Tuning a ground plane
 

How would you go about tuning a ground plane antenna? Is a ground plane
a good antenna for 2 meters/440?

On another note, I have read about discone's being very broad banded.
Are these the best antenna for scanner listening?

On 8 Jan 2005 18:19:19 -0800, wrote:

How would you go about tuning a ground plane antenna? Is a ground plane
a good antenna for 2 meters/440?

On another note, I have read about discone's being very broad banded.
Are these the best antenna for scanner listening?


A 1/4 wave ground plane is tuned by varying the length of the
radiating element. Calculate the length, add a bit for good measure,
build it then tune it by pruning the length (in small increments).
The tuning can be done using an SWR analyzer or as most of us do, with
a radio and an SWR meter.

Discone's do offer broadband coverage, though I don't have direct
experience to say they actually work well, great or poorly. I do know
that for my scanner I use a 1/4 wave ground plane that was built for
220 MHz and it works fine - for a reference point though I am in an
urban area and most of what I listen to is within a 15 mile radius.
In order to decide what's best you should first establish your
purpose; are you in a fringe area, do you need directional coverage,
do you scan a wide range of frequencies or are your listening
interests all in the same "neck of the RF spectrum"?

Howard wrote:
On 8 Jan 2005 18:19:19 -0800, wrote:

How would you go about tuning a ground plane antenna? Is a ground
plane
a good antenna for 2 meters/440?

On another note, I have read about discone's being very broad
banded.
Are these the best antenna for scanner listening?


A 1/4 wave ground plane is tuned by varying the length of the
radiating element. Calculate the length, add a bit for good measure,
build it then tune it by pruning the length (in small increments).
The tuning can be done using an SWR analyzer or as most of us do,
with
a radio and an SWR meter.

Discone's do offer broadband coverage, though I don't have direct
experience to say they actually work well, great or poorly. I do
know
that for my scanner I use a 1/4 wave ground plane that was built for
220 MHz and it works fine - for a reference point though I am in an
urban area and most of what I listen to is within a 15 mile radius.
In order to decide what's best you should first establish your
purpose; are you in a fringe area, do you need directional coverage,
do you scan a wide range of frequencies or are your listening
interests all in the same "neck of the RF spectrum"?

Do 1/4 wave ground planes work well for 2 meters? (Send and receive).
Would they work as well as a j pole? What if you use different size
elements?

I just did not know what a discone would do for 2 meter send and
recieve compared to a ground plane.

On the scanner, I live in a fringe area for police but can pick up the
police on a homemade wire 1/4 wave for 450 mhz about 20 miles away.

What eventually I would like to do is pick up air traffic. And also
pick up various other frequencies like ambulance, state police, etc.
or your scanner do you use one antenna or several?

Please buy and READ some antenna books or search the web

It would take pages here to explain antennas to you.

--
Caveat Lector



wrote in message
oups.com...

Howard wrote:
On 8 Jan 2005 18:19:19 -0800, wrote:

How would you go about tuning a ground plane antenna? Is a ground
plane
a good antenna for 2 meters/440?

On another note, I have read about discone's being very broad
banded.
Are these the best antenna for scanner listening?


A 1/4 wave ground plane is tuned by varying the length of the
radiating element. Calculate the length, add a bit for good measure,
build it then tune it by pruning the length (in small increments).
The tuning can be done using an SWR analyzer or as most of us do,
with
a radio and an SWR meter.

Discone's do offer broadband coverage, though I don't have direct
experience to say they actually work well, great or poorly. I do
know
that for my scanner I use a 1/4 wave ground plane that was built for
220 MHz and it works fine - for a reference point though I am in an
urban area and most of what I listen to is within a 15 mile radius.
In order to decide what's best you should first establish your
purpose; are you in a fringe area, do you need directional coverage,
do you scan a wide range of frequencies or are your listening
interests all in the same "neck of the RF spectrum"?

Do 1/4 wave ground planes work well for 2 meters? (Send and receive).
Would they work as well as a j pole? What if you use different size
elements?

I just did not know what a discone would do for 2 meter send and
recieve compared to a ground plane.

On the scanner, I live in a fringe area for police but can pick up the
police on a homemade wire 1/4 wave for 450 mhz about 20 miles away.

What eventually I would like to do is pick up air traffic. And also
pick up various other frequencies like ambulance, state police, etc.
or your scanner do you use one antenna or several?

Howard wrote:
On 8 Jan 2005 18:19:19 -0800, wrote:

How would you go about tuning a ground plane antenna? Is a ground
plane
a good antenna for 2 meters/440?

On another note, I have read about discone's being very broad
banded.
Are these the best antenna for scanner listening?


A 1/4 wave ground plane is tuned by varying the length of the
radiating element. Calculate the length, add a bit for good measure,
build it then tune it by pruning the length (in small increments).
The tuning can be done using an SWR analyzer or as most of us do,
with
a radio and an SWR meter.

Discone's do offer broadband coverage, though I don't have direct
experience to say they actually work well, great or poorly. I do
know
that for my scanner I use a 1/4 wave ground plane that was built for
220 MHz and it works fine - for a reference point though I am in an
urban area and most of what I listen to is within a 15 mile radius.
In order to decide what's best you should first establish your
purpose; are you in a fringe area, do you need directional coverage,
do you scan a wide range of frequencies or are your listening
interests all in the same "neck of the RF spectrum"?


What if you are trying to tune a ground plane for the aircraft band? I
mean, you cant transmit on this. I just want to listen.

On 10 Jan 2005 06:32:51 -0800, wrote:


Howard wrote:
On 8 Jan 2005 18:19:19 -0800, wrote:

How would you go about tuning a ground plane antenna? Is a ground
plane
a good antenna for 2 meters/440?

On another note, I have read about discone's being very broad
banded.
Are these the best antenna for scanner listening?


A 1/4 wave ground plane is tuned by varying the length of the
radiating element. Calculate the length, add a bit for good measure,
build it then tune it by pruning the length (in small increments).
The tuning can be done using an SWR analyzer or as most of us do,
with
a radio and an SWR meter.

Discone's do offer broadband coverage, though I don't have direct
experience to say they actually work well, great or poorly. I do
know
that for my scanner I use a 1/4 wave ground plane that was built for
220 MHz and it works fine - for a reference point though I am in an
urban area and most of what I listen to is within a 15 mile radius.
In order to decide what's best you should first establish your
purpose; are you in a fringe area, do you need directional coverage,
do you scan a wide range of frequencies or are your listening
interests all in the same "neck of the RF spectrum"?


What if you are trying to tune a ground plane for the aircraft band? I
mean, you cant transmit on this. I just want to listen.

Figure out the middle frequency of the range you are interested in,
cut your radiator & radials for that length, build it, install it,
listen with it. I wouldn't bother trying to tune it. Figuring that
traffic on VHF air is typically @ 120 - 136 MHz the end result is to
cut elements about 22 inches long. Being as you indicate you are also
interested in the 2 meter ham band you're probably about as well off
to just make it for that band and you can use it for both.

I really suggest you spend a few dollars on the ARRL Antenna book, you
will find all your answers and more in that text as well as gaining a
better overall understanding of antennas that will serve you well.

Just make it for 2 meters or the ham band?
What can I use to power my scanner and my radio with one antenna?

A discone.

wrote in message
ups.com...
Just make it for 2 meters or the ham band?
What can I use to power my scanner and my radio with one antenna?

Stryped wrote:
'"How would you go about tunibg a ground plane antenna?"

Ed Laport explains how to tune a ground plane with (4) equally-spaced
too-short radials. He connected one radial with its partner sharing the
same alignment to make a resonant 1/2-wavelength. He determined
resonance as maximum current in the loading coils. He writes on page 140
of "Radio Antenna Engineering":
"Tuning (the radial`s loading coil) is done by maximum current in the
two (radial) wires using a center-connected ammeter or wavemeter near
one of the (lloading) coils away from the oscillator to avoid direct
pickup from the oscillator."

Lacking loading coils, one can determine maximum current at resonance in
the radial wire itself.

Best regards, Richard Harrison, KB5WZI

Bill-kb3gun wrote:
A discone.

wrote in message
ups.com...
Just make it for 2 meters or the ham band?
What can I use to power my scanner and my radio with one antenna?


I meant if I have two antennas and want to use them both on my scanner
and 2 meter, how owuld I do that?