[1000mp] Sound card interface to FT-1000MP mic input

[Joe Subich, W4TV]

Using the speaker output of a sound card is a prescription for 
disaster.  First, the audio amplifier in the sound cards is not 
very good (lots of internally generated IMD in many cases) and 
the level is much, much, much too high to drive a microphone 
input.  Where a line output will require about a 10:1 voltage 
divider (20 dB attenuation) the speaker output may require 
100:1 (40 dB) or more.  

73, 

   ... Joe Subich, W4TV 
       microHAM America, LLC 
       www.microHAM-USA.com 

 

> -----Original Message-----
> From: 1000mp-bounces at mailman.qth.net 
> [mailto:1000mp-bounces at mailman.qth.net] On Behalf Of Robert 
> Dorchuck W6VY
> Sent: Tuesday, September 20, 2005 4:59 PM
> To: All about Yaesu 1000mp
> Subject: RE: [1000mp] Sound card interface to FT-1000MP mic input
> 
> 
> The question was the speaker output from the sound card
> and they are 8 ohms.  Agee if the line out is used.
> 
> Bob  W6VY
> 
> 
> --- Pete Smith <n4zr at contesting.com> wrote:
> 
> > Depends.  Every sound card I've dealt with has had a 600 ohm line
> > output, which either drive amplified speakers or could be connected
> > directly to a line level input.  The big thing you need to feed the
> > line output of a typical sound card to an MP mike jack (I do that
> > here) is an isolation transformer and a roughly 10:1 voltage divider
> > to get the level down to what the mike input can handle.
> > 
> > 73, Pete N4ZR
> > 
> > At 09:38 AM 9/20/2005, Robert Dorchuck W6VY wrote:
> > >The sound card speaker output is 8 ohms.  Mic input on the 
> MP is 600
> > >ohms.  I would use a 8:600 ohm transformer.  I do not think 1:1
> > would
> > >be appropriate.  Available at Mouser, etc.
> > >
> > >Bob  W6VY
> > >
> > >
> > >--- "A.J.C." <n2ki at amsat.org> wrote:
> > >
> > >> Dave,
> > >> 
> > >> You can use the 1:1 isolation transformer from Radio Shack.  They
> > are
> > >> fine.
> > >> 
> > >> Tony - N2KI
> > >> SYSOP - N2KI DX CLUSTER
> > >> dxc.n2ki.com:7300
> > >> RF Gateway 145.650
> > >> Website: www.n2ki.com
> > >> DX Spoken Here
> > >> 
> > >> 
> > >> > -----Original Message-----
> > >> > From: 1000mp-bounces at mailman.qth.net [mailto:1000mp-
> > >> > bounces at mailman.qth.net] On Behalf Of Dave Hawes
> > >> > Sent: September 20, 2005 05:35
> > >> > To: 1000mp at mailman.qth.net
> > >> > Subject: [1000mp] Sound card interface to FT-1000MP mic input
> > >> > 
> > >> > Can anyone suggest an appropriate audio isolation 
> transformer to
> > >> use
> > >> > between a computer sound card speaker output and the microphone
> > >> > input
> > >> > on the MP?  This will be used for contest voice memory keying. 
> > >> Radio
> > >> > Shack, Mouser, DigiKey, etc. all would be OK.
> > >> > 
> > >> > Thanks in advance.
> > >> > 
> > >> > 73 - Dave N3RD
> > 
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> 
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