K3 and Expert Amp

[Gary Slagel]

 I'm looking at the SPE Expert Amp 1K-FA.  The SPE amps both recommend using an ALC connection to automatically control the radio's output power thus preventing amplifier overdrive.

I talked to an SPE rep and I understood him to say that I couldn't use the ALC connection with a K3 and there was an alternative way to allow the SPE to control the K3 output power by manually configuring the SPE to set the K3 output power on a band by band basis.  I looked at the SPE manual and it outlines a method to set up a flex-radio that does not have the ALC connection but doesn't talk about the K3.  I assume the k3 setup would be the same as for the flex-radio. 

Does anyone have experience with setting this up with the K3 and SPE 1K-FA.  Or, experience using the K3 ext ALC with and SPE? 

Thanks,
 
Gary Slagel
KT0A
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[Don Wilhelm-4]

Gary,

SPE has some misconception that their ALC is fast enough that the
amplifier will not be overdriven - they do instruct the user to set the
drive power to maximum and let the amplifier control the drive.

That just does not make sense to me - by the time the amplifier detects
that it is being overdriven, the distortion has already occurred, and
then it takes a finite length of time for the amp to increase the ALC
and throttle back the driving power.  I just don't understand how that
can work in either zero or negative time to prevent distortion.

I would suggest you drive the SPE amps just like any other - adjust the
drive power to produce the desired power output on each band (yes, the
K3 will remember the drive power on a per band basis). That way, the
amplifier is never driven into the ALC region, and no distortion occurs.

The ALC line can be connected just in case there is some fault - the
amplifier can reduce the drive level to protect itself.

73,
Don W3FPR

On 9/21/2012 12:37 PM, Gary Slagel wrote:
>   I'm looking at the SPE Expert Amp 1K-FA.  The SPE amps both recommend using an ALC connection to automatically control the radio's output power thus preventing amplifier overdrive.
>
> I talked to an SPE rep and I understood him to say that I couldn't use the ALC connection with a K3 and there was an alternative way to allow the SPE to control the K3 output power by manually configuring the SPE to set the K3 output power on a band by band basis.  I looked at the SPE manual and it outlines a method to set up a flex-radio that does not have the ALC connection but doesn't talk about the K3.  I assume the k3 setup would be the same as for the flex-radio.
>
> Does anyone have experience with setting this up with the K3 and SPE 1K-FA.  Or, experience using the K3 ext ALC with and SPE?
>
>

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[Jim Brown-10]

On 9/21/2012 9:37 AM, Gary Slagel wrote:
>   I'm looking at the SPE Expert Amp 1K-FA.  The SPE amps both recommend using an ALC connection to automatically control the radio's output power thus preventing amplifier overdrive.

It is NEVER a good idea to use ALC to set drive level to a power amp.
Doing so is a recipe for distortion, key clicks, and splatter. ALWAYS
control the amplifier output power by setting the POWER OUTPUT of the
transceiver so that the transceiver produces just enough output power to
get the desired power from the amplifier.

IF you want to use ALC, use it ONLY to protect the power amp from
failures in the antenna system.  Think of it as "belt and suspenders."  
FWIW, I've NEVER used ALC between any rig and amp that I've owned or
operated.

Modern amplifiers do NOT need ALC -- indeed, "modern" includes my
vintage Ten Tec Titan power amps that were designed in the late '70s and
built well into the '80s. The manual notes that although an ALC output
is provided for compatibility with older rigs, it should not be used
except as I've described.

73, Jim K9YC
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[Richard Squire - HB9ANM]

Spot on, Jim!
I have NEVER used ALC with any PA. BTW, most ACOM amps for instance do not have an ALC output - they must know why! Misuse of ALC is the cause of many bad (not to say horrible) signals we hear on the bands...
It's so easy to reduce input power... And my K3/KPA500 combo does it automatically.

73
Richard - HB9ANM

Jim Brown-10 wrote

On 9/21/2012 9:37 AM, Gary Slagel wrote:
It is NEVER a good idea to use ALC to set drive level to a power amp.
Doing so is a recipe for distortion, key clicks, and splatter. ALWAYS
control the amplifier output power by setting the POWER OUTPUT of the
transceiver so that the transceiver produces just enough output power to
get the desired power from the amplifier.

[Gary Slagel]

Thanks for your responses to my earlier question.  It sounds like I don't want to use ALC to control power output on the Expert Amp.  One more question for the Expert amp users though. 
 
I'd suppose, if I did use the ALC connection, when I hit the half power button on the amp it would just cut back the power level on the K3 to generate a 500W output from the amp.  So, If I'm not using the ALC connection does this make the SPE full/half power button useless?
 
I know this might be a better discussion for the SPE yahoo group but I've been trying for a couple days to get into that group and my membership is still pending.  Thanks much for any input.

Gary Slagel
KT0A

 


________________________________
From: Gary Slagel <[hidden email]>
To: "[hidden email]" <[hidden email]>
Sent: Friday, September 21, 2012 10:37 AM
Subject: K3 and Expert Amp


 I'm looking at the SPE Expert Amp 1K-FA.  The SPE amps both recommend using an ALC connection to automatically control the radio's output power thus preventing amplifier overdrive.

I talked to an SPE rep and I understood him to say that I couldn't use the ALC connection with a K3 and there was an alternative way to allow the SPE to control the K3 output power by manually configuring the SPE to set the K3 output power on a band by band basis.  I looked at the SPE manual and it outlines a method to set up a flex-radio that does not have the ALC connection but doesn't talk about the K3.  I assume the k3 setup would be the same as for the flex-radio. 

Does anyone have experience with setting this up with the K3 and SPE 1K-FA.  Or, experience using the K3 ext ALC with and SPE? 

Thanks,
 
Gary Slagel
KT0A
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[Joe Subich, W4TV-4]

> It sounds like I don't want to use ALC to control power output on
> the  Expert Amp.

You don't want to rely on it to control power.  However, it is best to
connect it, set the level just slightly above the point where it starts
to reduce power from the K3 and allow it to function as a "safety".

> I'd suppose, if I did use the ALC connection, when I hit the half
> power button on the amp it would just cut back the power level on the
> K3 to generate a 500W output from the amp.

The "half power" button should be reducing voltage to the Expert FETs
to reduce current and heat dissipation (most other amps do the same).
You will need to reduce drive at the same time.  Again, if you connect
ALC and set it about 10% above the activation point, it might provide
some protection in case you hit the half-power button and forget to
turn down the power on the K3.

73,

    ... Joe, W4TV


On 9/23/2012 10:36 AM, Gary Slagel wrote:

> Thanks for your responses to my earlier question.  It sounds like I don't want to use ALC to control power output on the Expert Amp.  One more question for the Expert amp users though.
>
> I'd suppose, if I did use the ALC connection, when I hit the half power button on the amp it would just cut back the power level on the K3 to generate a 500W output from the amp.  So, If I'm not using the ALC connection does this make the SPE full/half power button useless?
>
> I know this might be a better discussion for the SPE yahoo group but I've been trying for a couple days to get into that group and my membership is still pending.  Thanks much for any input.
>
> Gary Slagel
> KT0A
>
>
>
>
> ________________________________
> From: Gary Slagel <[hidden email]>
> To: "[hidden email]" <[hidden email]>
> Sent: Friday, September 21, 2012 10:37 AM
> Subject: K3 and Expert Amp
>
>
>   I'm looking at the SPE Expert Amp 1K-FA.  The SPE amps both recommend using an ALC connection to automatically control the radio's output power thus preventing amplifier overdrive.
>
> I talked to an SPE rep and I understood him to say that I couldn't use the ALC connection with a K3 and there was an alternative way to allow the SPE to control the K3 output power by manually configuring the SPE to set the K3 output power on a band by band basis.  I looked at the SPE manual and it outlines a method to set up a flex-radio that does not have the ALC connection but doesn't talk about the K3.  I assume the k3 setup would be the same as for the flex-radio.
>
> Does anyone have experience with setting this up with the K3 and SPE 1K-FA.  Or, experience using the K3 ext ALC with and SPE?
>
> Thanks,
>
> Gary Slagel
> KT0A
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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[Jim Brown-10]

On 9/23/2012 7:36 AM, Gary Slagel wrote:
> I'd suppose, if I did use the ALC connection, when I hit the half power button on the amp it would just cut back the power level on the K3 to generate a 500W output from the amp.

While I know nothing about that specific amp, some of my 30 year old Ten
Tec Titans (which are tube amps) have a half power switch that simply
reduces the plate voltage by about one-third.  As I recall, that switch
was deleted on later models because they decided that it was a bad idea.

73, Jim K9YC
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