On Tue, 15 Jul 2003 17:43:20 -0700, "denton"
wrote:

Ask any trucker about a co-phased cb antenna system....same principal
applies

My understanding of that setup is that the two cophased whips need to
be a quarter wavelength apart in order for it to work properly,
although I may have been misinformed.

However, if this is correct, it's gonna be tough to find a vehicle
that will let you separate two cophased whips by a quarter wavelength
at 80 meters - and driving it down most city streets would probably be
quite an experience even if you could find one that large. (Maybe the
tractor that moves the space shuttle from the vehicle assembly
building to the launch pad...top speed is slower than most folks can
walk, though)

73 DE John, KC2HMZ

Mobile antenna balancing ?
 

I wonder if radiated energy would increase measureably if one were to try to
balance mobile whip antenna by having another whip connected directly to the
body and tuning it. If it would, how would one locate, size, and tune it?
tnx
hank wd5jfr

On Tue, 15 Jul 2003 16:07:15 -0500, "Henry Kolesnik"
wrote:

I wonder if radiated energy would increase measureably if one were to try to
balance mobile whip antenna by having another whip connected directly to the
body and tuning it. If it would, how would one locate, size, and tune it?
tnx
hank wd5jfr


Hi Hank,

The body is already the balancing whip you propose. Your addition
would be like adding a thin radial to an already massive one (like the
needle on a cactus).

Actually, what most Hams consider to be their antenna, it is actually
a tuned radial to the larger radiating frame. There is little
distinction between such primitive elements at large wavelengths if
you are talking about 80M or so. Some would argue that their
screwdriver elongates the current loop (the indicator of gain against
the overwhelming short dimensions) to qualify it as radiator, that is
simply a trick of symmetry and their being able to tune a thin element
instead of the more massive one (unless they drive a variable-stretch
limo).

73's
Richard Clark, KB7QHC

Ask any trucker about a co-phased cb antenna system....same principal
applies
"Henry Kolesnik" wrote in message
...
I wonder if radiated energy would increase measureably if one were to try
to
balance mobile whip antenna by having another whip connected directly to
the
body and tuning it. If it would, how would one locate, size, and tune
it?
tnx
hank wd5jfr

Ok I stand corrected.....
"TeeAye" wrote in message
...
On Tue, 15 Jul 2003 17:43:20 -0700, denton wrote:

Ask any trucker about a co-phased cb antenna system....same principal
applies

__________________________________________________ ______________

No, no, no. Different principle entirely. He's talking about using the
second whip connected directly to the body of the vehicle - in effect
using
it for the missing half of the dipole.

This has been done in the past by a number of folks and they seemed to
like
it. Whether it is worth the trouble is questionable. Give it a try and
let us know how it works out.

--
73, Bill W7TI

denton wrote:
Ask any trucker about a co-phased cb antenna system....same principal
applies

It works on 11m pretty well when the two whips are low loss.
Not well at all on 75m.
--
73, Cecil http://www.qsl.net/w5dxp



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W5DXP wrote in message
...
denton wrote:
Ask any trucker about a co-phased cb antenna system....same principal
applies

It works on 11m pretty well when the two whips are low loss.
Not well at all on 75m.
--
73, Cecil http://www.qsl.net/w5dxp


Well, maybe yes and no. I think I heard that it is called "series tuning".
Now you would have to
mount the things on opposite ends of the car. Whether there is anything to
be gained, I haven't
tested it. It eliminates the matching network, tho. Heck, I've got enough
antennas on my car
without that.


Jerry
K4KWH



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Jerry Oxendine wrote:

W5DXP wrote in message
It works on 11m pretty well when the two whips are low loss.
Not well at all on 75m.

Well, maybe yes and no. I think I heard that it is called "series tuning".

I was thinking it was simply a resonant 1/4WL director or reflector
which would be very lossy on 75m.
--
73, Cecil http://www.qsl.net/w5dxp



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TeeAye wrote:
The original question was *not* about co-phasing. It was about using
another whip as a replacement for the missing half of a dipole. The second
whip would be connected directly to the car body and become an extension of
the body.

Assuming one whip is pointing up, which way is the other whip pointing?
--
73, Cecil http://www.qsl.net/w5dxp



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You tell me, that's part of the question.
tnx
hank wd5jfr
"W5DXP" wrote in message
...
TeeAye wrote:
The original question was *not* about co-phasing. It was about using
another whip as a replacement for the missing half of a dipole. The
second
whip would be connected directly to the car body and become an extension
of
the body.

Assuming one whip is pointing up, which way is the other whip pointing?
--
73, Cecil http://www.qsl.net/w5dxp



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Henry,
Don't waste your time, won't work as intended. Did
you really ask someone where to put/stick that other
half of the antenna??
'Doc

On Wed, 16 Jul 2003 21:15:13 -0500, 'Doc sent into the
ether:



Henry,
Don't waste your time, won't work as intended. Did
you really ask someone where to put/stick that other
half of the antenna??
'Doc
Nice restraint on your part Doc :}
Dan, N9JBF
Amateur radio - What a hobby!
Remove left x for direct reply

When a car body is not available to provide the "other half" of the antenna,
you provide the other half of the dipole.

http://user.mc.net/~jdewey/sleeve_di...iew_of_car.jpg

A commercial version is also available

http://www.antenna.com/lm_cat/lmrpg10.html


"Henry Kolesnik" wrote in message
...
I wonder if radiated energy would increase measureably if one were to try
to
balance mobile whip antenna by having another whip connected directly to
the
body and tuning it. If it would, how would one locate, size, and tune
it?
tnx
hank wd5jfr

When the "co-phased" CB whips were introduced into the market years ago,
I saw it for the master stroke it was -- a whole lot of CB'ers who in
the past would have bought only one antenna now bought two, effectively
doubling the revenue of the antenna manufacturers. A brilliant move. And
the placebo effect guarantees that the users will see superior results.
Makes everyone happy, manufacturers and users alike.

Sounds like we're on the nexus of another breakthrough.

Roy Lewallen, W7EL

Assuming one whip is pointing up, which way is the other whip pointing?

The way I saw it done, the other whip was at the other end of the car
and also pointing up. I have no knowledge of whether this was actually
useful, but apparently the user thought it was.

In which case, it is a phased vertical array, not a dipole. With
a spacing of 1/8WL, one can get 4 dB gain that way.
--
73, Cecil http://www.qsl.net/w5dxp



Actually, I read about this in Don Johnson of Screwdriver antenna fame's
book on mobile radio operation. IIRC, the folks experimenting with it
put the second whip on the far end of the car - tied to the frame, ie
grounded - not driven. When tuned to resonance an increase in RF current
in the car body was noticed and I think they also saw about a 3db
increase in radiated signal. I imagine it's not very popular because of
the difficulty of tuning two antennas instead of one, and the visual
aspect of a second large antenna on the vehicle. It just isn't that
practical even for a 3 db increase in signal.

It wasn't presented as being a dipole or any form of phased array. Just
as empirical data that picked up along the way that was interesting.

73,
Kevin, WB2EMS

Roy Lewallen wrote:
When the "co-phased" CB whips were introduced into the market years ago,
I saw it for the master stroke it was -- a whole lot of CB'ers who in
the past would have bought only one antenna now bought two, effectively
doubling the revenue of the antenna manufacturers. A brilliant move. And
the placebo effect guarantees that the users will see superior results.
Makes everyone happy, manufacturers and users alike.

Sounds like we're on the nexus of another breakthrough.

They could have done a lot better if they had co-phased them front
to back instead of side to side.
--
73, Cecil, W5DXP

W5DXP wrote:

In which case, it is a phased vertical array, not a dipole. With
a spacing of 1/8WL, one can get 4 dB gain that way.

In your dreams.

Roy Lewallen, W7EL

Roy Lewallen wrote:
W5DXP wrote:
In which case, it is a phased vertical array, not a dipole. With
a spacing of 1/8WL, one can get 4 dB gain that way.

In your dreams.

I'm dreaming of The ARRL Antenna Book, 15th edition, page 8-6. Spacing 1/8WL,
phasing=135 deg, Gain = 4.1 dB. Remember, this is for two 10m verticals mounted
in line with the vehicle, not one on each side of the vehicle. It is essentially
a two element vertical beam with a cardioid radiation pattern and a large
front/back ratio.
--
73, Cecil http://www.qsl.net/w5dxp



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Kevin,
It would also be directional, and probably usless
at least 50% of the time on a mobile...
'Doc

Cecil, is that not a driven collinear array?

Deacon Dave, W1MCE

W5DXP wrote:

Roy Lewallen wrote:

W5DXP wrote:

In which case, it is a phased vertical array, not a dipole. With
a spacing of 1/8WL, one can get 4 dB gain that way.


In your dreams.


I'm dreaming of The ARRL Antenna Book, 15th edition, page 8-6. Spacing
1/8WL,
phasing=135 deg, Gain = 4.1 dB. Remember, this is for two 10m verticals
mounted
in line with the vehicle, not one on each side of the vehicle. It is
essentially
a two element vertical beam with a cardioid radiation pattern and a large
front/back ratio.

F. Feeney wrote:
Actually, I read about this in Don Johnson of Screwdriver antenna fame's
book on mobile radio operation. IIRC, the folks experimenting with it
put the second whip on the far end of the car - tied to the frame, ie
grounded - not driven. When tuned to resonance an increase in RF current
in the car body was noticed and I think they also saw about a 3db
increase in radiated signal. I imagine it's not very popular because of
the difficulty of tuning two antennas instead of one, and the visual
aspect of a second large antenna on the vehicle. It just isn't that
practical even for a 3 db increase in signal.

It wasn't presented as being a dipole or any form of phased array. Just
as empirical data that picked up along the way that was interesting.

It would be a vertical beam with the boom (vehicle) capacitively
coupled to ground. It would work best on 10m-11m but should work
pretty well all the way down to 14 MHz. Probably not very useful
except for stationary use.

Actually, I experienced the same effect from a rear bumper mounted
screwdriver on my pickup. At the frequency where the truck is 1/4WL,
I experienced considerable gain in the direction the front of the
truck was pointed compared to off the sides of the truck. On one
Alaska contact from Arizona, it made the difference in being able
to carry on a QSO or not. It was a V-beam effect.
--
73, Cecil, W5DXP