Don White wrote in
:

When our skipper bought a Mirage 33 sailboat, it came with a Garmin 75
(I believe a 1993 model) That thing was expensive in it's day...about
$1k CDN but you could unscrew the stubby antenna and hook up the unit to
a cable attached to a bigger antenna mounted on the stern rail while you
were in the cabin.



The "antenna" in the Garmin 75 series GPS wasn't just an antenna. DC power
is fed up the coax from the 75 to a microwave amplifier and downconverter
which makes a much-lower-frequency IF signal, properly amplified, before it
is fed down the same coax to the 75. There used to be an Xray picture of
the Garmin 75's grey plastic antenna on the net and I stored it showing the
helical dipole array actually made of flexible printed circuit board and
wrapped into a cylinder inside the plastic radome, but it is off the net,
google couldn't find it and my hard drive is long gone....

Because the RF between this antenna/converter and the GPS75 is a lower
intermediate frequency, not the 2400 Mhz microwaves from the birds, any
coaxial extension cord with a BNC male on one end and BNC female connector
on the other works great to move the antenna away from the GPS75, Same
old, cheap RG-58 from RatShack works fine.

Just make SURE the coax center conductor is ISOLATED from its shield or it
will burn up the tuning circuitry in the GPS-75 from the shorting of its
tuning voltage output!

I programmed a mint condition GPS75 for a visiting old sailor single-
handing a 28' sloop on our dock just yesterday! He'd had it for years and
NEVER USED IT! I gave him a little GPS/Garmin 75 school from what I could
remember about mine...(c;

--
Larry

You know you've had a rough night when you wake up and you're outlined in
chalk.

In article ,
Larry W4CSC wrote:

Because the RF between this antenna/converter and the GPS75 is a lower
intermediate frequency, not the 2400 Mhz microwaves from the birds, any
coaxial extension cord with a BNC male on one end and BNC female connector
on the other works great to move the antenna away from the GPS75, Same
old, cheap RG-58 from RatShack works fine.

Well close but no cigar on the above.....GPS runs at 1.6Ghz, and I have
never seen a Garmin GPS that downconverts in the remote antenna. Mostly
what Garmin does is have a Powered LNA and Patch Antenna in their remote
antennas that feed the Reveiver at Frequency. My Garmin GPS3 and GPS3+
both are this way, and all the earlier Garmins with external antenna
capability are the same as they can use the same remote antennas.


Bruce in alaska one who remebers, it is the first active RF Device
that sets the Noise Floor.......
--
add a 2 before @

HI Bruce, what is the favorite while navigation through the inside passage.
I learned that the US government are spending money to upgrade their Loran
chain?

"Bruce in Alaska" wrote in message
...
In article ,
Larry W4CSC wrote:

Because the RF between this antenna/converter and the GPS75 is a lower
intermediate frequency, not the 2400 Mhz microwaves from the birds, any
coaxial extension cord with a BNC male on one end and BNC female
connector
on the other works great to move the antenna away from the GPS75, Same
old, cheap RG-58 from RatShack works fine.

Well close but no cigar on the above.....GPS runs at 1.6Ghz, and I have
never seen a Garmin GPS that downconverts in the remote antenna. Mostly
what Garmin does is have a Powered LNA and Patch Antenna in their remote
antennas that feed the Reveiver at Frequency. My Garmin GPS3 and GPS3+
both are this way, and all the earlier Garmins with external antenna
capability are the same as they can use the same remote antennas.


Bruce in alaska one who remebers, it is the first active RF Device
that sets the Noise Floor.......
--
add a 2 before @

Your wife's GPS in her car does cheat. When you are underground you
lose all satellite reception and it then assumes that you are
continuing the last course. They call it dead reckoning. Automotive
GPS systems will typically watch your speed on the speedometer and also
your course vectors based upon any turns you have made, and tries to
keep you on course based upon that information. This is an important
feature in cars as many times in the middle of big cities satellite
reception can be very poor or non-existent if you are surrounded by
sky-scrapers. Then every time the GPS gains satellite reception back
it will correct itself again, the snapping back you see.

Slacker

Could it be the balsa core below the deck is wet enough to block the signal?

"Larry W4CSC" wrote in message
...
Rich Hampel wrote in
:

Brian is correct .....
NO GPS can 'see' through steel or fiberglass, etc. The antenna MUST
have a clear unobstructed view of the satelites .... no wet sail, no
leaves, no roofs, no dodger or bimini, no steel panels.



Pure hogwash. Any RF-transparent material can be used between the GPS
antenna and the satellites....same as that radome on the radar the RF
passes through coming and going to the target. It CANNOT see through
steel, or any other CONDUCTIVE material. Bimini rails hardly pose a
threat
as they occupy so small a footprint on the sky. GPS can see through any
non-metallic bimini material just fine....or our heavily built fiberglass
hardtop.

I've attempted to post a picture taken from behind the helmsman showing
off
our redesigned electronics suite. To the left of them console is a little
winch that works lines through the windscreen to haul the mainsheet
traveler back and forth from the helm under the hardtop.

To the left of that winch, there is mounted to the flat surface of the
helm
station, a Raymarine Raystar satellite-compensated GPS receiver and the
GPS
antenna to our old Garmin 185 backup GPS. These both shoot through the
plexiglass windscreen and the very thick fiberglass hardtop. Because the
solar panel is on the starboard topside of the hardtop, GPS was put way
port to keep from being shielded by the RF-shield of the solar panel...a
conductor.

Hope the picture shows up on alt.binaries.pictures.sports.ocean of this.
I've had trouble posting to it but usenetserver tells me they stopped
identifying my posts to it as spam, blocking them.

--
Larry

You know you've had a rough night when you wake up and you're outlined in
chalk.

In article ,
"Denis Marier" wrote:

HI Bruce, what is the favorite while navigation through the inside passage.
I learned that the US government are spending money to upgrade their Loran
chain?

"Bruce in Alaska" wrote in message
...
In article ,
Larry W4CSC wrote:

Because the RF between this antenna/converter and the GPS75 is a lower
intermediate frequency, not the 2400 Mhz microwaves from the birds, any
coaxial extension cord with a BNC male on one end and BNC female
connector
on the other works great to move the antenna away from the GPS75, Same
old, cheap RG-58 from RatShack works fine.

Well close but no cigar on the above.....GPS runs at 1.6Ghz, and I have
never seen a Garmin GPS that downconverts in the remote antenna. Mostly
what Garmin does is have a Powered LNA and Patch Antenna in their remote
antennas that feed the Reveiver at Frequency. My Garmin GPS3 and GPS3+
both are this way, and all the earlier Garmins with external antenna
capability are the same as they can use the same remote antennas.


Bruce in alaska one who remebers, it is the first active RF Device
that sets the Noise Floor.......
--
add a 2 before @



I suspect that GPS is favored over Loran these days....TD's for that area
are 15, 28, and 48, if I recall. Fallon Nv., Near Ketchikan Ak., Yakatat
Ak, and Tok Ak., and Kodiak Ak. I think it is 5990 and then 9940 as you
clear Cape Spencer. Been a while since I actually did any work on a
Loran System, but that is what I think I remeber.... could also just be
a "Senior Moment".....


Bruce in alaska who enjoys reading "Me's" comments.......
--
add a 2 before @

"MMC" wrote in
m:

Could it be the balsa core below the deck is wet enough to block the
signal?


Boy, if we can confirm that is true it will mean a great tool to find
moisture in deck coring with a handheld GPS watching the satellite strength
display.

Anyone got a known wet core to test it?

--
Larry

You know you've had a rough night when you wake up and you're outlined in
chalk.