[Elecraft] ALC control of W6PQL amp from my K3

[John Simmons]

I have seen overshoot in the TUNE mode.

-John NI0K

> Don Wilhelm <mailto:donwilh at embarqmail.com>
> Sunday, March 10, 2019 2:40 PM
> I am left wondering if some K3 users who are seeing "Overshoot" are 
> actually seeing what is referred to as "Power Hunting".
> That would occur mostly in Voice or DATA modes when the audio level is 
> not set high enough.
>
> With insufficient audio, the K3 can initially go up to the set power, 
> and then will quickly settle back to a low power, and then gradually 
> climb to the full power set by the power knob - that behavior is 
> seldom seen in CW mode, but can be seen in DATA modes and Voice modes 
> if the audio levels are not set correctly.
>
> The cure for that behavior is to drive the audio as indicated in the 
> manual.  For voice modes, adjust the MIC Gain to produce 5 to 7 bars 
> on the ALC meter.
> For DATA modes, adjust the audio levels to produce 4 bars solid with 
> the 5th bar flashing.
>
> If your data mode application has a "POWER" slider, it is not properly 
> named (complain to Joe Taylor) - it is just another audio level control.
>
> The Elecraft transceivers control power differently than all other 
> amateur transceivers, so ignore the common internet advice to control 
> the power with the audio level.  Set the audio as indicated in my 
> website article (same information is in the K3/K3S/KX3/KX2 manual) and 
> adjust the desired power with the POWER knob.
>
> Other transceivers may be able to use the audio level to control the 
> output power, but Elecraft transceivers are different, do not "do it 
> that a-way".
>
> Look at the article on my website www.w3fpr.com.  Scroll down the left 
> column and click to open the document.
>
> BTW: The originator of this thread is now on the right track, I have 
> exchanged several email messages with him (and I built his transverters).
>
> 73,
> Don W3FPR
>
>
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> Jim Brown <mailto:jim at audiosystemsgroup.com>
> Sunday, March 10, 2019 2:02 PM
>
>
> I've had an LP100 in line for several years, always set to read peak 
> power, and the most overshoot I've seen from either of my two K3s is 
> less than 1 dB. The K3s are driving a pair of 87As, and I have NEVER 
> used ALC between rig and amp.
>
> The earliest advice I've seen about this was in the user manual for 
> the Ten Tec Titan 425, designed around 1979, and using a pair of the 
> same 3CX8007 triodes used in the 87A. The manual said that ALC output 
> was provided only for historical reasons, and advised against using it 
> to control output power.
>
> When you look ONLY at output power, you miss the mess that ALC causes. 
> To see it, you must look at (or listen to) the transmitted frequency 
> spectrum. A P3 on a second radio, or an SDR receiver will clearly 
> reveal the splatter and clicks.
>
> 73, Jim K9YC
>
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> John Simmons <mailto:jasimmons at pinewooddata.com>
> Sunday, March 10, 2019 1:34 PM
> Wes,
>
> Once I got my LP100, I began to see the same behavior with my K3. This 
> type of output anomaly is a huge reason to use ALC.
>
> 73,
> -John NI0K
>
>
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> Wes <mailto:wes_n7ws at triconet.org>
> Sunday, March 10, 2019 9:39 AM
> Indeed.  Folks who would never think to turn off the AGC in their 
> receivers get weak-kneed at the thought of AGC (ALC) being used in the 
> transmit loop.  In "Fundamentals of SSB", Collins radio speaks of ALC 
> (pp.7-10,11) without any negativity, and in fact calls it a form of 
> speech compression.  As in many things, the devil is in the details.
>
> I suspect most of the Elecraft faithful would also be surprised to 
> know that their beloved K3s use internal ALC as well as digital power 
> control. This is not perfect, I've observed overshoot, power slowly 
> increasing to set level and low level power jitter*.
>
> * You need a spectrum analyzer to see this and it's unlikely to be 
> heard on the air, but it's there.
>
> Wes  N7WS
>
>
>
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