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

Sun May 1 12:24:27 EDT 2005

On Sun, 2005年05月01日 at 17:41 +0200, Peter Voelpel wrote:
> ----- Original Message -----
> From: "James Duffer" <dufferjames at hotmail.com>
> To: <df3kv at aol.com>; <antennas at mailman.qth.net>
> Sent: Sunday, May 01, 2005 4:58 PM
> Subject: Re: [Antennas] Isotron antenna <was> Re: 40m
> mobileantennae.r.p.compared
>>> >
> >
> > snip
> >
> >
> > >it´s quite typical for dummyloads to have large bandwith...
> > >
> > >as efficiency is depending on bandwith (Q) you can
> > >imagine what to expect
> >
> > Are you saying the wider the bandwidth, the greater the efficiency? Or
> are
> > you saying the the efficiency is inversely depending on bandwidth?
>> efficiency is inversely depending on bandwidth
>> >
> > I have never owned an Isotron, but I believe they have a very narrow
> > bandwidth and have to be tuned, i.e. high Q-narrow bandwidth requiring
> > retuning for just a small shift in frequency within the band.
>> yes, thats which one would expect, any large bandwith shows either
> poor concept or poor components when comparing antennas of same
> physical lenght
>> 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.
Bob, N7XY