Today's Message Index:
----------------------
1. 01:47 AM - Twisted pairs (JOHN TIPTON)
2. 05:35 AM - Re: Re: Robust transponder antennas (Robert L. Nuckolls, III)
3. 06:53 AM - Re: Twisted pairs (Robert L. Nuckolls, III)
4. 07:11 AM - Re: Twisted pairs (James Kilford)
5. 07:29 AM - Re: Twisted pairs (Bruce B. Bell)
6. 08:26 AM - Re: Twisted pairs (Robert L. Nuckolls, III)
7. 11:01 AM - D-sub crimper (Paul Kuntz)
8. 01:44 PM - Re: Twisted pairs (rayj)
9. 05:10 PM - Re: Buss Bar (John Grosse)
10. 08:05 PM - Re: Buss Bar (Bob McCallum)
11. 08:34 PM - Re: D-sub crimper (Robert L. Nuckolls, III)
12. 10:03 PM - Re: D-sub crimper (Paul Kuntz)
Message 1
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Generaly speaking: when are 'twisted pairs' required, and why ?
Best regards - John
Message 2
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| Subject: | Re: Robust transponder antennas |
I believe the antenna design in question is an approach to getting a
VERY broad range of frequency coverage (10-1) from a single
antenna. Note also that it was designed to operate from 30 to 30,000
MHz and the ATC transponder frequency is a single one at 1090 Mhz.
You certainly don't need the broad coverage and are almost certainly
better off with a single blade or stub designed for 1090 MHz than this.
The antennae on the B-52 needed to cover almost DC to light (400 khz
to 30 GHz) and this design was very workable.
All true. But keep in mind that the roots of
this thread went to robustness. All of the
antennas offered commercially for transponder/
DME service ran from cheap (single exposed
monopole) to rather expensive (aerodynamically
faired blade). All active portions of the antenna
are insulated from the airframe.
The feature of the scimitar antenna that attracted
us was the one-piece, all metal design grounded
to the airframe. Such antennas could be
crafted from two pieces of metal, a base and a
blade. Further, they could be rather thick, say
1/8 to 1/4 inches. Such a construction would be
MUCH more robust than any commercial offerings.
If such an antenna were attached to good structure
in the airplane, it might well double as a tie
down ring.
As I noted before, the patent given to this design
was curious. It was applied for years after some
of these antennas were already in production.
The patent was assigned to government in the
first paragraph. Finally, the patent was
long on geometry (you can make one "this" way,
or make one "that" way) and long on radiation
patterns. But not one word as to the reason
why one would make one this way, that way, or
dimension it for optimum performance at any
frequency.
Methinks this patent was issued as an afterthought
during the cold war when unwashed citizens
began to observe such antennas on military
aircraft. The patent was more a deterrent
to commercial development than to protect
new art. This leaves the modern day DIY
developer with the task of re-discovering
the simple-ideas behind the design. Not
difficult and even fun if you have the
test equipment.
Bob . . .
Message 3
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| Subject: | Re: Twisted pairs |
At 04:43 AM 1/21/2011, you wrote:
>Generaly speaking: when are 'twisted pairs' required, and why ?
Pairing two conductors effects very tight
coupling of the magnetic fields around current
carrying conductors. When one conductor is the
return path for current flow in the other
conductor, the two resulting fields are equal,
opposite and in intimate proximity to each
other thus canceling each other out. The
conductors can be simply parallel to each other
(hard to maintain in a wire bundle) or twisted
such that they cannot get separated.
The corollary accurately suggests that the
same pair of wires are just as vulnerable to
externally impressed magnetic fields. Suppose you
have an itty-bitty signal you want to carry
from one place to another. Suppose further
that the wires carrying that signal are to
be bundled with lots of other wires carrying
who knows what . . . and worse yet, SINGLE
wires with @#$@-ugly currents flowing in
them.
They physics of magnetic coupling for pairing
outbound and return paths for currents
COMBINED with the physics of electro-static
coupling (easily broken by shielding) makes
the shielded-twisted pair a very robust
guard against signal contamination.
But as I mentioned earlier this week, fast
rise antagonists are rare in airplanes and
electro-static coupling is weak. Hence,
shielding is not nearly the guardian of
signal purity as is pairing (or twisting)
of the two conductors. I suggested that
the simple twisting of potentially vulnerable
or antagonistic current paths was about 99%
of everything a system integrator could
ask for in terms of interference control.
Bob . . .
Message 4
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| Subject: | Re: Twisted pairs |
Another brilliant and succinct explanation! Thanks Bob.
do not archive
On 21 January 2011 13:49, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 04:43 AM 1/21/2011, you wrote:
>
> Generaly speaking: when are 'twisted pairs' required, and why ?
>
>
> Pairing two conductors effects very tight
> coupling of the magnetic fields around current
> carrying conductors. When one conductor is the
> return path for current flow in the other
> conductor, the two resulting fields are equal,
> opposite and in intimate proximity to each
> other thus canceling each other out. The
> conductors can be simply parallel to each other
> (hard to maintain in a wire bundle) or twisted
> such that they cannot get separated.
>
> The corollary accurately suggests that the
> same pair of wires are just as vulnerable to
> externally impressed magnetic fields. Suppose you
> have an itty-bitty signal you want to carry
> from one place to another. Suppose further
> that the wires carrying that signal are to
> be bundled with lots of other wires carrying
> who knows what . . . and worse yet, SINGLE
> wires with @#$@-ugly currents flowing in
> them.
>
> They physics of magnetic coupling for pairing
> outbound and return paths for currents
> COMBINED with the physics of electro-static
> coupling (easily broken by shielding) makes
> the shielded-twisted pair a very robust
> guard against signal contamination.
>
> But as I mentioned earlier this week, fast
> rise antagonists are rare in airplanes and
> electro-static coupling is weak. Hence,
> shielding is not nearly the guardian of
> signal purity as is pairing (or twisting)
> of the two conductors. I suggested that
> the simple twisting of potentially vulnerable
> or antagonistic current paths was about 99%
> of everything a system integrator could
> ask for in terms of interference control.
>
>
> Bob . . .
>
> *
>
> *
>
>
Message 5
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| Subject: | Re: Twisted pairs |
DO NOT ARCHIVE!
My 1949 A35 Bonanza has twisted pairs to the mag compass light. It is
mounted on the windshield. Came out the factory door June 1948. Noted
when replacing the windshield 47 years ago. BBB
From: Robert L. Nuckolls, III
Sent: Friday, January 21, 2011 7:49 AM
Subject: Re: AeroElectric-List: Twisted pairs
At 04:43 AM 1/21/2011, you wrote:
Generaly speaking: when are 'twisted pairs' required, and why ?
Pairing two conductors effects very tight
coupling of the magnetic fields around current
carrying conductors. When one conductor is the
return path for current flow in the other
conductor, the two resulting fields are equal,
opposite and in intimate proximity to each
other thus canceling each other out. The
conductors can be simply parallel to each other
(hard to maintain in a wire bundle) or twisted
such that they cannot get separated.
The corollary accurately suggests that the
same pair of wires are just as vulnerable to
externally impressed magnetic fields. Suppose you
have an itty-bitty signal you want to carry
from one place to another. Suppose further
that the wires carrying that signal are to
be bundled with lots of other wires carrying
who knows what . . . and worse yet, SINGLE
wires with @#$@-ugly currents flowing in
them.
They physics of magnetic coupling for pairing
outbound and return paths for currents
COMBINED with the physics of electro-static
coupling (easily broken by shielding) makes
the shielded-twisted pair a very robust
guard against signal contamination.
But as I mentioned earlier this week, fast
rise antagonists are rare in airplanes and
electro-static coupling is weak. Hence,
shielding is not nearly the guardian of
signal purity as is pairing (or twisting)
of the two conductors. I suggested that
the simple twisting of potentially vulnerable
or antagonistic current paths was about 99%
of everything a system integrator could
ask for in terms of interference control.
Bob . . .
Message 6
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| Subject: | Re: Twisted pairs |
At 10:24 AM 1/21/2011, you wrote:
>My 1949 A35 Bonanza has twisted pairs to the mag compass light. It
>is mounted on the windshield. Came out the factory door June 1948.
>Noted when replacing the windshield 47 years ago. BBB
Great observation! The compass is tasked with
aligning itself to Momma Earth's very weak
magnetic field. It doesn't take much interference
to generate significant error in the compass reading.
This is why each compass installation is individually
calibrated (swung). Further, the calibration is
accomplished with certain conditions noted and
placarded (like radios ON).
A single illumination conductor up to the compass has
significant potential for adding magnetic interference
to the compass reading when illumination is on. Further,
the magnitude of that error would run up and down
with panel light dimmer settings. I've suggested that
the builder could also used a shielded wire where
the inner conductor is power up and shield was power
down from the light. The vast majority of such installations
do use a twisted pair to accomplish the same
result.
Bob . . .
Message 7
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I have a supply of gold-plated D-sub pins and a ratchet crimper -- both pins
and crimper were purchased from B&C. I will be using 20 ga and 22 ga wiring
in my aircraft, but note that there is no adjustment on the crimper for
different wire gauges. I saw in an EAA informational video the use of a
D-sub crimper that had an adjustment to adapt it to different wire gauges.
Do I need one of these adjustable crimpers? If I use the one from B&C and
give each pin a pull test after crimping, is that good enough?
Thanks,
Paul Kuntz
Message 8
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| Subject: | Re: Twisted pairs |
do not archive
FWIW, in all my years around marine compasses I've never seen an
illuminated one that didn't use a twisted pair for illumination.
Raymond Julian
Kettle River, MN
On 01/21/2011 09:24 AM, Bruce B. Bell wrote:
> DO NOT ARCHIVE!
> My 1949 A35 Bonanza has twisted pairs to the mag compass light. It is
> mounted on the windshield. Came out the factory door June 1948. Noted
> when replacing the windshield 47 years ago. BBB
> *From:* Robert L. Nuckolls, III <mailto:nuckolls.bob@aeroelectric.com>
> *Sent:* Friday, January 21, 2011 7:49 AM
> *To:* aeroelectric-list@matronics.com
> <mailto:aeroelectric-list@matronics.com>
> *Subject:* Re: AeroElectric-List: Twisted pairs
> At 04:43 AM 1/21/2011, you wrote:
>> Generaly speaking: when are 'twisted pairs' required, and why ?
>
> Pairing two conductors effects very tight
> coupling of the magnetic fields around current
> carrying conductors. When one conductor is the
> return path for current flow in the other
> conductor, the two resulting fields are equal,
> opposite and in intimate proximity to each
> other thus canceling each other out. The
> conductors can be simply parallel to each other
> (hard to maintain in a wire bundle) or twisted
> such that they cannot get separated.
>
> The corollary accurately suggests that the
> same pair of wires are just as vulnerable to
> externally impressed magnetic fields. Suppose you
> have an itty-bitty signal you want to carry
> from one place to another. Suppose further
> that the wires carrying that signal are to
> be bundled with lots of other wires carrying
> who knows what . . . and worse yet, SINGLE
> wires with @#$@-ugly currents flowing in
> them.
>
> They physics of magnetic coupling for pairing
> outbound and return paths for currents
> COMBINED with the physics of electro-static
> coupling (easily broken by shielding) makes
> the shielded-twisted pair a very robust
> guard against signal contamination.
>
> But as I mentioned earlier this week, fast
> rise antagonists are rare in airplanes and
> electro-static coupling is weak. Hence,
> shielding is not nearly the guardian of
> signal purity as is pairing (or twisting)
> of the two conductors. I suggested that
> the simple twisting of potentially vulnerable
> or antagonistic current paths was about 99%
> of everything a system integrator could
> ask for in terms of interference control.
>
>
> Bob . . .
>
> *
>
> href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List
> href="http://forums.matronics.com">http://forums.matronics.com
> href="http://www.matronics.com/contribution">http://www.matronics.com/c
> *
>
> *
>
>
> *
Message 9
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Bob, I'm not quite sure I understand. Are you saying that aluminum is
unsuitable for some reason or just that copper or brass is better? I'm
not questioning your opinion. I'm just interested in the "why" one works
or doesn't work.
John
Robert L. Nuckolls, III wrote:
> At 09:15 AM 1/19/2011, you wrote:
>> <grosseair@comcast.net>
>>
>> A combination of threaded studs for the large wires and riveted fast
>> on connectors for the rest.
>
> Rivets are designed for use in shear, not in tension.
> Further, your fast-on lugs are no doubt going to be
> of a material dissimilar to the bus bar.
>
> Suggest you go to a hardware store or hobby shop
> and get a chunk of sheet brass or better yet copper.
> Roofing companies often have scraps of copper flashing
> around from which you can get a suitable piece. Also
> check around on Ebay.
>
> * http://tinyurl.com/5sa26kp*
>
> Here's a nice chunk of .062" sheet that you can
> shear up for what you need and offer lots of similar
> chunks to other builders.
>
> Use copper pop-rivets to fixture the fast-on
> lugs and then solder using electronic 63/37
> solder.
>
> There are ways to do the best we know how to
> do at minimal time and dollars but bolting up
> an array of terminals on a piece of aluminum is
> not the best we know how to do.
>
> Bob . . .
>
> *
>
>
> *
Message 10
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Different Bob here, but---
What Bob is saying is that first of all it's very difficult to keep aluminum
clean enough for a good "gas tight" connection as it oxidizes almost
instantly after it is cleaned and aluminium oxide is an excellent insulator.
Secondly the assembly method you are proposing using rivets is unsuitable
because a rivet is not designed to provide the tension in a joint which you
require to get the necessary "gas tight" joint. Rivets are designed to be
loaded in shear. Thirdly the dissimilar metals in your connections will
almost certainly result in galvanic corrosion within the joints when you
join the copper wires/lugs/bolts to the aluminium bars. Where and when
aluminium is used for current carrying purposes great pains are taken to
alleviate the above issues through the use of special compounds within the
joints, such as Burndy's penetrox. (see http://tinyurl.com/4gnx4q7) The
above factors are why the attempt to use aluminium wires for household
wiring in the 60's was such a failure and resulted in many homes burning
down. The difficulties in getting reliable joints are significant whereas
using copper or brass there are no such problems.
Bob McC
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-
> server@matronics.com] On Behalf Of John Grosse
> Sent: Friday, January 21, 2011 7:50 PM
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Buss Bar
>
<grosseair@comcast.net>
>
> Bob, I'm not quite sure I understand. Are you saying that aluminum is
> unsuitable for some reason or just that copper or brass is better? I'm
> not questioning your opinion. I'm just interested in the "why" one works
> or doesn't work.
> John
>
> Robert L. Nuckolls, III wrote:
> > At 09:15 AM 1/19/2011, you wrote:
> >> <grosseair@comcast.net>
> >>
> >> A combination of threaded studs for the large wires and riveted fast
> >> on connectors for the rest.
> >
> > Rivets are designed for use in shear, not in tension.
> > Further, your fast-on lugs are no doubt going to be
> > of a material dissimilar to the bus bar.
> >
> > Suggest you go to a hardware store or hobby shop
> > and get a chunk of sheet brass or better yet copper.
> > Roofing companies often have scraps of copper flashing
> > around from which you can get a suitable piece. Also
> > check around on Ebay.
> >
> > * http://tinyurl.com/5sa26kp*
> >
> > Here's a nice chunk of .062" sheet that you can
> > shear up for what you need and offer lots of similar
> > chunks to other builders.
> >
> > Use copper pop-rivets to fixture the fast-on
> > lugs and then solder using electronic 63/37
> > solder.
> >
> > There are ways to do the best we know how to
> > do at minimal time and dollars but bolting up
> > an array of terminals on a piece of aluminum is
> > not the best we know how to do.
> >
> > Bob . . .
> >
> > *
> >
> >
> > *
>
> _-
> ====================================================
> ======
> _-
> ====================================================
> ======
> _-
> ====================================================
> ======
> _-
> ====================================================
> ======
>
>
Message 11
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| Subject: | Re: D-sub crimper |
At 01:57 PM 1/21/2011, you wrote:
>I have a supply of gold-plated D-sub pins and a ratchet crimper --
>both pins and crimper were purchased from B&C. I will be using 20
>ga and 22 ga wiring in my aircraft, but note that there is no
>adjustment on the crimper for different wire gauges. I saw in an
>EAA informational video the use of a D-sub crimper that had an
>adjustment to adapt it to different wire gauges. Do I need one of
>these adjustable crimpers? If I use the one from B&C and give each
>pin a pull test after crimping, is that good enough?
The B&C crimper (mfg by Eclipse) has been
on the market now for 10 years that I know
of. It has performed well with 20 and 22AWG
wire in d-sub pins.
Bob . . .
Message 12
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| Subject: | Re: D-sub crimper |
Thanks for your always prompt and useful information, Bob.
Paul Kuntz
On Fri, Jan 21, 2011 at 7:30 PM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> nuckolls.bob@aeroelectric.com>
>
>
> At 01:57 PM 1/21/2011, you wrote:
>
>> I have a supply of gold-plated D-sub pins and a ratchet crimper -- both
>> pins and crimper were purchased from B&C. I will be using 20 ga and 22 ga
>> wiring in my aircraft, but note that there is no adjustment on the crimper
>> for different wire gauges. I saw in an EAA informational video the use of a
>> D-sub crimper that had an adjustment to adapt it to different wire gauges.
>> Do I need one of these adjustable crimpers? If I use the one from B&C and
>> give each pin a pull test after crimping, is that good enough?
>>
>
> The B&C crimper (mfg by Eclipse) has been
> on the market now for 10 years that I know
> of. It has performed well with 20 and 22AWG
> wire in d-sub pins.
>
>
> Bob . . .
>
>
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