sharing a GPS NMEA feed

I would like to use a GPS antenna that I could send NMEA data to both
my Glide Computer and my PDA running flight sortware.

Any thoughts on how something like that would be wired up?

I have a Gilsson antenna with a brass plug that fits into my iPAQ 310,
if that same unit would work, I would get another one, cut the plug
off and find the NMEA send wire, of course having the schematic would
help too.

Brad

Hi Brad,

I'm sorry, but I don't think that is possible.

It is possible to have a GPS send NMEA data to 2 soaring instruments or
PDAs. But each GPS engine needs its own antenna. I don't think a single
GPS antenna can be connected to 2 different GPS units - which is what I
think you are trying to do.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.

"Brad" wrote in message
...
I would like to use a GPS antenna that I could send NMEA data to both
my Glide Computer and my PDA running flight sortware.

Any thoughts on how something like that would be wired up?

I have a Gilsson antenna with a brass plug that fits into my iPAQ 310,
if that same unit would work, I would get another one, cut the plug
off and find the NMEA send wire, of course having the schematic would
help too.

Brad

On Dec 31, 2:30*pm, "Paul Remde" wrote:
Hi Brad,

I'm sorry, but I don't think that is possible.

It is possible to have a GPS send NMEA data to 2 soaring instruments or
PDAs. *But each GPS engine needs its own antenna. *I don't think a single
GPS antenna can be connected to 2 different GPS units - which is what I
think you are trying to do.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.

"Brad" wrote in message

...



I would like to use a GPS antenna that I could send NMEA data to both
my Glide Computer and my PDA running flight sortware.

Any thoughts on how something like that would be wired up?

I have a Gilsson antenna with a brass plug that fits into my iPAQ 310,
if that same unit would work, I would get another one, cut the plug
off and find the NMEA send wire, of course having the schematic would
help too.

Brad- Hide quoted text -

- Show quoted text -

Antenna feeds can be split to feed multiple GPS receivers, but it
often requires a splitter with a pre-amp*, and they're not cheap.
Additionally, signal strength from the splitter/pre-amp needs to be
tailored to the receiver. Not all GPS receivers are the same, and
overdriving the signal to a receiver can cause (at least) it not to
receive properly.
Antennas are cheap, it would be better to buy another one.
The NMEA sentences are the OUTPUT of the GPS receiver (though I don't
know if the 310 outputs them). The signal from the antenna is a very
low level psuedo-random-noise L band radio frequency signal.
* and all that I've worked with require an external power source.

Brad,

Like Paul mentioned, sharing a GPS engine between two device is a common "Poor Man's" navigation solution. For several years I have been driving both an EW Model D flight recorder and Compaq Aero 1550 with a Garmin 12xl.

Any FAI acceptable GPS unit can be substituted for the Garmin 12xl. The Goddard SPS-1 is a good power and device connection solution.
http://www.cumulus-soaring.com/goddard/sps-1.jpg

Wayne





"Paul Remde" wrote in message ...
Hi Brad,

I'm sorry, but I don't think that is possible.

It is possible to have a GPS send NMEA data to 2 soaring instruments or
PDAs. But each GPS engine needs its own antenna. I don't think a single
GPS antenna can be connected to 2 different GPS units - which is what I
think you are trying to do.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.

"Brad" wrote in message
...
I would like to use a GPS antenna that I could send NMEA data to both
my Glide Computer and my PDA running flight sortware.

Any thoughts on how something like that would be wired up?

I have a Gilsson antenna with a brass plug that fits into my iPAQ 310,
if that same unit would work, I would get another one, cut the plug
off and find the NMEA send wire, of course having the schematic would
help too.

Brad

"Paul Remde" wrote:

I'm sorry, but I don't think that is possible.

Of course it is. E.g. http://www.vtec.ch/avionik.htm , scroll down to
"AntSplit".



Uncle Fuzzy wrote:

Antennas are cheap, it would be better to buy another one.

Multiple GPS antennas can be a mess, because they mustn't be located
near each other.

On Dec 31, 4:04*pm, John Smith wrote:
"Paul Remde" wrote:
I'm sorry, but I don't think that is possible.

Of course it is. E.g.http://www.vtec.ch/avionik.htm, scroll down to
"AntSplit".

Uncle Fuzzy wrote:
Antennas are cheap, it would be better to buy another one.

Multiple GPS antennas can be a mess, because they mustn't be located
near each other.

News to me. I have several within a foot of each other on a
building. Been operating that way for 8 years now with no issues.
Two are mounted on the same ground plane, nearly touching.

In article "Paul Remde" writes:
Hi Brad,

I'm sorry, but I don't think that is possible.

It is possible to have a GPS send NMEA data to 2 soaring instruments or
PDAs. But each GPS engine needs its own antenna. I don't think a single
GPS antenna can be connected to 2 different GPS units - which is what I
think you are trying to do.

Good Soaring,

Paul Remde
Cumulus Soaring, Inc.

Sure it can. You just need an L-band splitter with a DC block on one of
the outputs and DC pass through from the other. Then the antenna's active
amplifier can be powered by one of the receivers.

If you have receivers that both use passive antennas, it is also easy, but
you are at a bit more of a risk from signal level.

If one is active and one passive, you have a bit of engineering to do.

Alan

Uncle Fuzzy wrote:

News to me. I have several within a foot of each other on a
building. Been operating that way for 8 years now with no issues.
Two are mounted on the same ground plane, nearly touching.

Lucky you. My experience is that one foot between the antennas is about
the minmal distance for reliable functionality.

On Dec 31, 2:24*pm, Brad wrote:
I would like to use a GPS antenna that I could send NMEA data to both
my Glide Computer and my PDA running flight sortware.

Any thoughts on how something like that would be wired up?

I have a Gilsson antenna with a brass plug that fits into my iPAQ 310,
if that same unit would work, I would get another one, cut the plug
off and find the NMEA send wire, of course having the schematic would
help too.

Brad

Hmmmm...............let me clarify what I wrote earlier.

Situation: I have a iPAQ 3850 with no GPS, I also have an Ilec SB-8
with the Final Glide unit, this can accept NMEA data from a GPS.

What I want to do is buy one of those GPS "mouse" units, and send the
NMEA information to both of those units.

I mentioned the iPAQ 310 earlier just because I had an external
antenna and that it helped track more sattelites, and perhaps if I got
another Antenna, that I could use it.......or a mouse.

Thanks,
Brad

On Dec 31, 5:15*pm, Brad wrote:
On Dec 31, 2:24*pm, Brad wrote:

I would like to use a GPS antenna that I could send NMEA data to both
my Glide Computer and my PDA running flight sortware.

Any thoughts on how something like that would be wired up?

I have a Gilsson antenna with a brass plug that fits into my iPAQ 310,
if that same unit would work, I would get another one, cut the plug
off and find the NMEA send wire, of course having the schematic would
help too.

Brad

Hmmmm...............let me clarify what I wrote earlier.

Situation: I have a iPAQ 3850 with no GPS, I also have an Ilec SB-8
with the Final Glide unit, this can accept NMEA data from a GPS.

What I want to do is buy one of those GPS "mouse" units, and send the
NMEA information to both of those units.

I mentioned the iPAQ 310 earlier just because I had an external
antenna and that it helped track more sattelites, and perhaps if I got
another Antenna, that I could use it.......or a mouse.

Thanks,
Brad

Brad

Several manufactures make an RS-232 mouse. More come with USB only and
maybe an adapter, obviously you want to find a real RS-232 one. You
also want one with a GPS receiver that supports WGS-84 ellipsoid, you
would think that is standard but there have been a few that have
problems here. That result in ~50-100' errors in places.

Most devices we use that listen to NMEA are incredibly dumb and don't
talk back to the GPS device, even for XON/XOFF flow control so you can
often just wire devices in parallel with both your PDA and flight
computer listening the the same RS-232 data pin. A buffering splitter
like Goddard make is usually _not_ needed in this case.

On the other hand you might find the redundancy of two completely
separate GPS antennas/receivers a nice idea. One option is to drive
the PDA with either a bluetooth GPS receiver or a CF card based
receiver and use a separate serial mouse GPS for the flight computer.
The advantage there is that both can be completely independent of the
ships main battery supply. I tend to prefer a CF car receiver plugged
into the PDA (maybe with an extended battery if available on the PDA)
then power the PDA m ountfrom the ships power, that way if you lose
main ships power the PDA and its on-board GPS may be capable of
running for many hours.

You don't mention badges or records. Obviously if that is an issue
then you might want to look at an IGC approved flight recorder (yes I
know about the new COTS GPS rule, a real IGC recorder is still the way
to go). In that case I recommend driving the PDA from the NMEA output
from the IGC recorder, that way you should become very aware things
are not working if there is a flight recorder GPS problem (plus you
should get to see the real pressure altitude the flight recorder is
reporting).

Does that help?

Darryl