Today's Message Index:
----------------------
1. 05:39 AM - Re: Re: Proposed Z-14 implementation (Robert L. Nuckolls, III)
2. 06:24 AM - Fw: Re: Proposed Z-14 implementation (Earl Schroeder)
3. 07:20 AM - Z-14 for electrically dependent engine (Krea Ellis)
4. 08:24 AM - Re: Z-14 for electrically dependent engine (Charlie England)
5. 09:34 AM - Re: Z-14 for electrically dependent engine (Robert L. Nuckolls, III)
6. 09:39 AM - Re: Z-14 for electrically dependent engine (Robert L. Nuckolls, III)
7. 10:49 AM - Z-14 implementation (Krea Ellis)
8. 12:10 PM - Re: Z-14 implementation (Foghorn Inc)
9. 12:18 PM - Re: Z-14 implementation (Robert L. Nuckolls, III)
10. 12:25 PM - Re: Z-14 for electrically dependent engine (Randy C-GRPY)
11. 05:02 PM - GPS notch filter? (Pat Little)
12. 05:21 PM - Re: Protecting the fat wires (Randy C-GRPY)
13. 06:23 PM - Re: GPS notch filter? (Robert L. Nuckolls, III)
14. 07:31 PM - Re: Protecting the fat wires (user9253)
15. 08:25 PM - Re: GPS notch filter? (Pat Little)
16. 09:15 PM - Re: GPS notch filter? (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Proposed Z-14 implementation |
>
> > So I'll repeat the question. Suppose all SDS
> > injectors were powered from one bus . . . each
> > protected by its own fuse. What failure condition
> > would bring down power necessary to kill the
> > engine?
>
>
>With their design I can't see how either. However, could they have
>installed a switch or
>an appropriately sized relay for each of the main feeds so that each
>could be turned on
>and off in sequence?
Sure . . . but consider that this increases parts
count, some of which have moving parts and arcing
contacts. All this fuss to raise confidence in
a battery, alternator or bus structure?
Would it not be more elegant to provide a
redundantly robust source delivered from
a single distribution point wherein no
additional hardware (or pilot workload)
is built into the system?
>As for the SDS, I think we are on the same page but maybe
>not. You've said that the
>bus and the feeding wires properly installed are incredibly reliable. I think
>that it is therefore safe to run all of the injectors (each properly
>protected),
>as well as the other components (also properly protected) off of a single bus
>that has two useable power feeds as the manufacturer has designed.
>No single battery or alternator failure will bring the house down. So to
>answer your last question in a different way, I don't think anything other
>than failure of the battery, the feeding wire, or the bus bar would
>kill the engine.
>
>Boy I hope that I'm not being thick headed with this. Thanks for
>your patience.
No problem . . .that's what we do here. You are
correct.
Put yourself in the shoes of an accessory designer/
manufacturer wherein the target market consists of
end users . . . consumers. While more understanding
of things technical, their range of skills covers
a lot of ground most of which isn't herding electrons.
So what's the best advice you can offer your customer with
respect to keeping YOUR rather critical piece of
hardware operating?
It's this kind of worrying that gave birth to
Lightspeed's main/aux battery recommendations
which were duplicated in other products. It
prompted some suppliers to incorporate standby
batteries right into their product. It has
encouraged the sales and incorporation of
countless standby batteries in OBAM aircraft.
The same philosophy drove sales of hundreds
if not thousands of 'flight bag batteries'
in the TC world.
I recall a vendor at OSH hawking one of the
earliest examples of an AGM battery along
with a cable to plug it into the ship's
cigar lighter. The idea was that when the
panel goes dark, you can turn the generator/
alternator and battery off then plug this
device in to get some stuff running again.
No STC required . . . not permanently
installed.
12 pounds of dead-weight carried around
in the cockpit . . . for what? A
hedge against failure in a CERTIFIED
system that place the mission, hardware
and people at risk. Ugh!
Garmin stepped up to their worries by
consideration of Z-14 as a recommended
architecture for OBAM aircraft installations
of their products . . . but stepped into
the tar-pit with ill-considered 'adjustments'.
While well meaning (and perhaps self serving
for reducing liabilities) any attempt
to keep ONE product energy independent
doesn't account a real need to keep LOTS if
not ALL products working.
The obvious solution is to ditch all the
electro-whizzy supplier's notions of back-up
systems and concentrate on a failure-tolerant
architecture that supports most if not
all the electro-whizzies.
Design goals should include minimized parts
count which goes to increased reliability,
reduced work load and decreased cost of
ownership.
If it's a good thing to worry about keeping sparks
and pumps running . . . is it any less
important to keep other things running too?
Especially when boring holes in clouds,
overflying mountains at night or hauling
a cabin full of fellow travelers?
I suggest it's far more elegant to ditch
all back-up systems targeted to support one
critical system in favor of one system
designed with the greatest reverence
for artful FMEA and craftsmanship.
Bob . . .
Message 2
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| Subject: | Re: Proposed Z-14 implementation |
Begin forwarded message:
> From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
> Date: February 2, 2020 at 7:44:27 AM CST
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Re: Proposed Z-14 implementation
>
>
>
> I suggest it's far more elegant to ditch
> all back-up systems targeted to support one
> critical system in favor of one system
> designed with the greatest reverence
> for artful FMEA and craftsmanship.
>
> Bob . . .
>
Hear Hear !!
Message 3
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| Subject: | Z-14 for electrically dependent engine |
Again, apologies for having to use email to post to the forum. Ive registered
and reached out to Matt a couple of times, but I still cannot log in and post
directly. Most of my emails bounce back too - although it appears someone is receiving
them.
Mr. Nuckolls and the others posting - thank you for your continued input on the
work we are all attempting for a safe implementation of a redundant and/or reliable
electrical system for our electrically dependent engines.
I really appreciate the lack of comments like just install magnetos or pMags and
mechanical fuel injection somewhat common on other forums.
Here are a couple of points and questions that may have been covered, but I would
like to reiterate.
1. At least with SDS on the 6 cylinder installations, providing independent power
sources to the fuel pumps, coil packs and ECUs is very straightforward using
the Z-14 architecture. Confirmation of proper operation of each component prior
to flight is also easily carried out.
2. As there is no redundancy with the fuel injectors and since they are powered
by the airframe, independent, redundant power is more difficult and/or complex.
Loss of an injector (or bank of injectors) is easily determined at any time,
but difficult to remedy during flight. Good news is that the injectors are
very reliable (assuming competent installation).
3. A dual bus fed diode protected engine or injector bus violates the very pure
separation that exists in Z-14, but as of right now - there are no dual power
source alternatives of which I am aware. I am using the term power source as
a single battery and alternator fed bus.
4. A single bus could be utilized for all injectors, but would provide no alternative
in the event of a loss of that one main bus. This would be the simplest
approach I believe, but provides less redundancy. Also less potential failure
points, but which bus of the two available do you use?
I am working with the folks at SDS on a scheme for providing a passive power path
to the injectors with each bank being fed independently and alternate paths
(using a more complex arrangement) to switch all injectors to one bus or the
other if needed due to the loss of one bus or the other. The downside of this
approach will clearly be additional components that will have failure points.
The counter to that these components will likely be very similar to those already
used and tested by SDS for the injector signal paths. Loss of signal (ground)
paths or loss of power is equally problematic in any SDS type installation.
More info to come hopefully later this week from SDS and I continue to lose sleep
over this issue. Probably overthinking this and as I have to remind myself
- we are not building Part 25 Transport Category Airplanes.
Thank you!
Krea Ellis
Message 4
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| Subject: | Re: Z-14 for electrically dependent engine |
On 2/2/2020 9:17 AM, Krea Ellis wrote:
>
> Again, apologies for having to use email to post to the forum. Ive registered
and reached out to Matt a couple of times, but I still cannot log in and post
directly. Most of my emails bounce back too - although it appears someone is
receiving them.
>
> Mr. Nuckolls and the others posting - thank you for your continued input on the
work we are all attempting for a safe implementation of a redundant and/or
reliable electrical system for our electrically dependent engines.
>
> I really appreciate the lack of comments like just install magnetos or pMags
and mechanical fuel injection somewhat common on other forums.
>
> Here are a couple of points and questions that may have been covered, but I would
like to reiterate.
>
> 1. At least with SDS on the 6 cylinder installations, providing independent
power sources to the fuel pumps, coil packs and ECUs is very straightforward using
the Z-14 architecture. Confirmation of proper operation of each component
prior to flight is also easily carried out.
> 2. As there is no redundancy with the fuel injectors and since they are powered
by the airframe, independent, redundant power is more difficult and/or complex.
Loss of an injector (or bank of injectors) is easily determined at any time,
but difficult to remedy during flight. Good news is that the injectors are
very reliable (assuming competent installation).
> 3. A dual bus fed diode protected engine or injector bus violates the very pure
separation that exists in Z-14, but as of right now - there are no dual power
source alternatives of which I am aware. I am using the term power source
as a single battery and alternator fed bus.
> 4. A single bus could be utilized for all injectors, but would provide no alternative
in the event of a loss of that one main bus. This would be the simplest
approach I believe, but provides less redundancy. Also less potential failure
points, but which bus of the two available do you use?
>
> I am working with the folks at SDS on a scheme for providing a passive power
path to the injectors with each bank being fed independently and alternate paths
(using a more complex arrangement) to switch all injectors to one bus or the
other if needed due to the loss of one bus or the other. The downside of this
approach will clearly be additional components that will have failure points.
The counter to that these components will likely be very similar to those already
used and tested by SDS for the injector signal paths. Loss of signal (ground)
paths or loss of power is equally problematic in any SDS type installation.
>
> More info to come hopefully later this week from SDS and I continue to lose sleep
over this issue. Probably overthinking this and as I have to remind myself
- we are not building Part 25 Transport Category Airplanes.
>
> Thank you!
>
> Krea Ellis
Hi Krea,
1st, I have *always* used email for this list/forum. When it started,
there was no forum format; it was purely email exchanges with an archive
of the emails. I realize that it isn't exactly '21st century', but it
can have the advantage of being able to retain a record of important
emails on members' local systems. So if you can post via email, roll
with it.
On your concerns about various engine bus redundancies: FWIW, when I
struggled with designing my alt engine stuff and ran into a seemingly
insurmountable issue/conflict, I eventually would come back to looking
at what's been done for decades in 'traditional' engine systems. I came
to realize that there is a single fuel delivery system, and while there
is a backup fuel pump, almost all traditional installations have failure
modes where *either* pump could fail the entire fuel delivery system.
Only the ignition system is truly redundant (and with the old 'dual mag'
modules, even that can be doubtful).
I finally realized that with reasonable 'best practices' when installing
the engine bus (which is simply a ATC fuse block), there just isn't
anything that can cause the bus itself, in its entirety, to fail. The
only thing that could bring down the entire bus would be the supply to
the bus. A 2nd source of power to the bus remedies that issue. If the
single 10-32 stud feeding the bus is a real concern, the most common ATC
fuse bus is relatively easy to modify to add a 2nd 10-32 stud at the
other end of the bus.
With all my engine 'stuff' on one engine bus, backup is now down to
flipping one, or at most two, switches. Whenever I'm pondering
multi-step, multi-layer troubleshooting in the air, I try to remember
the highly trained multi-person airline crew that flew an airliner into
the ground while running through checklists and flipping breakers. The
biggest thing that bothers me about my alt engine installation is the
more complex switchology and significant operational differences from
the systems I (and everyone else) have spent decades flying.
You're not going to be comfortable with your system until you're
comfortable with it. But it might be worth stepping back and looking
'big picture' for a bit. Checking every detail should happen, but
sometimes our initial premise may need re-evaluation. There are one or
two of my basic premises I'm currently rethinking a bit....
Charlie
Message 5
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| Subject: | Re: Z-14 for electrically dependent engine |
>
>3. A dual bus fed diode protected engine or
>injector bus violates the very =9Cpure=9D
>separation that exists in Z-14, but as of right
>now - there are no dual power source
>alternatives of which I am aware. I am using the
>term =9Cpower source=9D as a single battery and alternator fed
bus.
>4. A single bus could be utilized for all
>injectors, but would provide no alternative in
>the event of a loss of that one main bus.
How would that happen? EVERY branch feeder in Z-14
is QUAD sourced until some component fails in flight
(an exceedingly rare event). Two distribution
busses (main and aux) remain at least DUAL sourced
and sometimes TRIPLE sourced depending on nature of failure.
Complete loss of power on either bus just doesn't
happen . . . Z-12 (revised) is another solid
option where a single bus is TRIPLE fed and no
less than DUAL fed after loss of a single
component.
> This would be the simplest approach I believe,
> but provides less redundancy. Also less
> potential failure points, but which bus of the two available do you use?
take your pick . . . it doesn't matter.
>I am working with the folks at SDS on a scheme
>for providing a passive power path to the
>injectors with each bank being fed independently
>and alternate paths (using a more complex
>arrangement) to switch all injectors to one bus
>or the other if needed due to the loss of one bus or the other.
>The downside of this approach will clearly be
>additional components that will have failure
>points. The counter to that these components
>will likely be very similar to those already
>used and tested by SDS for the injector signal
>paths. Loss of signal (ground) paths or loss of
>power is equally problematic in any SDS type installation.
>
>More info to come hopefully later this week from
>SDS and I continue to lose sleep over this
>issue. Probably overthinking this and as I have
>to remind myself - we are not building Part 25 Transport Category
Airplanes.
Can you suggest that SDS contact me with a
goal of collaborating on a unified approach
to minimizing risks?
Bob . . .
Message 6
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| Subject: | Re: Z-14 for electrically dependent engine |
>
>1st, I have *always* used email for this list/forum. When it
>started, there was no forum format; it was purely email exchanges
>with an archive of the emails. I realize that it isn't exactly '21st
>century', but it can have the advantage of being able to retain a
>record of important emails on members' local systems. So if you can
>post via email, roll with it.
I have always used the email portal except when
participating away from the office . . . perhaps
on a computer not belonging to me.
Threads are seamless, locally archived and easy
to trim. I have copies of threads going back about
15 years that are easily searched for content.
Bob . . .
Message 7
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| Subject: | Z-14 implementation |
Clearly, my emails are getting through even though I get a reply from
the server that they are being rejected.
Thanks for all the valuable information and thoughtful responses.
You're not going to be comfortable with your system until you're
comfortable with it. But it might be worth stepping back and looking
'big picture' for a bit. Checking every detail should happen, but
sometimes our initial premise may need re-evaluation. There are one or
two of my basic premises I'm currently rethinking a bit....
Charlie
Agreed and I am stepping back and working hard to overcome the concerns
about multiple redundancies. Years of flying big iron I guess and a fear
about new ground (at least for me) with SDS.
How would that happen? EVERY branch feeder in Z-14
is QUAD sourced until some component fails in flight
(an exceedingly rare event). Two distribution
busses (main and aux) remain at least DUAL sourced
and sometimes TRIPLE sourced depending on nature of failure.
Complete loss of power on either bus just doesn't
happen . . . Z-12 (revised) is another solid
option where a single bus is TRIPLE fed and no
less than DUAL fed after loss of a single
component.
I need to keep things in perspective. In 1000 hours of GA flying and
multiple thousands of large airplanes, any electrical problems I have
had have been totally controllable and I have never had total electrical
failure - although there are plenty of anecdotal stories of that
happening. So the risk is probably very small.
I guess things are quad sourced if you assume you can close the cross
tie contactor. I was hoping to do that only for start and only in a
dire emergency in flight. But if the only source of power to the
injectors has failed, not much to lose by closing the cross tie and hope
it powers up. Screens in front are backed up by an IBBS battery and the
G5 has an internal battery, so we can keep the shiny side up no matter
if we are a glider.
Can you suggest that SDS contact me with a
goal of collaborating on a unified approach
to minimizing risks?
I will absolutely do that a greatly appreciate your willingness to help
me (and others) through this.
I am coming to the conclusion quickly that a single injector bus fed by
one of the two battery busses and with a good battery and an externally
regulated alternator is probably the best compromise of simplicity and
reliability. I=99d still like to consider a slightly more
redundant approach too.
Krea
Message 8
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| Subject: | Re: Z-14 implementation |
Here is what I=99m working on for my SDS powered RV8. This is a
work in progress. I=99m not sure about the diodes to the ENG BUS
since I can control power through the switches from the BATT BUSs one at
a time. The main ALT is a PP 60A internally regulated, until it fails,
then I=99m going to switch to a B&C externally regulated ALT. For
now I=99m going to give the PP and VPX the opportunity to run the
show.
Ok I=99m here to learn so help me get smarter.
Jeff Parker
> On 2Feb, 2020, at 13:45, Krea Ellis <krea.ellis@gmail.com> wrote:
>
> Clearly, my emails are getting through even though I get a reply from
the server that they are being rejected.
>
> Thanks for all the valuable information and thoughtful responses.
>
> You're not going to be comfortable with your system until you're
> comfortable with it. But it might be worth stepping back and looking
> 'big picture' for a bit. Checking every detail should happen, but
> sometimes our initial premise may need re-evaluation. There are one or
> two of my basic premises I'm currently rethinking a bit....
>
> Charlie
>
> Agreed and I am stepping back and working hard to overcome the
concerns about multiple redundancies. Years of flying big iron I guess
and a fear about new ground (at least for me) with SDS.
>
> How would that happen? EVERY branch feeder in Z-14
> is QUAD sourced until some component fails in flight
> (an exceedingly rare event). Two distribution
> busses (main and aux) remain at least DUAL sourced
> and sometimes TRIPLE sourced depending on nature of failure.
>
> Complete loss of power on either bus just doesn't
> happen . . . Z-12 (revised) is another solid
> option where a single bus is TRIPLE fed and no
> less than DUAL fed after loss of a single
> component.
>
> I need to keep things in perspective. In 1000 hours of GA flying and
multiple thousands of large airplanes, any electrical problems I have
had have been totally controllable and I have never had total electrical
failure - although there are plenty of anecdotal stories of that
happening. So the risk is probably very small.
>
> I guess things are quad sourced if you assume you can close the cross
tie contactor. I was hoping to do that only for start and only in a
dire emergency in flight. But if the only source of power to the
injectors has failed, not much to lose by closing the cross tie and hope
it powers up. Screens in front are backed up by an IBBS battery and the
G5 has an internal battery, so we can keep the shiny side up no matter
if we are a glider.
>
> Can you suggest that SDS contact me with a
> goal of collaborating on a unified approach
> to minimizing risks?
>
> I will absolutely do that a greatly appreciate your willingness to
help me (and others) through this.
>
> I am coming to the conclusion quickly that a single injector bus fed
by one of the two battery busses and with a good battery and an
externally regulated alternator is probably the best compromise of
simplicity and reliability. I=99d still like to consider a
slightly more redundant approach too.
>
> Krea
Message 9
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| Subject: | Re: Z-14 implementation |
>
>I guess things are quad sourced if you assume
>you can close the cross tie contactor. I was
>hoping to do that only for start and only in a dire emergency in flight.
The whole reason for the cross-feed contactor
is to PREVENT a 'dire emergency' . . . not
react to one.
If system components never failed, FBOs would
be out of business. Tires and batteries wear
out. Radios go belly up.
> But if the only source of power to the
> injectors has failed, not much to lose by closing the
>cross tie and hope it powers up.
Okay, failure of WHAT component would prompt closing
the cross-tie? Will failure of that component result
in instant loss of engine?
> Screens in front are backed up by an IBBS
> battery and the G5 has an internal battery,
> so we can keep the shiny side up no matter if we are a glider.
Batteries which, in my never humble opinion,
only add cost of ownership and offer little
benefit in terms of mission reliability.
If one of these batteries is ever called
upon to do it's job, it's because you
probably DO HAVE a real EMERGENCY borne
of poor design and/or craftsmanship.
>Can you suggest that SDS contact me with a
>goal of collaborating on a unified approach
>to minimizing risks?
>
>I will absolutely do that a greatly appreciate
>your willingness to help me (and others) through this.
>
>I am coming to the conclusion quickly that a
>single injector bus fed by one of the two
>battery busses and with a good battery and an
>externally regulated alternator is probably the
>best compromise of simplicity and reliability.
>I=99d still like to consider a slightly more redundant approach too.
Define 'slightly' and articulate the
sequence of failure events that would
bring that benefit into play.
This is what failure mode effects analysis
is all about. You need to have confidence
in your minimally configured, well considered
constellation of airframe systems. Otherwise,
the benefit of a 'slightly more redundant'
feature is reduced to the same utility
as carrying a rabbit's foot.
What you're going through here is equivalent
to a process I've participated in dozens of
times. They're called Preliminary and Critical
Design Reviews. I've stood in front of a
Power Point screen many times in a room full
of Navy engineers, technicians, pilots and
program managers along with other members
of my project group.
In my later years, I 'ran the gauntlet'
and sold the idea(s) most of the time.
On occasion, I took some hits. But in
any case, the process was invaluable
in that it prevented bad ideas from
going to production.
I suggest that what we're doing here
has the same goals. Another goal is to
eliminate the word 'emergency' from the
lexicon of electrics-speak . . . we're
just not going to have one.
Bob . . .
Message 10
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| Subject: | Re: Z-14 for electrically dependent engine |
nuckolls.bob(at)aeroelect wrote:
>
> >
> > 3. A dual bus fed diode protected engine or injector bus violates the very
pure separation that exists in Z-14, but as of right now - there are no dual
power source alternatives of which I am aware. I am using the term power source
as a single battery and alternator fed bus.
> > 4. A single bus could be utilized for all injectors, but would provide no
alternative in the event of a loss of that one main bus.
>
> How would that happen? EVERY branch feeder in Z-14
> is QUAD sourced until some component fails in flight
> (an exceedingly rare event). Two distribution
> busses (main and aux) remain at least DUAL sourced
> and sometimes TRIPLE sourced depending on nature of failure.
>
> Complete loss of power on either bus just doesn't
> happen . . . Z-12 (revised) is another solid
> option where a single bus is TRIPLE fed and no
> less than DUAL fed after loss of a single
> component.
>
>
>
> > This would be the simplest approach I believe, but provides less redundancy.
Also less potential failure points, but which bus of the two available do you
use?
>
> take your pick . . . it doesn't matter.
>
>
>
> > I am working with the folks at SDS on a scheme for providing a passive power
path to the injectors with each bank being fed independently and alternate paths
(using a more complex arrangement) to switch all injectors to one bus or
the other if needed due to the loss of one bus or the other.The downside of this
approach will clearly be additional components that will have failure points.
The counter to that these components will likely be very similar to those already
used and tested by SDS for the injector signal paths. Loss of signal (ground)
paths or loss of power is equally problematic in any SDS type installation.
> >
> > More info to come hopefully later this week from SDS and I continue to lose
sleep over this issue. Probably overthinking this and as I have to remind myself
- we are not building Part 25 Transport Category Airplanes.
>
>
> Can you suggest that SDS contact me with a
> goal of collaborating on a unified approach
> to minimizing risks?
>
>
> Bob . . .
I emailed Ross with your offer Bob.
Randy
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494604#494604
Message 11
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| Subject: | GPS notch filter? |
Rooting around in boxes at the hangar the other day I came across a
"thingy" (technical term) with part number TED 4-70-54. Apparently it is a
notch filter to stop radio harmonics interfering with GPS reception
(see SkyGeek
listing
<https://www.skygeek.com/ted-4-70-54-inline-gps-notch-filter-bnc.html>).
I'm using an MGL V16 radio, and GPS in the form of a Garmin G5 (internal
antenna) and a SkyFYX for the ADS-B setup, plus possibly iPad on the panel
and/or handhelds. The V16 will be under the passenger's seat, the SkyFYX
above the passenger's head, and the G5 on the pilot's side of the panel.
Airplane is a Zenith STOL CH 750.
Is there any good reason to incorporate the notch filter in my design? And
if so, where best to put it?
Pat
Message 12
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| Subject: | Re: Protecting the fat wires |
user9253 wrote:
> Mount 40 amp automotive relays (B&C S8009-1) within 3" of battery positive
> posts. Connect 14 AWG between battery positive and relay. This 14 AWG
> wire will serve as a fuselink. No fuses needed. Connect the relay output to
> the engine bus with 10 AWG. Diodes could be installed per your diagram, but
> they are not required. The pilot can control which battery is connected to the
> engine bus by turning on one or both relays.
Joe, would a contactor within 3 of the battery also be an option? Why the automotive
relay?
Randy
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494606#494606
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| Subject: | Re: GPS notch filter? |
At 06:59 PM 2/2/2020, you wrote:
>Rooting around in boxes at the hangar the other
>day I came across a "thingy" (technical term)
>with part number TED 4-70-54. Apparently it is a
>notch filter to stop radio harmonics interfering
>with GPS reception (see=C2
><https://www.skygeek.com/ted-4-70-54-inline-gps-notch-filter-bnc.html>SkyGe
ek
>listing). I'm using an MGL V16 radio, and GPS in
>the form of a Garmin G5 (internal antenna) and a
>SkyFYX for the ADS-B setup, plus possibly iPad
>on the panel and/or handhelds. The V16 will be
>under the passenger's seat, the SkyFYX above the
>passenger's head, and the G5 on the pilot's side
>of the panel. Airplane is a Zenith STOL CH 750.
>
>Is there any good reason to incorporate the
>notch filter in my design? And if so, where best to put it?
It would not hurt anything to
install it in the antenna feedline
for vhf comm. The 13th harmonic
of vhf comm energy falls in close
proximity to the gps signals at 1575
or so MHz. GPS signals are very weak . . .
in fact you cannot generaly tune them
in on a normal receiver. Their signals
are literally below the atmospheric
noise floor.
The predictable, encoded nature of
received gps signals allows digital
processing to sniff out these tiny
voices and make sense of them.
Up until the dawn of gps implementation
on civil aircraft, there was no special
attention given to DO160 qualification
of vhf comm transceivers to offer special
protection to gps spectrum . . . after
all it WAS the 13th harmonic we're fussing
about.
But it turns out that significant numbers
of vhf comm systems already in place
generated 13th harmonic energy bad enough
to degrade if not snafu a gps signal.
Hence, the 'gps notch' filter band-aid
allowed these slightly-less-than-civilized
transceivers to coexist with gps equipment
on board an aircraft.
In the interim, gps receiver performance has
taken some quantum leaps . . . you got the
things in cell phones, cameras and wrist-watches.
At the same time, DO160 qualification requirements
added a band of additional protection to gps
spectrum. You can buy surface-mount gps notch
filters to be included in your vhf-comm
offering . . . and getting your DO160
blue ribbon requires that these frequencies
be protected.
The short answer is, you probably don't
need it. But do some flight testing to see
if gps signal strength values are depressed
while transmitting . . . you'd want to do
testing at 25 Khz steps from 120 MHz to
122 MHz . . .
-OR-
Check with the manufacturer of your transceiver
as to compliance with CURRENT gps protection
requirements . . .
-OR-
Stick the thing in anyhow . . . won't hurt a thing.
Bob . . .
Message 14
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| Subject: | Re: Protecting the fat wires |
Yes, a contactor will work, but is heavier and its coil uses more current than
a relay.
A 40 amp relay will be adequate for fuel pumps and ignition.
In either case, an arc suppression diode should be installed across the coil.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494608#494608
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| Subject: | Re: GPS notch filter? |
Thanks, Bob. As always, a very helpful and complete answer.
On Sun, Feb 2, 2020 at 7:29 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 06:59 PM 2/2/2020, you wrote:
>
> Rooting around in boxes at the hangar the other day I came across a
> "thingy" (technical term) with part number TED 4-70-54. Apparently it is
a
> notch filter to stop radio harmonics interfering with GPS reception (see
=C3=82 SkyGeek
> listing
> <https://www.skygeek.com/ted-4-70-54-inline-gps-notch-filter-bnc.html>).
> I'm using an MGL V16 radio, and GPS in the form of a Garmin G5 (internal
> antenna) and a SkyFYX for the ADS-B setup, plus possibly iPad on the pane
l
> and/or handhelds. The V16 will be under the passenger's seat, the SkyFYX
> above the passenger's head, and the G5 on the pilot's side of the panel.
> Airplane is a Zenith STOL CH 750.
>
> Is there any good reason to incorporate the notch filter in my design? An
d
> if so, where best to put it?
>
>
> It would not hurt anything to
> install it in the antenna feedline
> for vhf comm. The 13th harmonic
> of vhf comm energy falls in close
> proximity to the gps signals at 1575
> or so MHz. GPS signals are very weak . . .
> in fact you cannot generaly tune them
> in on a normal receiver. Their signals
> are literally below the atmospheric
> noise floor.
>
> The predictable, encoded nature of
> received gps signals allows digital
> processing to sniff out these tiny
> voices and make sense of them.
>
> Up until the dawn of gps implementation
> on civil aircraft, there was no special
> attention given to DO160 qualification
> of vhf comm transceivers to offer special
> protection to gps spectrum . . . after
> all it WAS the 13th harmonic we're fussing
> about.
>
> But it turns out that significant numbers
> of vhf comm systems already in place
> generated 13th harmonic energy bad enough
> to degrade if not snafu a gps signal.
>
> Hence, the 'gps notch' filter band-aid
> allowed these slightly-less-than-civilized
> transceivers to coexist with gps equipment
> on board an aircraft.
>
> In the interim, gps receiver performance has
> taken some quantum leaps . . . you got the
> things in cell phones, cameras and wrist-watches.
> At the same time, DO160 qualification requirements
> added a band of additional protection to gps
> spectrum. You can buy surface-mount gps notch
> filters to be included in your vhf-comm
> offering . . . and getting your DO160
> blue ribbon requires that these frequencies
> be protected.
>
> The short answer is, you probably don't
> need it. But do some flight testing to see
> if gps signal strength values are depressed
> while transmitting . . . you'd want to do
> testing at 25 Khz steps from 120 MHz to
> 122 MHz . . .
>
> -OR-
>
> Check with the manufacturer of your transceiver
> as to compliance with CURRENT gps protection
> requirements . . .
>
> -OR-
>
> Stick the thing in anyhow . . . won't hurt a thing.
>
> Bob . . .
>
Message 16
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| Subject: | Re: GPS notch filter? |
At 06:59 PM 2/2/2020, you wrote:
>Rooting around in boxes at the hangar the other
>day I came across a "thingy" (technical term)
>with part number TED 4-70-54. Apparently it is a
>notch filter to stop radio harmonics interfering
>with GPS reception (see=C2
><https://www.skygeek.com/ted-4-70-54-inline-gps-notch-filter-bnc.html>SkyGe
ek
>listing). I'm using an MGL V16 radio, and GPS in
>the form of a Garmin G5 (internal antenna) and a
>SkyFYX for the ADS-B setup, plus possibly iPad
>on the panel and/or handhelds. The V16 will be
>under the passenger's seat, the SkyFYX above the
>passenger's head, and the G5 on the pilot's side
>of the panel. Airplane is a Zenith STOL CH 750.
>
>Is there any good reason to incorporate the
>notch filter in my design? And if so, where best to put it?
It would not hurt anything to
install it in the antenna feedline
for vhf comm. The 13th harmonic
of vhf comm energy falls in close
proximity to the gps signals at 1575
or so MHz. GPS signals are very weak . . .
in fact you cannot generaly tune them
in on a normal receiver. Their signals
are literally below the atmospheric
noise floor.
The predictable, encoded nature of
received gps signals allows digital
processing to sniff out these tiny
voices and make sense of them.
Up until the dawn of gps implementation
on civil aircraft, there was no special
attention given to DO160 qualification
of vhf comm transceivers to offer special
protection to gps spectrum . . . after
all it WAS the 13th harmonic we're fussing
about.
But it turns out that significant numbers
of vhf comm systems already in place
generated 13th harmonic energy bad enough
to degrade if not snafu a gps signal.
Hence, the 'gps notch' filter band-aid
allowed these slightly-less-than-civilized
transceivers to coexist with gps equipment
on board an aircraft.
In the interim, gps receiver performance has
taken some quantum leaps . . . you got the
things in cell phones, cameras and wrist-watches.
At the same time, DO160 qualification requirements
added a band of additional protection to gps
spectrum. You can buy surface-mount gps notch
filters to be included in your vhf-comm
offering . . . and getting your DO160
blue ribbon requires that these frequencies
be protected.
The short answer is, you probably don't
need it. But do some flight testing to see
if gps signal strength values are depressed
while transmitting . . . you'd want to do
testing at 25 Khz steps from 120 MHz to
122 MHz . . .
-OR-
Check with the manufacturer of your transceiver
as to compliance with CURRENT gps protection
requirements . . .
-OR-
Stick the thing in anyhow . . . won't hurt a thing.
Bob . . .
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