wrote:
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.

The ARRL Antenna Book assumes ~10 ohms of ground loss
for mobile antennas. I've found that 12.5 ohms is the
lowest I can get for a 75m mobile antenna feedpoint.
--
73, Cecil http://www.w5dxp.com

The ARRL Antenna Book assumes ~10 ohms of ground loss
for mobile antennas. I've found that 12.5 ohms is the
lowest I can get for a 75m mobile antenna feedpoint.



Yes, but most mobiles are cars or pickups. Wouldn't you think that
losses might be less on a large vehcle like an RV or truck, especially
with such a high feedpoint as previously suggested ( 10 feet ) ?



Ed

Ed wrote:
The ARRL Antenna Book assumes ~10 ohms of ground loss
for mobile antennas. I've found that 12.5 ohms is the
lowest I can get for a 75m mobile antenna feedpoint.

Yes, but most mobiles are cars or pickups. Wouldn't you think that
losses might be less on a large vehcle like an RV or truck, especially
with such a high feedpoint as previously suggested ( 10 feet ) ?

Sorry, I've been out of town for a few days and didn't
realize that an RV was being discussed.
--
73, Cecil http://www.w5dxp.com

Ed wrote:
"Wouldn`t you think that losses might be less on a large vehicle like an
RV or Truck,---."

I earlier rederred to an article by W1DBM in QST and an ARRL Antenna
Anthology from the 1970`s. The title was: "Antennas for Trailers and
Campers".

Everything old is new again. Please see the article: "Compact 40 Meter
Loop for Your Recreational Vehicle" by W6NBC on page 41 of the March
2007 QST.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Everything old is new again.

In one of the CA 75m shootouts, the strongest signal by far
was from a large RV with a motor-erected vertical on top.
Of course, it violated the 12.5 foot height-above-ground
limit for official entries. Heck, the top of the RV was
almost 12.5 foot above ground.
--
73, Cecil, w5dxp.com

Cecil Moore wrote in news:u%gIh.9028$jx3.5787
@newssvr25.news.prodigy.net:

Richard Harrison wrote:
Everything old is new again.

In one of the CA 75m shootouts, the strongest signal by far
was from a large RV with a motor-erected vertical on top.
Of course, it violated the 12.5 foot height-above-ground
limit for official entries. Heck, the top of the RV was
almost 12.5 foot above ground.
--
73, Cecil, w5dxp.com



A beautifully constructed 23' marine antenna on the roof with custom
fabricated lift mechanism, I believe? I think I saw that rig at Quartzite
in January. Fantastic.


Ed

(Richard Harrison) wrote in news:12998-
:

Ed wrote:
"Wouldn`t you think that losses might be less on a large vehicle like
an
RV or Truck,---."

I earlier rederred to an article by W1DBM in QST and an ARRL Antenna
Anthology from the 1970`s. The title was: "Antennas for Trailers and
Campers".

Everything old is new again. Please see the article: "Compact 40 Meter
Loop for Your Recreational Vehicle" by W6NBC on page 41 of the March
2007 QST.

Best regards, Richard Harrison, KB5WZI




I saw that. Neat idea, but as previously mentioned, I think, my
needed antenna design is for 80M, operation only while stopped, must be
vertical, and lastly, must not require me to climb up to the RV rooftop
to put it up or take it down. I have a good idea where I'm going with
this and will discuss the final product when it is completed ... probably
several weeks from now.



Ed




Ed

Ed wrote:
... as previously mentioned, I think, my
needed antenna design is for 80M, operation only while stopped, must be
vertical, and lastly, must not require me to climb up to the RV rooftop
to put it up or take it down. I have a good idea where I'm going with
this and will discuss the final product when it is completed ... probably
several weeks from now.

At one of the CA 75m shootouts, Sanford, W6YY had
a motorized 30 foot vertical mounted on top of his
huge RV. While he was traveling, it laid down against
the top of the RV. When he was stopped, he had it
motorized so he could raise it to a vertical position.
He beat the best of the best 75m mobile bugcatchers
and screwdrivers by 2 dB and beat a 75m hamstick
by about 14 dB. It's certainly worth considering.
--
73, Cecil http://www.w5dxp.com

On Mar 8, 10:01 pm, Cecil Moore wrote:
wrote:
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.

The ARRL Antenna Book assumes ~10 ohms of ground loss
for mobile antennas. I've found that 12.5 ohms is the
lowest I can get for a 75m mobile antenna feedpoint.
--
73, Cecil http://www.w5dxp.com


Well, in my book, they state it varied for the size vehicle. They
state as
low as 4-6 ohms, but I agree, thats kinda optimistic...
But it still really doesn't matter as far as designing the antenna.
It's going to be the same no matter what... And it's consideration
of current distribution, etc, etc, will be important.
My antenna design will be the same , no matter what the ground
loss. So I don't worry about it too much. I just accept what I get..
BTW, my book is getting a little old, "90's something" so maybe they
have changed that section.
MK