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Adjusting dead key ??

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johnyb-21
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Adjusting dead key ??

Post by johnyb-21 » Thursday, 30 November 2006, 16:37 PM

How do you adjust the dead key on a Cobra 29 ??


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Post by GOTA Go » Thursday, 30 November 2006, 17:13 PM

OK Big Bopper where you at?
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Romans 10:9



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Mr. Fixit
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Adj Deadkey on Cobra 29

Post by Mr. Fixit » Monday, 25 December 2006, 20:05 PM

Adjust Deadkey @ L-10 :D

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Post by crazymikey555 » Monday, 25 December 2006, 21:52 PM

hey what i did is i got a modulator from sparky so i can adjust it with a turn of a knob easy to put in. you can put it right in the swr knob works like a charm.

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Adjusting DeadKey

Post by Mr. Fixit » Tuesday, 26 December 2006, 6:16 AM

Thats a good Idea for sure. Sparky is the Best. :D


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Re: Adj Deadkey on Cobra 29

Post by Siniste Minster » Sunday, 09 March 2008, 18:49 PM

Mr. Fixit wrote: Adjust Deadkey @ L-10 :D
Please explain in more detail as there is no adjust ments on L-10..Thank you..

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Re: Adj Deadkey on Cobra 29

Post by Siniste Minster » Sunday, 09 March 2008, 18:54 PM

If you want to keep the carrier reasonably high (no AMP) make R1=33 ohm.

If R1 is 68 ohm, will give a Carrier of about one and a half Watt Dead Key and an Audio Swing of about 12-14 Watts PEP. RMS will be one and a half Watt Dead Key to about 5 Watts RMS!

If R1 is 82 ohm, will give a Carrier of about 1 Watt Dead Key and an Audio Swing of about 12-14 Watts PEP. RMS will be 1 Watt Dead Key to about four and a half to 5 Watts RMS!

R1 Must be rated at 2 Watts metal film. C1 is rated at 35VDC.

NOTE: When doing this modification, the AMC should be adjusted back a little, for an audio swing of about 9 or 10 Watts PEP, this will reduce transmit distortion.

NOTE 2: In the diagram, the notation that says add a 68 pF disk cap to C-62, I have found this in some cases does not produce the desired effect so disregard it.

WARNING! DO NOT cut the limiter or you will have a radio that sounds over modulated!

I have found that on the small Amps, a dead key of three quarters to 1 Watt to be acceptable. After all, Super Modulation is the object, right?

Foot Note: If these Changes are done, you will have changed the Radio to a different Class of Amplifier, a Modulator.

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Re: Adj Deadkey on Cobra 29

Post by 216 » Sunday, 09 March 2008, 18:56 PM

Mr. Fixit wrote: Adjust Deadkey @ L-10 :D



That is incorrect

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Re: Adj Deadkey on Cobra 29

Post by Tezterz » Sunday, 09 March 2008, 19:30 PM

Siniste Minster wrote:If you want to keep the carrier reasonably high (no AMP) make R1=33 ohm.

If R1 is 68 ohm, will give a Carrier of about one and a half Watt Dead Key and an Audio Swing of about 12-14 Watts PEP. RMS will be one and a half Watt Dead Key to about 5 Watts RMS!

If R1 is 82 ohm, will give a Carrier of about 1 Watt Dead Key and an Audio Swing of about 12-14 Watts PEP. RMS will be 1 Watt Dead Key to about four and a half to 5 Watts RMS!

R1 Must be rated at 2 Watts metal film. C1 is rated at 35VDC.

NOTE: When doing this modification, the AMC should be adjusted back a little, for an audio swing of about 9 or 10 Watts PEP, this will reduce transmit distortion.

NOTE 2: In the diagram, the notation that says add a 68 pF disk cap to C-62, I have found this in some cases does not produce the desired effect so disregard it.

WARNING! DO NOT cut the limiter or you will have a radio that sounds over modulated!

I have found that on the small Amps, a dead key of three quarters to 1 Watt to be acceptable. After all, Super Modulation is the object, right?

Foot Note: If these Changes are done, you will have changed the Radio to a different Class of Amplifier, a Modulator.




Ok you left some stuff out ... That's word for word from Pegleg's website. The modification it is talking about is the modulation mod, and diagram it is referring to is this one.

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Re: Adjusting dead key ??

Post by 4600 Turbo » Sunday, 09 March 2008, 22:55 PM

johnyb-21 wrote:How do you adjust the dead key on a Cobra 29 ??




I believe it's L11. It looks like a small brown tube with wax on top. It near the rear of the radio near the large spring.

Take the wax off and you'll see the tuning pot.

Turn up to get more DK and down for less.

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Re: Adj Deadkey on Cobra 29

Post by Siniste Minster » Sunday, 09 March 2008, 23:39 PM

Tezterz wrote:
Siniste Minster wrote:If you want to keep the carrier reasonably high (no AMP) make R1=33 ohm.

If R1 is 68 ohm, will give a Carrier of about one and a half Watt Dead Key and an Audio Swing of about 12-14 Watts PEP. RMS will be one and a half Watt Dead Key to about 5 Watts RMS!

If R1 is 82 ohm, will give a Carrier of about 1 Watt Dead Key and an Audio Swing of about 12-14 Watts PEP. RMS will be 1 Watt Dead Key to about four and a half to 5 Watts RMS!

R1 Must be rated at 2 Watts metal film. C1 is rated at 35VDC.

NOTE: When doing this modification, the AMC should be adjusted back a little, for an audio swing of about 9 or 10 Watts PEP, this will reduce transmit distortion.

NOTE 2: In the diagram, the notation that says add a 68 pF disk cap to C-62, I have found this in some cases does not produce the desired effect so disregard it.

WARNING! DO NOT cut the limiter or you will have a radio that sounds over modulated!

I have found that on the small Amps, a dead key of three quarters to 1 Watt to be acceptable. After all, Super Modulation is the object, right?

Foot Note: If these Changes are done, you will have changed the Radio to a different Class of Amplifier, a Modulator.




Ok you left some stuff out ... That's word for word from Pegleg's website. The modification it is talking about is the modulation mod, and diagram it is referring to is this one.

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OK,Thank you..

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Re: Adjusting dead key ??

Post by Siniste Minster » Sunday, 09 March 2008, 23:41 PM

4600 Turbo wrote:
johnyb-21 wrote:How do you adjust the dead key on a Cobra 29 ??




I believe it's L11. It looks like a small brown tube with wax on top. It near the rear of the radio near the large spring.

Take the wax off and you'll see the tuning pot.

Turn up to get more DK and down for less.
I may be wrong but L11 is a TVI trap and should not be touched..Correct me if I am wrong....

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Post by 216 » Monday, 10 March 2008, 6:38 AM

Those slugs are set for peak output only and nowhere else.This will be 4 watts on an accurate wattmeter,which is the design of the RF strip in the radio.The only correct way to drop the output power is to drop the voltage to the driver using a pass transistor,tip31/tip41 and a front panel potentiometer to make it variable.

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Re: Adjusting dead key ??

Post by Tezterz » Monday, 10 March 2008, 8:10 AM

Siniste Minster wrote:
4600 Turbo wrote:
johnyb-21 wrote:How do you adjust the dead key on a Cobra 29 ??




I believe it's L11. It looks like a small brown tube with wax on top. It near the rear of the radio near the large spring.

Take the wax off and you'll see the tuning pot.

Turn up to get more DK and down for less.
I may be wrong but L11 is a TVI trap and should not be touched..Correct me if I am wrong....



You are correct. DON'T adjust L11.
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Variable DEAD KEY for Cobra

Post by COPENHAGEN » Tuesday, 11 March 2008, 1:30 AM

Find and remove C70 & JP6(near Final).

Disconnect Orange and Brown wires from the RF Gain Control,then connect these wires together.

Install Q1(see diagram) where JP6 was.The right leg(emitter) of Q1 in the hole near the final.The Centre leg(collector) in the other hole.

Solder a wire from the left leg(base) of Q1 to the centre tag of the RF Gain Control.

Remove VR5(near transformer)

Connect the last tag of the RF Gain Control to a 100ohm resistor and solder to L6 pot.

Solder a wire from the upper tag of the RF Gain Control to the top connection of VR5(already removed)

Cut D9 out of the circuit (this is the Clipping Diode)

Put plenty of heat sink compound onto the tab of Q1, then using the proper mounting hardware mount to heat sink (make sure that the tab of Q1 is insulated from the heat sink)
Unit 306 from the back woods of north east Georgia JUST GOT DOWN




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