| Author |
Message |
    
Audiophile73
New member
Username: Audiophile73
Post Number: 9
Registered: 5-2004
| | Posted on Thursday, August 05, 2004 - 8:12 pm: | 
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hey guys i just got a modulator and I don't want to pay 25 bucks to have someone lower my dead key. Is there one thing that sets the dead key and more for swing or how does that work, thx |
Tech548
Moderator
Username: Tech548
Post Number: 202
Registered: 5-2004
| | Posted on Friday, August 06, 2004 - 12:41 am: |
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Audiophile73
Not all radios are the same and therefore not all tuning procedures are the same.
What kind of radio (make and model) are you refering to?
Jeff
Tech548 |
Audiophile73
Junior Member
Username: Audiophile73
Post Number: 10
Registered: 5-2004
| | Posted on Friday, August 06, 2004 - 1:28 am: |
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its a cobra 25 nw st, and hey is there anything i can read or do to learn how to tune up a radio im kinda new to this. I wanna set up a bench at home to test them to. |
Tech548
Moderator
Username: Tech548
Post Number: 203
Registered: 5-2004
| | Posted on Friday, August 06, 2004 - 10:04 pm: |
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Audiophile73
This modification will allow you to easily drive a linear or modulator without "over-driving" it. It will work for both the Cobra 25 and 29. And be sure the radio has been peaked before doing this mod.
Here are the parts you will need.
1- 220uF (16 to 25 volt) electrolytic capacitor.
1- 200 ohm resistor (which will give you around a /2 watt deadkey) or a 400 ohm resistor (which will give you about a 1 watt dead-key).
If you will notice, the higher the resistance, the higher the dead-key will be. Personally, I recomend a very minimum of at least a 400 ohm resistor because that will key just about any linear without a problem. You can experiment with different values until you get the desired dead-key that you want.
Note: 1 to 1.5 watts works best for keying linears and modulators. Anything over 1.5 pretty
much defeats the purpose of this modification when used with a linear.
-------------------------------
1- Unsolder JP-6 found near the final.
2- Solder the 220uF capacitor in the now empty holes where the jumper was removed. Take note that the negative side of the capacitor faces the final.
3- On the printed side of the board, solder a 200 to 400 ohm resistor across the solder joints of the newly installed 220uF capacitor.
Remember now, the higher the resistor value, the higher the dead-key will be. Don't be afraid to experiment with different values until you get your desired dead-key.
Jeff
Tech548 |
Lasthighlander
Junior Member
Username: Lasthighlander
Post Number: 16
Registered: 8-2004
| | Posted on Sunday, September 05, 2004 - 11:21 am: |
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Audiophile,,copper has some great tune up manuals,,7 volumes I think. They cover all kinds of radios and explain alot of stuff. I started with them and still use them on older radios I don`t see much of. |
Silvereagle
New member
Username: Silvereagle
Post Number: 2
Registered: 4-2003
| | Posted on Tuesday, May 30, 2006 - 8:24 pm: |
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I have a cobra 142 GTL and would like to lower the dead key to about 1.5 watts.What modifications need to be done? |
1861
Advanced Member
Username: 1861
Post Number: 509
Registered: 2-2004
| | Posted on Tuesday, May 30, 2006 - 10:40 pm: |
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on the 142gtl just turn vr 6 to desired dk |
Tech808
Moderator
Username: Tech808
Post Number: 10149
Registered: 8-2002
| | Posted on Tuesday, May 30, 2006 - 10:51 pm: |
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Silvereagle,
LOOK to the LEFT of the Forum here and you will see:
Tools
Mic. Wiring
Frequency Chart
CB & Ham Lingo
Modification List
Just CLICK on Modification List and then go to Cobra and 142GTL and I have the Adjustment's / VR Pots listed there.
Hope this help's,
Lon
Tech808
CEF808
N9CEF
CVC#2 |
Allan
Intermediate Member
Username: Allan
Post Number: 155
Registered: 2-2006
| | Posted on Wednesday, May 31, 2006 - 7:37 pm: |
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[the higher the resistor value, the higher the dead-key will be.]
It'll lower the dead-key, won't it? |
Silvereagle
New member
Username: Silvereagle
Post Number: 3
Registered: 4-2003
| | Posted on Thursday, June 01, 2006 - 6:29 am: |
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many thanks for the help. |
