PowerFlarm at Uvalde?

On 08/09/2011 5:42 PM, Eric Greenwell wrote:
On 8/9/2011 1:01 PM, Luke wrote:
On 08/09/2011 12:58 AM, Rob Cluxton wrote:

Where are your GPS antenas located? 30cm away from GPS antennas AND the
compass is not realistic in most gliders...

How can the compass interfere with the GPS signal?

I'm not sure but here is a quote from the manual:


"The PowerFLARM® and any associated aerials should be located as far
away as possible -- at least 30 cm (1 ft) -- away from any other GPS
aerial and the magnetic compass."

Luke

At 21:48 09 August 2011, Luke wrote:
On 08/09/2011 5:42 PM, Eric Greenwell wrote:
On 8/9/2011 1:01 PM, Luke wrote:
On 08/09/2011 12:58 AM, Rob Cluxton wrote:

Where are your GPS antenas located? 30cm away from GPS antennas AND
the
compass is not realistic in most gliders...

How can the compass interfere with the GPS signal?

I'm not sure but here is a quote from the manual:


"The PowerFLARM� and any associated aerials should be located as far
away as possible -- at least 30 cm (1 ft) -- away from any other GPS
aerial and the magnetic compass."

Luke


You guys ARE joking, right??

Cookie

On 8/9/2011 2:48 PM, Luke wrote:
On 08/09/2011 5:42 PM, Eric Greenwell wrote:
On 8/9/2011 1:01 PM, Luke wrote:
On 08/09/2011 12:58 AM, Rob Cluxton wrote:

Where are your GPS antenas located? 30cm away from GPS antennas AND the
compass is not realistic in most gliders...

How can the compass interfere with the GPS signal?

I'm not sure but here is a quote from the manual:


"The PowerFLARM® and any associated aerials should be located as far
away as possible -- at least 30 cm (1 ft) -- away from any other GPS
aerial and the magnetic compass."

Maybe it's the aerials that interfere with the compass.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)

"The PowerFLARM� and any associated aerials should be located as far
away as possible -- at least 30 cm (1 ft) -- away from any other GPS
aerial and the magnetic compass."

Luke


You guys ARE joking, right??

Cookie

No one is joking but it is very disturbing to be told about this
installation constraint after having placed an order and sent in a
payment.

The constraint, if complied with, will make it almost impossible to fit the
unit in a glider equipped for contest flying.


Andy

Luke wrote:
On 08/09/2011 5:42 PM, Eric Greenwell wrote:
On 8/9/2011 1:01 PM, Luke wrote:
On 08/09/2011 12:58 AM, Rob Cluxton wrote:

Where are your GPS antenas located? 30cm away from GPS antennas AND the
compass is not realistic in most gliders...

How can the compass interfere with the GPS signal?

I'm not sure but here is a quote from the manual:


"The PowerFLARM® and any associated aerials should be located as far
away as possible -- at least 30 cm (1 ft) -- away from any other GPS
aerial and the magnetic compass."


The PowerFLARM would interfere with the compass, not the other way around.
The paragraph in the manual immediately following the quoted one makes this
clear:

"After installation, an inspection must be made to ensure that the
device does not interfere with any mechanical, electrical,
electronic (radio) or magnetic (e.g. compass) system, and this
fact must be recorded in the aircraft documents."

As a pragmatic matter, if the unit has to be placed within 30 cm of the
compass (and even if it isn't,) then simply turn it and all other
electronic flight equipment on and make a note of the magnetic deviation
using the usual procedure. It's a portable device, so such a note probably
woudn't be made on the permanent deviation card.

Andy Durbin wrote:
"The PowerFLARM� and any associated aerials should be located as
far
away as possible -- at least 30 cm (1 ft) -- away from any other GPS

aerial and the magnetic compass."

Luke


You guys ARE joking, right??

Cookie

No one is joking but it is very disturbing to be told about this
installation constraint after having placed an order and sent in a
payment.

The constraint, if complied with, will make it almost impossible to
fit the
unit in a glider equipped for contest flying.


Andy

This should not surprise anybody and I can think of a lot more to be
"highly disturbed" about in life than this. C'mon we really are not
whining about this are we?

You cannot undo the laws of electrodynamics. The compass is going to be
affected by components in the PowerFLARM and by electrical currents.
Cautious advice like this from a vendor is entirely appropriate for a
device that might well get put up on a glareshield near the compass in a
certified (even IFR) aircraft.

Now why is it a worry? How many of us rely on our compasses? To high
accuracy? The manual is just providing a suitable caution and covering
FLARM's ass.

What is actually much more important is the correct installation with
respect to the antennas being free of conductive obstructions/surfaces
as the manual warns. Still I just know we'll stumble across these units
and antennas buried behind panels with owners unsure why they don't work
properly.

Darryl

At 20:18 10 August 2011, Darryl Ramm wrote:
This should not surprise anybody and I can think of a lot more to be
"highly disturbed" about in life than this. C'mon we really are not
whining about this are we?

You cannot undo the laws of electrodynamics. The compass is going to be
affected by components in the PowerFLARM and by electrical currents.
Cautious advice like this from a vendor is entirely appropriate for a
device that might well get put up on a glareshield near the compass in a
certified (even IFR) aircraft.

Now why is it a worry? How many of us rely on our compasses? To high
accuracy? The manual is just providing a suitable caution and covering
FLARM's ass.

What is actually much more important is the correct installation with
respect to the antennas being free of conductive obstructions/surfaces
as the manual warns. Still I just know we'll stumble across these units
and antennas buried behind panels with owners unsure why they don't work
properly.

Darryl


Who said anyone was "highly disturbed"? I didn't.

Can you cite any other GPS based gliding equipment that requires the GPS
antenna to be installed more than 30cm from any other GPS antenna? I don't
give a rat's arse about the compass but I do care that my other GPS
receivers (currently 3 of them behind or on the panel) continue to work and
there are reports from Uvalde of interference to other GPS based equipment.


Sure FLARM is covering their arse. If there are problems of interference
with other equipment the first question will be "Did you meet the antenna
separation requirements?"

Why would anyone buy a piece of equipment knowing that they could not meet
the installation requirements? Why would anyone build equipment with
strict antenna separation requirements and then make the radiating antenna
non removable thus preventing it's relocation?

PowerFLARM has to work with closer antenna separation that 30cm. If it
cannot, it needs a design change. If it can, the user manual needs to be
revised.

Andy

On 8/10/2011 2:41 PM, Andy Durbin wrote:


Can you cite any other GPS based gliding equipment that requires the GPS
antenna to be installed more than 30cm from any other GPS antenna?

I've been told by Cambridge to separate the 302 GPS antenna from other
GPS antennas by "more than a foot" and "as much as possible".

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to
email me)
- "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm
http://tinyurl.com/yb3xywl
- "A Guide to Self-launching Sailplane Operation Mar/2004" Much of what
you need to know tinyurl.com/yfs7tnz

[snip]

Who said anyone was "highly disturbed"? I didn't.

OK you said "very disturbing". I am highly disturbed at all the
melodrama.

Can you cite any other GPS based gliding equipment that requires the
GPS
antenna to be installed more than 30cm from any other GPS antenna?

Classic FLARM product documentation for years has talked about 25cm
separation. So hopefully this type of spec is not a surprise to many
folks who have been interested in FLARM for a while. And there are
thousands and thousands of classic FLARM systems flying and those pilots
have managed to live with 25cm separation specs and the very occasional
need to jigger things around to reduce any interference issues.

The Flarm transmitter is ~1Ghz (~915 MHz in the USA). GPS receivers are
very sensitive and operate on 1.2/1.5 GHz and when you mix these things
together in a close environment there is just always going to be some
chance of interference. And I am not as worried about the engineering of
FLARM products as much as I am that of other systems that might suffer
interference. There are many shoddy/badly designed and installed devices
out there in the wild wild west of glider cockpit avionics.

The need in the USA for a permanently attached FLARM antenna was the
FCC's requirement not something FLARM wanted to do.

give a rat's arse about the compass but I do care that my other GPS
receivers (currently 3 of them behind or on the panel) continue to
work and
there are reports from Uvalde of interference to other GPS based
equipment.

Sure FLARM is covering their arse. If there are problems of
interference
with other equipment the first question will be "Did you meet the
antenna
separation requirements?"

Just install the unit, in the unlikely event you do have interference
issues move the GPS antennas and fix it. FLARM just cannot engineer a
transmitter that is guaranteed not to interfere with any random GPS or
other electronic product out there. And the first response from any
vendor in that type environment (where they have no control over the
engineering and installation of the other boxes) had to be to tell users
to first try separating the antennas.

I expect many pilots may well replace one existing GPS receiver as they
want the FLARM enhanced NMEA data. That obviously does not remove need
for other receivers or backup receivers but if you do happen to end up a
having problems and have three existing GPSAnyhow just install the unit,
in the unlikely chance you do have interference issues move the GPSs
antennas and fix it. FLARM just cannot engineer a transmitter that is
guaranteed not to interfere with any random GPS or other electronic
product out there. And the first response from any vendor in that type
environment (where they have no control over the engineering of the
other boxes) had to be to tell users to first try separating the
antennas.

if you do happen to end up with problems and really have three existing
receivers and a fourth in the FLARM it may be time to clean up/simplify
your avionics!

Why would anyone buy a piece of equipment knowing that they could not
meet
the installation requirements? Why would anyone build equipment with
strict antenna separation requirements and then make the radiating
antenna
non removable thus preventing it's relocation?

PowerFLARM has to work with closer antenna separation that 30cm. If
it
cannot, it needs a design change. If it can, the user manual needs to
be
revised.

The user manual could better explain the reasons these limits are there.


Darryl

A note on the vertical antenna on the FLARM unit. I didn't like
looking at it so the first mod to the OzFLARM in the Nimbus 3 was to
remove the black plastic casing from the antenna and replace it with
Tygon tubing.
The second mod was to buy a stick-on antenna and put it on the canopy.
Anyone at Uvalde can probably have a look at VJS, but I don't think
Steve is using that antenna yet. Photo also on Soaring Cafe. That
antenna was available from Nigel Andrews (RF Developments) who built
the OzFLARM. Perhaps still is available, or perhaps from Swift
Avionics who do have other remote FLARM antennas.
Jim