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nuckolls.bob(at)aeroelect
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 Posted: Wed May 28, 2014 7:32 am Post subject: Trio Avionics ProPilot 130 Mhz interference problem (was n |
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At 05:33 PM 5/27/2014, you wrote:
| Quote: | Glad to hear you solved your problem, Sacha. So much for vendors meeting standards like DO-160G. This Trio product is designed incorrectly to meet this standard, and their switching frequencies to move it away from 130.00 MHz is only a band-aid.
We had a discussion earlier about how an open antenna cable could cause damage to a transmitter, and I explained how the wave's voltage can double as it bounces back to the transmitter. Bob said that today's avionics are protected against such damage. I claim not all electronics are designed to DO-160 and if they are, sometimes engineers make mistakes or the product is manufactured incorrectly. As Bob said, it's a very small probability but it can happen. |
We're talking about two different critters here . . .
DO-160 is not a requirement but a validation guide
for design goals. It's sorta like the covenants you
sign with the homeowner's association that says you
both understand and agree to certain behaviors. It
gives you and your neighbors a level of confidence
for friendly co-existence in a close knit community.
Wrapping SWR protection around the final amplifier
of a transmitter is a common sense recognition of
risk followed by a behavior to design for SWR robustness
-or- automatic reduction of drive to the final amplifier
when excessive SWR is detected. Both approaches have been
part of the best we know how to do for decades. Neither
one is difficult. For writers in technical matters
to make blanket statements warning against test
operations into open transmission lines suggests
that they simply choose not to avail themselves
of pretty common knowledge. Consider the hand-held
transceiver that can be keyed into a constellation
of antennas presenting SWR values the hand-held
designer has no control over . . . but it's no
big deal . . . protection against such hazard
is rudimentary to the contemporary design process.
Not designing around the risks for high
SWR is like opening the hood of a modern car
to find a carburetor sitting on top of the engine
. . . everybody looks at each other and asks
"why would anyone do that?"
On the other hand, my first contact with Trio
suggests that they've treated DO-160 as a 'requirement'.
Given that they do not sell into the TC aircraft
market, they seem to think DO-160 is not applicable/
useful to their design efforts.
I'll see if I can help them deduce the
feature of their product that lets the interfering
energy get outside their box . . . and hopefully
there is a relatively painless solution. We'll
see. It would be useful for them -AND- their
customers to understand that DO-160 guidelines
are recipes for blissful living in the
community of airplane owners no matter where
the airplane was built.
Bob . . . [quote][b]
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henador_titzoff(at)yahoo.
Guest
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| Posted: Wed May 28, 2014 11:46 am Post subject: Trio Avionics ProPilot 130 Mhz interference problem (was n |
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Thanks, Bob, for understanding that DO-160 is a verification standard that lists and specifies requirements for:
- temperature effects
- altitude effects
- humidity effects
- shock and vibration effects
- explosion susceptibility and water proofness
- fluids susceptibility, sand and dust intrusion
- fungus resistance
- salt and fog resistance
- magnetic effect on ship compass
- power input variations effects
- voltage spike effects
- audio frequency conducted susceptibility
- RF susceptibility and emissions
- lightning susceptibility
- icing effects
- ESD susceptibility
- flammability analysis
Since the above parameters are verified, it stands to reason that the avionics designer must design for them in order to pass the DO-160 standard. In Trio's case, they violated RF emissions requirements.
If you do talk to them, please note that the most likely culprit is the PCB design. Proper design here will contain the energy that leaks out the sides of the board and also minimizes radiated RF energy by using microstrip and stripline designs. There are tools such as Mentor Graphics Hyperlynx that can simulate the design and thus minimize it by offering standard solutions as well as making changes and iterating the simulation to see what effect the change made. I've seen designs go from obnoxiously loud to very quiet by using proper design techniques and simulation.
Henador Titzoff
| Quote: | From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
To: aeroelectric-list(at)matronics.com
Sent: Wednesday, May 28, 2014 11:29 AM
Subject: Re: Trio Avionics ProPilot 130 Mhz interference problem (was noise problem on radio)
At 05:33 PM 5/27/2014, you wrote:
| Quote: | Glad to hear you solved your problem, Sacha. So much for vendors meeting standards like DO-160G. This Trio product is designed incorrectly to meet this standard, and their switching frequencies to move it away from 130.00 MHz is only a band-aid.
We had a discussion earlier about how an open antenna cable could cause damage to a transmitter, and I explained how the wave's voltage can double as it bounces back to the transmitter. Bob said that today's avionics are protected against such damage. I claim not all electronics are designed to DO-160 and if they are, sometimes engineers make mistakes or the product is manufactured incorrectly. As Bob said, it's a very small probability but it can happen. |
We're talking about two different critters here . . .
DO-160 is not a requirement but a validation guide
for design goals. It's sorta like the covenants you
sign with the homeowner's association that says you
both understand and agree to certain behaviors. It
gives you and your neighbors a level of confidence
for friendly co-existence in a close knit community.
Wrapping SWR protection around the final amplifier
of a transmitter is a common sense recognition of
risk followed by a behavior to design for SWR robustness
-or- automatic reduction of drive to the final amplifier
when excessive SWR is detected. Both approaches have been
part of the best we know how to do for decades. Neither
one is difficult. For writers in technical matters
to make blanket statements warning against test
operations into open transmission lines suggests
that they simply choose not to avail themselves
of pretty common knowledge. Consider the hand-held
transceiver that can be keyed into a constellation
of antennas presenting SWR values the hand-held
designer has no control over . . . but it's no
big deal . . . protection against such hazard
is rudimentary to the contemporary design process.
Not designing around the risks for high
SWR is like opening the hood of a modern car
to find a carburetor sitting on top of the engine
. . . everybody looks at each other and asks
"why would anyone do that?"
On the other hand, my first contact with Trio
suggests that they've treated DO-160 as a 'requirement'.
Given that they do not sell into the TC aircraft
market, they seem to think DO-160 is not applicable/
useful to their design efforts.
I'll see if I can help them deduce the
feature of their product that lets the interfering
energy get outside their box . . . and hopefully
there is a relatively painless solution. We'll
see. It would be useful for them -AND- their
customers to understand that DO-160 guidelines
are recipes for blissful living in the
community of airplane owners no matter where
the airplane was built.
Bob . . .
| Quote: | http://www.matronics.com/Navigator?AeroE_blank" href="http://forums.matronics.com/">http://forums.matronics.com</ rel="nofollow" target="_blank" href="http://www.matronics.com/contri===
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[quote][b]
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uuccio(at)gmail.com
Guest
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| Posted: Thu May 29, 2014 12:40 pm Post subject: Trio Avionics ProPilot 130 Mhz interference problem (was n |
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>Glad to hear you solved your problem, Sacha.
Thank you.
| Quote: | On the other hand, my first contact with Trio
suggests that they've treated DO-160 as a 'requirement'.
Given that they do not sell into the TC aircraft
market, they seem to think DO-160 is not applicable/
useful to their design efforts.
|
| Quote: | I'll see if I can help them deduce the
feature of their product that lets the interfering
energy get outside their box . . . and hopefully
there is a relatively painless solution. We'll
see. It would be useful for them -AND- their
customers to understand that DO-160 guidelines
are recipes for blissful living in the
community of airplane owners no matter where
the airplane was built.
|
Bob, I have met the folks at Trio personally and believe that they would appreciate your help. In fact they are the people who first pointed me to the AeroElectric list. I’ll forward this conversation to them to see if they have any interest.
Sacha
[quote][b]
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Fri May 30, 2014 6:48 am Post subject: Re: Trio Avionics ProPilot 130 Mhz interference problem (w |
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I designed PCBs for medical devices for 25 years. Some very high-power devices were so quiet that the test lab couldn't tell if the devices were on or not. So a device like Trio Avionics ProPilot and its interference problem does not seem to be a difficult fix. Changing the Xtal DOES seem like a bean-counter fix, but sometimes that is the only way to go. I'd LOVE to inspect the PCB.
In the future Bob and many PCB layout gurus can suggest how to build a PCB and case that will generate fewer customer problems. My absolute conviction is:
1) Short and decoupled clock line;
2) Four layer PCB (solves 90% of the problems).
3) Examine and minimize every single current loop.
I can suggest Kimmel and Gerke of course, but also many online guides like:
http://www.ti.com/lit/an/scaa082/scaa082.pdf
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Fri May 30, 2014 1:41 pm Post subject: Trio Avionics ProPilot 130 Mhz interference problem (was n |
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At 09:48 AM 5/30/2014, you wrote:
--> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net>
I designed PCBs for medical devices for 25 years. Some very high-power devices were so quiet that the test lab couldn't tell if the devices were on or not. So a device like Trio Avionics ProPilot and its interference problem does not seem to be a difficult fix. Changing the Xtal DOES seem like a bean-counter fix, but sometimes that is the only way to go. I'd LOVE to inspect the PCB.
Makes two of us . . . I've offered . . . we'll
see . . .
In the future Bob and many PCB layout gurus can suggest how to build a PCB and case that will generate fewer customer problems. My absolute conviction is:
1) Short and decoupled clock line;
2) Four layer PCB (solves 90% of the problems).
3) Examine and minimize every single current loop.
Yup . . . another great prophylactic is to
use micro-controllers where all the i/o
and clocking is on-board . . . the radiation/
susceptibility apertures are exceedingly
small on a chunk of LSI silicon!
Sometimes you're hosed . . . working a project
now that duty-cycle switches a PM motor at
300 amps and 14 Khz . . . they're closed to
taming this beast but it wasn't easy.
I can suggest Kimmel and Gerke of course, but also many online guides like:
http://www.ti.com/lit/an/scaa082/scaa082.pdf
Absolutely. Took their three-day seminar about
20 years ago from Mr. Kimmel hisself. Good
teacher with eye-opening revelations to offer.
Bob . . . [quote][b]
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