On Fri, 29 Oct 2004 22:45:21 +1000, "Troy R."
said in alt.radio.scanner:

I am after a good V/UHF airband antenna and found this on a Google search.
Anybody actually own one and can tell me how they perform?

http://www.nevadaradio.co.uk/acatalo...airmaster.html

They don't seem to know much about it. Discones aren't resonant
antennas, but they do pick up signals from the design frequency to
daylight..

Al Klein schrieb:
On Fri, 29 Oct 2004 22:45:21 +1000, "Troy R."
said in alt.radio.scanner:


I am after a good V/UHF airband antenna and found this on a Google search.
Anybody actually own one and can tell me how they perform?


http://www.nevadaradio.co.uk/acatalo...airmaster.html


They don't seem to know much about it. Discones aren't resonant
antennas, but they do pick up signals from the design frequency to
daylight..

Not having read the linked page....
Discones ARE resonant on an extremly wide range.
Therefore they have nearly no gain above the (theortical) isotropic
antenna. This means they have a loss of around 1/2 S-unit against a
dipole or a half-wave vertikal antenna on a specified frequency. Not too
bad for a compromise.
The resonant range of a well designed and built discone is spread 1:10
on wich you can transmit. This is 50 to 500 Mhz or 100 to 1000Mhz for
example, covering the most wanted frequencies for scannists and is also
usable on ham-bands or FRS to transmit.
The receiving range -allowing an impedance mismatch- is much wider when
(usually) allowing a loss of 1 S-unit (-6dB). The difference you only
will notice on faint signals.
There are some other antennas too -directional and omnidirectional-,
providing a relatively wide resonant range but not nearly as wide as a
discone.

On Sat, 30 Oct 2004 11:55:50 +0200, Volker Tonn
said in alt.radio.scanner:

Al Klein schrieb:
On Fri, 29 Oct 2004 22:45:21 +1000, "Troy R."
said in alt.radio.scanner:

They don't seem to know much about it. Discones aren't resonant
antennas, but they do pick up signals from the design frequency to
daylight..

Not having read the linked page....
Discones ARE resonant on an extremly wide range.
Therefore they have nearly no gain above the (theortical) isotropic
antenna. This means they have a loss of around 1/2 S-unit against a
dipole or a half-wave vertikal antenna on a specified frequency. Not too
bad for a compromise.
The resonant range of a well designed and built discone is spread 1:10
on wich you can transmit. This is 50 to 500 Mhz or 100 to 1000Mhz for
example, covering the most wanted frequencies for scannists and is also
usable on ham-bands or FRS to transmit.

We're using different definitions of "resonant". The definition I use
says that an antenna can only resonate on a frequency. (Pretty much,
the frequency a dip meter will indicate when coupled to the antenna.)
It can have a bandwidth over which it can be used, but the resonant
point is (usually) one single frequency. Discones look like dipoles
with the 2 legs being different lengths, so the best one could say -
using my definition - is that they "resonate" on the frequency at
which the disc is 1/2 wavelength in diameter and the frequency at
which the cone element length is 1/4 wavelength.

But they probably are the best tradeoff for multi-band scanning.

Snip...
We're using different definitions of "resonant". The definition I use
says that an antenna can only resonate on a frequency. (Pretty much,
the frequency a dip meter will indicate when coupled to the antenna.)
It can have a bandwidth over which it can be used, but the resonant
point is (usually) one single frequency. Discones look like dipoles
with the 2 legs being different lengths, so the best one could say -
using my definition - is that they "resonate" on the frequency at
which the disc is 1/2 wavelength in diameter and the frequency at
which the cone element length is 1/4 wavelength.

But they probably are the best tradeoff for multi-band scanning.

Let's use an accepted engineering definition- resonance is defined when the
input Z has zero reactance- a properly designed discone (disc and cone- not
a skeletal version) is virtually reactance free over a very wide band.
Discones may look like dipoles- although you really have to be imaginitive,
is a derivative of the bicone antenna (replace the disk with another cone).
With proper included cone angle and proper machining of the junction (this
limits hi end performance) it is a wonderfully broadbanded antenna.

Dale W4OP

So what you are saying Dale is that a bicone antenna is a good wideband
antenna? Do they exhibit any gain?


"Dale Parfitt" wrote in message
news:uSQgd.874$cA4.853@trnddc01...
Snip...
We're using different definitions of "resonant". The definition I use
says that an antenna can only resonate on a frequency. (Pretty much,
the frequency a dip meter will indicate when coupled to the antenna.)
It can have a bandwidth over which it can be used, but the resonant
point is (usually) one single frequency. Discones look like dipoles
with the 2 legs being different lengths, so the best one could say -
using my definition - is that they "resonate" on the frequency at
which the disc is 1/2 wavelength in diameter and the frequency at
which the cone element length is 1/4 wavelength.

But they probably are the best tradeoff for multi-band scanning.

Let's use an accepted engineering definition- resonance is defined when
the
input Z has zero reactance- a properly designed discone (disc and cone-
not
a skeletal version) is virtually reactance free over a very wide band.
Discones may look like dipoles- although you really have to be
imaginitive,
is a derivative of the bicone antenna (replace the disk with another
cone).
With proper included cone angle and proper machining of the junction (this
limits hi end performance) it is a wonderfully broadbanded antenna.

Dale W4OP

Troy R. schrieb:
So what you are saying Dale is that a bicone antenna is a good wideband
antenna? Do they exhibit any gain?

Gain? ...compared to what?
Yes, the bicone antenna has gain!
It's gain is comparable to a dipole.
But a bicone is far away to be as broadband as a discone.

"Volker Tonn" wrote in message
...

Troy R. schrieb:
So what you are saying Dale is that a bicone antenna is a good wideband
antenna? Do they exhibit any gain?

Gain? ...compared to what?
Yes, the bicone antenna has gain!
It's gain is comparable to a dipole.
But a bicone is far away to be as broadband as a discone.


Can you show me a text indicating that a bicone has a bandwidth different
from a discone?

Dale W4OP

Al Klein schrieb:

On Sat, 30 Oct 2004 11:55:50 +0200, Volker Tonn
said in alt.radio.scanner:


Al Klein schrieb:

On Fri, 29 Oct 2004 22:45:21 +1000, "Troy R."
said in alt.radio.scanner:


They don't seem to know much about it. Discones aren't resonant
antennas, but they do pick up signals from the design frequency to
daylight..


Not having read the linked page....
Discones ARE resonant on an extremly wide range.
Therefore they have nearly no gain above the (theortical) isotropic
antenna. This means they have a loss of around 1/2 S-unit against a
dipole or a half-wave vertikal antenna on a specified frequency. Not too
bad for a compromise.
The resonant range of a well designed and built discone is spread 1:10
on wich you can transmit. This is 50 to 500 Mhz or 100 to 1000Mhz for
example, covering the most wanted frequencies for scannists and is also
usable on ham-bands or FRS to transmit.


We're using different definitions of "resonant". The definition I use
says that an antenna can only resonate on a frequency. (Pretty much,
the frequency a dip meter will indicate when coupled to the antenna.)
It can have a bandwidth over which it can be used, but the resonant
point is (usually) one single frequency. Discones look like dipoles
with the 2 legs being different lengths, so the best one could say -
using my definition - is that they "resonate" on the frequency at
which the disc is 1/2 wavelength in diameter and the frequency at
which the cone element length is 1/4 wavelength.

To say so, a discone has it's "middle frequency". But impedance curve
stays constantly over a very wide range around. So in theoretics you can
get a frequency modulated signal with center frequency of let's say
500Mhz and a bandwidth of 800Mhz through a discone with a straight power
curve wich has no loss by mismatching of the antennea.
I don't know of any TRX providing such a signal :-)

As I understand the principle of a discone the disc is a load plate wich
spreads the bandwidth in conjunction wich the conical "antenna wire". So
the "resonant" wavelength is more related to the length of the cone
measured from the the top plate in 90 degree angle to the bottom.
You may correct me if I'm wrong :-)
Have a nice weekend.