Today's Message Index:
----------------------
1. 03:52 AM - Revmaster with EFIS (William)
2. 06:10 AM - Re: Coaxial Cable (Charlie England)
3. 07:01 AM - Re: Coaxial Cable (Alec Myers)
4. 07:09 AM - Re: Revmaster with EFIS (user9253)
5. 08:02 AM - Re: Coaxial Cable (Charlie England)
6. 08:04 AM - Re: Coaxial Cable (Robert McCallum)
7. 08:30 AM - Re: Coaxial Cable (Alec Myers)
8. 09:36 AM - Re: Reedswitch (Airdog77)
9. 09:46 AM - Re: Coaxial Cable (Charlie England)
10. 09:52 AM - Re: Re: Reedswitch (Charlie England)
11. 10:12 AM - Re: Re: Reedswitch (Robert McCallum)
12. 10:33 AM - Re: Reedswitch (user9253)
13. 10:43 AM - Re: Reedswitch (Airdog77)
14. 10:44 AM - Re: Coaxial Cable (Kelly McMullen)
15. 10:45 AM - Re: Coaxial Cable (Kelly McMullen)
16. 11:46 AM - Contactors (Wladimir Kummer)
17. 01:26 PM - Re: Contactors (Stephen Richards)
18. 01:26 PM - Re: Contactors (Charlie England)
Message 1
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Subject: | Revmaster with EFIS |
I am working on my electrical bus diagram.
Is it better to have both PM Alternators connected at the same time or
switch between them?
I have not been able to find much on this.
Ive included my rough draft version.
Thanks
Bill
Thatcher CX-5
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Subject: | Re: Coaxial Cable |
Here are links to cable specs for RG58a/u (stranded; note that RG58 can be
had with solid center conductor, so beware when ordering), and RG400. I
picked this site/brand to get both sets of specs in the same format.
http://www.awcwire.com/part.aspx?partname=m17/28-rg58
http://www.awcwire.com/part.aspx?partname=m17/128-rg400
Relevant data:
400's center conductor is 0.0384" vs 58's 0.0355"
dielectric (center insulation) is the same dia, but 400 has marginally
better properties; relevant only at the extreme high end of design use:
capacitance of 400 is 29.4pF/ft, vs 58's 30.8pF/ft
test freq of 400 is 12.4 GHz, vs 58's 1 GHz (but we use the cable at a max
of ~1 GHz)
400's loss at 1 GHz is 14.7 dB/100ft; 58's is 22.6 dB/100ft (unfortunately,
I had to pull this spec from other sources; it doesn't show up in the
linked pages)
Doing the math, for a 10 foot run (more than enough to mount the antenna on
the belly of most planes), 400's loss would be 1.47dB vs 58's 2.26dB. For
those that don't know, dB's are a logarithmic measurement. 0.79dB of
difference is so small that it could get lost in the noise of connector
quality, installation technique, phase of the moon...
At comm & nav frequencies (~100 MHz; 1/10 thefrequency), the spread would
be even smaller.
Biggest difference is the outer jacket material; 400 is rated to 200 C,
while 58 is PVC rated to 85 C. Unless you're bonding it to your cylinder
head, that shouldn't be a big factor.
Yes, 400 is 'better'. But is 58 good enough? There are planes flying with
58 that is still good after 40 years.....
Charlie
On Thu, Feb 23, 2017 at 10:52 PM, Art Zemon <art@zemon.name> wrote:
> Folks,
>
> I have been following this thread because I, too, am trying to decide
> which coax to buy for my plane. I'm a computer engineer; I shied away from
> EE in college and especially antenna design because... well... I heard that
> antenna designers were a special kind of crazy.. :-)
>
> Seriously, though, if I understand correctly, in the context of an
> installation in a homebuilt airplane, the biggest difference between RG58
> and RG400 seems to be that the RG400 is less loss-y. Yes? In other words,
> if an antenna puts a weak signal in one end of the coax, the signal that
> reaches the radio receiver will be stronger if the coax is RG400 than if it
> is RG58.
>
> I'm looking at 10 feet of coax from the GPS and comm antennas to the
> receivers, including service loops. I am looking at 20 feet for the VOR/GS
> antenna. The transponder antenna will be less than 10 feet.
>
> At those distances, does RG400 vs RG58 matter? How do I evaluate it?
>
> And then there is the LMR-195 that Bob just showed us. How does that fit
> in?
>
> Thanks,
> -- Art Z.
>
> --
> https://CheerfulCurmudgeon.com/
>
> *"If I am not for myself, who is for me? And if I am only for myself, what
> am I? And if not now, when?" Hillel*
>
Message 3
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Subject: | Re: Coaxial Cable |
I've been following this discussion. Isn't it better to move away from PVC jacketed
cables, for fire safety reasons? Who uses PVC wire vs 22759-16 ETFE insulated
stuff?
On 24Feb2017, at 9:06 AM, Charlie England <ceengland7@gmail.com> wrote:
Here are links to cable specs for RG58a/u (stranded; note that RG58 can be had
with solid center conductor, so beware when ordering), and RG400. I picked this
site/brand to get both sets of specs in the same format.
http://www.awcwire.com/part.aspx?partname=m17/28-rg58
http://www.awcwire.com/part.aspx?partname=m17/128-rg400
Relevant data:
400's center conductor is 0.0384" vs 58's 0.0355"
dielectric (center insulation) is the same dia, but 400 has marginally better properties;
relevant only at the extreme high end of design use: capacitance of
400 is 29.4pF/ft, vs 58's 30.8pF/ft
test freq of 400 is 12.4 GHz, vs 58's 1 GHz (but we use the cable at a max of ~1
GHz)
400's loss at 1 GHz is 14.7 dB/100ft; 58's is 22.6 dB/100ft (unfortunately, I had
to pull this spec from other sources; it doesn't show up in the linked pages)
Doing the math, for a 10 foot run (more than enough to mount the antenna on the
belly of most planes), 400's loss would be 1.47dB vs 58's 2.26dB. For those that
don't know, dB's are a logarithmic measurement. 0.79dB of difference is so
small that it could get lost in the noise of connector quality, installation
technique, phase of the moon...
At comm & nav frequencies (~100 MHz; 1/10 thefrequency), the spread would be even
smaller.
Biggest difference is the outer jacket material; 400 is rated to 200 C, while 58
is PVC rated to 85 C. Unless you're bonding it to your cylinder head, that shouldn't
be a big factor.
Yes, 400 is 'better'. But is 58 good enough? There are planes flying with 58 that
is still good after 40 years.....
Charlie
On Thu, Feb 23, 2017 at 10:52 PM, Art Zemon <art@zemon.name> wrote:
Folks,
I have been following this thread because I, too, am trying to decide which coax
to buy for my plane. I'm a computer engineer; I shied away from EE in college
and especially antenna design because... well... I heard that antenna designers
were a special kind of crazy.. :-)
Seriously, though, if I understand correctly, in the context of an installation
in a homebuilt airplane, the biggest difference between RG58 and RG400 seems
to be that the RG400 is less loss-y. Yes? In other words, if an antenna puts a
weak signal in one end of the coax, the signal that reaches the radio receiver
will be stronger if the coax is RG400 than if it is RG58.
I'm looking at 10 feet of coax from the GPS and comm antennas to the receivers,
including service loops. I am looking at 20 feet for the VOR/GS antenna. The
transponder antenna will be less than 10 feet.
At those distances, does RG400 vs RG58 matter? How do I evaluate it?
And then there is the LMR-195 that Bob just showed us. How does that fit in?
Thanks,
-- Art Z.
--
https://CheerfulCurmudgeon.com/
"If I am not for myself, who is for me? And if I am only for myself, what am I?
And if not now, when?" Hillel
Message 4
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Subject: | Re: Revmaster with EFIS |
Alternators with field coils can fight each other if the regulator voltage set
points are near each other. I do not know about permanent magnet dynamos. But
regardless, I would leave the switch controls as they are. Leave it up to the
pilot to turn on one at a time or both at once. Trying to design it so that
only one dynamo will supply power at a time will result in a single failure
point.
The indicator lights are not necessary or even desired. The pilot will soon
become accustomed to one being on and ignore the lights. The EFIS should warn
of low voltage.
A PDF schematic would be much easier to read then a blurry JPG.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466572#466572
Message 5
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Subject: | Re: Coaxial Cable |
http://www.wikiwand.com/en/ETFE
"Combustion of ETFE occurs in the same way as a number of
otherfluoropolymers <http://www.wikiwand.com/en/Fluoropolymer>, in terms
of releasing hydrofluoric acid (HF). HF is extremely corrosive and
toxic, and so appropriate caution must be exercised."
You decide.
On 2/24/2017 8:59 AM, Alec Myers wrote:
>
> I've been following this discussion. Isn't it better to move away from PVC jacketed
cables, for fire safety reasons? Who uses PVC wire vs 22759-16 ETFE insulated
stuff?
>
>
> On 24Feb2017, at 9:06 AM, Charlie England <ceengland7@gmail.com> wrote:
>
> Here are links to cable specs for RG58a/u (stranded; note that RG58 can be had
with solid center conductor, so beware when ordering), and RG400. I picked this
site/brand to get both sets of specs in the same format.
> http://www.awcwire.com/part.aspx?partname=m17/28-rg58
>
> http://www.awcwire.com/part.aspx?partname=m17/128-rg400
>
> Relevant data:
> 400's center conductor is 0.0384" vs 58's 0.0355"
>
> dielectric (center insulation) is the same dia, but 400 has marginally better
properties; relevant only at the extreme high end of design use: capacitance
of 400 is 29.4pF/ft, vs 58's 30.8pF/ft
>
> test freq of 400 is 12.4 GHz, vs 58's 1 GHz (but we use the cable at a max of
~1 GHz)
>
> 400's loss at 1 GHz is 14.7 dB/100ft; 58's is 22.6 dB/100ft (unfortunately, I
had to pull this spec from other sources; it doesn't show up in the linked pages)
>
> Doing the math, for a 10 foot run (more than enough to mount the antenna on the
belly of most planes), 400's loss would be 1.47dB vs 58's 2.26dB. For those
that don't know, dB's are a logarithmic measurement. 0.79dB of difference is
so small that it could get lost in the noise of connector quality, installation
technique, phase of the moon...
>
> At comm & nav frequencies (~100 MHz; 1/10 thefrequency), the spread would be
even smaller.
>
> Biggest difference is the outer jacket material; 400 is rated to 200 C, while
58 is PVC rated to 85 C. Unless you're bonding it to your cylinder head, that
shouldn't be a big factor.
>
> Yes, 400 is 'better'. But is 58 good enough? There are planes flying with 58
that is still good after 40 years.....
>
> Charlie
>
> On Thu, Feb 23, 2017 at 10:52 PM, Art Zemon <art@zemon.name> wrote:
> Folks,
>
> I have been following this thread because I, too, am trying to decide which coax
to buy for my plane. I'm a computer engineer; I shied away from EE in college
and especially antenna design because... well... I heard that antenna designers
were a special kind of crazy.. :-)
>
> Seriously, though, if I understand correctly, in the context of an installation
in a homebuilt airplane, the biggest difference between RG58 and RG400 seems
to be that the RG400 is less loss-y. Yes? In other words, if an antenna puts
a weak signal in one end of the coax, the signal that reaches the radio receiver
will be stronger if the coax is RG400 than if it is RG58.
>
> I'm looking at 10 feet of coax from the GPS and comm antennas to the receivers,
including service loops. I am looking at 20 feet for the VOR/GS antenna. The
transponder antenna will be less than 10 feet.
>
> At those distances, does RG400 vs RG58 matter? How do I evaluate it?
>
> And then there is the LMR-195 that Bob just showed us. How does that fit in?
>
> Thanks,
> -- Art Z.
>
Message 6
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Subject: | Re: Coaxial Cable |
Charlie;
I've followed your many posts and generally "good opinions" on many subjects
over a lengthy period of time and respect those opinions and advice, but in this
case I'm curious.
Did you wire your bird with automotive PVC wire because it was "good enough" or
did you use Tefzel insulated wire because that's what is recognized as "correct"
current practice? Did you use "hardware store" hardware because it's probably
"good enough" or did you use correct "AN hardware"? Did you use proper "braided
hoses" (Aeroquip style) or did you use "good enough" rubber hoses?
I'm a bit mystified why you seem to be advocating "good enough" RG-58 when
"better" (by how much may be debatable) RG-400 is readily available for a small
overall increase in $$$$. Wouldn't it seem that doing "the best we know how" be
the most prudent "best" approach?? There is no labour difference, the fittings
are essentially the same, the only actual "difference" might be a hundred
dollars or so which in the overall scheme of things is peanuts for the average
finished project? There's also "pride of workmanship" and the self satisfaction
of doing it right as opposed to "good enough". Just my alternate view two cents
worth.
Respectfully
Bob McC
> ---------- Original Message ----------
> From: Charlie England <ceengland7@gmail.com>
> Date: February 24, 2017 at 9:06 AM
>
> Here are links to cable specs for RG58a/u (stranded; note that RG58 can be
> had with solid center conductor, so beware when ordering), and RG400. I picked
> this site/brand to get both sets of specs in the same format.
> http://www.awcwire.com/part.aspx?partname=m17/28-rg58
>
> http://www.awcwire.com/part.aspx?partname=m17/128-rg400
>
> Relevant data:
> 400's center conductor is 0.0384" vs 58's 0.0355"
>
> dielectric (center insulation) is the same dia, but 400 has marginally
> better properties; relevant only at the extreme high end of design use:
> capacitance of 400 is 29.4pF/ft, vs 58's 30.8pF/ft
>
> test freq of 400 is 12.4 GHz, vs 58's 1 GHz (but we use the cable at a max
> of ~1 GHz)
>
> 400's loss at 1 GHz is 14.7 dB/100ft; 58's is 22.6 dB/100ft
> (unfortunately, I had to pull this spec from other sources; it doesn't show up
> in the linked pages)
>
> Doing the math, for a 10 foot run (more than enough to mount the antenna
> on the belly of most planes), 400's loss would be 1.47dB vs 58's 2.26dB. For
> those that don't know, dB's are a logarithmic measurement. 0.79dB of
> difference is so small that it could get lost in the noise of connector
> quality, installation technique, phase of the moon...
>
> At comm & nav frequencies (~100 MHz; 1/10 thefrequency), the spread would
> be even smaller.
>
> Biggest difference is the outer jacket material; 400 is rated to 200 C,
> while 58 is PVC rated to 85 C. Unless you're bonding it to your cylinder head,
> that shouldn't be a big factor.
>
> Yes, 400 is 'better'. But is 58 good enough? There are planes flying with
> 58 that is still good after 40 years.....
>
> Charlie
>
> On Thu, Feb 23, 2017 at 10:52 PM, Art Zemon < art@zemon.name
> <mailto:art@zemon.name> > wrote:
>
> > > Folks,
> >
> > I have been following this thread because I, too, am trying to
> > decide which coax to buy for my plane. I'm a computer engineer; I shied away
> > from EE in college and especially antenna design because... well... I heard
> > that antenna designers were a special kind of crazy.. :-)
> >
> > Seriously, though, if I understand correctly, in the context of an
> > installation in a homebuilt airplane, the biggest difference between RG58
> > and RG400 seems to be that the RG400 is less loss-y. Yes? In other words, if
> > an antenna puts a weak signal in one end of the coax, the signal that
> > reaches the radio receiver will be stronger if the coax is RG400 than if it
> > is RG58.
> >
> > I'm looking at 10 feet of coax from the GPS and comm antennas to the
> > receivers, including service loops. I am looking at 20 feet for the VOR/GS
> > antenna. The transponder antenna will be less than 10 feet.
> >
> > At those distances, does RG400 vs RG58 matter? How do I evaluate it?
> >
> > And then there is the LMR-195 that Bob just showed us. How does that
> > fit in?
> >
> > Thanks,
> > -- Art Z.
> >
> > --
> > https://CheerfulCurmudgeon.com/ <https://CheerfulCurmudgeon.com/>
> >
> > "If I am not for myself, who is for me? And if I am only for myself,
> > what am I? And if not now, when?" Hillel
> >
> > >
>
Message 7
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Subject: | Re: Coaxial Cable |
The noxious gases released are only one consideration - some others might be ease
of initial flammability, tendency to spread fire along the cable, melting point,
and probably some others I haven't thought of. I don't know how FEP-insulated
RG-400 stacks up but I believe PVC is pretty bad in these respects. Noting
that your coax doesn't carry any current, and a short circuit because the insulation
has melted isn't a further ignition risk, I'm genuinely surprised that
RG58 is still on the table.
On 24Feb2017, at 9:59 AM, Alec Myers <alec@alecmyers.com> wrote:
I've been following this discussion. Isn't it better to move away from PVC jacketed
cables, for fire safety reasons? Who uses PVC wire vs 22759-16 ETFE insulated
stuff?
On 24Feb2017, at 9:06 AM, Charlie England <ceengland7@gmail.com> wrote:
Here are links to cable specs for RG58a/u (stranded; note that RG58 can be had
with solid center conductor, so beware when ordering), and RG400. I picked this
site/brand to get both sets of specs in the same format.
http://www.awcwire.com/part.aspx?partname=m17/28-rg58
http://www.awcwire.com/part.aspx?partname=m17/128-rg400
Relevant data:
400's center conductor is 0.0384" vs 58's 0.0355"
dielectric (center insulation) is the same dia, but 400 has marginally better properties;
relevant only at the extreme high end of design use: capacitance of
400 is 29.4pF/ft, vs 58's 30.8pF/ft
test freq of 400 is 12.4 GHz, vs 58's 1 GHz (but we use the cable at a max of ~1
GHz)
400's loss at 1 GHz is 14.7 dB/100ft; 58's is 22.6 dB/100ft (unfortunately, I had
to pull this spec from other sources; it doesn't show up in the linked pages)
Doing the math, for a 10 foot run (more than enough to mount the antenna on the
belly of most planes), 400's loss would be 1.47dB vs 58's 2.26dB. For those that
don't know, dB's are a logarithmic measurement. 0.79dB of difference is so
small that it could get lost in the noise of connector quality, installation
technique, phase of the moon...
At comm & nav frequencies (~100 MHz; 1/10 thefrequency), the spread would be even
smaller.
Biggest difference is the outer jacket material; 400 is rated to 200 C, while 58
is PVC rated to 85 C. Unless you're bonding it to your cylinder head, that shouldn't
be a big factor.
Yes, 400 is 'better'. But is 58 good enough? There are planes flying with 58 that
is still good after 40 years.....
Charlie
On Thu, Feb 23, 2017 at 10:52 PM, Art Zemon <art@zemon.name> wrote:
Folks,
I have been following this thread because I, too, am trying to decide which coax
to buy for my plane. I'm a computer engineer; I shied away from EE in college
and especially antenna design because... well... I heard that antenna designers
were a special kind of crazy.. :-)
Seriously, though, if I understand correctly, in the context of an installation
in a homebuilt airplane, the biggest difference between RG58 and RG400 seems
to be that the RG400 is less loss-y. Yes? In other words, if an antenna puts a
weak signal in one end of the coax, the signal that reaches the radio receiver
will be stronger if the coax is RG400 than if it is RG58.
I'm looking at 10 feet of coax from the GPS and comm antennas to the receivers,
including service loops. I am looking at 20 feet for the VOR/GS antenna. The
transponder antenna will be less than 10 feet.
At those distances, does RG400 vs RG58 matter? How do I evaluate it?
And then there is the LMR-195 that Bob just showed us. How does that fit in?
Thanks,
-- Art Z.
--
https://CheerfulCurmudgeon.com/
"If I am not for myself, who is for me? And if I am only for myself, what am I?
And if not now, when?" Hillel
Message 8
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Bob, et al,
I'm a little confused on the implementation of a reed switch in a scenario as you
have shown in the diagram on page 3 of your document: "Failure Warning w/ On
Annunciation".
I guess I don't understand why when using an LED to annunciate that is sourced
with the SAME power as to the load being monitored. Why not just tie into the
relay (say out of the FastOn connector) with a separate wire with a 470 ohm resistor
to the LED, then to ground.
IF using the SAME power as the end component being monitored (here, pitot heat),
isn't an added wire as I described above really the end result that the reed
switch provides when it's activated/closed?
I could understand using the reed switch in a manner as a "poor man's relay" if
the power source for the LED was completely separate from power source of the
monitored load (again, here a pitot tube). But in using the same power as the
pitot heat, in this case, it seems like a bit of added complexity for no real
gain?
I hope my question makes sense. Not trying to be snarky, just trying to learn
so I can implement the simplest, cleanest system possible ... and I have this
exact issue for driving a few annunciator LEDs.
Thanks!
Wade
--------
Airdog
Wade Parton
Building Long-EZ 916WP
www.longezpush.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466587#466587
Message 9
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Subject: | Re: Coaxial Cable |
I used tefzel wire for almost everything, because the cost difference
really was negligible to get the tougher insulation, and I knew that I'd
have big bundles carrying (in some cases) significant current and some
really tight routing. Fire hazard wasn't a consideration; either product
will produce toxic fumes. Around the engine, long term heat resistance
*would* be a factor for me.
Yes, I use a/n hardware.
Yes, I use a/n style (but not actual certified) hoses for oil lines. But
for my water cooled engine's coolant lines, I'm using reinforced silicone
fluid lines. Some have used a/n hoses & fittings for these lines, but they
weigh a *lot* more and there's no evidence that they actually improve
safety over quality silicone hoses *in that application*. (This ignores, of
course, the massive difference in cost.) A/n hoses are 'better' than
aluminum tubing, which is 'better' than tygon, yet early RV-x's are still
flying with tygon brake lines, and the new kits still ship with aluminum
brake lines. Either are 'good enough', though the aluminum is safer if the
operator (the guy standing on the brakes constantly) isn't.
A lot of guys building RV-x's are replacing the $40 brass/nylon fuel
selector (included in the price of the kit) with a $400+ Andair fuel
selector. No doubt, the Andair is 'better'; it's got to be, for 10X the
money, right? But is it, after factoring in weight, altered fittings
needed, altered line routing, and expense? Thousands of RV's flying the
brass valve prove that it's 'good enough', even if it isn't 'aircraft
quality'. (Of course, the Andair isn't *certified* a/c quality either, but
that doesn't deter devotees.)
Four part Urethane paint is 'better' than acrylic enamel (at ~10 times the
cost). It's also quite capable of killing you, if sprayed without perfectly
functioning protective gear. Yet lots of planes are still flying with
decent looking enamel, 40 years later.
Honestly, if I were buying 10' of coax, I'd probably (well, I might) go
ahead & order the 400; it's certainly prettier. But I've got a box of 58 on
hand, and I'm pre-wiring for ELT, comm, nav, glideslope, xponder, GPS,spare
GPS, both wingtips, etc with what I have on hand. Whatever I don't use can
be easily removed to save weight. I wouldn't have done the same thing with
400, at up to $4/ft.
You're right; a hundred dollars over the total cost of a project is
'peanuts'. You could say the same thing about a $.50 ATC fuse vs a $20
aircraft quality circuit breaker. Now multiply that (and the weight
difference) times 30. Which is 'better'? Now extrapolate that over the
dozens (hundreds?) of other decisions throughout the airframe.
Everybody should make their own decisions based on valid data and their
comfort levels, but they shouldn't make them based on paranoia or worse,
bad data. The 58 is certainly good enough, and it *is* aircraft quality
cable. If you want 'better', there's certainly nothing wrong with that.
Charlie
On Fri, Feb 24, 2017 at 10:02 AM, Robert McCallum <
robert.mccallum2@sympatico.ca> wrote:
> Charlie;
>
> I've followed your many posts and generally "good opinions" on many
> subjects over a lengthy period of time and respect those opinions and
> advice, but in this case I'm curious.
>
> Did you wire your bird with automotive PVC wire because it was "good
> enough" or did you use Tefzel insulated wire because that's what is
> recognized as "correct" current practice? Did you use "hardware store"
> hardware because it's probably "good enough" or did you use correct "AN
> hardware"? Did you use proper "braided hoses" (Aeroquip style) or did you
> use "good enough" rubber hoses?
>
> I'm a bit mystified why you seem to be advocating "good enough" RG-58 when
> "better" (by how much may be debatable) RG-400 is readily available for a
> small overall increase in $$$$. Wouldn't it seem that doing "the best we
> know how" be the most prudent "best" approach?? There is no labour
> difference, the fittings are essentially the same, the only actual
> "difference" might be a hundred dollars or so which in the overall scheme
> of things is peanuts for the average finished project? There's also "pride
> of workmanship" and the self satisfaction of doing it right as opposed to
> "good enough". Just my alternate view two cents worth.
>
> Respectfully
>
> Bob McC
>
>
> ---------- Original Message ----------
> From: Charlie England <ceengland7@gmail.com>
> Date: February 24, 2017 at 9:06 AM
>
> Here are links to cable specs for RG58a/u (stranded; note that RG58 can be
> had with solid center conductor, so beware when ordering), and RG400. I
> picked this site/brand to get both sets of specs in the same format.
> http://www.awcwire.com/part.aspx?partname=m17/28-rg58
>
> http://www.awcwire.com/part.aspx?partname=m17/128-rg400
>
> Relevant data:
> 400's center conductor is 0.0384" vs 58's 0.0355"
>
> dielectric (center insulation) is the same dia, but 400 has marginally
> better properties; relevant only at the extreme high end of design use:
> capacitance of 400 is 29.4pF/ft, vs 58's 30.8pF/ft
>
> test freq of 400 is 12.4 GHz, vs 58's 1 GHz (but we use the cable at a max
> of ~1 GHz)
>
> 400's loss at 1 GHz is 14.7 dB/100ft; 58's is 22.6 dB/100ft
> (unfortunately, I had to pull this spec from other sources; it doesn't show
> up in the linked pages)
>
> Doing the math, for a 10 foot run (more than enough to mount the antenna
> on the belly of most planes), 400's loss would be 1.47dB vs 58's 2.26dB.
> For those that don't know, dB's are a logarithmic measurement. 0.79dB of
> difference is so small that it could get lost in the noise of connector
> quality, installation technique, phase of the moon...
>
> At comm & nav frequencies (~100 MHz; 1/10 thefrequency), the spread would
> be even smaller.
>
> Biggest difference is the outer jacket material; 400 is rated to 200 C,
> while 58 is PVC rated to 85 C. Unless you're bonding it to your cylinder
> head, that shouldn't be a big factor.
>
> Yes, 400 is 'better'. But is 58 good enough? There are planes flying with
> 58 that is still good after 40 years.....
>
> Charlie
>
> On Thu, Feb 23, 2017 at 10:52 PM, Art Zemon < art@zemon.name> wrote:
>
> Folks,
>
> I have been following this thread because I, too, am trying to decide
> which coax to buy for my plane. I'm a computer engineer; I shied away from
> EE in college and especially antenna design because... well... I heard that
> antenna designers were a special kind of crazy.. :-)
>
> Seriously, though, if I understand correctly, in the context of an
> installation in a homebuilt airplane, the biggest difference between RG58
> and RG400 seems to be that the RG400 is less loss-y. Yes? In other words,
> if an antenna puts a weak signal in one end of the coax, the signal that
> reaches the radio receiver will be stronger if the coax is RG400 than if it
> is RG58.
>
> I'm looking at 10 feet of coax from the GPS and comm antennas to the
> receivers, including service loops. I am looking at 20 feet for the VOR/GS
> antenna. The transponder antenna will be less than 10 feet.
>
> At those distances, does RG400 vs RG58 matter? How do I evaluate it?
>
> And then there is the LMR-195 that Bob just showed us. How does that fit
> in?
>
> Thanks,
> -- Art Z.
>
> --
> https://CheerfulCurmudgeon.com/
>
> *"If I am not for myself, who is for me? And if I am only for myself, what
> am I? And if not now, when?" Hillel*
>
>
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On Fri, Feb 24, 2017 at 11:32 AM, Airdog77 <Airdog77@gmail.com> wrote:
>
> Bob, et al,
>
> I'm a little confused on the implementation of a reed switch in a scenario
> as you have shown in the diagram on page 3 of your document: "Failure
> Warning w/ On Annunciation".
>
> I guess I don't understand why when using an LED to annunciate that is
> sourced with the SAME power as to the load being monitored. Why not just
> tie into the relay (say out of the FastOn connector) with a separate wire
> with a 470 ohm resistor to the LED, then to ground.
>
> IF using the SAME power as the end component being monitored (here, pitot
> heat), isn't an added wire as I described above really the end result that
> the reed switch provides when it's activated/closed?
>
> I could understand using the reed switch in a manner as a "poor man's
> relay" if the power source for the LED was completely separate from power
> source of the monitored load (again, here a pitot tube). But in using the
> same power as the pitot heat, in this case, it seems like a bit of added
> complexity for no real gain?
>
> I hope my question makes sense. Not trying to be snarky, just trying to
> learn so I can implement the simplest, cleanest system possible ... and I
> have this exact issue for driving a few annunciator LEDs.
>
> Thanks!
> Wade
>
> --------
> Airdog
> Wade Parton
> Building Long-EZ 916WP
> www.longezpush.com
>
> If the LED is wired directly to the power wire, and the wire breaks
anywhere after your attach point for the LED, the LED is still lit but you
have no pitot heat and no awareness. If the pitot heater itself fails, your
LED is still lit, but you have no pitot heat & no awareness.
Using the coil & reed switch senses *current flow* through the heating
element. If the circuit opens for any reason, the LED goes out, telling you
you have no pitot heat.
Message 11
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Wade;
The LED connected to the load as you describe only confirms that voltage is
available at the load, not that the load is actually working. The read switch
scenario confirms that current is being drawn by the load and therefore the
pitot heater is actually heating and is not burned out.
Bob McC
>
> ---------- Original Message ----------
> From: Airdog77 <Airdog77@gmail.com>
> Date: February 24, 2017 at 12:32 PM
>
>
>
> Bob, et al,
>
> I'm a little confused on the implementation of a reed switch in a scenario
> as you have shown in the diagram on page 3 of your document: "Failure Warning
> w/ On Annunciation".
>
> I guess I don't understand why when using an LED to annunciate that is
> sourced with the SAME power as to the load being monitored. Why not just tie
> into the relay (say out of the FastOn connector) with a separate wire with a
> 470 ohm resistor to the LED, then to ground.
>
> IF using the SAME power as the end component being monitored (here, pitot
> heat), isn't an added wire as I described above really the end result that the
> reed switch provides when it's activated/closed?
>
> I could understand using the reed switch in a manner as a "poor man's
> relay" if the power source for the LED was completely separate from power
> source of the monitored load (again, here a pitot tube). But in using the same
> power as the pitot heat, in this case, it seems like a bit of added complexity
> for no real gain?
>
> I hope my question makes sense. Not trying to be snarky, just trying to
> learn so I can implement the simplest, cleanest system possible ... and I have
> this exact issue for driving a few annunciator LEDs.
>
> Thanks!
> Wade
>
> --------
> Airdog
> Wade Parton
> Building Long-EZ 916WP
> www.longezpush.com
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=466587#466587
>
>
>
>
>
>
>
>
>
>
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Double pole reed switches (Form C) are available with normally closed contacts.
The circuit could be wired so that a red LED illuminates only when the pitot
heating element burns open.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466591#466591
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Ahh, ok! I was looking at it more from the binary on/off of the pitot tube. But
now I see the reed switch allows for a more qualitative monitoring of the pitot
heat element's health in case it goes inop, wiring issue, etc.
Thanks all. Love this forum!
Cheers,
Wade
--------
Airdog
Wade Parton
Building Long-EZ 916WP
www.longezpush.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=466592#466592
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Subject: | Re: Coaxial Cable |
If one uses the available information, RG-58 is and has been more than
adequate for VHF applications for the past 50 years or so. In fact, much
of that installed in aircraft 50 years ago is still doing a fine job.
The only application that gets a noticeable benefit from the expensive
RG-400 is those devices operating in the Gigahertz frequency spectrum
such as GPS and transponders and DME. Most Mode C transponders and DME
will in fact operate satisfactorily, passing all required performance
checks with RG-58 coax if the coax length isn't excessive.
The only case I can think of where RG-58 has needed to be removed and
replaced with RG-400 is for certified WAAS GPS installations, where
Garmin specifically upgraded their requirement due to their design
needing a certain insertion loss for the proper performance. They could
have used a different design that would have eliminated the need for
coax entirely. (see the Dynon 2020 GPS as an example that meets ADS-B
performance without coax).
Unlike the type certified advanced technology half million dollar
production wonders, most amateur built aircraft are necessarily on a
tight budget, and not spending $200-300 on unnecessary coax makes a
difference. Using RG-400 for VHF com and nav antennas is huge overkill.
Using RG-58 for those applications is not wrong, and makes the servicing
in Timbuktu and 50 miles from Nowheresville substantially simpler. AFAIK
Radio Shack and Fry's still don't stock RG-400 connectors. In fact, for
under $15 one could carry a spare 10 or 20 ft RG-58 cable with BNC
connectors installed.
JMHO.
Kelly
A&P/IA
EAA Tech Counselor
On 2/24/2017 12:01 AM, Bernie Willis wrote:
> Ive got to submit my two cents worth on the conversation about coax.
> As an A&P IA what I hate the most is having to do something over
> because I did it wrong. Typically coax is under the floor boards or
> above the head liner. Most times it goes places where its hard to get
> at and left there. The extra money for the best is soon forgotten but
> the frustration for replacement just goes on and on.
>
> The radio shop in our area, which is very busy, urges RG400. The
> installation money is all the same to me.
>
> Bernie
>> On Feb 23, 2017, at 9:36 PM, don van santen <donvansanten@gmail.com
>> <mailto:donvansanten@gmail.com>> wrote:
>>
>> After Bob posted the info on the LMR-195 I looked for additional
>> information. One thing that seems a little strange is that it is solid
>> core. It is also said to be flexible. It was my understanding that
>> solid core cable is less flexible than multi strand cable. Any one
>> know the minimum bend radius for LMR-195?
>> Don.
>>
>> On Feb 23, 2017 21:14, "Art Zemon" <art@zemon.name
>> <mailto:art@zemon.name>> wrote:
>>
>> Folks,
>>
>> I have been following this thread because I, too, am trying to
>> decide which coax to buy for my plane. I'm a computer engineer; I
>> shied away from EE in college and especially antenna design
>> because... well... I heard that antenna designers were a special
>> kind of crazy.. :-)
>>
>> Seriously, though, if I understand correctly, in the context of an
>> installation in a homebuilt airplane, the biggest difference
>> between RG58 and RG400 seems to be that the RG400 is less loss-y.
>> Yes? In other words, if an antenna puts a weak signal in one end
>> of the coax, the signal that reaches the radio receiver will be
>> stronger if the coax is RG400 than if it is RG58.
>>
>> I'm looking at 10 feet of coax from the GPS and comm antennas to
>> the receivers, including service loops. I am looking at 20 feet
>> for the VOR/GS antenna. The transponder antenna will be less than
>> 10 feet.
>>
>> At those distances, does RG400 vs RG58 matter? How do I evaluate it?
>>
>> And then there is the LMR-195 that Bob just showed us. How does
>> that fit in?
>>
>> Thanks,
>> -- Art Z.
>>
>> --
>> https://CheerfulCurmudgeon.com/ <https://cheerfulcurmudgeon.com/>
>>
>> /"If I am not for myself, who is for me? And if I am only for
>> myself, what am I? And if not now, when?" Hillel/
>>
>
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Subject: | Re: Coaxial Cable |
I'm with Charlie. There are huge differences with the other examples you
cite, such as hardware store fasteners vs AN hardware.
The difference in performance and safety between RG58 and RG400 is
minuscule for a very real price difference.
RG58 has been the accepted aircraft coax for at least 50 yrs. AFAIK
RG400 didn't become recommended until after the turn of the century.
Mainly over performance with WAAS GPS, not safety, not anything else
that matters for other avionics.
I'll not argue Tefzel vs automotive wire. There is a huge durability
difference there, as well as insulation thickness difference.
OTOH I have inspected many aircraft with RG58 installed 50-60 yrs ago
and it is still performing fine. Unlike the general wiring that was used
back then.
On 2/24/2017 9:02 AM, Robert McCallum wrote:
> Charlie;
>
> I've followed your many posts and generally "good opinions" on many
> subjects over a lengthy period of time and respect those opinions and
> advice, but in this case I'm curious.
>
> Did you wire your bird with automotive PVC wire because it was "good
> enough" or did you use Tefzel insulated wire because that's what is
> recognized as "correct" current practice? Did you use "hardware store"
> hardware because it's probably "good enough" or did you use correct "AN
> hardware"? Did you use proper "braided hoses" (Aeroquip style) or did
> you use "good enough" rubber hoses?
>
> I'm a bit mystified why you seem to be advocating "good enough" RG-58
> when "better" (by how much may be debatable) RG-400 is readily available
> for a small overall increase in $$$$. Wouldn't it seem that doing "the
> best we know how" be the most prudent "best" approach?? There is no
> labour difference, the fittings are essentially the same, the only
> actual "difference" might be a hundred dollars or so which in the
> overall scheme of things is peanuts for the average finished project?
> There's also "pride of workmanship" and the self satisfaction of doing
> it right as opposed to "good enough". Just my alternate view two cents
> worth.
>
> Respectfully
>
> Bob McC
>
>
>> ---------- Original Message ----------
>> From: Charlie England <ceengland7@gmail.com>
>> Date: February 24, 2017 at 9:06 AM
>>
>> Here are links to cable specs for RG58a/u (stranded; note that RG58
>> can be had with solid center conductor, so beware when ordering), and
>> RG400. I picked this site/brand to get both sets of specs in the same
>> format.
>> http://www.awcwire.com/part.aspx?partname=m17/28-rg58
>>
>> http://www.awcwire.com/part.aspx?partname=m17/128-rg400
>>
>> Relevant data:
>> 400's center conductor is 0.0384" vs 58's 0.0355"
>>
>> dielectric (center insulation) is the same dia, but 400 has marginally
>> better properties; relevant only at the extreme high end of design
>> use: capacitance of 400 is 29.4pF/ft, vs 58's 30.8pF/ft
>>
>> test freq of 400 is 12.4 GHz, vs 58's 1 GHz (but we use the cable at a
>> max of ~1 GHz)
>>
>> 400's loss at 1 GHz is 14.7 dB/100ft; 58's is 22.6 dB/100ft
>> (unfortunately, I had to pull this spec from other sources; it doesn't
>> show up in the linked pages)
>>
>> Doing the math, for a 10 foot run (more than enough to mount the
>> antenna on the belly of most planes), 400's loss would be 1.47dB vs
>> 58's 2.26dB. For those that don't know, dB's are a logarithmic
>> measurement. 0.79dB of difference is so small that it could get lost
>> in the noise of connector quality, installation technique, phase of
>> the moon...
>>
>> At comm & nav frequencies (~100 MHz; 1/10 thefrequency), the spread
>> would be even smaller.
>>
>> Biggest difference is the outer jacket material; 400 is rated to 200
>> C, while 58 is PVC rated to 85 C. Unless you're bonding it to your
>> cylinder head, that shouldn't be a big factor.
>>
>> Yes, 400 is 'better'. But is 58 good enough? There are planes flying
>> with 58 that is still good after 40 years.....
>>
>> Charlie
>>
>> On Thu, Feb 23, 2017 at 10:52 PM, Art Zemon < art@zemon.name
>> <mailto:art@zemon.name>> wrote:
>>
>> Folks,
>>
>> I have been following this thread because I, too, am trying to
>> decide which coax to buy for my plane. I'm a computer engineer; I
>> shied away from EE in college and especially antenna design
>> because... well... I heard that antenna designers were a special
>> kind of crazy.. :-)
>>
>> Seriously, though, if I understand correctly, in the context of an
>> installation in a homebuilt airplane, the biggest difference
>> between RG58 and RG400 seems to be that the RG400 is less loss-y.
>> Yes? In other words, if an antenna puts a weak signal in one end
>> of the coax, the signal that reaches the radio receiver will be
>> stronger if the coax is RG400 than if it is RG58.
>>
>> I'm looking at 10 feet of coax from the GPS and comm antennas to
>> the receivers, including service loops. I am looking at 20 feet
>> for the VOR/GS antenna. The transponder antenna will be less than
>> 10 feet.
>>
>> At those distances, does RG400 vs RG58 matter? How do I evaluate it?
>>
>> And then there is the LMR-195 that Bob just showed us. How does
>> that fit in?
>>
>> Thanks,
>> -- Art Z.
>>
>> --
>> https://CheerfulCurmudgeon.com/ <https://CheerfulCurmudgeon.com/>
>>
>> /"If I am not for myself, who is for me? And if I am only for
>> myself, what am I? And if not now, when?" Hillel/
>>
>>
>
>
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Could one use a starter contactor as a battery contactor? I understand they are
subjected to different duties but also understand the on/off action is when they
are most abused. Would I be wasting too much power just by keeping the contactor
on (power to the coils)?
Wlad
Message 17
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Message 18
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On Fri, Feb 24, 2017 at 12:54 PM, Wladimir Kummer <wladimirkummer@gmail.com>
wrote:
> wladimirkummer@gmail.com>
>
> Could one use a starter contactor as a battery contactor? I understand
> they are subjected to different duties but also understand the on/off
> action is when they are most abused. Would I be wasting too much power just
> by keeping the contactor on (power to the coils)?
>
> Wlad
>
> I think most starter contactors are rated 'intermittent duty'. assuming
that's correct, you'd risk not just wasting current, but overheating the
coil in the contactor.
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