Garmin 396 Reception Problems Solved!

O.K. That's great. We now know where the interference is coming from. My
question now is: "why?". I have had several GPS receivers and none of
them fritzed out in this plane like the 396 is doing. I would think that
the new Garmin Gee-Whiz box would be BETTER at rejecting noise and
interference than previous units. I have a 12 year old Apollo that never
had these problems in many, many years of use.

My answer to Garmin on the below is: "Thanks for the answer, but that is
unacceptable. Fix it!". For $2300 this unit should do handstands, perfectly.

Anyone know why this particular model line does this?

Thanks,
Mike
On Tue, 18 Sep 2007 18:06:25 -0500, Mike Spera
wrote:


Well, as many of you can remember, I have posted my saga about
intermittent reception problems with my Garmin GPSMAP 396 from day one.


The same reason my 196 loses reception, from Garmin's support database

"
Question: Why is my GPS losing satellites in the middle of my flight?
Answer:

Portable GPS units have the ability to experience loss of satellite
reception as a result of RF interference caused by a variety of
sources. These sources can be as simple as a portable MP3 Player used
for in flight entertainment to a ground based air traffic control
radar antenna on an airport. When these devices are powered on and are
in close proximity to the portable GPS or antenna, the GPS may lose
satellite acquisition as a result. Another common source of RF
interference is aircraft communication and navigation radios. When
certain radios are tuned to a specific frequency there is the
potential for enough RF interference to be released that the Portable
GPS unit will experience loss of satellite reception as though the
signals were being jammed. An article in the Aviation Consumer, dated
February 15th, 1994 has outlined a list of aviation communication
radios and frequencies that may cause a portable GPS unit to lose
satellite reception in the aircraft. This information is listed below.

Radio Frequencies That May Jam GPS Receivers.

Transmit 131.285 and 121.186 Receive

Narco MK 12D/E Com 810/811, Nav 824/825 Com 131.220 and 119.285 Nav
115.464 and 109.672

King KX 155/165 Com 131.820 and 119.885 Nav 116.128 and 109.564

King KX 170/175 Com 122.285 and 130.186 Nav 113.651

Collins Microline Com 132.720 and 120.785 Microline Nav 116.028 and
109.464

Notes: KX 155/165 transmitting on 118.15 ws shown to jam an external
mounted antenna. Narco MK 16 tuned to any 115 or 109 Nav channel was
shown to jam a hand held GPS. Narco MK 12D/E and Nav 824/825, if not
wired with memory keep alive, will default to 115.5 MHz in the active
channel and will jam any GPS receiver.
Last modified on: 08/30/2007

"

If I understand the reply, noted below, then the intereference is a
stronger signal than the satellites. You cannot fix the impossible!
Either you increase the power of the satellites many miles away to
make it stronger than the local interference or remove the local
interference.

As for the older equipment it was probably less sensitive or used
different frequencies within the receiver. Sadly that's how
electronics works. If you put the GPS antenna close to a source of
interference it will pick it up.

Interferece problems were often reported by viewers, of TV in UK,
using indoor antennas. Whilst they may work it is more by luck.



On Wed, 03 Oct 2007 20:46:35 -0500, Mike Spera
wrote:

O.K. That's great. We now know where the interference is coming from. My
question now is: "why?". I have had several GPS receivers and none of
them fritzed out in this plane like the 396 is doing. I would think that
the new Garmin Gee-Whiz box would be BETTER at rejecting noise and
interference than previous units. I have a 12 year old Apollo that never
had these problems in many, many years of use.

My answer to Garmin on the below is: "Thanks for the answer, but that is
unacceptable. Fix it!". For $2300 this unit should do handstands, perfectly.

Anyone know why this particular model line does this?

Thanks,
Mike
On Tue, 18 Sep 2007 18:06:25 -0500, Mike Spera
wrote:


Well, as many of you can remember, I have posted my saga about
intermittent reception problems with my Garmin GPSMAP 396 from day one.


The same reason my 196 loses reception, from Garmin's support database

"
Question: Why is my GPS losing satellites in the middle of my flight?
Answer:

Portable GPS units have the ability to experience loss of satellite
reception as a result of RF interference caused by a variety of
sources. These sources can be as simple as a portable MP3 Player used
for in flight entertainment to a ground based air traffic control
radar antenna on an airport. When these devices are powered on and are
in close proximity to the portable GPS or antenna, the GPS may lose
satellite acquisition as a result. Another common source of RF
interference is aircraft communication and navigation radios. When
certain radios are tuned to a specific frequency there is the
potential for enough RF interference to be released that the Portable
GPS unit will experience loss of satellite reception as though the
signals were being jammed. An article in the Aviation Consumer, dated
February 15th, 1994 has outlined a list of aviation communication
radios and frequencies that may cause a portable GPS unit to lose
satellite reception in the aircraft. This information is listed below.

Radio Frequencies That May Jam GPS Receivers.

Transmit 131.285 and 121.186 Receive

Narco MK 12D/E Com 810/811, Nav 824/825 Com 131.220 and 119.285 Nav
115.464 and 109.672

King KX 155/165 Com 131.820 and 119.885 Nav 116.128 and 109.564

King KX 170/175 Com 122.285 and 130.186 Nav 113.651

Collins Microline Com 132.720 and 120.785 Microline Nav 116.028 and
109.464

Notes: KX 155/165 transmitting on 118.15 ws shown to jam an external
mounted antenna. Narco MK 16 tuned to any 115 or 109 Nav channel was
shown to jam a hand held GPS. Narco MK 12D/E and Nav 824/825, if not
wired with memory keep alive, will default to 115.5 MHz in the active
channel and will jam any GPS receiver.
Last modified on: 08/30/2007

"

Exactly.

All those radios were designed long before GPS. They are noisy and will
interfere with GPS.

That's the reason King made the "A" series of the 155 and 165. They are
designed to co-exist with GPS.


Karl
wrote in message
...
If I understand the reply, noted below, then the intereference is a
stronger signal than the satellites. You cannot fix the impossible!
Either you increase the power of the satellites many miles away to
make it stronger than the local interference or remove the local
interference.

As for the older equipment it was probably less sensitive or used
different frequencies within the receiver. Sadly that's how
electronics works. If you put the GPS antenna close to a source of
interference it will pick it up.

Interferece problems were often reported by viewers, of TV in UK,
using indoor antennas. Whilst they may work it is more by luck.

"karl gruber" wrote in message ...
Exactly.

All those radios were designed long before GPS. They are noisy and will interfere with GPS.

That's the reason King made the "A" series of the 155 and 165. They are designed to co-exist with GPS.


Karl

Garmin designed the 396 stuff for airplanes. Those radios are in airplanes. Garmin made the wrong design choices when
making those boxes. Didn't Garmin buy Apollo? You would think they would have some lessons learned in there somewhere...

Agreed..

I have a Lowrance 2000C, and before that, the 1000..

Neither had (or has now) any problem with the "old" radios in our
"old" (1976) Warrior

A bit of testing would have most likely shown these issues before
production.

If part time pilots can find the problem, you would think the pros
would also..

But then there was the "Magnets in the antenna thingy " as well...



Dave







On Thu, 4 Oct 2007 19:06:46 -0400, "Blueskies"
wrote:


"karl gruber" wrote in message ...
Exactly.

All those radios were designed long before GPS. They are noisy and will interfere with GPS.

That's the reason King made the "A" series of the 155 and 165. They are designed to co-exist with GPS.


Karl

Garmin designed the 396 stuff for airplanes. Those radios are in airplanes. Garmin made the wrong design choices when
making those boxes. Didn't Garmin buy Apollo? You would think they would have some lessons learned in there somewhere...

On Thu, 4 Oct 2007 19:06:46 -0400, "Blueskies"
wrote:


"karl gruber" wrote in message ...
Exactly.

All those radios were designed long before GPS. They are noisy and will interfere with GPS.

That's the reason King made the "A" series of the 155 and 165. They are designed to co-exist with GPS.


Karl

Garmin designed the 396 stuff for airplanes. Those radios are in airplanes. Garmin made the wrong design choices when
making those boxes. Didn't Garmin buy Apollo? You would think they would have some lessons learned in there somewhere...


Maybe if you buy all the equipment from the same manufacturer it would
work. When you mix manufacturers they build things slightly
differently using different fequencies.

It may be a poor analogy but if you bought a door for your car would
you expect it to fit all other cars? :-)

The best cure is an external antenna which is therefore shielded from
the avionics equipment so less vulnerable to interference.

I once came across a problem with a commercial TV transmitter breaking
through into a taxi radio some 40 miles away. The TV transmitter was
well in specification and the spurious were very very low but the taxi
radio has a very sensitive receiver. The taxi firm had to use another
frequency but that's how electronics works!