On Mar 2, 3:23*am, "noel.wade" wrote:
Any electric gurus out there willing to help?

Ever since re-doing the wiring in my DG-300 last year, I get
intermittent loud static on my radio. *It seems to be connected to
whether or not I have ship's power going to my EW MicroRecorder. *The
odd thing is that I followed the Becker wiring instructions and made
sure to use a shielded wire for the connection from the Becker to the
remote speaker/PCB assembly. *I would love ideas on how to help stop
this! *Details below - any thoughts, see anything obvious that I'm
failing to do?

Powered Equipment in the panel:
-----
Becker Radio AR3201
Cambridge S-Nav (LCD and quick-response vario)
Tasman V1000 Vario
B400 (backup vario)
EW Avionics MicroRecorder
iPAQ 4700 (powered through the MicroRecorder via Goddard DB9f & I38C-1
connectors with ferrite rings at each end)

Wiring description:
-----
All connections are done with Anderson Powerpole connectors.
The battery (mounted behind the seat and appropriately fused) provides
power to a central block of connections under the instrument pedestal
- via an unshielded ~6-foot run of 18-gauge Tefzel wire. *The central
block consists of a common power bar and a common grounding bar, both
covered with plastic and with Powerpole connectors soldered to them
(done by a commercial outfit, not me).
From the central block, power is routed through 3 different Klixon
Circuit Breakers (one for the Radio, one for the Tasman & EW, one for
the B400 & SNAV).
From the circuit breakers, the wires route to a block of Powerpole
connectors that are joined together to make a "quick disconnect" block
so that the instrument pedestal can be easily removed.
(NOTE: Anderson powerpole connectors have plastic housings that slide
together to form these blocks, but all electrical connections are
still distinct and physically isolated from each other).
The power wire for the EW route from this quick-disconnect block
through a SPST switch (so I can force the EW & PDA to run off their
internal batteries if I have a concern about ship's power levels).
The B400 also has its power wire run through a 3-position switch to
control whether it is off, running on ship's power, or running on its
backup battery.
The Becker has a simple run of wire from the circuit breaker to the
main harness; and from the harness (attached at the back of the
transceiver), it runs as a big bundle back to an area behind the seat
where the remote speaker & circuit-board are located (this runs
through the same flex conduit as the ship's power line - my options
for routing are limited). *As stated before, the speaker wire in this
harness is a single-conductor shielded wire, with the shield being
used as the ground.

I thought that shielding the speaker wire was all that I needed to do,
to isolate it from noise generated by the other systems; but
apparently that's not enough.

A little help, anyone?

Thanks, take care,

--Noel

Obviously, first thing is turn all stuff off and see what makes
problem go away. Ensure squelch is functional.
Second- Yes this is not elegant- start wrapping everything in foil
with foil gounded. Make sure all grounds come to a common point.
See what happens.
Also check that you don't have side tone from mike circuit enabled.
Good luck.
UH
Moving antennas and wires is a common solution.