GPS receiver for LNAV

I have a Cambridge LNAV and I want to replace my LX400, which is currently being used purely as a GPS receiver, with something else to provide a GPS feed to the LNAV, preferably without taking up a space on my instrument panel.

Any suggestions?

On Sat, 25 Apr 2009 17:28:51 +0100, soaringtheskies wrote:

I have a Cambridge LNAV and I want to replace my LX400, which is
currently being used purely as a GPS receiver, with something else to
provide a GPS feed to the LNAV, preferably without taking up a space on
my instrument panel.

What NMEA sentences does it need?

Why does it need a GPS? Just for wind calcs or do you want it to do more?

The NMEA sentence information will hopefully be in its manual. Knowing
that will help you select a suitable GPS.

I just went though a similar exercise when I replaced my Garmin GPS II+
with a Binatone PNA running XCSoar. This has no way to output GPS data.

Anyway, I wanted my SDI C4 vario to still calculate wind, so I connected
a blind GPS that I hid behind the panel: I have room on my panel for the
GPS II+ OR the PNA and no spare slots. Like all blind GPS receivers mine
only outputs GPRMC sentences, which is the same as a GPS II+ does without
an active waypoint or task. However, the C4 also needs destination
sentences (GPRMB, GPWPL and GPR00) to calculate wind, so all the blind
GPS is doing right now is draining my battery.

The point being, that, if the LNAV needs destination data to calculate
wind, you'll not be able to use a blind GPS. You'll need one that you can
enter a waypoint or a task into, so it will probably occupy panel space.

Your LNAV may be the same. If you can't find anything in the manual for
the LNAV or the LX400, and nobody else on r.a.s knows what sentences it
needs, there are a couple of other ways to find out:

- connect the LX400 to a laptop with a serial port set to 4800 baud,
1 stop bit and 8 data bits/no parity and run any program that can
display or capture the data coming down the serial line.

Alternatively, borrow a datascope, and use that to show you what
the LX400 outputs.

- Another way is to borrow a Garmin GPS II+ or a 12XL, connect it to
the LNAV. If the LNAV is like my C4, it will not calculate wind until
you put a waypoint into the GPS.

Of course, there is another way: accept that the LNAV will become a
simple TE compensated averaging vario, buy a PNA and run XCSoar on it.
XCSoar is both a moving map navigation system and a glide computer. Its a
cheap solution: XCSoar is free Open Source software and will run on any
PNA with an SD card slot and Windows Mobile 5. PNAs are inexpensive: my
Binatone X.350 cost £50 (about $US 75) plus £5 ($US 7.50) for a 2GB SD
card.

HTH


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

At 20:08 25 April 2009, Martin Gregorie wrote:
On Sat, 25 Apr 2009 17:28:51 +0100, soaringtheskies wrote:

I have a Cambridge LNAV and I want to replace my LX400, which is
currently being used purely as a GPS receiver, with something else to
provide a GPS feed to the LNAV, preferably without taking up a space
on
my instrument panel.

What NMEA sentences does it need?

Why does it need a GPS? Just for wind calcs or do you want it to do
more?

The NMEA sentence information will hopefully be in its manual. Knowing
that will help you select a suitable GPS.

I just went though a similar exercise when I replaced my Garmin GPS II+
with a Binatone PNA running XCSoar. This has no way to output GPS data.

Anyway, I wanted my SDI C4 vario to still calculate wind, so I connected

a blind GPS that I hid behind the panel: I have room on my panel for the

GPS II+ OR the PNA and no spare slots. Like all blind GPS receivers mine

only outputs GPRMC sentences, which is the same as a GPS II+ does without

an active waypoint or task. However, the C4 also needs destination
sentences (GPRMB, GPWPL and GPR00) to calculate wind, so all the blind
GPS is doing right now is draining my battery.

The point being, that, if the LNAV needs destination data to calculate
wind, you'll not be able to use a blind GPS. You'll need one that you
can
enter a waypoint or a task into, so it will probably occupy panel space.

Your LNAV may be the same. If you can't find anything in the manual for

the LNAV or the LX400, and nobody else on r.a.s knows what sentences it
needs, there are a couple of other ways to find out:

- connect the LX400 to a laptop with a serial port set to 4800 baud,
1 stop bit and 8 data bits/no parity and run any program that can
display or capture the data coming down the serial line.

Alternatively, borrow a datascope, and use that to show you what
the LX400 outputs.

- Another way is to borrow a Garmin GPS II+ or a 12XL, connect it to
the LNAV. If the LNAV is like my C4, it will not calculate wind until
you put a waypoint into the GPS.

Of course, there is another way: accept that the LNAV will become a
simple TE compensated averaging vario, buy a PNA and run XCSoar on it.
XCSoar is both a moving map navigation system and a glide computer. Its a

cheap solution: XCSoar is free Open Source software and will run on any
PNA with an SD card slot and Windows Mobile 5. PNAs are inexpensive: my
Binatone X.350 cost £50 (about $US 75) plus £5 ($US 7.50) for a 2GB SD

card.

HTH


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |


The downside of using a standalone PNA (in e.g. a competition) is that
your Airspace altitude warnings will not match the airspace. PNA on its
own has only GPS altitude, possible Airspace infringements will be checked
against barometric altitude recorded in your FR (logger).

On Apr 25, 12:28*pm, soaringtheskies soaringtheskies.
wrote:
I have a Cambridge LNAV and I want to replace my LX400, which is
currently being used purely as a GPS receiver, with something else to
provide a GPS feed to the LNAV, preferably without taking up a space on
my instrument panel.

Any suggestions?

--
soaringtheskies

You need to give us a little more information:

- Does the GPS need to provide logging capability (or do you have
another logger).
- Assuming you do need a logger, does it need to be an IGC-approved
type?
- If it is IGC-approved, for what level do you need it (i.e. basic
badges, record flying, etc.)

A simple solution is to find a used CAI model 20 or 25 which can be
mounted remote from the panel and is designed to integrate with the
LNAV. However, this is NOT approved for all badges. You could buy a
302A if full approval is required.

On Apr 26, 12:51*am, Papa3 wrote:
On Apr 25, 12:28*pm, soaringtheskies soaringtheskies.

wrote:
I have a Cambridge LNAV and I want to replace my LX400, which is
currently being used purely as a GPS receiver, with something else to
provide a GPS feed to the LNAV, preferably without taking up a space on
my instrument panel.

Any suggestions?

--
soaringtheskies

You need to give us a little more information:

- *Does the GPS need to provide logging capability (or do you have
another logger).
- *Assuming you do need a logger, does it need to be an IGC-approved
type?
- *If it is IGC-approved, for what level do you need it (i.e. basic
badges, record flying, etc.)

A simple solution is to find a used CAI model 20 or 25 which can be
mounted remote from the panel and is designed to integrate with the
LNAV. *However, this is NOT approved for all badges. *You could buy a
302A if full approval is required.

Ooops. The comment on the Model 20/25 should be that they are NOT
approved for all flights (e.g. World Records). They are approved for
all badges.

My LNAV (Rev4.2) needs GPRMB (destination) and GPRMC (position)
sentences. PCAIB sentence is optional.
I think that any GPS with Waypoint/ GOTO functionality provides the
GPRMB and GPRMC sentences.
I am currently replacing the brick in my cockpit (GPSMAP195) which has
been feeding the LNAV for years, with a smaller GPS.

The PCAIB sentence is Cambridge proprietary and contains waypoint name
and waypoint elevation.
This is used for automatic final glide calculation.
If you are using a non-Cambridge GPS, which will lack the PCAIB
sentence, you will still get the wind calculation, but for final glide
you have to enter your arrival MSL altitude (+margin) manually.
Very inconvenient.

It would not be too difficult to have any of the PDA/PNA soaring
packages to output these 3 sentences based on the selected waypoint.
I was using SoarPilot on the Palm platform.
Paul Gleeson build me a version with these outputs, but my Tungsten
gave up and I could not test it.
In the mean time I switched to the Ipaq310 PNA platform and I am still
trying to convince some developers to output these sentences for
connection to the LNAV through BlueTooth.
Yes, I know that the PNA/PDA also has final glide calculation.
Still nice to have another reference at nearly no additional cost.
The whole point here is NOT to have to spent $2500 for the 302, when
you have an LNAV that is still working alright.
Approved logging is not relevant for me. (Just OLC acceptance of the
PNA IGC files is fine for me)

Hans Van Weersch



On Apr 25, 1:08*pm, Martin Gregorie
wrote:
On Sat, 25 Apr 2009 17:28:51 +0100, soaringtheskies wrote:
I have a Cambridge LNAV and I want to replace my LX400, which is
currently being used purely as a GPS receiver, with something else to
provide a GPS feed to the LNAV, preferably without taking up a space on
my instrument panel.

What NMEA sentences does it need?

Why does it need a GPS? Just for wind calcs or do you want it to do more?

The NMEA sentence information will hopefully be in its manual. Knowing
that will help you select a suitable GPS.

I just went though a similar exercise when I replaced my Garmin GPS II+
with a Binatone PNA running XCSoar. This has no way to output GPS data.

Anyway, I wanted my SDI C4 vario to still calculate wind, so I connected
a blind GPS that I hid behind the panel: I have room on my panel for the
GPS II+ OR the PNA and no spare slots. Like all blind GPS receivers mine
only outputs GPRMC sentences, which is the same as a GPS II+ does without
an active waypoint or task. However, the C4 also needs destination
sentences (GPRMB, GPWPL and GPR00) to calculate wind, so all the blind
GPS is doing right now is draining my battery.

The point being, that, if the LNAV needs destination data to calculate
wind, you'll not be able to use a blind GPS. You'll need one that you can
enter a waypoint or a task into, so it will probably occupy panel space.

Your LNAV may be the same. If you can't find anything in the manual for
the LNAV or the LX400, and nobody else on r.a.s knows what sentences it
needs, there are a couple of other ways to find out:

- connect the LX400 to a laptop with a serial port set to 4800 baud,
* 1 stop bit and 8 data bits/no parity and run any program that can
* display or capture the data coming down the serial line.

* Alternatively, borrow a datascope, and use that to show you what
* the LX400 outputs.

- Another way is to borrow a Garmin GPS II+ or a 12XL, connect it to
* the LNAV. If the LNAV is like my C4, it will not calculate wind until
* you put a waypoint into the GPS.

Of course, there is another way: accept that the LNAV will become a
simple TE compensated averaging vario, buy a PNA and run XCSoar on it.
XCSoar is both a moving map navigation system and a glide computer. Its a
cheap solution: XCSoar is free Open Source software and will run on any
PNA with an SD card slot and Windows Mobile 5. PNAs are inexpensive: my
Binatone X.350 cost £50 (about $US 75) plus £5 ($US 7.50) for a 2GB SD
card.

HTH

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

there are likely a number of simple or handheld GPS receivers that can be used and supply the needed info for L/Nav but the easiest and most common connection is with a GPS/Data-Logger. Nearly any current GPS data-logger will provide the needed data for the L/Nav including the Cambridge 302 or (cheaper) 302A, Colibri, and also look at new "Erixx" Flight Recorder on my website http://www.wingsandwheels.com/page11.htm, these are FAI/IGC approved loggers for all flight records and badges and by comparison in the same relative price range as typical GPS handheld units with aviation data strings available and price worthy of consideration in the place of most used GPS data-loggers.
tim
Please visit the Wings & Wheels website at www.wingsandwheels.com


"soaringtheskies" wrote in message ...

I have a Cambridge LNAV and I want to replace my LX400, which is
currently being used purely as a GPS receiver, with something else to
provide a GPS feed to the LNAV, preferably without taking up a space on
my instrument panel.

Any suggestions?




--
soaringtheskies

The LNAV, according to the manual, requires GPRMB and GPRMC sentences. I'm wanting to use as much of it's functionality as possible. I'm using an EW MicroRecorder as a logger, unfortunately although this can be used to supply a GPS signal to other things (it has it's own receiver) it does not transmit GPRMB sentences. So "all" I'm after is a GPS that will transmit both GPRMB and GPRMC sentences to my LNAV, it doesn't need to be able to log anything, although I see the point about needing something to transmit the next waypoint to it. Might end up putting that LX back in...there must be soemthing simpler out there though.

I'm also running SeeYou Mobile off a PDA, but I don't think there's any easy way of getting this to talk to the LNAV.

On Apr 28, 2:05*pm, soaringtheskies soaringtheskies.
wrote:
The LNAV, according to the manual, requires GPRMB and GPRMC sentences.
I'm wanting to use as much of it's functionality as possible. *I'm
using an EW MicroRecorder as a logger, unfortunately although this can
be used to supply a GPS signal to other things (it has it's own
receiver) it does not transmit GPRMB sentences. *So "all" I'm after is
a GPS that will transmit both GPRMB and GPRMC sentences to my LNAV, it
doesn't need to be able to log anything, although I see the point about
needing something to transmit the next waypoint to it. *Might end up
putting that LX back in...there must be soemthing simpler out there
though.

I'm also running SeeYou Mobile off a PDA, but I don't think there's any
easy way of getting this to talk to the LNAV.

--
soaringtheskies

Any older inexpensive Garmin with transmit the sentences you need and
allow you to transmit the next waypoint.

Richard
www.craggyaero.com

On Tue, 28 Apr 2009 18:45:48 -0700, rhpf wrote:

On Apr 28, 2:05Â*pm, soaringtheskies soaringtheskies.
wrote:
The LNAV, according to the manual, requires GPRMB and GPRMC sentences.
I'm wanting to use as much of it's functionality as possible. Â*I'm
using an EW MicroRecorder as a logger, unfortunately although this can
be used to supply a GPS signal to other things (it has it's own
receiver) it does not transmit GPRMB sentences. Â*So "all" I'm after is
a GPS that will transmit both GPRMB and GPRMC sentences to my LNAV, it
doesn't need to be able to log anything, although I see the point about
needing something to transmit the next waypoint to it. Â*Might end up
putting that LX back in...there must be soemthing simpler out there
though.

I'm also running SeeYou Mobile off a PDA, but I don't think there's any
easy way of getting this to talk to the LNAV.

--
soaringtheskies

Any older inexpensive Garmin with transmit the sentences you need and
allow you to transmit the next waypoint.

The OP wanted to avoid taking up panel space with the GPS, which rules
out putting a waypoint into it.

However, putting that type behind the panel merely provides another
gotcha with at least some of them: the ON switch.

If the GPS has a mechanical on switch, no problem. Just wire it to the
main battery and strap it down behind the panel, making sure the
batteries are out and the switch is ON. This way it will wake up when you
turn the master switch on.

However, many Garmins have a 'soft' power switch. I know the GPS II+ has
one and IIRC the 12XL has as well. The problem here is that after the
glider power is on you still have to prod the 'on' switch on the GPS,
which is hard to do if its OOS behind the panel.

====

Another problem with the older Garmins is that they will all stop working
in a few years. The 12 channel Garmin models (12XL, II+, III+ and others
of the same vintage) all contain battery-backed RAM which is kept alive
by a factory-fitted lithium cell. Will replacements for these cells still
be available when they start to die some time after 2011?

My first GPS II+, bought in 2001, was from a batch fitted with faulty
lithium cells. In mine it failed just after the GPS guarantee ran out. I
rang Garmin, expecting to pay for a new cell to be fitted but they told
me that that, although the GPS guarantee was quite short (1-2 years), the
Li cell had a 10 year guarantee and offered to replace it for free.
However, I noticed that in fact they replaced the entire GPS, so swapping
out the Li cell may be quite a difficult job.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |