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Subject: HamDigitalDigest 99/323A
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Ham-Digital Digest Tue, 21 Dec 99 Volume 99 : Issue 323
Today's Topics:
Connecting sound card to Computer (2 msgs)
FA: MFJ 1278 Multi-mode Data Controller (Packet, RTTY, CW, FAX)
ground loops and audio isolation transformers (4 msgs)
Help: MFJ Multicom on HP200LX (2 msgs)
Kenwood Control program that runs on Liunx AND Windows!!!!!
PicoPacket and Tripmate APRS Tracker
Req: info on routing in packet radio networks
Tekk ks-960 help
WinAPRS vs UI View?? (3 msgs)
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We trust that readers are intelligent enough to realize that all text
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policies or positions of any party. Your mileage may vary. So there.
Loop-Detect: Ham-Digital:99/323
----------------------------------------------------------------------
Date: Mon, 20 Dec 1999 23:55:30 -0500
From: "Rob" <NoEmail@NoWay.com>
Subject: Connecting sound card to Computer
IMPORTANT -- CORRECTION -- PLEASE READ
The mic jack on a sound card is a MONO circuit but uses a STEREO JACK with
one channel carrying the audio to the sound card from the mic and the other
channel carrying a DC voltage to power a mic.
I made a big mistake. THE TIP OF THE MIC CONNECTOR CARRIES THE DC NOT THE
AUDIO AS I SUGGESTED IN MY LAST POSTING!
Most people use one of the channels of the sound card's LINE INPUT and do
NOT use the sound card's mic input for good reason.
IN ANY EVENT, EVEN IF one is going to connect a cable from a Radio's audio
output to the Computer's sound card LINE INPUT, I strongly suggest that one
uses a STEREO connector and ONLY use the centre ring which carries the
audio to the sound card and the lower ring for the mic ground return.
DO NOT USE the TIP of the connector. Leave it unconnected!
This is the best approach! If you accidentally plug this cable into the MIC
jack of the sound card instead of the LINE INPUT, you will not cause any
damage to your sound card! In fact, the cable will even work and provide an
audio signal from the radio to your sound card!
(If you don't follow this recommendation, you MIGHT damage your sound card.
It depends on whether your sound card has any short circuit protection etc)
73's
Rob
VA2FB
"Rob" <NoEmail@NoWay.com> wrote in message
news:NcX64.198992$5r2.503233@tor-nn1.netcom.ca...
> Bob,
>
> Many thanks for the info.
>
> I understand that it is alright to fed both channels of the sound card
line
> input.
>
> BUT I heard it is a different story for the MIC input. I was told that
the
> mic jack on a sound card is a MONO circuit but uses a STEREO JACK with one
> channel carrying the audio and the other carrying a DC voltage for the
mic.
> It was suggested that I use a STEREO connector and ONLY use the TIP which
> carries the audio. (AND DON'T USE the RING which carries the polarizing
> voltage).
>
> Since HAMS like me sometimes plug cables in the wrong jack (especially if
> the mic and line input jacks are beside each other), it sounds to me like
a
> good idea to only use one channel carried in the tip (even if you PLAN to
> connect it to the line input jack where it doesn't matter)
>
> Any thoughts?
>
> Rob
>
> "Bob Lewis" <aa4pb@erols.com> wrote in message
> news:83hcep$prq$1@bob.news.rcn.net...
> > > I heard that it is NOT a good idea to connect both channels (Left
> > and Right)
> > > of the sound card's line output to the Rig's mic input. It might
> > cause
> > > distortion.
> >
> > It is NOT a good idea. When you connect the two outputs together you
> > are shorting the outputs. Whether this causes any distortion depends
> > on the sound card output circuit design and how well balanced the two
> > outputs are. If, for example, you had the mixer balance all the way
> > to one side, the dead side would attempt to short the output of the
> > other. The output impedance *may* be high enough to prevent
> > distortion or damage but you never know how it was designed. It's
> > best not to do it and there's no advantage to it that I can think of.
> > In pro audio a resistor is often inserted into each channel in order
> > to provide a "resistive combiner" circuit to feed a stereo channel
> > into a mono channel. With PSK31 both channels have the same signal so
> > there's no reason to do it.
> >
> > > (On the other hand, I heard it doesn't matter whether the rig's
> > > speaker output is connected to both channels of the sound card's
> > line input
> > > or mic input).
> >
> > It doesn't matter because because you are shorting two inputs. The
> > load impedance drops to one-half but it's still plenty high enough
> > not to overload the receiver's output.
> >
> > > I also heard if you just used a mono plug for the sound card's line
> > output
> > > (or speaker output), it will short out one of the channels and may
> > cause
> > > distortion. It is best to use a stereo plug and only use one of
> > the
> > > channels. Is this good advice?
> >
> > Good advice! A mono plug will short one output. It may not cause
> > distortion in the other channel, but it's never good practice to
> > short an output unless you know for sure that the circuit design can
> > handle it.
> >
> >
> >
>
>
>.
------------------------------
Date: Tue, 21 Dec 1999 09:51:25 GMT
From: nomail@pe1chl.demon.nl (Rob Janssen)
Subject: Connecting sound card to Computer
Rob <NoEmail@NoWay.com> wrote:
>DO NOT USE the TIP of the connector. Leave it unconnected!
>This is the best approach! If you accidentally plug this cable into the MIC
>jack of the sound card instead of the LINE INPUT, you will not cause any
>damage to your sound card! In fact, the cable will even work and provide an
>audio signal from the radio to your sound card!
>(If you don't follow this recommendation, you MIGHT damage your sound card.
>It depends on whether your sound card has any short circuit protection etc)
I presume that anything that uses a (mini-)jack connector has some form
of short circuit protections, as these connectors routinely short out their
To be continued in digest: hd_99_323B
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