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



W7JZE
08-31-2013, 10:29 PM
OK, one week ago I started getting on the air with JT-65A using JT-65HF software. Addictive(!!!146938)!!!

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.

K0SPN
08-31-2013, 10:52 PM
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.

K0BG
08-31-2013, 11:10 PM
I trust you're not confusing ALC with AGC?????

K0SPN
08-31-2013, 11:14 PM
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?

W7JZE
09-01-2013, 12:37 AM
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.

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!

W7JZE
09-01-2013, 12:42 AM
I trust you're not confusing ALC with AGC?????

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 146952. I sometimes make the craziest mistakes when writing.

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

KE5MC
09-01-2013, 01:27 AM
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.

Mike

K0SPN
09-01-2013, 01:41 AM
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/
(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.

W7JZE
09-01-2013, 12:33 PM
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!

KE5MC
09-01-2013, 02:06 PM
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.

Mike

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



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!

W7JZE
09-01-2013, 06:27 PM
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.

Mike

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

Hi Mike,

Many thanks for sticking with me on this. I took my time with the set-up this morning and I carefully documented all of my tests. Hopefully the screen print imports below make sense. Your method DOES seem to be the best! Thank you for motivating me to keep trying. About 7:30 on the SignaLink TX dial seems to be best.

Here are the results of all of my dummy load testing. Note that when switching to my (well matched) antenna, no changes were needed to the SignaLink settings and I saw a reduction to only (2) little green ALC bars. One less than even Zero Power out achieved into the dummy load (weird, that...).

147025

147026

Clicking on the images should make them larger.

Many thanks!

M0GVZ
09-01-2013, 06:39 PM
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.


If when transmitting, your ALC meter showed a reading he was probably seeing a splattering signal in the waterfall.

KE5MC
09-01-2013, 09:10 PM
Great you continued to try working the different configurations and observe the resulting response. It's not really my method, but the one from all the online setups for digital modes I read when I first was starting out.

With your TX knob at 7:30 position you are experiencing the input sensitivity of the 7000 as you are nearly at the end limit stop of the pot. Likely you can hit near full power before you get to the 12:00 position.

I had mine setup for about 15-20 watts out at 12:00 by inserting a resistor in the sound input to the radio in the SignaLink USB interconnect block. This helped to reduce the 7000 input sensitivity and allowed easier and smoother control of the power out level using the TX knob.

Mike

P.S. Clicking on screen shots did not work at 1st so I just went ahead and started typing. I went back and now I can see the enlarged screen shots. You got to 100 watts well before 12:00. The resistor trick will help move that max output over to the 4:00 position. Giving your more range of motion for the pot from 0 to full power. I have to admit having spend so many hours running JT65 and lately JT9 using 100% radio power and adjusting power out with the TX knob I don't clearly recall what my ALC is doing. My bad.:rolleyes:



Hi Mike,

Many thanks for sticking with me on this. I took my time with the set-up this morning and I carefully documented all of my tests. Hopefully the screen print imports below make sense. Your method DOES seem to be the best! Thank you for motivating me to keep trying. About 7:30 on the SignaLink TX dial seems to be best.

Here are the results of all of my dummy load testing. Note that when switching to my (well matched) antenna, no changes were needed to the SignaLink settings and I saw a reduction to only (2) little green ALC bars. One less than even Zero Power out achieved into the dummy load (weird, that...).

147025

147026

Clicking on the images should make them larger.

Many thanks!

K0SPN
09-02-2013, 03:25 AM
Something isn't right here as you go from 0W output to 125W then the power goes down as you increase the signal level.
There should be a smooth and slow-to-moderate power increase as you raise the signal level on the SLUSB.
Check this out from TigerTronic's page: http://www.tigertronics.com/slusbts.htm#The%20SignaLink%20USB%27s%20TX%20contr ol%20is%20%22touchy%22,%20making%20it%20difficult% 20to%20control%20my%20RF%20power
Do yourself a favor and go find some 1/4w resistors to put in the SLUSB to lower the signal level. Would probably be a bit expensive, but Radio Shack should have some of those values or maybe an assortment so you can try different values and see what works best.

Also, you don't want to run anywhere near 100W out with a 100% duty cycle mode like JT (or PSK, RTTY, etc.) as you're just asking for damage to something in the radio.
Besides, JT doesn't need that kind of power (normally) as it's designed to be decodable even when you can't hear it by ear.

W7JZE
09-02-2013, 10:32 AM
Something isn't right here as you go from 0W output to 125W then the power goes down as you increase the signal level.
There should be a smooth and slow-to-moderate power increase as you raise the signal level on the SLUSB.
Check this out from TigerTronic's page: http://www.tigertronics.com/slusbts.htm#The%20SignaLink%20USB%27s%20TX%20contr ol%20is%20%22touchy%22,%20making%20it%20difficult% 20to%20control%20my%20RF%20power
Do yourself a favor and go find some 1/4w resistors to put in the SLUSB to lower the signal level. Would probably be a bit expensive, but Radio Shack should have some of those values or maybe an assortment so you can try different values and see what works best.

Also, you don't want to run anywhere near 100W out with a 100% duty cycle mode like JT (or PSK, RTTY, etc.) as you're just asking for damage to something in the radio.
Besides, JT doesn't need that kind of power (normally) as it's designed to be decodable even when you can't hear it by ear.

Hi Brent,

Thanks for the note...

1) Yup, agreed... I do not run 100-125W on JT-65. The Excel sheets above (click to make larger) were for testing into a dummy load only. I only ran the Icom-7000 like that for as long as it took to make my full range of test readings; about 15 - 20 seconds per reading (I read slow :-). I left a minute or three between each reading to let the finals and the dummy load cool down.

2) Yah, I agree that it was weird that the last two measurements showed slightly decreased RF power output as the SignaLink TX pot was cranked hard over CW to deliver maximum drive. My only guess is that overdriving it like that might have kicked in a stronger ALC response which pulled back the power on the last part of the tone cycle so that the average power of the tone cycle was slightly reduced. Also possible that the overdriven tones were getting very distorted delivering "who knows what" final envelope shape. Just some guessing on that, and with the resistor mod suggested, I won't be getting up to those drive levels any more so that weirdness may not reappear and I probably won't run that bit of strangeness to root cause.

3) Yup, again... I'll look into the resistor mod. I agree with you and the other posters that trimming the SignaLink-USB between fully CCW and 7:30 o'clock is T*O*U*C*H*Y (147137).

4) Yup, yup 147138... Radio shack $/part is expensive, but I need so few parts, and instant gratification and no shipping is worth some $$. It looks like an easy mod and I have a Radio Shack within walking distance. They even stock twist-on PL-259 connectors(!).

Thanks again for the all of the hints and suggestions.

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