Copper Talk » Open Forum » Archived Messages » 2002 » 09/01/2002 to 09/30/2002 » Talk back for a cobra « Previous Next »

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woodyinpa
Posted on Sunday, September 15, 2002 - 2:58 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

is there a simple way to get talk back on a cobra 25? it has pa and an ext. speaker mounted against it. it's a company radio and i don't want to put much into it, thanks
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Ncrebel
Posted on Sunday, September 15, 2002 - 4:56 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

umm I used to know.....I know you can ground the speaker to the chassis and get talkback but there was a better way to do it that had something to do with grounding the ex speaker jack I think...wanna say I grounded the speaker jack to the chassis and I put a resistor along with it to keep it from making feedback.It worked great when I had it.There's other methods of doing this...you can make it where you can switch it on and off or make it varible as far as how loud it is.Just whatever you wanna do.73's
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Tech808
Posted on Sunday, September 15, 2002 - 5:20 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

woodyinpa,

Look to the left of this column where it says SEARCH, CLICK on By Keyword: Then type in TALKBACK.

It will answer your question's.

Hope this helps!

Lon
tech808
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Wyatt_Earp
Posted on Sunday, September 15, 2002 - 6:55 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

solder a resistor to the pa jack and the ext. speaker jack. I used to know the value range that would give you the right amount of volume. Maybe around 250ohms?
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Tech671
Posted on Monday, September 16, 2002 - 5:55 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

You solder a 75-150 ohm 1/2w resistor across the pads ot the ext spkr and pa jacks at the very rear of the board.
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Hotrod
Posted on Monday, September 16, 2002 - 10:14 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I USUALLY USE A 47 OHM OR 68 OHM.DEPENDS ON HOW LOUD YOU WANT IT. THE LOWER THE RESISTOR # THE LOUDER IT WILL BE AND THE MORE FEED BACK YOU WILL GET.JUST REMEMBER TO PUT THE YELLOW BAND OF RES.TO EXT.SPKR.IF YOU USE 47 OHM.IT WILL BE BLUE BAND IN A 68 OHM..
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Ncrebel
Posted on Monday, September 16, 2002 - 4:35 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

umm I thought you could put resistors in either direction?They don't have a positive or negative side do they?
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307
Posted on Monday, September 16, 2002 - 9:20 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

No they do not..Use a 200 Ohm pot with OFF/ON (Rad-Shack) and you can have it variable...

307