Isotron antennas
 

I've been seeing pictures of these weird antennas for years. Near as I can
tell from the picture, it's essentially a heavily-loaded very short dipole
with two large capacity hats at the ends. But it's impossible to tell from
the pictures what the exact configuration is. Can anyone tell me exactly
what's happening? Is the mast part of the radiating system? The feedline?
The literature (including the manuals) sort of implies that it is.

Also, from the pictures, I get the impression that the standard mast-mount
configuration is mostly vertically polarized. This would certainly account
for reports I have read that the antenna is a bit of a dud at short range
on 80m.

If someone has a computer model for it for MMHAMSOFT's modeller, that would
be GREAT!

The reason I'm asking is that I'm in the process of trying to design
something really low profile for a second floor apartment balcony for 75
and 80m.

--
Dave Oldridge+
VA7CZ
ICQ 1800667

Isotron antennas
 

If you can get a copy of the November, 2005 "World Radio", check out
"Kurt N Sturba"'s column, under "Aerials", on pg.55.-- he no dummy
when coms to antennas, ect, and hides behind that nome d'plume to avoid
conflicts with finger pointers. Tho on these antennas, a couple hundred
words, but informative. In essence, he sez that these are very lossey,
That a dipole (66 ft) on 40 meters would have a given bandwidth, IF
the Isotron had the same effeciency for it's size, it would have a band-
width of about 11 KHz. What it really has is a bandwidth of around 400
KHz this results in a signal about 2 "S" units , or 12 dB down from
THAT reference dipole. In other words, there are better more effecient
ways of radiating a signal! As information-- Jim NN7K




Dave Oldridge wrote:
I've been seeing pictures of these weird antennas for years. Near as I can
tell from the picture, it's essentially a heavily-loaded very short dipole
with two large capacity hats at the ends. But it's impossible to tell from
the pictures what the exact configuration is. Can anyone tell me exactly
what's happening? Is the mast part of the radiating system? The feedline?
The literature (including the manuals) sort of implies that it is.

Also, from the pictures, I get the impression that the standard mast-mount
configuration is mostly vertically polarized. This would certainly account
for reports I have read that the antenna is a bit of a dud at short range
on 80m.

If someone has a computer model for it for MMHAMSOFT's modeller, that would
be GREAT!

The reason I'm asking is that I'm in the process of trying to design
something really low profile for a second floor apartment balcony for 75
and 80m.

Isotron antennas
 

Gee, I'm sorry to hear that. I was hoping that you could get something for
nothing. :-)
-- John, N9JG

"Jim - NN7K" wrote in message
. com...
If you can get a copy of the November, 2005 "World Radio", check out
"Kurt N Sturba"'s column, under "Aerials", on pg.55.-- he no dummy
when coms to antennas, ect, and hides behind that nome d'plume to avoid
conflicts with finger pointers. Tho on these antennas, a couple hundred
words, but informative. In essence, he sez that these are very lossey,
That a dipole (66 ft) on 40 meters would have a given bandwidth, IF
the Isotron had the same effeciency for it's size, it would have a band-
width of about 11 KHz. What it really has is a bandwidth of around 400
KHz this results in a signal about 2 "S" units , or 12 dB down from
THAT reference dipole. In other words, there are better more effecient
ways of radiating a signal! As information-- Jim NN7K

Isotron antennas
 

Dave Oldridge wrote:
The reason I'm asking is that I'm in the process of trying to design
something really low profile for a second floor apartment balcony for 75
and 80m.

A small one-turn loop is hard to beat.
--
73, Cecil http://www.qsl.net/w5dxp

Isotron antennas
 

THAT was also quoted in the same article I stated. But would think a
mobile antenna (this on second floor apt.), and a tripod mount, with
radials for a counterpoise over a balcony (at night) would be much more
effective than this dawg! think mfj or another outfit has the setup for
this --- (maybe Outbacker, and that NOT that great)! Jim nn7k

Cecil Moore wrote:
Dave Oldridge wrote:

The reason I'm asking is that I'm in the process of trying to design
something really low profile for a second floor apartment balcony for
75 and 80m.


A small one-turn loop is hard to beat.

Isotron antennas
 

Jim - NN7K wrote:
THAT was also quoted in the same article I stated. But would think a
mobile antenna (this on second floor apt.), and a tripod mount, with
radials for a counterpoise over a balcony (at night) would be much more
effective than this dawg!

Yes, more effective than the Isotron but disappointing, nevertheless
(been there done that). A balcony-mounted mobile screwdriver is still
pretty far down from a properly designed small loop on 75m. However,
a vertical longer than a mobile screwdriver would be something worth
considering. I think HighSierra has one of those.
--
73, Cecil http://www.qsl.net/w5dxp

Isotron antennas
 

Jim - NN7K wrote in news:J9vdf.11022
:

THAT was also quoted in the same article I stated. But would think a
mobile antenna (this on second floor apt.), and a tripod mount, with
radials for a counterpoise over a balcony (at night) would be much more
effective than this dawg! think mfj or another outfit has the setup for
this --- (maybe Outbacker, and that NOT that great)! Jim nn7k

Actually, I *am* thinking outbacker or MFJ. The balcony is large and
aluminum-railed, which should actually form a decent counterpoise if it
doesn't blast my sat. TV and 2m stuff all to heck.

I just wondered what the theory is with the isotron. If it's actually
exciting its mast (as some antennas do), then maybe I could use a similar
technique to excite the balcony rail itself.

A loop is not out of the question either, but to be at all efficient, it
would have to be made of 1" or even 2" copper pipe.


--
Dave Oldridge+
ICQ 1800667

Isotron antennas
 

If you might consider a loop antenna, check out two electronic books, which
are produced by antenneX Online Magazine. The two books are "The Loop Book"
by Ted Hart, W5QJR, and "Small Magnetic Loops, Construction & Use" from
antenneX. See
http://www.antennex.com/Sshack/loopbk.htm
http://www.antennex.com/Sshack/newloop.htm
John, N9JG

"Dave Oldridge" wrote in message
9...
Jim - NN7K wrote in news:J9vdf.11022
:

THAT was also quoted in the same article I stated. But would think a
mobile antenna (this on second floor apt.), and a tripod mount, with
radials for a counterpoise over a balcony (at night) would be much more
effective than this dawg! think mfj or another outfit has the setup for
this --- (maybe Outbacker, and that NOT that great)! Jim nn7k

Actually, I *am* thinking outbacker or MFJ. The balcony is large and
aluminum-railed, which should actually form a decent counterpoise if it
doesn't blast my sat. TV and 2m stuff all to heck.

I just wondered what the theory is with the isotron. If it's actually
exciting its mast (as some antennas do), then maybe I could use a similar
technique to excite the balcony rail itself.

A loop is not out of the question either, but to be at all efficient, it
would have to be made of 1" or even 2" copper pipe.


--
Dave Oldridge+
ICQ 1800667

Isotron antennas
 

Dave Oldridge wrote:
If someone has a computer model for it for MMHAMSOFT's modeller, that would
be GREAT!

I've been looking for an EZNEC model of the Isotron for the past 6
months, Dave. I haven't found anybody who has modeled one. I understand
the Isotron is "lossy" and "nothing but radiating feedline" but it
would still be interesting to see it on a grid or check the numbers in
NEC. And - just like every antenna, you'll find people who use these
things and love them, proving that "the best antenna is one that works
for you". I've got to agree with what others are telling you. A small
loop is the best performing antenna I've been able to find for my very
challenging antenna environment. Other than the small bandwidth, I know
it's working better than any inverted-vee or shortened dipole I've ever
been able to get up amid the power lines and CATV cables here.

Good luck.

Kip W6KIP

Isotron antennas
 

"Kip W6KIP" wrote in
ups.com:


Dave Oldridge wrote:
If someone has a computer model for it for MMHAMSOFT's modeller, that
would be GREAT!

I've been looking for an EZNEC model of the Isotron for the past 6
months, Dave. I haven't found anybody who has modeled one. I
understand the Isotron is "lossy" and "nothing but radiating feedline"
but it would still be interesting to see it on a grid or check the
numbers in NEC. And - just like every antenna, you'll find people who
use these things and love them, proving that "the best antenna is one
that works for you". I've got to agree with what others are telling
you. A small loop is the best performing antenna I've been able to
find for my very challenging antenna environment. Other than the small
bandwidth, I know it's working better than any inverted-vee or
shortened dipole I've ever been able to get up amid the power lines
and CATV cables here.

I actually have a fairly good ground--a balcony rail that forms an
aluminum grid about 40 feet in length and 3 feet in height. That's bound
to have a decent capacative coupling to real ground inside the building,
even if the rails are bolted into wood.


--
Dave Oldridge+
ICQ 1800667

Isotron antennas
 

I don't know much about these antennas but I have a friend in Colorado who
has one and we often talk on 20 or 40 meters. He has only 100 watts output
and he puts a strong signal into Alabama. It certainly seems to work for
him. I have a Carolina Windom and I believe his Isotron performs better
than my windom.


Bill W4WEG


"Dave Oldridge" wrote in message
9...
I've been seeing pictures of these weird antennas for years. Near as I
can
tell from the picture, it's essentially a heavily-loaded very short dipole
with two large capacity hats at the ends. But it's impossible to tell
from
the pictures what the exact configuration is. Can anyone tell me exactly
what's happening? Is the mast part of the radiating system? The
feedline?
The literature (including the manuals) sort of implies that it is.

Also, from the pictures, I get the impression that the standard mast-mount
configuration is mostly vertically polarized. This would certainly
account
for reports I have read that the antenna is a bit of a dud at short range
on 80m.

If someone has a computer model for it for MMHAMSOFT's modeller, that
would
be GREAT!

The reason I'm asking is that I'm in the process of trying to design
something really low profile for a second floor apartment balcony for 75
and 80m.

--
Dave Oldridge+
VA7CZ
ICQ 1800667

Isotron antennas
 

Bill Grimwood wrote:
I don't know much about these antennas but I have a friend in Colorado who
has one and we often talk on 20 or 40 meters. He has only 100 watts output
and he puts a strong signal into Alabama. It certainly seems to work for
him. I have a Carolina Windom and I believe his Isotron performs better
than my windom.

Due, no doubt, to radiation from his feedline. If you both
replaced the vertical section of your feedline with a good
ground-plane vertical, it might improve even more.
--
73, Cecil http://www.qsl.net/w5dxp

Isotron antennas
 

Cecil Moore wrote:
Bill Grimwood wrote:

I don't know much about these antennas but I have a friend in Colorado
who has one and we often talk on 20 or 40 meters. He has only 100
watts output and he puts a strong signal into Alabama. It certainly
seems to work for him. I have a Carolina Windom and I believe his
Isotron performs better than my windom.


Due, no doubt, to radiation from his feedline. If you both
replaced the vertical section of your feedline with a good
ground-plane vertical, it might improve even more.


Bill;

The best antenna for you is the antenna that works. I use a B&W folded
dipole antenna daily. It does the job I need it to do. There are those
that deride it as a "lossy dummy load". What it is is an antenna that
dumps any excess energy into a 600 ohm resistor. The excess energy is
that which is reflected back into the finals by any other antenna. It
allows me to QSY and be tuned to any frequency I wish to use. In that I
use NTIA frequencies in addition to Ham frequencies this it the best
antenna for my use. As I said it works.

Dave WD9BDZ

Isotron antennas
 

David G. Nagel wrote:
The excess energy is
that which is reflected back into the finals by any other antenna.

Sorry, in a tuned system, the "excess energy" is re-reflected
back toward the antenna at the match point. Here's an example:

100w XMTR--50 ohm coax--+--1/2WL of 300 ohm twinlead--50 ohm antenna

More than half the forward power is reflected from the antenna
but it is turned around and re-reflected back toward the antenna
at the coax/twinlead junction at point '+'. The reflected energy
reaching the finals is ZERO!

Reflected energy, per se, is not bad. Reflected energy that is
allowed to reach the finals is bad. In most systems, an antenna
tuner solves the problem.
--
73, Cecil http://www.qsl.net/w5dxp