On 28 Oct 2003 05:05:13 -0800, (Parallax)
wrote:


I never said I had good ideas. However, I realize that somehow you
better disconnect the connection when the VHF or radar is used. I
also forgot about impedance matching (my god, alzheimers, I taught an
engineering lab on impedance matching once). I really don't know how
a radar antenna works on small boats. If it is just a rotating dish,
it oughta work with the right transducer.


The kind with a dome has a printed-circuit board with an array of
little antenna elements with fixed phase relationship that produces
the beam and receives the echoes. The open ones are slotted wave
guides AFIK. I don't see how either would help a cell phone.



Rodney Myrvaagnes NYC J36 Gjo/a

"Religious wisdom is to wisdom as military music is to music."

In article ,
(Parallax) wrote:

For ppl who really want to stay connected while afloat ( I dunno why
but they do). Useless Idea #3734

snipped for being "to Stupid to Republish"

I never said I had good ideas. However, I realize that somehow you
better disconnect the connection when the VHF or radar is used. I
also forgot about impedance matching (my god, alzheimers, I taught an
engineering lab on impedance matching once). I really don't know how
a radar antenna works on small boats. If it is just a rotating dish,
it oughta work with the right transducer.

OK, an even worse idea.......Use your radar (I dont have one) as a
high gain antenna to point toward a cell tower. It ought to work for
900 Mhz. Some electronics could figger out the direction to the best
tower.

would be nice if folks who don't have a clue would just say they 'Don't
have a clue"


From Jim Woodward

3) The radar antenna idea actually has some technical merit,

and this "technical merit" would be?????
Cellphone 800Mhz
xBand radar 10Ghz
Bzzzt, Try again.......

Well not that the "Moorons" have finished lets hope Sanity wins out.....

Bruce in alaska
--
add a 2 before @

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 27 Oct 2003 15:39:00 -0800,
Parallax wrote:
My posts havent been gittin through fer some reason so I'm gonna
repost this one.

For ppl who really want to stay connected while afloat ( I dunno why
but they do). Useless Idea #3734

Put a T in the output of your VHF so your cellphone can be connected
to your VHF antenna waaaaaaaaay up thar on your mast. Since your 900
Mhz cellphone is even more line-of-sight than vhf, this will give you
more more coverage when you are a few miles out. In this case, I
expect coverage will then be limited by cellphone power instead of by
not being able to see a tower. I would expect to be able to get
coverage from 15 miles out. I once experimented, while standing on my
cabin top, I was able to use my cell phone while being 6 miles
offshore. Would a cell phone booster be illegal?


Wrong kind of antenna, most Cell phones are 800-900MHz, PCS is around
1.2GHz IIRC, and some are 1.8GHz. The VHF antenna, is expecting to see
about 150MHz. Bast case scenario, it simply doesn't work. If you were so
unfortunate as to key up the VHF while it was connected, that acrid
smell you'd experience, would be the death throes of the the cell phone.

THat's without getting into the whole issue of impedence mismatch. In
short, don't even go there.


Get a booster, buy a type approved one, and you'll be fine.

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.3 (GNU/Linux)

iD8DBQE/n1DVd90bcYOAWPYRAn0iAJwPNTQnx9XhdNIMNlp9SxalrnzQPw Cg5kam
yLS6xkLP/nF3mQkEm83+kz0=
=cnWj
-----END PGP SIGNATURE-----

--
Jim Richardson http://www.eskimo.com/~warlock
If ignorance is bliss, why aren't more people happy?

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Tue, 28 Oct 2003 16:18:57 -0500,
Rodney Myrvaagnes wrote:
On 28 Oct 2003 05:05:13 -0800, (Parallax)
wrote:


I never said I had good ideas. However, I realize that somehow you
better disconnect the connection when the VHF or radar is used. I
also forgot about impedance matching (my god, alzheimers, I taught an
engineering lab on impedance matching once). I really don't know how
a radar antenna works on small boats. If it is just a rotating dish,
it oughta work with the right transducer.


The kind with a dome has a printed-circuit board with an array of
little antenna elements with fixed phase relationship that produces
the beam and receives the echoes. The open ones are slotted wave
guides AFIK. I don't see how either would help a cell phone.


If they were the right freq, it would work, at least the antenna part.
Still have to deal with impedence issues.

The slotted wavguide type, are called "Alford" antenna's and they
basically act like an array of verticle dipoles. Except they are
horizontally polarized. The PCB looking ones, are microstrip patch
arrays.

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.3 (GNU/Linux)

iD8DBQE/n1Ghd90bcYOAWPYRAl2zAJ4qlPPEVjtuT9JC8Vvu49wI6E/ycgCfV7J4
F2dRPD5SOoPUGOU0TpBs5fY=
=vosS
-----END PGP SIGNATURE-----

--
Jim Richardson http://www.eskimo.com/~warlock
Think for yourselves and allow others the privilege to do the same.
- Voltare

Come on, Bruce, lighten up. Of course it's a really dumb idea -- many
of Parallax's ideas are dumb and he says so. Occasionally, though, he
gets me thinking along unconventional lines, so I go along with the
gag on some of his dumbest ones....

Jim Woodward
www.mvFintry.com

Bruce in Alaska wrote in message ...
In article ,
(Parallax) wrote:

For ppl who really want to stay connected while afloat ( I dunno why
but they do). Useless Idea #3734

snipped for being "to Stupid to Republish"

I never said I had good ideas. However, I realize that somehow you
better disconnect the connection when the VHF or radar is used. I
also forgot about impedance matching (my god, alzheimers, I taught an
engineering lab on impedance matching once). I really don't know how
a radar antenna works on small boats. If it is just a rotating dish,
it oughta work with the right transducer.

OK, an even worse idea.......Use your radar (I dont have one) as a
high gain antenna to point toward a cell tower. It ought to work for
900 Mhz. Some electronics could figger out the direction to the best
tower.

would be nice if folks who don't have a clue would just say they 'Don't
have a clue"


From Jim Woodward

3) The radar antenna idea actually has some technical merit,

and this "technical merit" would be?????
Cellphone 800Mhz
xBand radar 10Ghz
Bzzzt, Try again.......

Well not that the "Moorons" have finished lets hope Sanity wins out.....

Bruce in alaska

"Meindert Sprang" wrote in message ...
"Parallax" wrote in message
om...
I really don't know how
a radar antenna works on small boats. If it is just a rotating dish,
it oughta work with the right transducer.

Most, if not all, radar antenna's on boats are slotted waveguides. That is a
piece of rectangular tube with slots in it. Such a waveguide and slots
resonate on 10GHz and will not transport and transmit cellphone signals at
900MHz (aka 0.9GHz).

Apart from that, the cellphone system works with datapackets in very tight
time-slots. The system compensates for the distance between the tower and
the phone (TA: Timing Advance) with a TA value between 0 and 63, for every
550 meters the phone is further away from the tower. This imposes a hard
limit on the maximum distance of 550 x 63 = 34.6km or 18.7 miles. So no
matter how high your antenna is and how much power you have available, 18,7
miles is the limit.

Meindert


Meindart:

Thanks for the useful info, I agree, the waveguide antenna wouldnt
work. Boat radar doesnt use a parabolic antenna with the waveguide
horn at the focal point? Why not?

"Parallax" wrote in message
om...

Thanks for the useful info, I agree, the waveguide antenna wouldnt
work. Boat radar doesnt use a parabolic antenna with the waveguide
horn at the focal point? Why not?

Because a slotted waveguide is cheaper and smaller than a parabolic antenna
with a precisely manufactured curvature and a horn.

Meindert

On Tue, 28 Oct 2003 09:02:16 -0500, "Jeff Morris"
jeffmo@NoSpam-sv-lokiDOTcom wrote (with possible editing):

Why don't you just get a cell phone antenna and if needed, an amplifier? With a 4 foot
antenna on the stern rail we had contact with ATT for the entire East Coast. The only
problem area was Maine, where the coves can be blocked by hills.

BTW, one of the proposals for "next generation" cell technology was by a company that
specializes in small supercomputers for Defense Dept. radar and sonar systems. The same
technology that can "aim" radar can be used to aim cell bandwidth to the customer that
needs it at the moment.

....snip

Actually, what might make more sense are the new satellite cell
phones. I believe they go for around $600, but the per-minute charge
is down to around $0.35 and they're good just about anywhere.
--

Larry
Email to rapp at lmr dot com

In article ,
(Parallax) wrote:

Boat radar doesnt use a parabolic antenna with the waveguide
horn at the focal point? Why not?

Because Marine Radar Antenna's are designed to provide a very narrow
Horazontal Beamwidth, so as to descriminate small targets, and a very
large Vertical Beamwidth, so as to eliminate loss of targets due to
Heeling, Rolling, and pitching for the radar platform......

Bruce in alaska
--
add a 2 before @

"Bruce in Alaska" wrote in message
...
In article ,
(Parallax) wrote:

Boat radar doesnt use a parabolic antenna with the waveguide
horn at the focal point? Why not?

Because Marine Radar Antenna's are designed to provide a very narrow
Horazontal Beamwidth, so as to descriminate small targets, and a very
large Vertical Beamwidth, so as to eliminate loss of targets due to
Heeling, Rolling, and pitching for the radar platform......

Which can also be achived with a parabolic antenna, with different
curvatures in horizontal and vertical direction. See navy ships...
So again, it all comes down to cost.

Meindert