Welcome to the new FlexRadio Community! Please review the new Community Rules and other important new Community information on the Message Board.
If you are having a problem, please refer to the product documentation or check the Help Center for known solutions.
Need technical support from FlexRadio? It's as simple as Creating a HelpDesk ticket.

ALC with Expert 2K-FA

KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
edited February 2020 in SmartSDR for Windows
When I connect the ALC from the Expert 2K-FA to my 6700 and enable the ALC in hardware, the ALC totally clips the signal.  Likely I have too much drive power?

But if I run the combination without the ALC enabled using DDUTIL to limit Power to the 2K-FA everything seems OK.

The ALC from the 2K-FA ranges from 0V to -11V
BUT the 6700 is limited to a range of  0V to -4V

I could built a small interface to limit the voltage to -4V to the 6700  and likely dampen the ALC effect but I am not sure its worth the effort?

What is everyone else doing with ALC?

Do you use Hardware ALC? 

Or do you use DDUTIL to Limit Power?


  • Paul Christensen, W9AC
    Paul Christensen, W9AC Member ✭✭
    edited February 2017
    I don't run ALC with my SPE 1K-FA. Have a look at the schematic and you'll see that they cleverly designed a fault summing system from various circuit sampling locations. Upon overdrive, bias is instantaneously applied to the MOSFETs. True, that's of no help with clipping but I'm confident the SPE can protect itself from anything I give it. If you're more comfortable with an ALC, a simple potentiometer between the Flex and SPE ALC line will take the SPE's -11V and bring it down to the desired -4V threshold on the Flex 6K. Since it's just a resistive voltage divider, it's not adding any damping or delay to the ALC line. If not looked at the SPE 2K’s menu, perhaps ALC level can be adjusted through the software. Anyway, it’s worth validating before building an external **** circuit. Paul, W9AC
  • Sergey R5AU
    Sergey R5AU Sergey Member ✭✭
    edited April 2017
    Hi Howard, I have resistor devider and activated ALC circuit for AMP protection only. In any mode i am focusing on linear signal means i am limiting power (ssdr persistence) to prevent generating ALC signal at all - one power level for all modes in one band.
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited January 2017
    I originally thought of using a resistor divider to protect the Amp...but I am leaning towards running my usual way without ALC altogether.... DDUTIL does an excellent job of managing power outputs per band.

    Your idea of setting power and using the resister divider and activated ALC for protection is a good one...

    I will try both solutions to see which one works for me.

    Observation... The wattmeter on the 2K-FA is limited to 600, 1200 and 2400 Watts readouts.  But according to my external Digital Wattmeter I see that I can easily drive the Amp to 900 W or more on Low - which makes the internal wattmeter rather useless as I will always need to rely on the more accurate external one to make sure it is driven correctly...
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited December 2014
    Where did you get the schematic?
    There was no schematic with my 2K-FA
  • Peter Bentley
    Peter Bentley Member ✭✭
    edited April 2014
    I do not use ALC with my 6700 and expert2k, I also do not use ddutil.

    Like this it works fine

  • Paul Christensen, W9AC
    Paul Christensen, W9AC Member ✭✭
    edited November 2016
    You'll need to ask for a copy from SPE.
  • W5UN_Dave
    W5UN_Dave Member ✭✭
    edited February 2019
    The 2k-FA manual says to use ALC and turn the drive all the way up. This seems idiotic to me. I let my 6700 persistence keep the proper drive level on each band. No ALC here
  • Sergey R5AU
    Sergey R5AU Sergey Member ✭✭
    edited April 2015
    You know Dave, such suggestion is usual for every amp, but in this case, increasing of the trcvr output power should stopped with alc level -4v and regulation inside the alc loop should be precisely excellent, and you know I never seen such implementation of the alc circuit. My suggestion what I guess will be applicable for any one: tune you trcvr power up to level with beginning of alc regulation( or a bit below), this is will meet all requirements with signal quality and protect you amp from overdriving
  • Tom
    Tom Member ✭✭
    edited November 2014
    Are there any news with ALC or is it still not working properly with Expert 2K. I haven't tried yet because my F 6700 and Expert 2K are not on the same location but one of these days will definitely try.

    I can only say that ALC between Yaesu 2000D / Yaesu 9000D and Expert 2K is working flawlessly. You just set power mode (HI/MID/LOW) on Expert 2K and leave power to max. on transceiver. No clipping.

    I dont like the idea to use DDUtil to program power limitations per band.

    BTW, if it is still not working properly is it to assume that ALC implementation on Flex is not standard knowing that ALC with other brands works perfectly?

    if so, does Flex plan to correct the issue?


    Tom, 9A6TKS
  • KY6LA_Howard
    KY6LA_Howard La Jolla, CA. Paris and Sablet FranceMember ✭✭✭
    edited February 2017
    Tom ALC works on my 6700 The only issue is that The ALC from the 2K-FA ranges from 0V to -11V BUT the 6700 is limited to a range of 0V to -4V I did try the resistor divider It worked OK BUT. I went back to using DDUTIL which allows me to set the desired output power for each band. Even with a SteppIR MonstIR, each band needs different drive power As you know the 2K can easily put our more than 2K PEP But in the USA we are limited to 1.5K PEP So just turning up the power all the way. Might not be legal here I also found that DDUTIL produced a cleaner TX result. Than ALC. Frankly virtually everything I read in the technical literature recommends that one should no longer use ALC with modern Radios
  • Sergey R5AU
    Sergey R5AU Sergey Member ✭✭
    edited April 2017
    Tom, i have 3 statements concering DDUTIL
    1.  ALC circuit in my 6700 not work as i want even with divider, means i have a chance with overload my 2k amps - i am happy in my 2k exist divider with CPU on the RF input stage
    2.  In Rus we have legal power limit too, but i use output with MAX selection to keep for final transistors 50v what give max linearity - again DDUTIL protect me
    2. Any feedback circuits - a chance to get oscillation in case unproper realisation and as a fact - destroy something 

    Persistance (i guess will be improved) + DDUTIL (i need protection my HW and RF linearity) - this is a right way for today !

    P.S. BTW i believe ALC will be imrpoved
  • Paul Christensen, W9AC
    Paul Christensen, W9AC Member ✭✭
    edited November 2016
    Generally, ALC functions as a closed, gain-control loop based on feedback from the amp.  ALC circuits that are designed as a system (e.g., an Icom transceiver feeding an Icom amp), can better control the amplitude and response times needed to achieve the overdrive objective.

    Frankly, I don't understand why SPE recommends full-tilt output power from the rig, only using their ALC to control output power.  That requires an ALC well-matched with the driving transceiver or transmitter.  

    To SPE's credit, they have a nearly indestructible overdrive protection system.  Referring to the schematic, a logical "OR" fault buss is created and sums six or seven sample points.  If any one of the sample points goes out of tolerance, the gates to the power MOSFETs are immediately inhibited.  I have tried to overdrive my 1K-FA amp with excessive power but the protection circuit takes over and immediately take the amp off line.  Four years later, and after many subsequent and accidental power faults, the amp just doesn't care.

    I haven't used ALC since high school when using a Yaesu FT-101EE with a Heath SB-230 amp.  The SB-230 has zero grid overdrive protection but I was probably fooling myself into thinking the SB-230 provided an adequate ALC return to the FT-101EE.  ALC can help level power, but by the time rig and amp can act, grid damage has already occurred as many ALC systems are just not fast enough to protect from this kind of damage.

    Paul, W9AC
  • Mike - N8MSA
    Mike - N8MSA Member
    edited February 2017
    I use an Expert 2K with my 6700. I continuously monitor my TX signal with a LeCroy 1GHz / 2.5 G-sample oscilloscope, and I have yet to see any overshoot from the 6700 - or from the 2K. Note that using ALC will not ensure linearity through your signal chain. 

    73 de Mike - N8MSA

Leave a Comment

Rich Text Editor. To edit a paragraph's style, hit tab to get to the paragraph menu. From there you will be able to pick one style. Nothing defaults to paragraph. An inline formatting menu will show up when you select text. Hit tab to get into that menu. Some elements, such as rich link embeds, images, loading indicators, and error messages may get inserted into the editor. You may navigate to these using the arrow keys inside of the editor and delete them with the delete or backspace key.