Electrical Help? Shielded speaker wires, but still static...

So in true troubleshooting/gremlin fashion, I spent over an hour
trying to get the radio to make static yesterday, and couldn't. :-P
Argh!

If this is a problem that only appears when I'm airborne, it's going
to be a real pain to track down!
*sigh*

--Noel

On Mar 7, 9:39*am, "noel.wade" wrote:
So in true troubleshooting/gremlin fashion, I spent over an hour
trying to get the radio to make static yesterday, and couldn't. :-P
Argh!

If this is a problem that only appears when I'm airborne, it's going
to be a real pain to track down!
*sigh*

--Noel

Noel

Do you have a transponder? If not ignore the rest of this post.

If you do this could be related to transponder interrogation. Possibly
a combination of noise from two sources breaking squelch.

With a transponder the same basic comments apply, with coupling either
through the power supplies or RF. If you switch briefly to standby in
flight does the noise go away? If so start with the power supplies and
try putting a filter/choke on the transponder power supply leads close
to the unit. Also look at the transponder coax cable for problems.

Ground radars will interrogate your transponder typically at 5 second
(approach radar) or 12 second (area radar) intervals, of course you
may be interrogated by multiple radars and also TCAS and similar
systems (that can be at much higher rates (~1/sec). On the ground you
may be outside of radar interrogation and if your transponder antenna
is under the glider (where it usually should be) may not see TCAS
interrogations on the ground. TCAS interrogations will come and go but
radar will be consistent. Repeatable noise bursts at these kind of
rates can be a clue its transponder related.

Darryl

Noel,

One quick test that I didn't see mentioned - does the interference go
away when you disconnect the antenna connector to the radio? If it
does, then the interference is coupled in through an air path to the
radio antenna or antenna coax at RF frequencies. If it doesn't, then
the interference is probably coupled in from one set of power leads to
another. It is also possible to have power lead coupling at RF freqs,
and this is what RF chokes (beads) are intended to address.

Another very effective method of suppressing interference via power
leads is to use a separate power & ground pair from each instrument,
and twist each pair for most of its length. A properly done 'twisted
pair' is quite effective at suppressing 'common-mode' interference at
all frequencies, while a ferrite RF choke is only effective above
100MHz or so. I use a cordless drill to form twisted pairs as this
forms a more uniform twist. A well formed twisted pair will shorten
the normal wire length by a factor of 1.5 to 2. In other words, if
you form a twisted pair from two individual 5' long wires, you will
wind up with a twisted-pair cable about 2.5 - 3.3' long. If possible,
the untwisted portions at each end should be less than 6" (i.e. less
than about 0.1 wavelengths at 150MHz).

Hope this helps,

Frank TA

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?

I've a Becker panel radio. Last year it suddenly became unusable due
to loud intermittent "static" noise. I finally tried turning the
squelch screw on the side of the case, you may have to remove your
radio to get at it. That fixed it. Have no idea what changed. Has
worked flawlessly ever since.

Regards,

-Doug

On Mar 2, 11:34*am, Doug Hoffman wrote:
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?

I've a Becker panel radio. *Last year it suddenly became unusable due
to loud intermittent "static" noise. *I finally tried turning the
squelch screw on the side of the case, you may have to remove your
radio to get at it. *That fixed it. *Have no idea what changed. *Has
worked flawlessly ever since.

Regards,

-Doug

That may make the symptom go away but the risks now is not being able
to hear weak radio transmissions.
The extra concern here was you described it as a "loud noise". If its
something that is breaking squelch with a large signal turning up
squelch to silence this is a bad idea.

If this suddenly started happening it could be something as simple as
a wire behind the panel moved closer to another, a poor connector or
break developing in a coaxial cable (cable flexed differently than
previously), etc. It it may be worth trying to diagnose the root
cause. Start with identifying what device is causing the periodic
interference. Start by turning down the squelch so that you get fairly
often occurring interference then poke around to make that better/
worse.

Darryl

On Mar 2, 2:48*pm, Darryl Ramm wrote:

That may make the symptom go away but the risks now is not being able
to hear weak radio transmissions.

It it may be worth trying to diagnose the root
cause. Start with identifying what device is causing the periodic
interference.

Thanks Darryl,

I'll check it out.

Regards,

-Doug