If the ideal lenght of an antenna is 1/4 Wave lenght then wayare the Car Cellular antennas are longer then this ?
 

There is a simple answer, and others have given good advice:

The premis of the question is incorrect. A simple antenna such as a
collinear using a quarter wave with a phasing coil and topped with
another half wavelength segment will give power gain by modifying the
radiation pattern.
That statement should work better than OK.



tomerbr wrote:
this was a qustion from my instractor in college

If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ?
 

"tomerbr" wrote in message
oups.com...
this was a qustion from my instractor in college

The assumption may be an error to begin with.
For starters I would say a 5/8 wave antenna may be "more ideal".
If you picture the radiation pattern similar to a balloon with a finite
amount of water (the 'power') , the coverage of the antenna can be
represented by the shape of the containment.
If you press down on the balloon center with your hand then the circle of
coverage will be larger - since we assume the cell towers will be on the
same plane as the antenna, you can see that a flat, circular shape will
cover more map area than a spherical shape would cover. A 5/8 wave antenna
is but one of many types which can exhibit 'gain' by distributing the
pattern in more usable directions.
I suspect the antenna the Instructor is referring to is 5/8 wave, and he
tried to throw you off with the 'Ideal antenna" statement.
Merry Christmas

If the ideal lenght of an antenna is 1/4 Wave lenght then wayare the Car Cellular antennas are longer then this ?
 

Do you actually have any hard data on this Paul? Not that I dont believe
you, just would like to know how many dB we are talking about. "sucked"
doesnt translate very well...

I was surprised when I visited the US for the first time how much higher
the cell towers were compared to Australia's. From what I understand
though cell use in Australia (per unit pop) topped the world for a while
and it was undesirable to have high towers because the larger cell size
meant co-cell interference was more likely. Towers and antennas then
ended up on shorter towers and building sides to allow for the higher
density of users.

Towers in rural areas were of course a lot higher but they had an upper
limit when you factored in the 32km limit for GSM systems. It was often
frustrating when travelling in thee areas to see 3-4 cells sites in
strong signal range but unable to make/receive calls because of that max
distance restriction.

Cheers Bob W5/VK2YQA

Paul Johnson wrote:

A couple hundred feet is taller than most (all?) cell towers. Nextel used
to boast about having the tallest towers, around 110 feet max. Sprint's
towers were the shortest before Nextel bought them at around 60 feet. This
is why Sprint's signal really sucked balls before Nextel bought them out.

If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ?
 

Top posting reduces readability and destroys context. It is harmful.
http://ursine.ca/Top_Posting

Bob Bob wrote:

Do you actually have any hard data on this Paul? Not that I dont believe
you, just would like to know how many dB we are talking about. "sucked"
doesnt translate very well...

Alas, none that I can share except in the abstract due to nondisclosure
agreements.

--
Paul Johnson
Email and Instant Messenger (Jabber):
Got jabber? http://ursine.ca/Ursine:Jabber

If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ?
 

Right you are.
Like I said - using a 5/8 wave vertical flattens out the "doughnut of
propogation."
And using two - back-to-back as a dipole will exhibit gain as well - over a
dipole.

If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ?
 

"Hal Rosser" wrote:
Right you are.
Like I said - using a 5/8 wave vertical flattens out the "doughnut of
propogation."
And using two - back-to-back as a dipole will exhibit gain as well -
over a dipole.
______________

If you mean gain over a _ 1/2-wave _ dipole, then all of the single
verticals 90 degrees in the plots I posted earlier (with their "image"
components) already have greater peak gain than that.

The peak, intrinsic gain of the 90 degree vertical and its image in my plots
exactly matches the free-space peak gain of a self-resonant, 1/2-wave dipole
(2.15 dBi).

The fact that all of the radiation from these verticals is confined to a 1/2
hemisphere adds 3 dB h-plane gain to all of the plots.

RF

If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ?
 

Just to start an argument, why is it that EZNEC shows zero gain for a
vertical antenna in the horizontal plane? Whereas, all your diagrams
show maximum gain along the horizontal.
----
Reg.

If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ?
 

"Richard Fry"
... confined to a 1/2 hemisphere adds 3 dB h-plane
gain to all of the plots.
______________

Sorry, delete the "1/2" in my statement above. My bad.

RF

If the ideal lenght of an antenna is 1/4 Wave lenght then way are the Car Cellular antennas are longer then this ?
 

"Reg Edwards" wrote
Just to start an argument, why is it that EZNEC shows zero gain for a
vertical antenna in the horizontal plane? Whereas, all your diagrams
show maximum gain along the horizontal.
____________

EZNEC shows the same patterns/gains as in the plots I posted,
when its models are set up correctly.

RF

If the ideal lenght of an antenna is 1/4 Wave lenght then wayare the Car Cellular antennas are longer then this ?
 

Reg Edwards wrote:

Just to start an argument, why is it that EZNEC shows zero gain for a
vertical antenna in the horizontal plane? Whereas, all your diagrams
show maximum gain along the horizontal.

Sometimes the maximum gain is zero dBi?
--
73, Cecil http://www.qsl.net/w5dxp