Jay:

Thanks for your input.. A couple of things, though..

If the coax is being used as a counterpoise, it's not part of a
capacitive grounding system.

The capacitive ground comes from the metallic base/magnet mount to the
vehicle body, not from the coax.

-SSB

Jay in the Mojave wrote:

Hello All:

I have been reading most of the thread here and its quit good reading.

Great inputs from Frank, Sideband, Jimmie Lancer, Tnom, and others.

One main consideration on the magnetic mount antennas is that the coax
is being used as a counter poise and a lead for capacitance to ground.
So I can see where a manufacture will specify a 3/4 wavelength length of
coax, 18 feet.

Anytime you use the coax as a counter poise or other end of the antenna
coax lengths will effect the SWR, as the coax is no longer a simply a
transmission line, but now also a antenna. I would love to have the time
to do more testing.

You will not see this type of design in Military, Commercial, or Amateur
Antennas.

I got a old Wilson 5000 magnetmatic mount antenna that I rebuilt and use
on my car. I replaced the Krapy RG58C coax with "18" Ft of RG142B Teflon
type coax that is bullet proof. It works great. I get it surplus at times.

But I wanted to add 3 or 4 each, 9 foot ground plane radial wires, being
run over the body of the car, from the base of the antenna, connected to
the shield of the coax. And do a few tests. Food for thought.

One thing I may do as a quick add on improvement is add in a Toroid Core
in the coax about 9 feet down the coax from the antenna. Wrapping the
coax around a 2.4 inch OD Amidon Toroid Core, will choke the outer coax
shield currents from going farther down the coax, but allowing a 1/4
wave of coax to be a counter poise. Worth a try I think. It will also
reduce some interference noise heard by the radio, that are coming in
from the ungrounded shield of the coax. Neat-Oh!

Suggested Toroid Core Amidon FT-240-61
Amidon is at: http://www.amidoncorp.com/aai_productselection.htm

Jay in the Mojave

Kreedentials:
Rock n Roll Fan
Owner 1967 Ford F250, 4x4, with worlds loudest PA System
Took Electronics in 8th grade, way more better than that ackademic crap
that schools now teach kids now a days ancient European history, liberal
arts, and in incoming paper clips, in place of industrial arts.
Paid Member of Mojave Desert Radio Club, 9 dollars now.
Radio enthusiast type of guy

On Fri, 05 Nov 2004 22:22:03 GMT, sideband wrote
in :

Jay:

Thanks for your input.. A couple of things, though..

If the coax is being used as a counterpoise, it's not part of a
capacitive grounding system.

The capacitive ground comes from the metallic base/magnet mount to the
vehicle body, not from the coax.


That was an issue when I did the mag-mount tests a few months ago. As
it turns out, the coax can provide plenty of capacitive coupling to
the vehicle, even more than the mag-mount under certain conditions.
But neither of them provide much coupling, not nearly as much as would
be needed to compare with a properly mounted base.






----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

Agreed on the not-enough ground.. that's why counterpoise kits were
available for the W1000's... I had one that worked tits.

-SSB

Frank Gilliland wrote:

On Fri, 05 Nov 2004 22:22:03 GMT, sideband wrote
in :


Jay:

Thanks for your input.. A couple of things, though..

If the coax is being used as a counterpoise, it's not part of a
capacitive grounding system.

The capacitive ground comes from the metallic base/magnet mount to the
vehicle body, not from the coax.



That was an issue when I did the mag-mount tests a few months ago. As
it turns out, the coax can provide plenty of capacitive coupling to
the vehicle, even more than the mag-mount under certain conditions.
But neither of them provide much coupling, not nearly as much as would
be needed to compare with a properly mounted base.






----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---

Hello Sideband:

Really! What counterpoise kits?!?!?!?!?!??!!??!?!?!?
Who sold them, what, when, where?

Jay in the Mojave

Kreedentials:
Rock n Roll Fan
Owner 1967 Ford F250, 4x4, with worlds loudest PA System
Took Electronics in 8th grade, way more better than that ackademic crap
that schools now teach kids now a days, ancient European history,
liberal arts, and in incoming paper clips, in place of industrial arts.
Paid Member of Mojave Desert Radio Club, 9 dollars now. (Big party
coming up soon)
Radio enthusiast type of guy

sideband wrote:
Agreed on the not-enough ground.. that's why counterpoise kits were
available for the W1000's... I had one that worked tits.

-SSB

It was a snazzy little "8-pointed star" contraption that scewed onto
the magmount base, then the antenna coil screwed onto it.. Cost about
$15.. and they were worth their weight in gold, let me tell you. I got
mine in So.Cal. when I was stationed on Pandelton. BTW, if you get
down there, pop on ch 13 and tell Master Blaster that Crazy 1 said howdy.

Wish I could remember the name of the manufacturer, but I can't ... sorry.

-SSB

Jay in the Mojave wrote:

Hello Sideband:

Really! What counterpoise kits?!?!?!?!?!??!!??!?!?!?
Who sold them, what, when, where?

Jay in the Mojave

Kreedentials:
Rock n Roll Fan
Owner 1967 Ford F250, 4x4, with worlds loudest PA System
Took Electronics in 8th grade, way more better than that ackademic crap
that schools now teach kids now a days, ancient European history,
liberal arts, and in incoming paper clips, in place of industrial arts.
Paid Member of Mojave Desert Radio Club, 9 dollars now. (Big party
coming up soon)
Radio enthusiast type of guy

sideband wrote:

Agreed on the not-enough ground.. that's why counterpoise kits were
available for the W1000's... I had one that worked tits.

-SSB

"sideband" wrote in message
m...
It was a snazzy little "8-pointed star" contraption that scewed onto
the magmount base, then the antenna coil screwed onto it.. Cost about
$15.. and they were worth their weight in gold, let me tell you. I got
mine in So.Cal. when I was stationed on Pandelton. BTW, if you get
down there, pop on ch 13 and tell Master Blaster that Crazy 1 said howdy.

Wish I could remember the name of the manufacturer, but I can't ... sorry.

-SSB

Is this the same concept as the 3 point thing they used to sell for the 102"
whip that supposedly acted as ground radials?

Dr. D:

No.. This groundplane was actually on the shield side of the
equation.. the centerlead was never touched except for the passthru to
the coil. One PL-259 male and one PL-259 female connector on it, and
it screwed right on to the base.

-SSB

DR. Death wrote:

Is this the same concept as the 3 point thing they used to sell for the 102"
whip that supposedly acted as ground radials?

On Sat, 06 Nov 2004 16:12:37 GMT, sideband wrote:

It was a snazzy little "8-pointed star" contraption that scewed onto
the magmount base, then the antenna coil screwed onto it.. Cost about
$15.. and they were worth their weight in gold, let me tell you. I got
mine in So.Cal. when I was stationed on Pandelton. BTW, if you get
down there, pop on ch 13 and tell Master Blaster that Crazy 1 said howdy.


Surely you jest. Those little 3 inch "radial" kits were nothing more
than a gimmick. First of all, they were attached to the "active" side
of the antenna, and secondly they were way too small to make any
appreciable affect on signal.

To make any difference, it would have to provide a counterpoise which
was greater than the surface area of the car the antenna was attached
to.

I've known people who ran them, and other than look cool, they did
nothing for them........

Dave
"Sandbagger"

Dave:

I noted increased signal strength with it on, on both transmit and
receive..

The star didn't touch the "active" side at all.. it was on the shield
side of the equation..

Perhaps the star, being so close to the sheetmetal of the roof (on the
magmount), increased the capacitance, thus increasing the capacitive
grounding, providing a better RF ground. Who knows. I didn't have the
equipment to test for that 10 years ago when I had one I don't now,
either.. All I know is, it did more than look cool.

-SSB

Dave Hall wrote:

Surely you jest. Those little 3 inch "radial" kits were nothing more
than a gimmick. First of all, they were attached to the "active" side
of the antenna, and secondly they were way too small to make any
appreciable affect on signal.

To make any difference, it would have to provide a counterpoise which
was greater than the surface area of the car the antenna was attached
to.

I've known people who ran them, and other than look cool, they did
nothing for them........

Dave
"Sandbagger"

Bingo.

Don
313

"Dave Hall" wrote in message
...
On Sat, 06 Nov 2004 16:12:37 GMT, sideband wrote:

It was a snazzy little "8-pointed star" contraption that scewed onto
the magmount base, then the antenna coil screwed onto it.. Cost about
$15.. and they were worth their weight in gold, let me tell you. I got
mine in So.Cal. when I was stationed on Pandelton. BTW, if you get
down there, pop on ch 13 and tell Master Blaster that Crazy 1 said howdy.


Surely you jest. Those little 3 inch "radial" kits were nothing more
than a gimmick. First of all, they were attached to the "active" side
of the antenna, and secondly they were way too small to make any
appreciable affect on signal.

To make any difference, it would have to provide a counterpoise which
was greater than the surface area of the car the antenna was attached
to.

I've known people who ran them, and other than look cool, they did
nothing for them........

Dave
"Sandbagger"