wrote in news:1173412553.256780.306530@
8g2000cwh.googlegroups.com:

On Mar 5, 11:40 pm, Ed wrote:
I am wondering how ground loss/resistance is effected by my
having the bottom/feedpoint of the antenna so high off the ground,
not
to mention, I wonder how to calculate or guess what it is at all.

The bigger the vehicle, and the higher the mount, the lower the ground
losses. But the type mount will effect also. IE: mounting directly on
a
roof will almost always be better than mounting on a ladder, with both
at the same height. I've found that the more metal under the base of
the antenna , the better. Mounting on a ladder, thin metal rail,
angle
iron, etc will usually result in inferior performance. But..Sometimes
there is nothing you can do about it if the mounting options are
limited. I ran into this on one of my trucks. At first I mounted the
antenna on a piece of angle iron that ran across the truck bed,
just behind the back window. Both ends were well grounded.
But, I kept seeing overall lousy performance. So I decided to
move it over on top of one the tool boxes, which has a good deal
more metal area under the antenna base. Made a large difference,
and woke the antenna up. That truck has a utility bed, and the
boxes are pretty much part of the body. I'm not talking about
a toolbox thrown into the back of the truck. Often those are
not the greatest, unless very well grounded. I don't see why
you need the exact ground loss. It's not going to effect your
antenna design. But when doodling with vertical programs, I'll
just stick in about 6-8 ohms as a "very good" mobile ground
example.. A huge truck with the antenna on top could be slightly
lower, but many small cars will be much higher. Knowing the
exact loss is really not critical. Your antenna design will still
come
out the same.
MK


Thank you very much for the helpful info to my situation. The RV roof
is fibreglass. All I have to really work with is the ladder, which in
itself is bonded to the aluminum frame in the back walls, as well as very
well bonded to the chassis underneath by means of large copper straps.
Bout the best I can do. The figures you suggested should help too.
Thanks again.

Ed K7AAT

On 09 Mar 2007 07:24:38 GMT, Ed
wrote:

Thank you very much for the helpful info to my situation. The RV roof
is fibreglass. All I have to really work with is the ladder, which in
itself is bonded to the aluminum frame in the back walls, as well as very
well bonded to the chassis underneath by means of large copper straps.
Bout the best I can do. The figures you suggested should help too.
Thanks again.

Hi Ed,

You've gotten several suggestions. 6-8 Ohms is no better than 10-12
Ohms as a guess; however, just what does this program do that this
number is so important in performing what it does?

73's
Richard Clark, KB7QHC

You've gotten several suggestions. 6-8 Ohms is no better than 10-12
Ohms as a guess; however, just what does this program do that this
number is so important in performing what it does?


mobile.exe is a little DOS based program that gives you radiation
efficiency, Q factor, etc, after you input several proposed design
measurements of a mobile antenna. When calculating these antenna
parameters for a "fixed station" type of mounting, ( not on a vehicle, I
guess), ground loss is one figure required for input. It is NOT a
required input when figuring for mounting on a vehicle, I just realized.


Ed

Ed wrote:
It is NOT a
required input when figuring for mounting on a vehicle, I just realized.

Does it require one to input the type of vehicle?
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote in news:ahiIh.6363$M65.6276
@newssvr21.news.prodigy.net:

Ed wrote:
It is NOT a
required input when figuring for mounting on a vehicle, I just
realized.

Does it require one to input the type of vehicle?


yes, input selections are pretty much based on vehicle size; largest
vehicle choice is a Van type. Last choice is "fixed station" which I
assume means no vehicle at all.. and that is the only choice requiring a
ground loss entry. Since my proposed antenna is for an RV, it appears I
really needn't have asked the ground loss question at all!

mobile.exe is a rather neat little DOS program located on the CD in
the back of newer ARRL antenna books, I believe.... maybe in the Handbook
too, I'm not sure on that.


Ed

On 09 Mar 2007 19:32:20 GMT, Ed
wrote:

mobile.exe is a rather neat little DOS program located on the CD in
the back of newer ARRL antenna books, I believe.... maybe in the Handbook
too, I'm not sure on that.

Hi Ed,

Doesn't sound worth the clock cycles to run it when a Magic 8-Ball
would be just as accurate.

You can get better results from the free version of EZNEC because you
know what you've put in and what relationship it has to the whole. If
you belly up to the bar and buy the full-blown version, then you can
design a model of your antenna, RV, ladder and frame.

73's
Richard Clark, KB7QHC

Richard Clark wrote in
:

On 09 Mar 2007 19:32:20 GMT, Ed
wrote:

mobile.exe is a rather neat little DOS program located on the CD in
the back of newer ARRL antenna books, I believe.... maybe in the
Handbook too, I'm not sure on that.

Hi Ed,

Doesn't sound worth the clock cycles to run it when a Magic 8-Ball
would be just as accurate.

You can get better results from the free version of EZNEC because you
know what you've put in and what relationship it has to the whole. If
you belly up to the bar and buy the full-blown version, then you can
design a model of your antenna, RV, ladder and frame.

73's
Richard Clark, KB7QHC



Didn't realize there was a free version. I had been thinking of biting
the bullet and buying it, but wasn't sure if I would like the program. A
freebie access to it will allow me to decide.

. . . off to download....



Ed