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N2OHH > HELP 14.03.05 17:51l 40 Lines 1311 Bytes #999 (0) @ WW
BID : FC0043N2OHH
Read: GUEST
Subj: Re: G4TZX > USB interface
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Sent: 050314/1156 @:K1UOL.CT.USA.NA #:52572 $:FC0043N2OHH
From: N2OHH@K1UOL.CT.USA.NA
To : HELP@WW
KB2VXA wrote:-
> Hi Gordon and readers,
>
> Unless an RF feedback problem is encountered transformers aren't needed.
KC2RLM recommends the use of isolation xfmrs on RX and TX audio as well as
opto-isolator for PTT. I agree, you might get by without but better to go
with. It works fine for 1k2 packet but for 9k6 you need full isolation with
opto-isolators for RX and TX audio.
> If one is you'd be better off cleaning up the RF in the shack,
> transformers unless designed for hi-fi or digital introduce phase shift
> and distortion.
>
> Connecting the speaker output directly to the sound card's line input is
> OK, matching and/or attenuation isn't needed. Connecting the card's
Some soundcards don't offer a line-in.
> output to the microphone input poses a too high level problem so a
> resistive attenuator (a simple L pad) will suffice.
>
> I believe in KISS (keep it simple stupid) and frugality so making it a
Some times the problem isn't RF but ground loops. Isolating your radio from
the computer will simplify the final design.
> DIY project worked for me. The only "magic" in an "interface" lies
> between your ears once you understand the requirements. (;->) It's only
> audio after all, nothing special.
>
7 3
Vin
03/13/05 (21:51)
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