[1000mp] Sound Card - FT1000MP

[George, W5YR]

Tom, sometime ago I posted a (too) lengthy report of a study of the little
RS isolation transformer. The bottom line was that it has a very restricted
frequency range and is notably limited as to signal level if distortion is
to be avoided.

RS sells a much superior and overall cheaper "stereo" isolation transformer
which is intended for mobile installations to "break ground loops." In one
plastic container they have two very good transformers with a wide frequency
range that are capable of handling large signals without distortion. The
units, which sell for about $15, are complete with RCA-terminated cables.

I do not have the RS part numbers at hand, but if  you are interested, I can
dig them up.

The ubiquitous little RS transformers are adequate for PSK31 use (frequency
range and signal levels) but should be avoided for voice applications. If
you are *really* interested, I can perhaps find a copy of my postings on
each of these units.

73, George W5YR
Fairview, TX
w5yr at att.net
http://www.w5yr.com


----- Original Message ----- 
From: "Tom McDermott" <tom.mcdermott4 at verizon.net>
To: <1000mp at mailman.qth.net>
Sent: Monday, May 24, 2004 2:51 AM
Subject: Re: [1000mp] Sound Card - FT1000MP




This is not good advice. A typical soundcard puts out a signal that
is 60 dB too hot (volts) for the mic or patch input of The FT1000MP
(millivolts). Lowering the output level of the soundcard *might* work (if
you are lucky) or might degrade the signal but not the noise (if you are
unlucky).

Lowering the MIC gain control is not the answer, as there are two
stages of audio gain in the MP before the MIC gain control. If you overdrive
those two stages, you will put out 3 KHZ of wideband trash or incredible
amounts of intermod products (I've seen way too much of that on the air).

If you use it for speech audio, you will hear LOTS and LOTS of HUM.

Simple solution is to attenuate the signal, Radio Shack sells a 60
dB. attenuating audio cable for about $3, no soldering required. An
isolating transformer helps clean up the HUM especially if you have the
speech processor turned on.

More details:

http://www.tapr.org/~n5eg/index_files/page0005.html


-- Tom, N5EG




> know I have posted this on the reflector before, but here it goes again.
>
> You do not need an interface with the FT-1000MP (plain vanilla). I have
had
> mine hooked up to a soundcard for several years without any problems
> whatsoever. Simply hook up the AF OUT on the MP to the LINE IN on the
> soundcard and hook up the SPEAKER on the soundcard to the PATCH on the MP.

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