Discone antenna & antenna tuner?
 

Greetings all!..I've got one of them discone antennas, you know, like
28-500mhz, blah..blah...on the roof...do I have to use an antenna
tuner if I would, let's say, try to operate on 2/6 or 440?... I don't
want to damage my UHF xcvr if there is a high SWR...any info from
you experts or who done did that is greatly appreciated...You all,
have a nice weekend & 73's....tony...wa9yoz...Amiga computer user
going over 12 years now.. Ciao!

Greetings all!..I've got one of them discone antennas, you know, like
28-500mhz, blah..blah...on the roof...do I have to use an antenna
tuner if I would, let's say, try to operate on 2/6 or 440?... I don't
want to damage my UHF xcvr if there is a high SWR...any info from
you experts or who done did that is greatly appreciated...You all,
have a nice weekend & 73's....tony...wa9yoz...Amiga computer user
going over 12 years now.. Ciao!

Hi Tony,

The true discone part only works above about 100 MHz. Occassionally these
hybrid antennas have spikes of SWR from 100 MHz to 440, but I would say you
should probably be fine--without tuner.

73,
Chip N1IR

"Fractenna" wrote in message
...
Greetings all!..I've got one of them discone antennas, you know, like
28-500mhz, blah..blah...on the roof...do I have to use an antenna
tuner if I would, let's say, try to operate on 2/6 or 440?... I don't
want to damage my UHF xcvr if there is a high SWR...any info from
you experts or who done did that is greatly appreciated...You all,
have a nice weekend & 73's....tony...wa9yoz...Amiga computer user
going over 12 years now.. Ciao!

Hi Tony,

The true discone part only works above about 100 MHz. Occassionally these
hybrid antennas have spikes of SWR from 100 MHz to 440, but I would say
you
should probably be fine--without tuner.

73,
Chip N1IR

Discone lower frequency cutoff is near the length of the skirt (1/4
wavelength) so measure it 100 Mhz is about 2.5 feet, 28 would be 9 foot.
Impeadance is great over the range, should not need tuner, unless the
discone is built cheap. I have a Mil one, good from near 200 to about 1.2
Ghz high power. It has 12 rods that make up the skirt. Google it to check.
UHF should be great.

On 15 Oct 2004 15:23:31 -0700, (Amigaman) wrote:

do I have to use an antenna
tuner if I would, let's say, try to operate on 2/6 or 440?

Hi OM,

The need for a tuner, and the justification for the use of an antenna
design are separate issues. A dummy load will always tune up....

As for this frequency spread, yes, the Discone could easily tune up on
these frequencies, and every one in between. You also need to
consider what will happen if you actually try to USE this antenna for
a purpose other than a dummy load.

For one or two octaves it may operate very usefully, but when you try
to stretch it over a decade of frequency you will find that its best
performance is straight up for occasional satellite work.

When you get into the high end of the "specified" range, the overall
dimension of antenna becomes end-fire straight up because it is
becoming significantly long in terms of wavelength. If your interest
is in activity along the horizon, then you would experience a
sensation of being "deaf."

This deafness is the most common complaint of mis-interpreting the
ability to tune with ability to use.

73's
Richard Clark, KB7QHC

"Mispan" wrote in message
...

"Fractenna" wrote in message
...
Greetings all!..I've got one of them discone antennas, you know, like
28-500mhz, blah..blah...on the roof...do I have to use an antenna
tuner if I would, let's say, try to operate on 2/6 or 440?... I don't
want to damage my UHF xcvr if there is a high SWR...any info from
you experts or who done did that is greatly appreciated...You all,
have a nice weekend & 73's....tony...wa9yoz...Amiga computer user
going over 12 years now.. Ciao!

Hi Tony,

The true discone part only works above about 100 MHz. Occassionally these
hybrid antennas have spikes of SWR from 100 MHz to 440, but I would say
you
should probably be fine--without tuner.

73,
Chip N1IR

Discone lower frequency cutoff is near the length of the skirt (1/4
wavelength) so measure it 100 Mhz is about 2.5 feet, 28 would be 9 foot.
Impeadance is great over the range, should not need tuner, unless the
discone is built cheap. I have a Mil one, good from near 200 to about 1.2
Ghz high power. It has 12 rods that make up the skirt. Google it to
check.
UHF should be great.

My understanding is that there is also a problem at the other frequency end.
For example, if it actually works on 6 meters, then, at 432 MHz you will
have very high angle radiation; i.e. going up, instead of along the horizon.

Tam/WB2TT

Richard,
Sorry I stepped on you. Hadn't read your posting.


Tam/WB2TT

My understanding is that there is also a problem at the other frequency end.
For example, if it actually works on 6 meters, then, at 432 MHz you will
have very high angle radiation; i.e. going up, instead of along the horizon.

Tam/WB2TT

Hi Tam,

If its the design I've worked with, it should be OK on the horizon on 432.

When the disc section no longer functions as a counterpoise, then multiple
resonances happen across the cone and you get a lobe on the horizon. That is
probably what you are describing.

73,
Chip N1IR

You say it covers from 28Mhz to 500Mhz. The one I am familiar with that
does this is a modified discone that acts as a 1/4 wl antenna with ground
plane at 28(probably 27Mhz) If this is the antena I am thinking about it has
a long whip coming out of the cneter of the disk and 3 or 4 extra long
radials in the skirt. These antennas worked on 144, 220, 432 bands with
reasonable SWR.

"Amigaman" wrote in message
m...
Greetings all!..I've got one of them discone antennas, you know, like
28-500mhz, blah..blah...on the roof...do I have to use an antenna
tuner if I would, let's say, try to operate on 2/6 or 440?... I don't
want to damage my UHF xcvr if there is a high SWR...any info from
you experts or who done did that is greatly appreciated...You all,
have a nice weekend & 73's....tony...wa9yoz...Amiga computer user
going over 12 years now.. Ciao!