"Cecil Moore" wrote in message
et...
Sum Ting Wong wrote:
Yeah, that was ugly. I also noticed the author used what appeared to
be a base loaded motorized antenna and then concluded that the
motorized antennas weren't worth a hoot. There are some decent center
loaded ones out there that would have given better results. Base
loaded antennas are probably the worst possible case, based on my
experience. Wonder how that article made it past the editor?

I added a top hat and "RV extension" to my HS-1600
that doubled the length of the bottom section. Here's
a picture and the combined results of three CA
shootouts from about 20 years ago. There don't seem to
have been any break-throughs since then.
--
73, Cecil http://www.w5dxp.com

Cecil,

I haven't read the article, but if the guy is claiming that his "tuner'
thing is better than a center-loaded bugcatcher or reasonable sized
screwdriver (FULL sized), I would LOVE to get in on any wagers he is
prepared to entertain! (Snickers and unintentional "razzberries" beginning a
crescendo and bursting into loud, uncontrollable guffaws and knee slaps!)

You mean they actually allow people like THAT to WRITE that s--- in
magazines?


73

Jerry
K4KWH

Jerry wrote:

I haven't read the article, but if the guy is claiming that his "tuner'
thing is *better than a center-loaded bugcatcher or reasonable sized
screwdriver (FULL sized), I would LOVE to get in on any wagers he is
prepared to entertain! (Snickers and unintentional "razzberries" beginning
a crescendo and bursting into loud, uncontrollable guffaws and knee
slaps!)



No, it wasn't quite that bad. The author though seems to have used a tuner
to match to the antennas being tested and then coming to some conclusion
about how well said antenna radiated energy to a relatively nearby field
strength meter (360 feet). One basic problem is that you then end up with
some signal level which may or may not be equal to the original output from
the rig (apparently an ICOM 706-MKIIG) reaching the antenna. That might
make the rig happy but it does leave the antenna with an awfully funny feed
at times, one that could be oh 3 dB or so down from what the rig puts out.

I haven't read the article, but are different mobile antennas being
compared on different vehicles, or the same vehicle? It's amazing how
many people don't realize that the vehicle is fully half the antenna,
and may in many cases play a more important role in determining overall
radiating efficiency than the supposed "antenna". So it's impossible to
draw any conclusions about mobile antennas based on comparisons done
when they're mounted on different vehicles. It's as much a test of the
vehicle's effectiveness as a radiator as it is the antenna's.

Roy Lewallen, W7EL

Roy Lewallen wrote:

I haven't read the article, but are different mobile antennas being
compared on different vehicles, or the same vehicle? It's amazing how
many people don't realize that the vehicle is fully half the antenna,
and may in many cases play a more important role in determining overall
radiating efficiency than the supposed "antenna". So it's impossible to
draw any conclusions about mobile antennas based on comparisons done
when they're mounted on different vehicles. It's as much a test of the
vehicle's effectiveness as a radiator as it is the antenna's.


Same vehicle, at least that part was correct

Roy Lewallen wrote:
I haven't read the article, but are different mobile antennas being
compared on different vehicles, or the same vehicle? It's amazing how
many people don't realize that the vehicle is fully half the antenna,
and may in many cases play a more important role in determining overall
radiating efficiency than the supposed "antenna". So it's impossible to
draw any conclusions about mobile antennas based on comparisons done
when they're mounted on different vehicles. It's as much a test of the
vehicle's effectiveness as a radiator as it is the antenna's.

Roy Lewallen, W7EL

OK Roy you lost me.

I'll confess that I'm one of those new no code guys that concentrated on
the answer pool for three months in order to get an Extra Class license.
What I'm trying to do now is relearn enough electronics to become a
competent communicator for EMCOM purposes. You see back when I was last
in radio your transmitter would keep you warm and provide enough light
to read the manual by. Now it is thirty years since my Novice license
expired and not only are the newer radios all solid state they do most
of their signal processing digitally. By my point of view that only
makes me as yet not fully trained rather than the devils personal
representative in amateur radio.

Are you being serious when you say that much of the difference in the
mobile rigs performance may be the vehicle on which it and therefore
it's antenna are mounted? IS the body of my half ton cargo van doing a
substantial amount of the job of radiating my signal? If I mounted the
same antenna with the same mount on my Saturn should I see a difference
on a field strength meter that is the same distance to the centimeter
from the antenna over the same parking lot with the antenna over exactly
the same spot?
--
Tom Horne, W3TDH

Tom Horne wrote:

OK Roy you lost me.

I'll confess that I'm one of those new no code guys that concentrated on
the answer pool for three months in order to get an Extra Class license.
What I'm trying to do now is relearn enough electronics to become a
competent communicator for EMCOM purposes. You see back when I was last
in radio your transmitter would keep you warm and provide enough light
to read the manual by. Now it is thirty years since my Novice license
expired and not only are the newer radios all solid state they do most
of their signal processing digitally. By my point of view that only
makes me as yet not fully trained rather than the devils personal
representative in amateur radio.

Fortunately, antennas still operate the same way they did back when
rectifiers glowed blue. In fact, the same as they did when you had to
poke a catwhisker around your rectifier.

Are you being serious when you say that much of the difference in the
mobile rigs performance may be the vehicle on which it and therefore
it's antenna are mounted?

Yes.

IS the body of my half ton cargo van doing a
substantial amount of the job of radiating my signal?

Yes.

If I mounted the
same antenna with the same mount on my Saturn should I see a difference
on a field strength meter that is the same distance to the centimeter
from the antenna over the same parking lot with the antenna over exactly
the same spot?

Yes.

Declaring a vehicle to be "ground" doesn't give it magic properties.
It's a conductor, just like the antenna. Exactly the same current that
flows upward on your antenna flows downward along your vehicle. The
vehicle and "antenna" comprise an asymmetrical dipole, and neither half
is inherently more or less important than the other.

Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
...
Tom Horne wrote:

OK Roy you lost me.

I'll confess that I'm one of those new no code guys that concentrated on
the answer pool for three months in order to get an Extra Class license.
What I'm trying to do now is relearn enough electronics to become a
competent communicator for EMCOM purposes. You see back when I was last
in radio your transmitter would keep you warm and provide enough light to
read the manual by. Now it is thirty years since my Novice license
expired and not only are the newer radios all solid state they do most of
their signal processing digitally. By my point of view that only makes
me as yet not fully trained rather than the devils personal
representative in amateur radio.

Fortunately, antennas still operate the same way they did back when
rectifiers glowed blue. In fact, the same as they did when you had to poke
a catwhisker around your rectifier.

Are you being serious when you say that much of the difference in the
mobile rigs performance may be the vehicle on which it and therefore it's
antenna are mounted?

Yes.

IS the body of my half ton cargo van doing a substantial amount of the
job of radiating my signal?

Yes.

If I mounted the same antenna with the same mount on my Saturn should I
see a difference on a field strength meter that is the same distance to
the centimeter from the antenna over the same parking lot with the
antenna over exactly the same spot?

Yes.

Declaring a vehicle to be "ground" doesn't give it magic properties. It's
a conductor, just like the antenna. Exactly the same current that flows
upward on your antenna flows downward along your vehicle. The vehicle and
"antenna" comprise an asymmetrical dipole, and neither half is inherently
more or less important than the other.

Roy Lewallen, W7EL

Roy is certainly right! The vehicle is the other half of the "dipole". It
is why if you stick a bugcatcher at random on a broomstick, it won't work:
SWR will be thru the roof.. Or you could hang a dipole for a given band
(your choice), then snip off the side that went to the coax shield (or vice
versa). So, yes, the vehicle is the other half of the antenna. You could
even look at it as an right-side up "L"!

73

Jerry
K4KWH

Jerry wrote:

Roy is certainly right! The vehicle is the other half of the "dipole". It
is why if you stick a bugcatcher at random on a broomstick, it won't work:
SWR will be thru the roof.. Or you could hang a dipole for a given band
(your choice), then snip off the side that went to the coax shield (or vice
versa). So, yes, the vehicle is the other half of the antenna. You could
even look at it as an right-side up "L"!

You have to look at where the currents go. If you had a completely
symmetrical vehicle and put the antenna at the very center of the top,
the horizontal currents along the top would produce fields that almost
completely cancel, just like a bunch of radials. But when they reach the
edge and flow downward, the fields are all in the same direction and
add. So it radiates just like a very fat wire.

But if you put an antenna on the edge of the roof, then the fields from
the horizontal currents won't cancel and you'll have some radiation from
the top as well as the sides. And so forth.

Roy Lewallen, W7EL

"Jerry" wrote in message
news

Roy is certainly right! The vehicle is the other half of the "dipole".
It
is why if you stick a bugcatcher at random on a broomstick, it won't work:
SWR will be thru the roof.. Or you could hang a dipole for a given band
(your choice), then snip off the side that went to the coax shield (or
vice
versa). So, yes, the vehicle is the other half of the antenna. You could
even look at it as an right-side up "L"!

Ditto.

I worked Navy EMI for many years. The US Navy uses a variety of antennas
for HF transmissions on its ships. The hull of the ship and everything in
it conduct the HF, no matter what the antenna. Everything on a ship is
conducting HF at such levels that they're often high enough to interfere
with other equipment.

If Paul Harvey were here, he'd say, " ... and now you know the rest of the
antenna."

"Roy Lewallen" wrote in message
...

Declaring a vehicle to be "ground" doesn't give it magic properties. It's
a conductor, just like the antenna. Exactly the same current that flows
upward on your antenna flows downward along your vehicle. The vehicle and
"antenna" comprise an asymmetrical dipole, and neither half is inherently
more or less important than the other.

Roy Lewallen, W7EL


That is rather simplistic and not reality reflecting explanation.
Like saying that ground plane, vertical antenna is a dipole.
Vehicle body represents "ground plane" similar to two or more radials. The
current flows along the surface of the vehicle, just as along the more
elaborate ground plane consisting of more than say 8 radials. Cancellation
of current along the body happens, just like in opposite radials in GP.
Radiation pattern is formed between the RADIATOR (whip) and GROUND PLANE
(vehicle body).
Additional effect is that vehicle "ground plane" is capacitively coupled to
the ground and this is reflected in changes in efficiency depending on the
surroundings ground conditions (salty, wet ground, reinforced concrete
bridges, etc.)

As far as I understand, dipole refers to dual pole antenna with symmetrical
current distribution. Vertical antenna mounted on conducting body of vehicle
has current distribution in the "other pole" far from symmetrical. This can
be seen in modeling in EZNEC. Try to compare vertical whip mounted on
vehicle, with dipole that has one leg horizontal and you will see the
difference, far from "nice dipole" antenna.

So as soon as we have more than one radial, and some (horizontal)
cancellation is happening it ain't no dipole. It is monopole forming
vertical pattern against the ground plane (radials, vehicle body).

That's the way I understand it, without involving photons, Gaussss and other
farticles :-)

73 Yuri, K3BU