Icom 7300/7610 Digital Mode ALC Zone

In the old days with traditional ham radio transceivers we adjusted the rigs output using the mic gain and RF power to just under having ALC deflection. No ALC was good.



In todays modern SDR radios like the Icom 7300 and Icom 7610, it's different. We can adjust the transceivers output to show ALC.

In the Icom manual it states, “When operating in the SSB data mode, adjust the device’s output level to be within the ALC zone.”



For the full article see:
Icom 7300/7610 Adjusting RF Power Digital Modes

 

You should always keep the alc meter in view when operating digital, as I have had, on more then one occasion , the software adjust the soundcard drive levels without my knowledge . The alc meter let me know the minute I hit transmit that I had a problem.

 

This is THE correct way to adjust and control the TX power out.
Although for the 7100, this is similar for other radios.

TX audio adjustment.
First go to Set>Connectors>USB Mod Level, set this to 20%.
Set the TX power out to 100%.
Run the WSJT-X program.
On the right side move the Pwr slider to MAX.
Position the JT windows for the next step, Right mouse click on the
speaker icon in the system tray and select Playback Devices.
Move this window so that it does not overlap the JT window.
Double click on USB Audio CODEC for it's properties.
Move this window for no overlap with JT window.
Click on the Enhancements Tab, turn off all enhancements.
Click on Levels Tab, set the slider at 50%.
In the JT program move the TX/RX cursor to 1200 Hz.
On the 7100, touch and hold the meter to have all the meters in view.
While transmitting into a dummy load, click the TUNE button in the
JT program, move the slider on the Levels Tab so that you have
100 watts, if not possible then unkey via the TUNE button.
Go back to the USB MOD level and increase this level to 30%
Again touch and hold the 7100 meter to display all meters.
Click the TUNE button again to check for 100 watts.
Readjust the Levels slider for 100 watts, the next step is important.
While still transmitting, observe the ALC meter, Lower the Levels Slider
until the last ALC bar goes out (Zero ALC reading)
On the JT program lower the Pwr slider to your desired power out.
To easily adjust this slider, left click on the slider button then use the mouse wheel
to raise or lower the slider to the desired power out. The slider on the Levels tab
can be done the same way.
At this point you have calibrated the ALC/Power out for a good
clean signal, you adjust the power out by the audio drive not by adjusting
the power out setting on the 7100.
The Levels slider for the 7100 CODEC (TX Audio) should not be touched
unless you see ALC action, this is the final point of TX audio calibration.
The TX audio adjustments are the Pwr slider in WSJT-X, the slider
on the Speakers (output) Tab and the USB MOD level in the 7100.
The TUNE button in WSJT-X is used for the TX power/audio adjustment.
Again the final point of adjustment is the slider on the Levels Tab
for the Speakers CODEC (TX Audio) and the final tweak is to lower the slider for no ALC reading.
I can achieve about 90 watts with Zero ALC on my 7100.
I never use the Mic jack for digital modes, I only use the ACC or USB connection.
The audio path goes through extra unneeded circuits via the Mic jack.

Hope this helps.

Bruce N7XGR

 

Hi Bruce:

That is "YOUR" correct way. There are many. Anyone's method that results in a clean signal and
successful QSO's is just fine. My method differs a lot, and I have 5100 contacts spanning 92 countries
with my "OTHER" correct way

Cheers,

Neal

 

Excellent advice. Something that needs monitoring.

73,

 

Hi Bruce,

Thanks for the info. That's an excellent way for the 7100, but I am using an SDR. ALC is recommended by Icom and other engineers.

I like the method you described, and have used it (mentioned in the video), but I could not maintain a steady ALC when increasing or decreasing power. In the video you see that example I gave. The ALC would not stay consistent. I wanted consistent ALC when changing power output.

With the described method on my website and the video I am able to maintain 50% ALC when increasing or decreasing RF Power. That's on the 7610. With the 7300, there is a slight varying of ALC, but not objectionable.

Thanks for your input, many will find it helpful.

Best 73,

 

Hi Neal,

Thank you for that. I totally agree.

Best 73,

 

Good article and comments on how to do it different ways.

My humble add on to it, is that contrary to the statement in the article the Fldigi does have the "power slider" but it is in the form of audio drive power output (in dB) located right next to the audio level input from the radio "diamond shape indicator" (black - too low, green -ok and yellow/red too high).

You change audio level in TX mode by clicking on the arrows, not sliding (range from -30dB to 0dB)

73 de KD8GGN

 

Rich, I have the 7300 as well and this is how I adjust this type of Icom. Once adjusted I only check for ALC occasionally because that part of the
setup is totally taken care of, I never change the power on the radio, I leave it at 100 watts. I only need to adjust the power via the Pwr slider
in WSJT-X. My tutorial along with another ham's tutorial has been merged into one PDF for downloading, https://ae2a.net/document-libraries
Scroll down to the bottom on the right. Years ago I was into digital but had no idea about this ALC thing, when I got back into digital
I found some tips online about ALC. I sat back and thought about how to adjust my setup and came up with this procedure and It works
perfectly for me. I have sent this tutorial to many hams along with the radios menu settings and WSJT-X settings. They get up and
in short order time. This recent PDF from Icom has some tips about the ALC, page 6.
https://icom.custhelp.com/ci/fattac...figuring+Digital+Mode+for+Radios+with+USB.pdf
It does indicate to have the power at 100% and adjust the TX audio levels to have Zero ALC, the same as in my tutorial.
The PDF has this, This Guide applies to newer Icom HF radios with a USB interface, such as the IC-7200, IC-7850, IC-7851, IC-7300, IC-7610, IC-7600, and IC-7100.
Neal, describe exactly how you adjust your setup. SDR or not that guide is right, the exception is with Elecraft where they require something like a 3-4 bar setting.

Bruce N7XGR

 

Gentleman,

ALC circuits affect all transmitted signals when they're indicating anything above "zero" on rigs' meters. The idea on all digital modes is NOT to affect or distort signal cleanliness with any amount of "ALC" limiting or compression whatsoever. That means adjusting digital and or analog input levels and transmitter gain circuitry for thresholds below where the ALC "limiting" circuit shows or indicates any level whatsoever. That means there should be NO ALC meter action whatsoever. No ALC action is desired.

Decent RF output of approximately 20 to 30 Watts can be had on digital modes without any ALC metering indication -- without the ALC limiter or compressor distorting the digital waveform. Uncompressed digital waveforms are critical to the ease of digital reception, signal cleanliness and or faithful reproduction.

ALC limited or compressed digital signals are not desired -- they are distorted! Why would we want to change digital waveforms using any ALC circuitry action? Makes no sense to me... and I find the thread starter's advice poor at best.

Modest use of ALC compression circuitry on SSB voice is a known technique and is quite viable. Use such ALC limiting with precise digital modulation schemes... again not so much.

Good grief.

 

Agree 100% Steve, today on 10 meters, I saw the worst ft 8 signal i have ever seen. sent by a 2 x 1 with a 0 call.


Yeah, about now some one will pop in and say it was just propagation,.................. not

 

Hi Steve:

You are absolutely correct for PSK31, NO/ZERO ALC. But for the JT and FT modes of modulation, normal range (on your rigs meter) ALC does not distort the signal. Over driving the audio will. We have run extensive testing with a spectrum analyzer and rigs such as Icom 7300 and Yaesu FT-ZDX3000; Using a moderate amount of ALC in the safe range as shown on the rigs meter helped keep the power output level steady, as you were working QSO's across the audio pass-band range. Notice that on most analog rigs (less so on the Icom 7300 SDR), the audio has a round curve response on the scope, not flat. Signals toward both ends
would have a lower power output than signal in the middle, like 1000hz to 1500hz. And signals toward the low and high end of the audio passband on JT-65 would
vary your power meter visibly during transmit. [We noticed that the audio pass-band on the Icom 7300 SDR was MUCH more flat from 200hz to 2700hz] Using up to 50% ALC (on either rig), we noticed the output level was kept constant, yet we saw no increase in distortion or bandwidth of the signal. This was both as seen on the spectrum analyzer and also as experienced doing hundreds of on-air QSO's. Again, this is only true for the JT and FT modulation scheme. PSK-31 will be utterly destroyed by any amount of ALC, due to a completely different modulation method.

Now, back to keeping the power level steady; It's for your own peace of mind, if you care.
The software does not care. And at approx 25w or even 50w, the amount of variation during transmit is so small in total percentage that it would hardly register on the receiving end S-meter. The point is that for WSJT-X (or JTDX) digital modes, ALC will not have much affect
on your signal.

Hope this helps.

Cheers,

Neal

 

I cannot believe any amount of ALC circuit action can be a good thing for ANY digitally modulated signal — any.

Nor I can believe that all ALC circuits in these few mentioned series of radios work identically (given reasonable tolerances) across thousands of fielded units. Why spread ops suggestions that operate radios at the bleeding edge of wrongful signal compression, or by your suggestion, into a compressed state?

What you offer makes no sense and is not needed. Faithful reproduction and signal purity trump ALC action effects.

73.

 

My error, thank you for pointing that out.

73,

 

Come on man! It was just propagation!