Turning ALC off in Icom-7000 for JT-65A (HF) digital mode. How to do this?

Discussion in 'Mobile Radio Systems' started by W7JZE, Aug 31, 2013.

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  1. W7JZE

    W7JZE QRZ Lifetime Member #84 Life Member Platinum Subscriber QRZ Page

    OK, one week ago I started getting on the air with JT-65A using JT-65HF software. Addictive(!!! Smilie QRZ 100%-Yellow Happy Face Smile.jpg )!!!

    My setup:
    • Icom-7000 running between 5W and 60W, depending...
    • SingaLink USB
    • JT-65HF software
    • "Horse Fence" style wide BW dipole up 20 feet.

    I've read that it is best to turn ALC down, or even just turn ALC OFF, if you can. The software instructions say it isn't "mandatory" but just preferred... as I understand the instructions.

    I've read the Icom-7000 manual cover to cover. Searched Internet forums and did my best Google-Fu to date, but I can't seem to find out how to turn ALC off on the Icom-7000. Turning down the mic gain to keep the ALC tamed and in the "ALC ZONE" is the best that I can find. I have my mic gain set at 40%.

    This morning I had a short JT-65A QSO (that's a joke... they are ALL short :) into Bullhead City, AZ. K6YWJ told me to turn off my ALC. He repeated this a few times and that is not easy and takes time on JT-65. I appreciate his effort getting this info to me real-time, from a real QSO. I am not sure what the negative effect it is he sees at his end, but some badness is apparently there.

    So, to any Icom-7000 users of JT-65A on HF... any idea on how to turn off the ALC on the Icom-7000, or am I worrying about nothing???

    Thanks in advance for any help y'all can provide.
  2. K0SPN

    K0SPN Ham Member QRZ Page

    While this could be different with JT-65 (which I haven't used), it should be the same as with AFSK PSK or RTTY (which I have used).
    It's best if you have a watt meter in line so you can see what you're doing, but it can be done with the internal meters if you must.

    Set your radio for max output and plug in to a dummy load.
    Set your mic gain to your normal setting for SSB, set the meter to ALC. If you are using the mic input rather than a dedicated data input, turn off any audio processing or EQ shaping.
    Set the volume control on the computer to lowest position.
    Start transmitting and slowly bring up the computer volume control until you see the desired power output. You should not see any ALC on the radio (or just the smallest bit).
    Switch to your normal antenna and go nuts.

    It can help to run up the computer volume on purpose (in the dummy load) so you have references as to what the max output will be with minimal ALC, just for future reference.
  3. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    I trust you're not confusing ALC with AGC?????
  4. K0SPN

    K0SPN Ham Member QRZ Page

    Didn't think of that, however both could be involved here as someone in a QSO wouldn't tell you to turn off your AGC. How would they know if your AGC is on?
  5. W7JZE

    W7JZE QRZ Lifetime Member #84 Life Member Platinum Subscriber QRZ Page

    Hi Brent,

    Thank you for the great response!

    To clarify, I am not using to mic input to the Icom-7000, but I am using the "Data Port" input into the "7000" from the SignaLink output.

    I have a great watt meter (MFJ-267) with 1500W dummy load inside and I will try exactly as you say. Many thanks for the great, simple instructions.

    Further info: My ALC meter on the "7000" runs about 3 bars to the right, when I transmit, of what I think the "ALC ZONE" is supposed to be on the "7000". Sometimes the ALC bars "vibrate" higher and lower (no clue why) as the transmission continues and sometimes it is rock solid for the 48 second transmission cycle of JT-65A.

    I'm off to set up and test as you suggest.

    Many thanks!
  6. W7JZE

    W7JZE QRZ Lifetime Member #84 Life Member Platinum Subscriber QRZ Page

    Hi Alan,

    ALC is the question I have regarding when I transmit (Not AGC). I wonder exactly WHAT K6YWJ saw as a problem down in Bullhead City, AZ when I was transmitting this morning? I think I'll PM / email him. He was very helpful during the QSO.

    Thanks for the ALC / AGC question. It helps to keep me straight and double checking my work in this great hobby Smilie QRZ 100%-Yellow Happy Face Smile.jpg . I sometimes make the craziest mistakes when writing.

    (Great mobile info on your site, also... extremely helpful!!!)
  7. KE5MC

    KE5MC Premium Subscriber QRZ Page

    Following up on K0SPN's comments as he didn't take into account the SignaLink USB device.

    Find the computer sound level that kicks the vox circuit ON in the SignaLink USB device then raise it another 10% to make sure slight variations from the computer does not allow the radio to drop out of transmit. Once at that point leave the computer sound level alone.

    Set the IC-7000 to 100% power level. Use the TX knob on the SignaLink USB to adjust your output power level. It has been reported that the back panel connector (small DIN) can have high sensitivity. This issue is addressed on the Tigertronics site by using a resistor in the jumper block inside the SignaLink USB. I forget the value I used, but seem to recall it was a little higher than commonly used/recommended.

    I monitor the power out with the LED meter on the LDG AT-100ProII Autotuner. I typically run an indicated 10-12.5 watts and have only gone to about 25 watts when my signal reports is near -24. With that setup I never have any ALC. ALC in the 7000 is not turned off. You setup so you can't get to that point.

    I am not sure if the radio indicates ALC when the SWR is high and the power is being reduce because of that. That's the only case that I can think of that might give ALC with 100% radio power setting and audio level that keep the RF output below 25 watts.

  8. K0SPN

    K0SPN Ham Member QRZ Page

    Yep, sorry I missed that bit about the SLUSB.
    I had one before with a Yaesu FT-450 and also did the resistor mod (and some others too, see Peter Frenning's site: http://www.frenning.dk/OZ1PIF_HOMEPAGE/SignaLinkUSB-mods.html )

    Don't know what it looks like with JT modes, but for PSK, overdriven audio looks like this: http://www.freewebs.com/m0hok/badpsk31.jpg

    More about ALC: http://www.hamradioandvision.com/how-to-use-an-alc-meter/

    Also, when changing the position of the transmit signal you have to adjust (or at least check) that you're sending the proper signal level as our transmitters don't have a completely even response over the audio range so you may find that at 800Hz you need more signal and at 1600Hz you need less.
    Another reason to have an external power meter so you can see both the output and the ALC indication.
    Last edited: Sep 1, 2013
  9. W7JZE

    W7JZE QRZ Lifetime Member #84 Life Member Platinum Subscriber QRZ Page

    Thank you all very much for your help...

    Here is one solution that I "think" I have found:

    • Put a Watt-Meter / Dummy load on Icom-7000 output
    • Transmit into Dummy Load with Icom-7000 RF output set "where you want it" (5W to 60W for me... Depending...)
    • Using the SignaLink USB, slowly turn the "TX" knob down from 12:00 Noon (Noon is the suggested setting from SignaLink setup).
    • Watch the Watt-Meter carefully.
    • As you turn down the "TX" on the SignaLink USB, nothing happens to RF out for a while, then *BANG* it drops rapidly to almost zero.
    • Increase "TX" back up until you just regain your RF power setting
    • The ALC bars are now well UNDER, and well within the "ALC Zone". No ALC bars to the right of the "ALC ZONE".

    I "THINK" this means ALC is NOT being activated. The ALC bars stay "Green" and only extend ~ 35% into the ALC Zone. No "Red" ALC bars at all. Power remains steady at 60W (or where ever it is set)

    I think that is it. Great help. Thank you everyone!
  10. KE5MC

    KE5MC Premium Subscriber QRZ Page

    You can do it that way, but as you have written you have some level of ALC. In the digital world you want none. Using the RF output to set power out on the radio is not recommended. Setting to 100% on the radio and using the TX knob on the SignaLink USB is.

    You are setup with a dummy load. Try this way and note the ALC reading as you take the TX knob on the SignaLink USB from min to max. I am betting no ALC until you are past 60 watts.Green ALC is OK for phone, but not for digital modes.


    P.S. Other features to avoid are compression on transmitting and DSP operations like Noise Reduction, Blanking and Notch on receive.

    Last edited: Sep 1, 2013
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