ext ALC problem

[Howard..K2HK]

I am having a problem with the external ALC. I am trying a new amp that requires ALC feedback. When I set it in the config menu regardless of the value -2 to -8 my output is reduced to 60 watts. As I raise the drive it increases until about 60 watts then cuts back. In the tune position which I have set for 15 watts I get only 1-2 watts out. This occurs regardless of whether I am connected to the amplifier or not. The SWR is between 1.2and 1.5. I do have the mod installed.

 

Ideas needed.

 

Howard..K2HK

 
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[Howard..K2HK]

Hi Monty,

I was just pointing out that the CX was the same connected to the amp or not. My K3 does put out in excess of 100 watts when ALC is turned off. I did adjust the ALC control on the amp. This had no result on the K3 output, i.e. 60 watts max ALC on, full output 100+ with ALC off.



 

> From: [hidden email]
> To: [hidden email]
> Subject: Re: [Elecraft] ext ALC problem
> Date: Thu, 28 May 2009 15:12:55 -0400
>
> Howard -
>
> If you are not connected to the amplifier, what is controlling the external
> ALC input to the K3? Has your K3 ever put out 100 watts? My amp's ALC
> needed calibration before I could use it.
>
> Monty K2DLJ
> >
> > I am having a problem with the external ALC. I am trying a new amp that
> > requires ALC feedback. When I set it in the config menu regardless of the
> > value -2 to -8 my output is reduced to 60 watts. As I raise the drive it
> > increases until about 60 watts then cuts back. In the tune position which
> > I have set for 15 watts I get only 1-2 watts out. This occurs regardless
> > of whether I am connected to the amplifier or not. The SWR is between
> > 1.2and 1.5. I do have the mod installed.
> >
> >
> >
> > Ideas needed.
> >
> >
> >
> > Howard..K2HK
> >
> >
> > ______________________________________________________________
> > Elecraft mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> > Post: mailto:[hidden email]
> >
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>

... [show rest of quote]

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[Jim Brown-10]

On Thu, 28 May 2009 19:04:17 +0000, Howard K2HK wrote:

>I am having a problem with the external ALC. I am trying a new amp
>that requires ALC feedback.

It is VERY rare for a modern power amp to REQUIRE ALC. The proper
way to drive an amp is to use the transceiver's power control to set
the drive level sufficient to get the desired output from the
amplifier. ALC should be used only as a "safety" to protect the
amplifier in those conditions when something goes wrong -- perhaps
an antenna or antenna tuner fails, the feedline shorts, etc.  

What do I mean by "modern power amp?"  Well, the manuals for my Ten
Tec tube and solid state amps, written in the early 80's,
specifically state that their ALC function should not be used to set
the drive power, but that the method I described is the right way to
do it.

With many power amps, using ALC to set the drive power will generate
clicks and other trash.  

73,

Jim Brown K9YC


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[Don Wilhelm-4]

Howard,

It sounds like the ALC voltage coming out of your amplifier is much
greater than the K3 ALC input range.

The ALC voltage from your amplifier is reducing the K3 power output.  I
believe the problem is with the amplifier, not the K3.

Remove the ALC connection to your amplifier, then using the K3 power
control, slowly increase the drive to your amplifier while measuring the
voltage being developed at the amplifier's ALC output.  It should be
zero or very close to zero until the amplifier comes near its power
limit.  If the voltage at the amplifier is in excess of the ALC
threshold you have set on the K3, then the K3 will reduce power.

In other words, if you want to set the K3 ALC Threshold at -4 volts,
adjust the amplifier's ALC circuits to produce -4 volts when the
amplifier's power limit is reached.

As others have pointed out, attempting to use the amp's ALC output to
control the power output of the K3 is bad practice and is likely to
produce distorted signals and splatter.

73,
Don W3FPR

Howard K2HK wrote:
> I am having a problem with the external ALC. I am trying a new amp that requires ALC feedback. When I set it in the config menu regardless of the value -2 to -8 my output is reduced to 60 watts. As I raise the drive it increases until about 60 watts then cuts back. In the tune position which I have set for 15 watts I get only 1-2 watts out. This occurs regardless of whether I am connected to the amplifier or not. The SWR is between 1.2and 1.5. I do have the mod installed.
>
>  
>
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[Howard..K2HK]

Don,

The output of the K3 decreases regardless of whether it is attached to amp or not when ALC is turned on. At this point I believe the problem to be in the area of the digital I/O board. If (when) I decide to use the external ALC I will check it out.

 

Howard

 

HK

 

 


From: [hidden email]
Howard,

It sounds like the ALC voltage coming out of your amplifier is much
greater than the K3 ALC input range.

The ALC voltage from your amplifier is reducing the K3 power output. I
believe the problem is with the amplifier, not the K3.

Remove the ALC connection to your amplifier, then using the K3 power
control, slowly increase the drive to your amplifier while measuring the
voltage being developed at the amplifier's ALC output. It should be
zero or very close to zero until the amplifier comes near its power
limit. If the voltage at the amplifier is in excess of the ALC
threshold you have set on the K3, then the K3 will reduce power.

In other words, if you want to set the K3 ALC Threshold at -4 volts,
adjust the amplifier's ALC circuits to produce -4 volts when the
amplifier's power limit is reached.

As others have pointed out, attempting to use the amp's ALC output to
control the power output of the K3 is bad practice and is likely to
produce distorted signals and splatter.

73,
Don W3FPR

Howard K2HK wrote:
I am having a problem with the external ALC. I am trying a new amp that requires ALC feedback. When I set it in the config menu regardless of the value -2 to -8 my output is reduced to 60 watts. As I raise the drive it increases until about 60 watts then cuts back. In the tune position which I have set for 15 watts I get only 1-2 watts out. This occurs regardless of whether I am connected to the amplifier or not. The SWR is between 1.2and 1.5. I do have the mod installed.

 

 

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[Don Wilhelm-4]

Howard,

You are correct, with nothing connected to  the K3 EXT ALC connection,
there should be no power reduction for the K3.  Yes, you should contact
[hidden email] to see if it can be tracked down and corrected.

I am sorry that we initially misinterpreted your email to the reflector.

73,
Don W3FPR

Howard K2HK wrote:

> Don,
>
> The output of the K3 decreases regardless of whether it is attached to amp or not when ALC is turned on. At this point I believe the problem to be in the area of the digital I/O board. If (when) I decide to use the external ALC I will check it out.
>
>  
>
> Howard
>
>  
>
> HK
>
>  
>
>  
>
>
> From: [hidden email]
> Howard,
>
> It sounds like the ALC voltage coming out of your amplifier is much
> greater than the K3 ALC input range.
>
> The ALC voltage from your amplifier is reducing the K3 power output. I
> believe the problem is with the amplifier, not the K3.
>
> Remove the ALC connection to your amplifier, then using the K3 power
> control, slowly increase the drive to your amplifier while measuring the
> voltage being developed at the amplifier's ALC output. It should be
> zero or very close to zero until the amplifier comes near its power
> limit. If the voltage at the amplifier is in excess of the ALC
> threshold you have set on the K3, then the K3 will reduce power.
>
> In other words, if you want to set the K3 ALC Threshold at -4 volts,
> adjust the amplifier's ALC circuits to produce -4 volts when the
> amplifier's power limit is reached.
>
> As others have pointed out, attempting to use the amp's ALC output to
> control the power output of the K3 is bad practice and is likely to
> produce distorted signals and splatter.
>
> 73,
> Don W3FPR
>
> Howard K2HK wrote:
> I am having a problem with the external ALC. I am trying a new amp that requires ALC feedback. When I set it in the config menu regardless of the value -2 to -8 my output is reduced to 60 watts. As I raise the drive it increases until about 60 watts then cuts back. In the tune position which I have set for 15 watts I get only 1-2 watts out. This occurs regardless of whether I am connected to the amplifier or not. The SWR is between 1.2and 1.5. I do have the mod installed.
>
>  
>
>  
>
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>  
>
>
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