Skip, I did have transformer coupling on the audio
lines out at the repeater with both sides of the
twisted pair isolated from ground, but did not try
putting transformers in the line back at the computer.
That would certainly be easy enough to do if I ever
hook it up again. One side of the twisted pair was
hooked to the ground of the computer. (The repeater
cabnet is bolted to the side of the tower out in the
middle of a pasture)
We have a wireless ISP at this site, and the ISP
provider decided to take away the public IP address
and assign us a private IP address, which no one can
reach from the internet. We can do everything we need
to do on the internet, but packets that were not asked
for cannot find their way back to the router here .
UDP packets in particular have no way to reach us.
73 - Jim W5ZIT
--- skipp025 <[EMAIL PROTECTED]> wrote:
> I didn't see a post where he actually tried a
> balanced pair
> connection with any type of xmfr, choke or hybrid.
> If he needs
> DC Current signaling we could even show him how to
> wire up a
> basic balanced hybrid with an optional DC Current
> Loop.
>
> In a poor mans method one could even use the low
> cost
> audio transformers from Radio Shack. True split
> winding xmfrs
> for hybrid aps are also cheap and easy to find.
>
> cheers,
> s.
>
> > [EMAIL PROTECTED] wrote:
> > Since the other remedies haven't worked
> completely, you might
> > file this away in case the situation arises
> again:
> >
> > You might be experiencing a ground loop even with
> coupling
> > transformers at each end due to the capacitance to
> ground
> > of the transformers. A common mode choke, if it
> has sufficient
> > reactance at the noise frequency, can eliminate
> the noise.
> >
> > A common mode choke is an inductor with a single
> core (toroidal
> > is good) and two identical windings connected such
> that each
> > winding is in series with one of the long lines.
> The choke
> > goes at the input end with the phasing dots on the
> same side,
> > i.e., either toward the line or toward the
> equipment input.
> >
> > The "desired signal" current flows in opposite
> directions on
> > the two lines and creates opposing magnetic fields
> in the choke,
> > which cancel. The desired signal never sees the
> choke and its
> > waveform is maintained.
>
> > The "undesired signal" (common mode) current flows
> in the
> > same direction in both lines and sees a lot of
> reactance
> > in the choke because the two magnetic fields add.
> Much of
> > the noise is eliminated.
> >
> > 73,
> > Bob
> >
> > Bob Schmid, WA9FBO, Member
> > S-COM, LLC
> > www.scomcontrollers.com
> >
> >
>
> >
> > Hi Jim,
> >
> > >The cable I used was armored with a spiral copper
> > shield over 5 twisted pair lines. I did try
> grounding
> > the shield at one end, and at both ends with no
> > results. Putting caps across the twisted pair and
> to
> > ground also did not eliminate the problem, but
> did
> > reduce it. I used 600:600 isolation transformers
> in
> > the audio input and output lines at the repeater.
> >
> > >It all became a mute point when the cable got
> mowed in
> > two during a grass cutting this last summer, and
> then
> > we lost the public IP address and EchoLink was no
> > longer usable. So any more trouble shooting
> exercises
> > will await the return (if ever) of the public IP
> > address.
> >
> >
>
>
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