[Elecraft] What happened to ALC?

[Bob McGraw]

I'll show my age by doing this, but lets revert mentally back to the 
Collins S Line.   The transceiver, using a pair of 6146's in the PA, was 
most efficient and linear when properly tuned and loaded.  It produced 
about 120 to 140 watts of PEP output.  And there was NO Power control or 
method to reduce the power as we know it today.   Introduce the 30L1 
linear amplifier, being 4 x 811's, which required about 60 to 80 watts 
of drive to reach maximum rated output.  So the issue now is, how do we 
get the properly tuned and loaded transceiver down to the correct drive 
level for the 30L1?   ALC is the Collins answer.  Thus the voltage 
determined by the amplifier grid current was fed back to the inter-stage 
of the driving transmitter to effectively reduce the output while still 
retaining the correct tuning and loading of the transceiver PA.


Today it seems that the designers have monkeyed around with the time 
constants in the ALC algorithm to improve certain aspects of the signal, 
thus reducing key clicks and overshoot,  but seemingly at the sacrifice 
of certain other areas of the signal.  Thus we find that ALC is not to 
be used to control power or raise the average power but designed to 
prevent over drive of any stage. Correctly, Speech Processing is deemed 
much more effectively used and with less undesired effects on speech 
than ALC.   In fact, one amp manufacturer says "run the transmitter at 
full power and let the Smart ALC in the amplifier adjust the required 
drive accordingly via the ALC signal".  Oh wow!  Certainly asking for 
trouble in my thinking.


In my world of audio, ALC is much like limiting with an input to output 
ratio of 20:1.  This says a 20 dB increase on the input causes only a 1 
dB change in output.  Now enter compression, where the input to output 
ratio is anywhere from 1:3 to about 10:3. Again a 10 dB input change 
yields a 3 dB output. Of course there are different attack times and 
release times applied to both limiting and compression.  Newer 
technology systems have the ability to analyze the various components of 
the input signal and adjust the attack and release times quite 
effectively.  Many Speech Processing algorithms have the same ability.  
Thus they are better suited for raising average PEP output.


A second factor existing is the issue where hams like to see their power 
meter indicate the rated transceiver power.  With some of the electronic 
power measuring devices that may work OK. However, with mechanical power 
indicating devices, the ballistics of the meter movement, meaning the 
slow response and overshoot damping, will not allow a mechanical meter 
to correctly show the energy level of ones SSB voice signal.  The 
typical mechanical movement shows about -6 dB less or 25 watts for a 100 
watt PEP signal. Of course speech processing will raise the average PEP 
level, but again the true PEP remains at 100 watts.


And as Paul Harvey would say; "and now you know the rest of the story".

73

Bob, K4TAX


On 1/31/2022 9:01 PM, elecraft-requ...@mailman.qth.net wrote:

On Jan 30, 2022, at 1:10 PM, Fred Jensen  wrote:

I can remember, shortly after SSB appeared on the ham bands that "ALC" showed 
up and was immediately inducted into that top category of things like canned beer and 
sliced bread.  It would reduce the dynamic range of your signal and fill out your RF 
envelope with DX inducing energy.  It didn't matter if you preferred the James Earl Jones 
sound by close talking your microphone, or the Storm Drain sound with the gain up and 
speaking from across the room.  Not to worry, ALC will take care of it for you and you 
will fully pack your RF envelope.

Tomorrow is the first day of February 2022 and ALC occupies a less than coveted spot in the same 
category that also contains last night's broccoli casserole.  One wonders why manufacturers even 
put connectors and meters labeled "ALC" on their radios.  "Four solid bars, and the 
fifth barely flashing because the fifth bar is where ALC starts.  Just barely flashing ... you DO 
NOT want to engage the ALC!"

I realize that while we believe that the rules of electricity don't change and 
none of us ever inspect our electricity very closely ... if we did we'd find 
the power company is selling us used electricity as if it was new ... what 
changed?  If ALC was slicker than snot back then, why isn't it now?

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County


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Re: [Elecraft] [POSSIBLE SPAM] RE: HI CURR indicator on K3S display

[Dr. William J. Schmidt]

5W RF power calibrates fine.  The 50W fails.  Gonna remove the 100W module 
today and see if I have a bad transistor…  Difficult to do here on the island… 
have not built up my test equipment stash here much more than a DVM and an 
antenna analyzer.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ 
VP2EHZ

 

email:    b...@wjschmidt.com

 

 

From: Ray  
Sent: Wednesday, February 2, 2022 12:55 AM
To: b...@wjschmidt.com; elecraft@mailman.qth.net
Subject: [POSSIBLE SPAM] RE: [Elecraft] HI CURR indicator on K3S display

 

Dr William………. 

Time to hook your radio up to a 50 Ohm Dummy Load, and Retake readings.

Ray WA6VAB  K3

 

 

From: Dr. William J. Schmidt  
Sent: Tuesday, February 1, 2022 6:40 PM
To: elecraft@mailman.qth.net  
Subject: Re: [Elecraft] HI CURR indicator on K3S display

 

Unfortunately, my metering outside of the radio shows only 10.1 amps when the 
radio shows 20+ amps.  Radio and outboard voltage metering showing 13.0 VDC.  
Also shown 6.6A for 5W out.  Something is up.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ 
VP2EHZ

 

email:  b...@wjschmidt.com  

 

 

-Original Message-

From: William Ferry mailto:jdbf...@comcast.net> > 

Sent: Tuesday, February 1, 2022 7:01 PM

To: b...@wjschmidt.com  

Subject: Re: [Elecraft] HI CURR indicator on K3S display

 

I recently had a problem where both my K3’s were taking over 30Amps (PS) and at 
times the K3 shut down.  

Surprisingly it happened with two different K3’s and two different power 
supplies (Astron RS 35 and M).  The K3 displays all read just over 20 Amps at 
near 100w output into a dummy load on both units.  I checked with Elecraft and 
they had high confidence the current read by the K3 was correct.

I decided to borrow a clamp-on Ammeter to measure the DC current independently. 

Yup. 20+ amps (like the K3)before it shut down.  

I found both supplies had issues.  One the current limit was set too low.  The 
other the current sensing resistor had been changed to the wrong value.  Plus 
the current meter were not calibrated correctly.  

Hence I suggest you find a meter to independently measure the power supply.

Regards,

Bill

K1BZM

PS I think we have worked on all bands from 80-6!

 

 

 

Sent from my iPhone

 

> On Feb 1, 2022, at 7:14 PM, Dr. William J. Schmidt   > wrote:

> 

> I remember some discussion about HI CURR issues and the causes here a 

> while ago.  I just noticed it on my radio.. Changing the display to 

> read amps, it indicates 21.6 amps, but the amp meter on the power 

> supply is only showing

> 10.1 amps.  The radio sensing circuit seems to be in error.  Anyone 

> else delt with this?

> 

> 

> 

> 

> 

> Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ 

> PJ2/K9HZ VP2EHZ

> 

> 

> 

> email:    b...@wjschmidt.com 
>  

> 

> 

> 

> 

> 

> __

> Elecraft mailing list

> Home: http://mailman.qth.net/mailman/listinfo/elecraft

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> Post: mailto:Elecraft@mailman.qth.net

> 

> This list hosted by: http://www.qsl.net Please help support this email 

> list: http://www.qsl.net/donate.html Message delivered to 

> jdbf...@comcast.net  

 

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Re: [Elecraft] RPN Calc App For Android

[Paul Jewell]

On 30/01/2022 04:53, Mike Morrow wrote:

The finest pure RPN (not RPL) machine ever made is the HP-42S (1988-1995).  It 
still brings prices above $300 on eBay and is worth it.


The owners manuals are on eBay in the UK for more than £100!!! Wow!

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