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ALC adjustment?

Discussion in 'On-Air Operations - Q&A' started by KK4JW, Oct 15, 2019.

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  1. KK4JW

    KK4JW Ham Member QRZ Page

    How should I properly adjust my ALC for SSB voice operation? I have an Icom 718 if it matters, with a digital "bar" ALC meter. I've read that I should adjust my microphone gain to the point where I'm three or four "bars" shy of totally peaking the ALC meter, and then turning on compression to just fully peak the ALC, but not go over. Is this correct? Should I do something different?

    I've played with compression and no compression, and I seem to get slightly better reports with compression turned on. Obviously I'm able to gain a tad PEP with compression as well, which doesn't matter much.

    Just trying to make sure my audio is clean and clear, and able to be understood well. :)
    Last edited: Oct 15, 2019
    N8AFT likes this.
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    I don't run an Icom 718 so YMMV, but FWIW I set mic gain for appropriate ALC response with compression disabled and then turn on speech compression and adjust compression gain independently. Proper ALC response is for the meter to only hit the top of the ALC range on voice peaks and not get pinned up there all the time. IOW, test into a dummy load speaking in a normal over the air voice saying things like your callsign and CQ and other things and watch the ALC meter which should swing up frequently on the louder voice peaks but not get pinned up high all the time nor exceed the ALC range.

    When setting speech compression I use the Monitor function on rigs that support that or listen to another receiver through headphones with no antenna connected, again while transmitting into a dummy load at reduced power if possible. It's usually pretty easy to hear the transition from a bit of useful compression to the distortion and artifacts that come from excessive speech compression. I try to find that point of degraded audio and back off the compression settings just a bit.

    I've used basically that same procedure on all the SSB rigs I've owned over the years but as posted above I haven't owned an IC-718 so things may differ a bit with that rig. Still a good guideline is that a little voice compression can go a long way and it's real easy to overdo compression so when in doubt a bit less is better than a bit more.

    FWIW, speech compression shouldn't increase your PEP as peak power is still peak power but it should increase your average voice power which is very helpful in tough band conditions. If you're truly seeing higher PEP with an active peak reading watt meter then I'd expect it has more to do with the peak capture circuitry in your power meter than actual increase of peak power, either that or you're actually under modulating the rig when compression is disabled which is possible if you've set ALC to never peak near the top of the ALC range on voice peaks.
    KF5KWO likes this.
  3. KK4JW

    KK4JW Ham Member QRZ Page

    Thank you. I don't think my 718 has an actual compression gain adjustment. There's just a on/off button for it.
  4. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Yeah, I've had a couple of rigs like that. In those cases I'd start by adjusting audio with compression disabled as described above (you should see the ALC meter hit the top of the ALC range on voice peaks) and then monitor the audio, through another receiver if necessary, and see what happens as you enable and disable compression. Sure if the compression brings in a lot of distortion then you may have to back off the mic gain but if that's the case then remember to increase the mic gain when you don't use compression, for instance during comfortable rag chews or QSOs in good band conditions where you don't need the extra punch.

    Bottom line, when not using compression you really should see the ALC meter hit full range on at least some of your voice peaks. If the rig forces you to back that down when compression is enabled to avoid distorted transmit audio then fine but don't forget to bump mic gain back up when not using compression or you'll be running weak audio at those times.
    KK4JW likes this.
  5. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    From discussions here long ago from...

    For ordinary operating where you just want a slight improvement without over-doing things.

    -Power to MAX
    -Compression ON.
    -While talking adjust MIC GAIN upwards until ALC meter just starts to move on voice peaks.

    The reasoning is that modern (pre-SDR) transmitters do a better job regulating ALC with the power level set high. MIC GAIN will also affect power output, and the slight amount of compression will provide prevent overmodulation without distorting your voice.

    I've found this to work pretty well. Of course when I don't need compression I turn it off, especially for rag chewing on quiet bands.

    Remember that the higher the ALC meter moves the more distorted and unnatural your voice sounds.

    Oh, lets not forget transmitted bandwidth. Newer radios often have selectable transmit bandwidth. WIDE will have more bass which sounds nice for a quiet band, while ragchewing but can be muffled and indistinct in poorer conditions. NARROW can be helpful when working noisy conditions or contesting by concentrating audio power in the central frequencies, but can be tiring to listen to.

    "Moderation in all things". Don't crank all the knobs to the right!
    Last edited: Oct 15, 2019
    KK4JW likes this.
  6. KK4JW

    KK4JW Ham Member QRZ Page

    What if I want to run less than 100W? I normally run 40-50W unless I hear a distant DX station that I want to try. Does the same settings still hold true?

    My radio doesn't have any kind of selectable bandwidth. That's why I like it. It's easy to operate (for the most part) and just does what a radio is supposed to do. :)
  7. KK4JW

    KK4JW Ham Member QRZ Page

  8. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Realistically, your average SSB power, even with the POWER knob at full, is probably more like 20-30W. Power is extremely variable on SSB. Most hams don't have true peak reading power/SWR meter. Even so, you can generally see that the power needle is typically quite low while speaking.
  9. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    We are in an era of hamming of great technology changes. There are vast differences between older radios capabilities and operating techniques, current low end radios like the IC-718 and high analog and SDR radios.

    I compare today's technology situation to that of the 1920's and 30's where radio theory and methods changed significantly from year to year. These are exciting times!!!

    It can be difficult to give universal advice on settings and operating techniques.
  10. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    To be more specific: You can always turn your POWER level down, and still use the method I gave.

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