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Fergus Kyle
Joined: 03 Jun 2007
Posts: 291
Location: Burlington ON Canada
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 Posted: Mon Oct 08, 2007 9:51 am Post subject: 912ULS and XCOM760 Problem] |
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Just a quick note to support Silvano's position:
I spent ten years chasing fellow Amateur Radio Licensees' poor
transmission faults - low output, garbled and intermittent signals, slow
deterioration. I would guess that about 95% of the trouble traced back to
BAD coaxial cable connectors The idea that if it fits, it's suitable is
faulty.
Strict attention to every detail in the assembly and installation of
coaxial connectors is essential to long and trouble-free transmission.
Reception is satisfactory through many of these searches and means little.
Intermittent shorts, and faulty connections will slowly choke the
transmitter and it quits.
In all these faults, go for the antenna connectors first.
Ferg
Europa Classic 914 mono
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Mon Oct 08, 2007 5:41 pm Post subject: 912ULS and XCOM760 Problem] |
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Funny... I found most of the bad connections on coax connectors had
something to do with cold solder joints. Lots of guys use pre-made cables
and generally they have the worst problems with strain relief, make that
lack of strain relief. I'd like nickel for every cracked centre conductor
of coax cable I've found and there was a lot of them! Generally that only
happens when it is a single conductor not a braided one.
Most (not all) radio and electrical faults in aircraft can be traced back to
poor grounding. This is especially true of aluminium aircraft. Regardless
of whether of not a plane is aluminium in I expect 90 % of problems bad
grounding was the root of the problem. Seldom was it as you might expect
connections to the battery.
Prime locations seem to be where the braid crosses the engine mount. You
wouldn't believe how many braids are either missing, connected to painted
surfaces or hanging on by a few strands. They should be nice and shiny
under the mounting nuts/bolts. I used to check the commercial planes I
worked on every 50 hr or so for clean grounds.
Another prime location for poor grounding is where the voltage regulator
mounts to the frame of the plane. Most of the newer (RTFM) solid state
regulator/rectifiers need to have a good ground at both the mounting point
and where the appropriate wire is grounded. I like to ground the designated
wire directly to the engine block. That gives it the same potential as the
ground on the alternator.
The third location I have found for poor grounds is the back of the
instrument panel. Often the fix for malfunctioning avionics is simply to
clean the grounding posts and make sure there is a nice braid somewhere
between the battery and the panel ground points.
The last common place I've found poor grounding is where nav lights are
mounted. That is usually an easy one to diagnose as there will only be one
light suffering from dimming. When I see this I just sand the base of the
light and its mounting point with aluminium oxide paper.
Did I mention most electrical and radio problems in aircraft can be traced
back to poor grounds???
Good!
Noel
P.S. in a few instances problems were found to be in poor installation and
shielding techniques. A sure sign of a Friday evening job.
[quote] --
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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