Today's Message Index:
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1. 01:47 AM - Coax termination, theory, and..do I balun? (CardinalNSB@aol.com)
2. 05:42 AM - Re: Z-19 Series Architecture (Mark Sletten)
3. 06:56 AM - Re: static system leak check procedure (Kevin Horton)
4. 07:32 AM - Re: static system leak check procedure (Ken)
5. 07:50 AM - Thanks (Speedy11@aol.com)
6. 08:02 AM - Re: Cheap "Coat Hanger" antenna (was Coax termination elect theory) ()
7. 05:36 PM - The difference between theory and practice (Richard Girard)
8. 10:13 PM - High density D-sub crimper (Ed Holyoke)
Message 1
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Subject: | Coax termination, theory, and..do I balun? |
I'm using a King KNS-80 and Narco 12D, and replacing the rg-58 in my spam
can with rg400 for my vor/glideslope catwhisker antenna,
Should I replicate the 40 year old balun where it mates with antenna? or
does the termination issue outweigh the benefits of the balun? Thanks Skip
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Message 2
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Subject: | Re: Z-19 Series Architecture |
Bob,
I was wondering if you had a chance to take a look at the Z-19 drawings in response
to my inquiry.
Specifically, the latest revs of the Z-19 drawings on your website show the E-bus
normal feed on a fused connection from the primary bus. Is there a reason for
supplying the E-bus on the Z-19 drawings this way?
Regards,
Mark
--------
Mark Sletten
Legacy FG N828LM
http://www.legacyfgbuilder.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=168391#168391
Message 3
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Subject: | Re: static system leak check procedure |
Yes, if they do the transponder check on the aircraft, they would
have to also connect to the pitot to put vacuum there, or they could
damage the ASI.
But, you really should do a pitot leak check anyway, as a leak in the
pitot side could affect ASI accuracy. Be aware that some pitot ports
have a water drain on the tube, which introduces a very small at the
tube. This doesn't affect ASI accuracy as it is so close to the
pitot tube, that any air that leaks out is quickly replaced without
affecting the pressure in the pitot line. But it does affect leak
checks - you need to block the water drain during the leak check, or
you'll end up looking for a phantom leak.
Kevin
On 6 Mar 2008, at 22:06, Ken wrote:
>
> I'm still wondering how the radio shop does a transponder check?
> I'm guessing they connect their vacuum source to the static port
> AND the pitot port?? If so, I'm going to need to check the pitot
> side of things for leakage as well I think.
> thank you
> Ken
>
> Kevin Horton wrote:
>> You can do an acceptable test much more simply than this. The
>> standard (as described in FAR 23.1325(b)(2)(i)) only calls for
>> enough vacuum to raise the indicated altitude 1000 ft above the
>> altitude of the test site. On my RV-8, I put a piece of tape over
>> one static port, and held a piece of rubber hose against the other
>> static port. I put the other end of the hose in my mouth, and
>> sucked until I had increased the altitude more than 1000 ft. I
>> put my tongue over the end of hose to trap the pressure, and made
>> sure to keep pushing the other end hard against the static port so
>> no air leaked out there. The altimeter dropped much less than 100
>> ft in a minute (the pass/fail criteria from FAR 23.1325), so my
>> system was OK.
>> There is no need to disconnect ASI or VSI (assuming you don't
>> introduce excessive vacuum, which could damage an ASI). In fact,
>> doing it with instruments removed invalidates the test, as you
>> might introduce a leak when you put those instruments back into
>> the static system. You really need to do an end-to-end leak check
>> with the whole static system in the state it would be when you fly
>> the airplane.
>> Kevin Horton
>
>
Message 4
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Subject: | Re: static system leak check procedure |
Thank you Kevin
Even with the water drain plugged, I suspect that my pitot probe will
leak a bit with about 8 psi vacuum (for a 20k feet test) so I will have
to address that.
Ken
do not archive
Kevin Horton wrote:
> <khorton01@rogers.com>
>
> Yes, if they do the transponder check on the aircraft, they would have
> to also connect to the pitot to put vacuum there, or they could damage
> the ASI.
>
> But, you really should do a pitot leak check anyway, as a leak in the
> pitot side could affect ASI accuracy. Be aware that some pitot ports
> have a water drain on the tube, which introduces a very small at the
> tube. This doesn't affect ASI accuracy as it is so close to the pitot
> tube, that any air that leaks out is quickly replaced without affecting
> the pressure in the pitot line. But it does affect leak checks - you
> need to block the water drain during the leak check, or you'll end up
> looking for a phantom leak.
>
> Kevin
>
Message 5
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Bob,
Thanks for your reply.
I'm slowly learning more as I go along.
Stan Sutterfield
Do not archive
Follow the instructions. If the wiring diagram
provided by the manufacturer SHOWS a ground connection
at both ends, then there's a reason for it an
the designer's intentions should be observed.
However, the general rule of thumb is that shields
are to be GROUNDED at one end only . . . that doesn't
mean that the shield is not CONNECTED at both ends . . .
the shield may have an important role to play with
respect to signal or power return paths.
A very common double-grounding error in aircraft
audio systems occurs when headset and microphone
jacks are allowed to find local ground at the
point of attachment to the airframe. This is why
insulating washers . . .
http://www.aeroelectric.com/Pictures/Connectors/Audio/Jack_Insulation_Washers.
jpg
are recommended where the jacks are to me mounted
to a conductive location on structure.
The schematic for wiring the product should be
quite explicit as to where the shields are connected.
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Message 6
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Subject: | Re: Cheap "Coat Hanger" antenna (was Coax termination |
elect theory)
No offense to Ernest or Bob, the old coat hanger
antennas that you terminated the coax with crimp on
lugs has not been used in production airplanes since
the 50's or early 60's.
Coat hanger antenna
http://www.aircraftspruce.com/catalog/avpages/av534.php
What Eric says about "EM field energy", which I recall
bits from physics and armature radio, the coax,
BNC connector is way more efficient. That inch of
exposed shield/core & important lost insulation does
count. The "coat hanger antenna connections are
subject to corrosion and fatigue way more than a BNC
connector. Just my opinion.
No one is seriously using the coat hanger wire antenna
on new OEM aircraft any more.
"Testimonials" that they work in the plane or bench are
great, but unless you do a test on the airframe in an
antenna test chamber (EMF / RF anechoic chamber),
we are guessing. Besides performance there is the
reliability of the installation.
Just from an installation standpoint, spend the $124
for the real antenna and leave the $50 coat hanger
antenna for the closet. Antenna energy, non-ionizing
radiation is EMF energy at high frequencies. It needs
"ducting" to be most effective.
Does the "strip-it crimp-it" antenna connection work?
Yes it "works", but gosh ughaaa, ugly.
We're talking about 5-8 watts of energy and communications
of 5 to 50 mile, line of sight, listening for even more powerful
transmitters, usually without obstacles. We can get away
with a weak antenna.
The coat hanger works, but its not ideal. We have better
ways. If I was restoring a classic Beech or something, yea
I'd keep the coat hanger antenna. Other wise coat hangers
are for the closet (pun intended).
$110-$150 for newer antenna design
http://www.aircraftspruce.com/catalog/avpages/av17.php
PS: Some have experienced RFI with unshielded antenna
connections thru gauges and avionics.
>From: Ernest Christley <echristley@nc.rr.com>
>Subject: Re: Coax termination and electrical theory
>explained.
>Eric M. Jones wrote:
>> Bob, in my humble opinion, needs a little nudge
>> on this. Here's how NOT to terminate coaxial
>> cable--
http://aeroelectric.com/articles/shldwire/shldwire.html
>The difference between theory and practice is that in
>theory they are the same.
> You have two copper strips to form an
>antennae. One must be connected to the center
>conductor, the other to the shield. Whether you
>terminate the coax with some fancy, expensive
>solution from an electronics catalogue or Bob's
>method, at some point the center conductor has to
>split out from the shield. The difference in actual
>performance in the flying airplane will be lost in
>the noise (pun intended). In theory, there is an
>advantage in the expensive, complicated solution.
>In practice, the advantage ain't worth the
>headache.
---------------------------------
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Message 7
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Subject: | The difference between theory and practice |
All this discussion about antenna connections brings to mind an old story
about a mathematician, a theoretical physicist, and an engineer. They began
pondering a thought experiment about a man and a beautiful naked red head
standing six feet apart. The question was this; if the man halves the
distance between himself and the red head each second, how long will it take
before he reaches her?
The mathematician and the physicist both immediately answered that of course
the man would never reach her.
The engineer calculated that in four seconds he'd be close enough for all
practical purposes.
This is what comes from listening to the annual "Prairie Home Companion"
joke show this evening.
Ya'll take it easy and have a nice Sunday.
Rick
Message 8
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Subject: | High density D-sub crimper |
Howdy,
I've got to crimp about 30 machined high density d-sub pins on an ACU
install and I don't think my standard density crimper (B&C) is gonna
work. I'd hate to spend $800 on a Daniels and postitioners for one
little deed. Any ideas?
I thought about getting a $30 crimper and some of the fold over pins.
Are those pins as reliable as the machined ones? Will the crimper (fold
over style, also B&C) do those little pins in one of it's slots?
Pax,
Ed Holyoke
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