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Author Topic: One Speaker, Two Radios  (Read 1642 times)
K8LEC
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Posts: 64




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« on: April 07, 2005, 01:18:35 PM »

This may be a very dumb question, but I've never proclaimesd myself a genius :-) so here goes...

If I have a single speaker that I'd like to hook two radios up to.  Is there any reason why I couldn't simply use a "y" connector and do so?  My concern is the two radios sending their audio signals at each other, which obviously would happen with a simple "y" adapter.  If that's not a viable option, what options might there be to hook a single speaker up from the external speaker outs of two radios.

Thanks!

Lars
K8LEC

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K8LEC
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Posts: 64




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« Reply #1 on: April 07, 2005, 01:20:40 PM »

See I can't even spell proclaimed right! :-)  Oops!
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AA4PB
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Posts: 12784




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« Reply #2 on: April 07, 2005, 01:40:10 PM »

It would be a bad thing to simply parallel two outputs with a "Y" cable. If you don't need to use both radios at the same time you can put in a simple A/B selector switch. If you want to run them at the same time with both outputs going to a single speaker then you'll have to build some type of mixer circuit. That generally involves properly loading both outputs, mixing the signals, and then sending them to another amplifier to drive the speaker.
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K5LXP
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« Reply #3 on: April 07, 2005, 02:40:42 PM »

Hi Lars;

Short of isolating, summing and reamplifying, the most direct approach is two speakers.  I did it for years, had two speakers in the same cabinet.  Even now that I have an amplified mixer setup I use two speakers, one for the active radio the the other at a few dB lower in volume for the rest.  Having spatial and amplitude diversity can be a good thing when trying to figure out which radio is talking.


Mark K5LXP
Albuquerque, NM
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WB2WIK
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Posts: 20567




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« Reply #4 on: April 07, 2005, 03:15:21 PM »

Two speakers are usually the best and most economical solution.

At low levels (line level or lower, with line level being 1V across 600 Ohms), a simple, inexpensive mixer would work and allow you to combine signals into a single load.  But at high level (typically >3V across 8 Ohms), the mixer becomes complicated and costly.

Two speakers are cheaper.

WB2WIK/6
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K1CJS
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Posts: 5997




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« Reply #5 on: April 07, 2005, 03:29:27 PM »

Lars, not only would two speakers be the best, most practical solution, but would also be best for both radios.  Mixers are fine, but may put a strain on the output circuitry of your sets under certain circumstances such as both feeding the output at the same time.

If you haven't, look at the communications speakers made for CB type radios, they'll work equally well on our sets, and the audio will be good too.  Two decent ones plus the wiring and plugs will run less than $30.00.
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N4ZOU
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Posts: 340




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« Reply #6 on: April 07, 2005, 03:41:41 PM »

A cheap and easy solution is to drop by some place like Big-Lots, Fred's, or Dollar General store and look for the cheap amplified computer speakers. Going price is around $10 and they're stereo which allows you to connect one radio to one side of the stereo speakers and the second radio to the other side of the stereo speakers. Radio Shack has a spliter cable that would allow you to do this with off the shelf parts if you don't want to home brew the cables. Best of all they actually sound good!
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AA4PB
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« Reply #7 on: April 07, 2005, 04:55:27 PM »

A "properly designed" mixer will not put any strain on the radios, even if they are both outputting signal at the same time. Of course it is possible to damage the radio if the mixer isn't done correctly.
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N6AJR
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Posts: 9914




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« Reply #8 on: April 07, 2005, 05:24:38 PM »

I buy cheep old kids stero speakers at garage sales and such.  those old 12 inch by 8 inch, by 4 inches deep and cover with wood grained paper and a black speaker, you know the type.  I hook them up to all my rigs.

I am hard of hearing so they are a bit more bassy and also they point the sound towards my ears , not up or down, that helps.

and the price is right.
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X-WB1AUW
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Posts: 559




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« Reply #9 on: April 07, 2005, 05:48:53 PM »

Aaaaaaah.  BUT, do you array all of those speakers in a fan shape?
73
Bob
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W5GNB
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Posts: 419




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« Reply #10 on: April 07, 2005, 07:51:15 PM »

From the hot side of the speaker lead on each radio, put a 10Uf capacitor rated at about 100 Volts in series with each output (Two Capacitors).  This will isolate the two radios from passing any possible DC voltages between each other yet the capacitors will pass sufficient audio.

Join the two ends at the speaker and you will have two radios with one speaker.

I have used this method for YEARS and it works just fine.

I once was just a POOR KID and couldn't afford two speakers at the time HIHI...

73's
Gary - W5GNB
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W8JI
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« Reply #11 on: April 08, 2005, 03:27:27 AM »

I run multiple radios into one speaker.

I terminate each radio in a 5 ohm 2 watt resistor, I have a 500 ohm pot between hot sides, and the wiper feeds a small audio amplifier (MFJ-616)that drives the speaker. A 100 ohm resistor goes from the wiper to ground.

I would not parallel two radios.

73 Tom
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WA4PTZ
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Posts: 528




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« Reply #12 on: April 08, 2005, 05:05:06 AM »

Multi-tap transformers can be handy for this use as
well. You can use an input amp or a T or L pad to help
match the impedance. You might even get lucky and find
an old transformer in a solid state device that will
be close enough. Solid state mixers,using op amps, are
pretty easy to build also.
73's
Tim
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K5DVW
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Posts: 2193




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« Reply #13 on: April 08, 2005, 06:02:35 AM »

I like Tom's (W8JI) approach and was going to suggest it. A good amplifier chip to look into for driving a small speaker is an LM386. Simple to use.
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AA4PB
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Posts: 12784




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« Reply #14 on: April 08, 2005, 06:41:51 AM »

Tom's approach is a good one. You *may* get away with paralleling outputs on some radios but there is no guarentee and I wouldn't consider it a good practice. Even if you isolate the DC voltage with a capacitor, you are still sending audio signals back into the output of the other radio. You just don't know what that AC voltage is going to do to its output stage. In addition, it may present a non-semetrical load and cause distortion in the audio.
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