I agree with Coy.
<snip>
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.
<snip>
Motorola used to make "public address" amplified speakers that would go loud
enough to make your ears to bleed for the Maxar and some of the other lower
end radios, the public safety guys often used these to get the audio output
of the better radios. They also had some of those for the Public Address
add-on for the maxtrac. I wonder if they are easily obtained these days?
They would be great for this application.
Wade - KR7K
----- Original Message -----
From: "Coy Hilton" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Saturday, January 01, 2005 12:08 AM
Subject: [Repeater-Builder] Re: Speaker Level Mixing
>
>
>
>
> --- 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")
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/Repeater-Builder/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
