I wrote an article for 73 many years ago where I effectively remade the
Isotron antenna with parts from Home Depot. At the time, a 20 meter
version could be built for about $15. I tested my version extensively
and for the most part a dipole made with two Hamsticks was quite superior.
They resonate, have good SWR bandwidth and generally radiate 5 watts of
the 100 watts that goes into them. A "magnetic loop" blows it away. I
sold the sample Isotron I bought at a hamfest for $5. (Bottom line -
they are, as we say in the software business, crapware)
Doug -- K0DXV
On 4/7/2016 5:12 PM, Jim Brown wrote:
This so-called "antenna" is at best dumb, and at worst a rip-off. As
master antenna-designer N6BT wrote some years ago, "everything
'works,' even a light bulb." He demonstrated this by mounting a a
light bulb on a wooden fencepost, feeding with coax that he had
carefully choked so that the coax could not radiate, and working all
continents with it.
As others have noted, antennas like magnetic loops, loaded whips
(HamSticks, etc.), and long wires are the weapons of choice with
limited space and/or requirements of minimal visibility. If the frame
of the building is non-metallic, indoor antennas can work (but can
also be mondo noisy on RX). If the frame is metallic, the antenna must
be outside. The good news is that the building frame will work fine as
a counterpoise (although it may block the antenna in the direction of
the building). A long wire launched away from the building is best --
small diameter enameled wire can be hard to see, and works fine as an
antenna.
73, Jim K9YC
On Thu,4/7/2016 2:41 AM, Petr, OK1RP/M0SIS wrote:
I am sure that David talked about an Isotron antennas like this:
https://www.isotronantennas.com/
I intensively tested/used this antenna in 90's on 40m (product from
Sigi,
DK9FN) and I have to say it is a nightmare in overall. From my own
experiences the performance of this toy was highly dependent to the
grounding availability, bandwidth was very small and tunning was
influenced
by ground only but also by closed objects a lot.
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