Today's Message Index:
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1. 05:52 AM - Re: Harbor Freight Hydraulic Crimper (eschlanser)
2. 10:43 AM - Re: Antenna Placement ?s (Robert L. Nuckolls, III)
3. 11:55 AM - Re: More Strobe Noise (Robert L. Nuckolls, III)
Message 1
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Subject: | Re: Harbor Freight Hydraulic Crimper |
Richard,
Thank you so much for your thoughtful opinion and generous offer to redo my work.
I can see you are worried and can relieve your concerns. First, the crimps
pass the go-no go gage. Second, the picture should show you the work is solid.
Thanks again for your concern.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=341186#341186
Attachments:
http://forums.matronics.com//files/rudder_cable2_112.jpg
Message 2
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Subject: | Re: Antenna Placement ?s |
At 12:03 AM 5/27/2011, you wrote:
>
>I'm building and RV9A. According to my antenna manufacturer, RAMI,
>Inc, instructions the antenna should be 24 inches from any other
>antenna and reflective surfaces, e.g. landing gear. My plan has
>been to mount a Com antenna under the pilot and passenger seats with
>the transponder antenna about 24 inches further aft. However this
>would put each of Com antennas within 24 inches of the landing gear
>and the step. The only way to avoid this would be to mount them on
>or about the center line on the belly along with the transponder antenna.
>
>Question, how much of a problem will I have if the antenna are
>within one foot to 18inches of the gear or the step. Secondarily,
>how much distance should I have between the Com antenna and the
>transponder antenna, which will also be mounted on the belly about
>24 inches behind the baggage bulk head (with the Dynon transponder
>in close proximity.)
Probably no effects that you will notice. There's
very little interaction between VHF comm systems
an UHF transponder. Do what you can for separations
but don't loose any sleep over the selected configuration.
Bob . . .
Message 3
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Subject: | Re: More Strobe Noise |
>If I unplug my antenna connection from the rear of the radio I get
>silence, so deducted that I had RFI that was coming into the radio
>from either the coax or the core. I ran a temporary wire from my
>antenna groundplane to a clean earth. Doing this, I got the first 3
>cracks, then the noise reduced to a hardly detectable level. Job
>done, I thought. SO I made this wiring permanent and tested again,
>same result; job done I thought, so closed everything up.
>Flight tested and found it back to it's normal levels - to the point
>where I won't turn the strobes on unless visibility really requires it.
Yup. Been there, done that.
When Cessna started looking at white, tip and tail strobes
for the single engine line, we discovered that the flash
tubes themselves are strong radiators of electromagnetic
chaos every time they fire.
I was only peripherally aware of the studies going on
in another area of engineering so I don't know what the
final outcome was. I do recall seeing some strobe tube
heads surrounded by a a fine screen of material grounded
to the head-shell . . . no doubt an experiment to see
if sufficient attenuation of the noise can be achieved.
Eventually, the tip and tail tubes did make it to our
products as a option to replace the legacy rotating beacon.
I don't know what change to design made them acceptable.
This was before DO-160 was being generally applied to all
electro-whizzies on the airplane. All radios were getting
the once-over but it was pretty much up to the installers
at the factory to be system integrators for fans, motors,
and . . . strobes.
>Is there a filter available to go in line with my coax and the radio?
>Should I change the coax to a known high grade and re-route?
No, no and no. I suspect that if you conduct yet
another experiment and signal-up your radio from a
an antenna on a long coax and located further from
the airplane, you'll find that the noise goes away.
There's a square-law in general effect here that
says every doubling the distance between victim and antagonist
reduces effects to 1/4.
This is an instance where the 'shielding/filtering' effort
needs to take place at the source. Grounded fine wire mesh
dome or cylinder over the tubes? I wish I could be more
encouraging. Perhaps someone associated more closely
with the early Wheelan/Garmin crowd will recall what
ultimately made these products airplane friendly.
I was outside that loop looking in.
Bob . . .
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