help- Mobile 10meters on a jeep
 

On Feb 3, 12:47 pm, Cecil Moore wrote:
Fred McKenzie wrote:
If the roll bar is thick enough, you can drill and tap it to mount the
whip directly. Then use a gamma match so you don't have to worry about
insulating the mount.

Just don't touch the roll bar. :-)
--
73, Cecil http://www.w5dxp.com

Thanks for all the ideas guys. I'm still really interested in the
cophasing thing. I have mounted a CB whip on the roll bar before, but
it has two disadvantages: Extreme height of the antenna and the
inability to close the soft top while the antenna's up. Could I not
cophase diagonally and therefore center the patten ?

help- Mobile 10meters on a jeep
 

KE5MBX wrote:
I'm still really interested in the
cophasing thing. I have mounted a CB whip on the roll bar before, but
it has two disadvantages: Extreme height of the antenna and the
inability to close the soft top while the antenna's up. Could I not
cophase diagonally and therefore center the patten ?

First a few thoughts. Co-phasing doubles the cost of
the antenna without outperforming a single whip (unless
the elements are separated by 1/4WL or more). So
why not a magmount on the hood with a single whip?
That would be my solution but I'm not very "cool". :-)
My contacts could not tell the difference between the
magmount on the roof of my pickup Vs on my hood.

Phasing would work best front-to-back. With 135 degree
phasing in elements separated by 1/8WL, a whopping 4 dB
gain is possible switchable from front to back. If 1/4WL
spacing is possible, bidirectional front and back gain
of 3.5 dB is possible with 180 degree phasing. If I were
driving an 18 wheeler, this is what I would do. Changing
the phasing to 90 degrees would give me a front or back
vertical beam.

There's no reason why your co-phasing idea will not work.
The feedpoint impedance of the two elements in parallel
will be 1/2 of the impedance of each element transformed
by the length of coax chosen. If you put the coax 'T' 1/4WL
back from each element, the impedance at that point should
be close to the feedpoint impedance of each element (assuming
35 ohms).
--
73, Cecil http://www.w5dxp.com

help- Mobile 10meters on a jeep
 

On Feb 3, 2:02 pm, Cecil Moore wrote:
KE5MBX wrote:
I'm still really interested in the
cophasing thing. I have mounted a CB whip on the roll bar before, but
it has two disadvantages: Extreme height of the antenna and the
inability to close the soft top while the antenna's up. Could I not
cophase diagonally and therefore center the patten ?

First a few thoughts. Co-phasing doubles the cost of
the antenna without outperforming a single whip (unless
the elements are separated by 1/4WL or more). So
why not a magmount on the hood with a single whip?
That would be my solution but I'm not very "cool". :-)
My contacts could not tell the difference between the
magmount on the roof of my pickup Vs on my hood.

Phasing would work best front-to-back. With 135 degree
phasing in elements separated by 1/8WL, a whopping 4 dB
gain is possible switchable from front to back. If 1/4WL
spacing is possible, bidirectional front and back gain
of 3.5 dB is possible with 180 degree phasing. If I were
driving an 18 wheeler, this is what I would do. Changing
the phasing to 90 degrees would give me a front or back
vertical beam.

There's no reason why your co-phasing idea will not work.
The feedpoint impedance of the two elements in parallel
will be 1/2 of the impedance of each element transformed
by the length of coax chosen. If you put the coax 'T' 1/4WL
back from each element, the impedance at that point should
be close to the feedpoint impedance of each element (assuming
35 ohms).
--
73, Cecil http://www.w5dxp.com

Excellent.. If I put my antennas on opposite corners of the Jeep as I
was thinking, I find that they will be 4.2 meters apart. I promise to
go home and see what the ARRL handbook says about cophasing, but I
only understood what you just told me partially. Are you describing a
way to get better front/back gain from a system with one antenna in
front and one in back, as opposed to the conventional "trucker"
setup? I have no particular use for directional gain on 10 meters, by
the way.

I know a lot of people are reluctant to do the superior front-to-back
cophasing because it looks goofy, but I can assure I'm not interested
in being "cool" either! I want the most efficient 10-m operation I
can get out of a Jeep Wrangler.

help- Mobile 10meters on a jeep
 

"KE5MBX" wrote in message
ups.com...
On Feb 3, 2:02 pm, Cecil Moore wrote:
KE5MBX wrote:
I'm still really interested in the
cophasing thing. I have mounted a CB whip on the roll bar before, but
it has two disadvantages: Extreme height of the antenna and the
inability to close the soft top while the antenna's up. Could I not
cophase diagonally and therefore center the patten ?

First a few thoughts. Co-phasing doubles the cost of
the antenna without outperforming a single whip (unless
the elements are separated by 1/4WL or more). So
why not a magmount on the hood with a single whip?
That would be my solution but I'm not very "cool". :-)
My contacts could not tell the difference between the
magmount on the roof of my pickup Vs on my hood.

Phasing would work best front-to-back. With 135 degree
phasing in elements separated by 1/8WL, a whopping 4 dB
gain is possible switchable from front to back. If 1/4WL
spacing is possible, bidirectional front and back gain
of 3.5 dB is possible with 180 degree phasing. If I were
driving an 18 wheeler, this is what I would do. Changing
the phasing to 90 degrees would give me a front or back
vertical beam.

There's no reason why your co-phasing idea will not work.
The feedpoint impedance of the two elements in parallel
will be 1/2 of the impedance of each element transformed
by the length of coax chosen. If you put the coax 'T' 1/4WL
back from each element, the impedance at that point should
be close to the feedpoint impedance of each element (assuming
35 ohms).
--
73, Cecil http://www.w5dxp.com

Excellent.. If I put my antennas on opposite corners of the Jeep as I
was thinking, I find that they will be 4.2 meters apart. I promise to
go home and see what the ARRL handbook says about cophasing, but I
only understood what you just told me partially. Are you describing a
way to get better front/back gain from a system with one antenna in
front and one in back, as opposed to the conventional "trucker"
setup? I have no particular use for directional gain on 10 meters, by
the way.

I know a lot of people are reluctant to do the superior front-to-back
cophasing because it looks goofy, but I can assure I'm not interested
in being "cool" either! I want the most efficient 10-m operation I
can get out of a Jeep Wrangler.


Just go with one antenna.

help- Mobile 10meters on a jeep
 

"KE5MBX" wrote in message
oups.com...
I have been advised by some hams that the best way I can hope to do 10-
meters on my jeep is to mount my antenna ON THE WINDSHIELD to get a
good ground plane. I read somewhere since then that the primary
reason for cophasing CB antennas on trucks is NOT to direct the gain
front and back, but to even the ground plane as though the antenna
were in the center of the truck. Could I achieve the same effect with
my Jeep by cophasing antennas on either side of the jeep by the
doors? Even better- could I do this diagonally across from one corner
of my jeep to the other? I heard the further apart the antennas are,
the better, and I'm not really trying to get front/back gain for DXing.

When it is all said and done, *I* would go with a single 102" whip cut for
10 Meters and mounted via ball mount on the left rear fender. This will
work well, it is simple, and you will not be able to measure any appreciable
benefit as to pattern or gain with any phasing arrangement. The thing about
"cophasing" is more hype from the CB world (gullible people buy MORE
antennas if they think some gadget will work better ;) )! To each his own,
but I wouldn't go to all the trouble.

73

K4KWH

help- Mobile 10meters on a jeep
 

On Feb 3, 9:06 pm, "Jimmie D" wrote:
"KE5MBX" wrote in message

ups.com...



On Feb 3, 2:02 pm, Cecil Moore wrote:
KE5MBX wrote:
I'm still really interested in the
cophasing thing. I have mounted a CB whip on the roll bar before, but
it has two disadvantages: Extreme height of the antenna and the
inability to close the soft top while the antenna's up. Could I not
cophase diagonally and therefore center the patten ?

First a few thoughts. Co-phasing doubles the cost of
the antenna without outperforming a single whip (unless
the elements are separated by 1/4WL or more). So
why not a magmount on the hood with a single whip?
That would be my solution but I'm not very "cool". :-)
My contacts could not tell the difference between the
magmount on the roof of my pickup Vs on my hood.

Phasing would work best front-to-back. With 135 degree
phasing in elements separated by 1/8WL, a whopping 4 dB
gain is possible switchable from front to back. If 1/4WL
spacing is possible, bidirectional front and back gain
of 3.5 dB is possible with 180 degree phasing. If I were
driving an 18 wheeler, this is what I would do. Changing
the phasing to 90 degrees would give me a front or back
vertical beam.

There's no reason why your co-phasing idea will not work.
The feedpoint impedance of the two elements in parallel
will be 1/2 of the impedance of each element transformed
by the length of coax chosen. If you put the coax 'T' 1/4WL
back from each element, the impedance at that point should
be close to the feedpoint impedance of each element (assuming
35 ohms).
--
73, Cecil http://www.w5dxp.com

Excellent.. If I put my antennas on opposite corners of the Jeep as I
was thinking, I find that they will be 4.2 meters apart. I promise to
go home and see what the ARRL handbook says about cophasing, but I
only understood what you just told me partially. Are you describing a
way to get better front/back gain from a system with one antenna in
front and one in back, as opposed to the conventional "trucker"
setup? I have no particular use for directional gain on 10 meters, by
the way.

I know a lot of people are reluctant to do the superior front-to-back
cophasing because it looks goofy, but I can assure I'm not interested
in being "cool" either! I want the most efficient 10-m operation I
can get out of a Jeep Wrangler.

Just go with one antenna.

With all due respect, Jimmie, I am looking into creating a better
antenna system than the conventional dipole-on-the-back-of-the-CJ,
even if it was adequate for you. I like antenna theory.

help- Mobile 10meters on a jeep
 

"KE5MBX" wrote in message
oups.com...
On Feb 3, 9:06 pm, "Jimmie D" wrote:
"KE5MBX" wrote in message

ups.com...



On Feb 3, 2:02 pm, Cecil Moore wrote:
KE5MBX wrote:
I'm still really interested in the
cophasing thing. I have mounted a CB whip on the roll bar before,
but
it has two disadvantages: Extreme height of the antenna and the
inability to close the soft top while the antenna's up. Could I not
cophase diagonally and therefore center the patten ?

First a few thoughts. Co-phasing doubles the cost of
the antenna without outperforming a single whip (unless
the elements are separated by 1/4WL or more). So
why not a magmount on the hood with a single whip?
That would be my solution but I'm not very "cool". :-)
My contacts could not tell the difference between the
magmount on the roof of my pickup Vs on my hood.

Phasing would work best front-to-back. With 135 degree
phasing in elements separated by 1/8WL, a whopping 4 dB
gain is possible switchable from front to back. If 1/4WL
spacing is possible, bidirectional front and back gain
of 3.5 dB is possible with 180 degree phasing. If I were
driving an 18 wheeler, this is what I would do. Changing
the phasing to 90 degrees would give me a front or back
vertical beam.

There's no reason why your co-phasing idea will not work.
The feedpoint impedance of the two elements in parallel
will be 1/2 of the impedance of each element transformed
by the length of coax chosen. If you put the coax 'T' 1/4WL
back from each element, the impedance at that point should
be close to the feedpoint impedance of each element (assuming
35 ohms).
--
73, Cecil http://www.w5dxp.com

Excellent.. If I put my antennas on opposite corners of the Jeep as I
was thinking, I find that they will be 4.2 meters apart. I promise to
go home and see what the ARRL handbook says about cophasing, but I
only understood what you just told me partially. Are you describing a
way to get better front/back gain from a system with one antenna in
front and one in back, as opposed to the conventional "trucker"
setup? I have no particular use for directional gain on 10 meters, by
the way.

I know a lot of people are reluctant to do the superior front-to-back
cophasing because it looks goofy, but I can assure I'm not interested
in being "cool" either! I want the most efficient 10-m operation I
can get out of a Jeep Wrangler.

Just go with one antenna.

With all due respect, Jimmie, I am looking into creating a better
antenna system than the conventional dipole-on-the-back-of-the-CJ,
even if it was adequate for you. I like antenna theory.


I do to, but I also have learned from experience. I think co-phased mobiles
has become just a CB trick to sell more antennas. I do undurstand it has a
pratical side when truckers use them to overcome blind spots but this is nt
needed on a small vehicle(more experience). Where else have you ever seen
dual antennas except for CB. Let me be the last one who would ever
discourage a person from learning by trying as I have tried some really
wierd stuff before.

Jimmie

help- Mobile 10meters on a jeep
 

Maxrad makes a base loaded quarterwave that looks like their other land
mobile offerings that covers the 10m band. I bought two with NMO style
mounts and they worked very well for 10m several years ago. The reason I
had two whips was one cut for the low end of the band and the other cut
for the FM portion. When 10m was open I had no problem working everyone I
heard.

The nice thing is that they are reasonably low profile--on the order of a
5/8 wave whip on 2m--and work very well with a typical NMO magnet mount
on the roof of my S-10 pickup.

Have fun!

- Nate

--

"The optimist proclaims that we live in the best of all possible worlds,
the pessimist fears this is true."

help- Mobile 10meters on a jeep
 

Simple! Mount a 1/4 wavelength vertical on a mount that is well fastened to the
bumper/frame with good ground straps or spot welded.

Forget about the whole CB thing of co-phasing.

Ten meter mobile is the easiest HF mobile installation you can ever do.

/s/ DD, W1MCE [50+ years active. 40+ years mobile]

KE5MBX wrote:

I have been advised by some hams that the best way I can hope to do 10-
meters on my jeep is to mount my antenna ON THE WINDSHIELD to get a
good ground plane. I read somewhere since then that the primary
reason for cophasing CB antennas on trucks is NOT to direct the gain
front and back, but to even the ground plane as though the antenna
were in the center of the truck. Could I achieve the same effect with
my Jeep by cophasing antennas on either side of the jeep by the
doors? Even better- could I do this diagonally across from one corner
of my jeep to the other? I heard the further apart the antennas are,
the better, and I'm not really trying to get front/back gain for DXing.

help- Mobile 10meters on a jeep
 

On Feb 3, 9:59 pm, "Jerry" wrote:
"KE5MBX" wrote in message

oups.com...

I have been advised by some hams that the best way I can hope to do 10-
meters on my jeep is to mount my antenna ON THE WINDSHIELD to get a
good ground plane. I read somewhere since then that the primary
reason for cophasing CB antennas on trucks is NOT to direct the gain
front and back, but to even the ground plane as though the antenna
were in the center of the truck. Could I achieve the same effect with
my Jeep by cophasing antennas on either side of the jeep by the
doors? Even better- could I do this diagonally across from one corner
of my jeep to the other? I heard the further apart the antennas are,
the better, and I'm not really trying to get front/back gain for DXing.

When it is all said and done, *I* would go with a single 102" whip cut for
10 Meters and mounted via ball mount on the left rear fender. This will
work well, it is simple, and you will not be able to measure any appreciable
benefit as to pattern or gain with any phasing arrangement. The thing about
"cophasing" is more hype from the CB world (gullible people buy MORE
antennas if they think some gadget will work better ;) )! To each his own,
but I wouldn't go to all the trouble.

73

K4KWH



All right, all right. I'm thinking about maybe just using the CB whip
ball mount I currently have on the front/left fender. If anyone can
think of a good reason to charge ahead with the cophased stuff,
"please come with your call sign".

73, and thanks so much for all the inputs

Nelson Blaha KE5MBX