Mobile antenna shootout results?
 

Looking for a website with results of mobile antenna shootouts. Google
returns lots of hits, but not what I'm looking for. Any help?

Thanks,


--
Bill, W6WRT

Mobile antenna shootout results?
 

Bill Turner wrote:
Looking for a website with results of mobile antenna shootouts. Google
returns lots of hits, but not what I'm looking for. Any help?

I've got a short summary of three 20th century CA
shootouts on my web page at: www.w5dxp.com/shootout.htm
What is it that you are looking for?
--
73, Cecil http://www.w5dxp.com

Mobile antenna shootout results?
 

ORIGINAL MESSAGE:

On Tue, 05 Sep 2006 15:31:53 GMT, Cecil Moore
wrote:

I've got a short summary of three 20th century CA
shootouts on my web page at: www.w5dxp.com/shootout.htm
What is it that you are looking for?

------------ REPLY FOLLOWS ------------

Your website answers my question. I was looking for comparisons
between the various antenna designs. Big coils and top hats win, knew
that already, but nice to see the dB figures.

Thanks.


--
Bill, W6WRT

Mobile antenna shootout results?
 

Bill Turner wrote:
Your website answers my question. I was looking for comparisons
between the various antenna designs. Big coils and top hats win, knew
that already, but nice to see the dB figures.

Big center-loaded coils with Big top hats on
Big vehicles win. :-)
--
73, Cecil http://www.w5dxp.com

Mobile antenna shootout results?
 

Bill Turner wrote:
ORIGINAL MESSAGE:

On Tue, 05 Sep 2006 15:31:53 GMT, Cecil Moore
wrote:

I've got a short summary of three 20th century CA
shootouts on my web page at: www.w5dxp.com/shootout.htm
What is it that you are looking for?

------------ REPLY FOLLOWS ------------

Your website answers my question. I was looking for comparisons
between the various antenna designs. Big coils and top hats win, knew
that already, but nice to see the dB figures.

I don't see any information at that web site about the type of vehicle.
Since the vehicle radiates an amount comparable to the antenna, it can
have a profound effect on the overall field strength. Were all those
antennas mounted on the same type of vehicle?

Roy Lewallen, W7EL

Mobile antenna shootout results?
 

Roy Lewallen wrote:
I don't see any information at that web site about the type of vehicle.
Since the vehicle radiates an amount comparable to the antenna, it can
have a profound effect on the overall field strength. Were all those
antennas mounted on the same type of vehicle?

Those are averages, Roy, not associated with any particular
vehicle. The average screwdriver beats the average hamstick
on 75m. Using similar antennas, the larger vehicles (GMC
pickups) usually beat the smaller vehicles (Honda Civics).
--
73, Cecil http://www.w5dxp.com

Mobile antenna shootout results?
 

"Cecil Moore" wrote in message
et...
Roy Lewallen wrote:
I don't see any information at that web site about the type of vehicle.
Since the vehicle radiates an amount comparable to the antenna, it can
have a profound effect on the overall field strength. Were all those
antennas mounted on the same type of vehicle?

Those are averages, Roy, not associated with any particular
vehicle. The average screwdriver beats the average hamstick
on 75m. Using similar antennas, the larger vehicles (GMC
pickups) usually beat the smaller vehicles (Honda Civics).
--
73, Cecil http://www.w5dxp.com

Makes sense.
Also confirms my experience.
I've also found optimum performance driving the antenna where it's resonant
and matching the (purely resistive) impedances with a transformer.
In this case a simple toroidal autoformer. At 40 meters, a Tarheel
screwdriver with a five-foot whip is about 20 ohms, for example.
73
H.

Mobile antenna shootout results?
 

H. Adam Stevens, NQ5H wrote:
"Cecil Moore" wrote in message
et...
Roy Lewallen wrote:
I don't see any information at that web site about the type of vehicle.
Since the vehicle radiates an amount comparable to the antenna, it can
have a profound effect on the overall field strength. Were all those
antennas mounted on the same type of vehicle?

Those are averages, Roy, not associated with any particular
vehicle. The average screwdriver beats the average hamstick
on 75m. Using similar antennas, the larger vehicles (GMC
pickups) usually beat the smaller vehicles (Honda Civics).
--
73, Cecil http://www.w5dxp.com

Makes sense.
Also confirms my experience.
I've also found optimum performance driving the antenna where it's resonant
and matching the (purely resistive) impedances with a transformer.
In this case a simple toroidal autoformer. At 40 meters, a Tarheel
screwdriver with a five-foot whip is about 20 ohms, for example.
73
H.

First time I noticed this was in the early 70s after I put a CB radio
on a school bus camper. The same radio and antenna had been on a
Volkswagon before. The difference was very noticable.

Mobile antenna shootout results?
 

"JIMMIE" wrote in message
oups.com...

H. Adam Stevens, NQ5H wrote:
"Cecil Moore" wrote in message
et...
Roy Lewallen wrote:
I don't see any information at that web site about the type of
vehicle.
Since the vehicle radiates an amount comparable to the antenna, it can
have a profound effect on the overall field strength. Were all those
antennas mounted on the same type of vehicle?

Those are averages, Roy, not associated with any particular
vehicle. The average screwdriver beats the average hamstick
on 75m. Using similar antennas, the larger vehicles (GMC
pickups) usually beat the smaller vehicles (Honda Civics).
--
73, Cecil http://www.w5dxp.com

Makes sense.
Also confirms my experience.
I've also found optimum performance driving the antenna where it's
resonant
and matching the (purely resistive) impedances with a transformer.
In this case a simple toroidal autoformer. At 40 meters, a Tarheel
screwdriver with a five-foot whip is about 20 ohms, for example.
73
H.

First time I noticed this was in the early 70s after I put a CB radio
on a school bus camper. The same radio and antenna had been on a
Volkswagon before. The difference was very noticable.


That must have been an increase in surface area for the ground side of
things of something like an order of magnitude.
I bet it was a striking difference.
73
H.

Mobile antenna shootout results?
 

Can I ask who uses what in the mobile antenna stakes.

To help narrow it down abit my car is a small one. a peugeot 206 sw /
estate.

Have just bought an HF radio for it and looking to find the "right" antenna.

Looking for opinions. I'm edging towards a little tarheel 2 but that means
getting it shipped to the uk.

the 20 meter monoband that i bought looks a bit on the long side.

Any advice?

Alan

Mobile antenna shootout results?
 

Alan wrote:
Can I ask who uses what in the mobile antenna stakes.

To help narrow it down a bit, my car is a small one. a peugeot 206 sw /
estate.

That's your first mistake. Get a full-sized pickup. :-)

Any advice?

Gigantic bugcatchers or screwdrivers with gigantic
top hats are the best.
--
73, Cecil http://www.w5dxp.com

Mobile antenna shootout results?
 

To help narrow it down a bit, my car is a small one. a peugeot 206 sw /
estate.

That's your first mistake. Get a full-sized pickup. :-)

Oh How i wish... trouble is we have to pay way way way too much for our fuel
over here.

Any advice?

Gigantic bugcatchers or screwdrivers with gigantic
top hats are the best.


I guessed they might be but does anybody use a smaller antenna as a
compromise?

Mobile antenna shootout results?
 

On Sun, 10 Sep 2006 08:02:14 GMT, "Alan" wrote:

I guessed they might be but does anybody use a smaller antenna as a
compromise?

Hi Alan,

Sure. So's the signal (a compromise). When you get into fractional
wavelength sizes (and we're talking on the order of less than 5% of
wavelength), you quickly get into fractional performance. It has to
do with the comparison of the radiation resistance which at 5% is 2
Ohms. This is 25:1 mismatch, and the matching components are going to
have to present less than 2 Ohms in themselves (not forgetting all the
connections that support the circulating currents) just to limit your
loss to 3dB.

If it were easy, few shootout contestants would be running 10dB below
the winners.

Still and all, even if your 100W signal ends up radiating 10W, lots of
folks have worked the world with less.

73's
Richard Clark, KB7QHC

Mobile antenna shootout results?
 

"Alan" wrote in message
...

To help narrow it down a bit, my car is a small one. a peugeot 206 sw /
estate.

That's your first mistake. Get a full-sized pickup. :-)

Oh How i wish... trouble is we have to pay way way way too much for our
fuel over here.

Any advice?

Gigantic bugcatchers or screwdrivers with gigantic
top hats are the best.


I guessed they might be but does anybody use a smaller antenna as a
compromise?


A center-loaded antenna will usually do best.
If you don't use a screwdriver or bug catcher, try a Hustler with the big
coil.
For lower bands the feed point impedance at resonance will be quite a bit
less than 50 ohms, so some impedance-matching scheme is in order.
The worst thing you can do is a whip and a tuner.
Cheers
H.
NQ5H

Mobile antenna shootout results?
 

On Sun, 10 Sep 2006 01:27:08 -0700, Richard Clark
wrote:

On Sun, 10 Sep 2006 08:02:14 GMT, "Alan" wrote:

I guessed they might be but does anybody use a smaller antenna as a
compromise?

Hi Alan,

Sure. So's the signal (a compromise). When you get into fractional
wavelength sizes (and we're talking on the order of less than 5% of
wavelength), you quickly get into fractional performance. It has to
do with the comparison of the radiation resistance which at 5% is 2
Ohms. This is 25:1 mismatch, and the matching components are going to
have to present less than 2 Ohms in themselves (not forgetting all the
connections that support the circulating currents) just to limit your
loss to 3dB.

Richard,

May I expand on a couple of your points.

Amateurs are very focused on VSWR.

Additionally, they hate narrowband mobile antennas.

Radiation resistance of short verticals on low HF bands is very low,
whether or not they are base loaded, centre loaded, top loaded,
capacitively loaded, or continuously loaded.

Even when the resistance of the radiating car body and earth coupling
are added in, the direct base impedance of a short loaded resonated
vertical mounted on a car is well below 50 ohms.

If the loading coil is made sufficiently lossy, then the feedpoint
resistance can be raised sufficiently to satisfy a "reasonable" VSWR
spec, in fact the better (lower) the VSWR spec for direct feeding, the
lossier the loading coil need to be.

The upside of this is that the bandwidth is expanded, isn't that good!

We have delivered on the two most important criteria!

Well, these things (simplified feed arrangement for tolerable VSWR,
better bandwidth) are obtained at the expense of efficiency.

If you view the world through an VSWR meter, you will be pleased with
short direct fed verticals for cars.

If you want efficiency, then it will almost certainly require a base
matching network.

With a suitable base matching network and low loss loading coils, you
may still achieve reasonable efficiency in a shorter vertical, though
low loss coils are not low profile! Secondly, commercial manufacturers
of low loss verticals skip straight to long antennas.

Like Richard, I am sure lots of people will be happy that anything
"works".

Owen
--

Mobile antenna shootout results?
 

Alan wrote:

Gigantic bugcatchers or screwdrivers with gigantic
top hats are the best.


I guessed they might be but does anybody use a smaller antenna as a
compromise?




Hard to catch those giant bugs that way ;)

Phil W7OX