--- In [email protected], Gary Pearce KN4AQ
<[EMAIL PROTECTED]> wrote:
> At 01:48 PM 12/30/2004, you wrote:
>
> >Anyone had experience with mixing the speaker output of 2 radios,
Say
> >Motorola GM300's to one speaker?
>
> I did that and more in a Saturn - feeding the right side of a dual-
band
> radio plus a 220 radio and the car radio into the car's right
speaker, and
> the left side of the dual-band plus the car radio into the car's
left
> speaker. It worked great. I could use everything at once, and
the
> fidelity of the ham equipment through the car speakers was good.
(I
> actually used a 30 watt stereo amplifier to obtain enough audio
from the
> ham rigs to drive the car speakers through blocking resistors,
complicating
> the installation some.
>
> I've attached a j-peg of the schematic, if this list will accept
> j-pegs. The schematic doesn't have component values, I think the
resistors
> were 20 ohm, 10 watt, and the capacitors were 1000 uF, 50 volt.
>
> Basically I put a blocking resistor on each side of each speaker
wire from
> each "rig" (actually from the output of the stereo amp). I put a
capacitor
> on each wire from the car speaker (4 total, 2 left and 2 right) to
block
> the DC that this audio system put on the speaker wires from
getting to the
> ham rigs.
What did you use to block the AC..(Audio) from feeding back into the
other radio?...........
That's the trouble with most of these post, and all of them using
transformers. You are still driving audio back into the other output
stage. That will sooner or later distroy the audio output PA !!!
I've replaced many expensive PA Moduls becaue someone pulled this
number. The only way to do it right is to load each`output with a
resistor, AC couple the audio (using caps on both sides of the
outputs) into a mixer circuit and then amplify the whole thing.
>
> There was a little interaction between the radios, with volume
dropping
> just a little when the "second" radio is turned on. I found that
> acceptable. But an active mixer is certainly a more elegant way
to go.
>
> 73,
> Gary KN4AQ
>
>
>
>
>
>
_____________________________________________________________________
_____
> Gary Pearce KN4AQ editor, SERA Repeater Journal
> Cary, NC www.sera.org
> 919-380-9944 [EMAIL PROTECTED]
> [EMAIL PROTECTED]
> AOL/Yahoo Instant Messenger: KN4AQ Radio
> (send e-mail to be put on my "buddy list")
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