-speak more/again here. I'm reading and
trying to retain this stuff so I can ask the right questions and
understand what is said in responce. But it's obvious I'm in over my head.


Sam Morgan
KA5OAI
mailto:ka5oai at qsl.net