If I'm treading old ground please excuse the post. Today at the local
hamfest I ran across a 20 meter Isotron that the seller touting. After
looking at its simplicity and hearing how great it was I couldn't resist
because it was only $10.00. So now that I have it, I'm curious as to the
theory behind it and how an 89 turn coil of No. 12 wire on a 3/4" piece of
PVC along with a 12" aluminum rod and a couple of aluminum plates can load
and dissipate 1000 watts. I've seen their ads for years and always thought
they were snake oil but at $10.00 I bit. Anyone really know the theory
behind these things?
tnx
Hank WD5JFR

On Sat, 20 Mar 2004 22:15:52 GMT, "Henry Kolesnik"
wrote:

If I'm treading old ground please excuse the post. Today at the local
hamfest I ran across a 20 meter Isotron that the seller touting. After
looking at its simplicity and hearing how great it was I couldn't resist
because it was only $10.00. So now that I have it, I'm curious as to the
theory behind it and how an 89 turn coil of No. 12 wire on a 3/4" piece of
PVC along with a 12" aluminum rod and a couple of aluminum plates can load
and dissipate 1000 watts. I've seen their ads for years and always thought
they were snake oil but at $10.00 I bit. Anyone really know the theory
behind these things?
tnx
Hank WD5JFR


Hi Hank,

This intersects with so many recent topics, it is hard to know where
to begin.

First, undoubtedly through the combination of capacitance (the plates)
the inductance (the windings) and radiation resistance, it resonates
and sheds heat like your grandmother's clothes iron. That it is so
small, it automatically removes it from concerns of being too big to
qualify as lumped components (I will bet the current into the coil
nearly equals the current into its other end).

Some claims bandied here would have us believe that its "high Q"
renders an efficiency (per unit length) unparalleled since the days of
Watt's steam engine. It must certainly be competitive with italian eh
models and show more gain than a Georgia AM station converted to cfa
(but only for the first 300 yards).

If none of this satisfies your quest for understanding; then you can,
of course, visit the vendor's site, observe their "how it works"
description and then find the exact same wording in an unbiased review
from 1996. ;-)

73's
Richard Clark, KB7QHC

Today at the local
hamfest I ran across a 20 meter Isotron that the seller touting.
Anyone really know the theory
behind these things?

As far as I can tell the Isotron is a parallel tuned circuit. On 20M it
should work as well as any other antenna of the same size and height above
ground, cause it depends on feed line radiation, just like all the other
"small' antennas. On 20 it should do ok, but try one on 80 or 160M.

I would not put a 20M Isotron on the air if someone gave me one. There are
too many other ways to get out a decent signal. I might take it apart and use
the aluminum plates, PVC, and wire on a later project, though.

73 Gary N4AST

I don't think the parts are worth $5.00 purchased retail.

Hank
"JGBOYLES" wrote in message
...
Today at the local
hamfest I ran across a 20 meter Isotron that the seller touting.
Anyone really know the theory
behind these things?

As far as I can tell the Isotron is a parallel tuned circuit. On 20M it
should work as well as any other antenna of the same size and height above
ground, cause it depends on feed line radiation, just like all the other
"small' antennas. On 20 it should do ok, but try one on 80 or 160M.

I would not put a 20M Isotron on the air if someone gave me one. There
are
too many other ways to get out a decent signal. I might take it apart and
use
the aluminum plates, PVC, and wire on a later project, though.

73 Gary N4AST

I don't think the parts are worth $5.00 purchased retail.

I agree Hank, if you want something small and cheap on 20M, lots of
alternatives.
73 Gary N4AST

The theory has been worked out for the last 100 years and your Isotron will
work exactly as the theory predicts.

Radiated power will be about 1 watt and the antenna itself will glow in the
dark.

I'm surprised you backward Yanks still believe sales blurbs. In Europe we
have what are known as "The Trades Description Acts" (Of parliament).
----
Reg.

Reg

Yanks started on snake oil in the old west and can't break the habit. I'm a
Canuck and didn't get as exposed! But a little more info would be
appreciated. Also I'm wondering if the angle of the dangle on the Isotron
is important, hi..hi..
73
Hank WD5JFR
"Reg Edwards" wrote in message
...
The theory has been worked out for the last 100 years and your Isotron
will
work exactly as the theory predicts.

Radiated power will be about 1 watt and the antenna itself will glow in
the
dark.

I'm surprised you backward Yanks still believe sales blurbs. In Europe we
have what are known as "The Trades Description Acts" (Of parliament).
----
Reg.

UK Trade Description Act, 1968.

It is an offence for a trader to apply a false or misleading description to
goods. (Note it is the trader, not the manufacturer, who is involved.)

All goods are covered except houses.

The local (the Council) Trading Standard Authorities are under a statutary
duty to enforce the act. The local Trading Standards Officer has powers of
entry, inspection and seizure of goods.

It is not the job of the Authority to obtain compensation for the offence
but to take steps necessary to prevent others from being deceived such as
confiscation of goods from shops.

It is up to the purchaser to take action in the civil courts for
compensation. With the support of the Authority he will very likely succeed.

But for the sake of a falsely-described, $10, second-hand radio antenna is
it worth the trouble?

The Trading Standards Officer would have to engage the services of
consultant radio engineers to conduct prolonged and expensive field trials
in order to prove the point.

A court of law would not accept a mere statement of Maxwells equations or
any of Terman's or Kraus's learned dissertations. A bewigged judge, of
course, would be well advised to seek the opinions to be found on this
newsgroup.
----
Reg, G4FGQ

I've just had a look in Google at the manufacturer's so-called specification
for the Isotron.

Very carefully, nothing is said which could cause dispute.

But there's no mention of by-far the most important characteristic -
radiating efficiency!

There's no law against NOT mentioning anything. This is precisely where the
manufacturer/trader has the advantage over a prospective gullible ignorant
customer.

Quality is a measure of conformance to the intended (as specified and
agreed) purpose.

If a buyer with a fistful of cash doesn't know what he wants he can't
complain if he doesn't get it.
----
Reg.

Reg Edwards wrote:

I've just had a look in Google at the manufacturer's so-called specification
for the Isotron.

Very carefully, nothing is said which could cause dispute.

But there's no mention of by-far the most important characteristic -
radiating efficiency!

There's no law against NOT mentioning anything. This is precisely where the
manufacturer/trader has the advantage over a prospective gullible ignorant
customer.


Unfortunately, the enthusiastic ham, most of whom have only a rudimentary
knowledge of antennas, is always looking for something that will help him
get his signal out. It is not so much that he is gullible or ignorant, but
desires to get his signal on the air in the easiest way possible. I've been
hamming since 58, spent my whole navy career in communications and electronics,
and after retiring became a journeyman technician -- and I am often tempted
to try some of these gadgets. Thanks to rec.radio.amateur.antenna I have
learned enough to know what is worth trying, and what is not.

Irv VE6BP




--
--------------------------------------
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Beating it with diet and exercise!
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58"/43"(!)/44" (already lower too!)
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--------------------
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Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada