Peter
I have operated for decades without any transformers or expensive interface
boxes. Often there is no need but some set ups will require isolation
transformers.
I suggest you first try without anything as the only cost is making up a
lead. If that works OK then no need to spend more money.
But on transmit if going to the microphone socket then you will need a
couple of resistors to attenuate the sound card signal to mike level. I
would suggest as a first try use a 10K series and a 1K to ground at the rig
end. If more attenuation is needed then reduce the 1K value by about 2 first
then by 4.
If going into a line in level on the rig then probability is no attenuation
is needed.
If a transformer is needed then wire it into the lead ideally for the
transmit lead a turns ratio of about 10:1 would provide the necessary
attenuation for a mike input on the TX otherwise 1:1 will do the job with
resistive attenuation. As the signal levels are low small transformers will
do the job. But make sure the transformers are nowhere near a large power
transformer as magnetic coupling can (and does occur).
73 David G3YYD
-----Original Message-----
From: RTTY [mailto:rtty-bounces@contesting.com] On Behalf Of Peter Laws
Sent: 19 October 2017 02:12
To: RTTY contest group
Subject: [RTTY] Audio isolation
I have a second radio I want to connect to my new NUC. Sound device will be
USB. Don't care to spend more money on a second interface (I already have a
RigBlaster). Since it's an Icom and will allow me to turn on the
transmitter via CI-V (as opposed to doing something across the serial port
to the PTT line), I was thinking of just getting something like this:
https://is.gd/hgbv2h (goes to Amazon). All we're trying to do is prevent
ground loops, right? So wouldn't an inline audio transformer like this (or
any of 3 dozen similar items) work?
NUC is great, BTW, but the 40GB SSD I had handy really wasn't big enough.
W10 fits and by removing the hibernation cache and cleaning up some other
stuff, I managed to get nearly 20 GB free, but I could see that it would be
a never-ending fight. Bought a larger one locally today (120GB/$70).
--
Peter Laws | N5UWY | plaws plaws net | Travel by Train!
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