Icom 7300/7610 Digital Mode ALC Zone

Thank you for commenting Robin. It's a new era in Ham Radio

Best 73,

 

OK I can believe that having high ALC values should not distort an FT8 signal, at least on the two DSP radios that were mentioned.

But then if that is the case, that leads me to question - why do you need ALC to be non-zero in the first place - wouldn't you get just as good of a signal if the ALC was zero? So why does it have to be adjusted to "30%" ? What does that do for you (other than it being a rote "recipe"). Why not 20% ALC, or 10%, or 50%, or zero?

 

Thanks for commenting and I appreciate the discussion.

What does it do for me? I'm using 1/2 the power I was using and I get better signal reports in FT8 mode.

In the video and my article, I'm just presenting an alternative method and it is completely legit because it is in the manuals. Many hams that I have talked too use ALC in data mode. Including very experienced hams that have done their own testing.

The 7300 changed things. Flex now has radios with knobs.

73,

 

And why is that? Microprocessor derived modulation drives analog IF and RF stages with said discussed radios -- big deal. The modulation of analog IF and or RF stages is NOT going away. These analog stages still need to be controlled by TGC/ALC circuits, therefore the chance of improperly driving said analog stages will still exist. Monitoring of and careful consideration of signal cleanliness still exists.

There's little room around this fact.

What's your take away?

 

First, I don't believe the thread star

After review of the IC-7300 service manual, I have discovered that is likely that all of the IF up-conversion circuitry is contained within the FPGA (IC1351). What is not discussed is how the rig's transmit ALC or TGC control circuits are derived or how they work. I assume there's some kind of feedback circuit between the RF amplification stage and the IF FPGA and or analog audio input amplification stages. Without further explanation -- which the Icom service manual fails to provide -- it's difficult to judge how the TX ALC metering and any TGC circuitry is derived or how these circuits work. Icom fails to provide an in-depth review (or any review) of the rig's control circuits. Figures... this is par-for-the-course with comm-electronics and telecom mfgr's today.

Apparently, it's pure, unadulterated manufacturer's MAGIC! It is disgusting to say the least.

So... who the hell knows!

 

I suppose it's time to read Adam Farson's reports on these new Icom rigs, and see what insight he's gained outside of pointless "service" manuals.
Perhaps it's pure FM with him as well.

 

But you say in the video that you set your output power at 30 watts (30%).

So you're using half of that? 15 watts? Or do you mean that you previously were using 60 watts and now using 30 watts? Is that peak power or average power?

Or is it that because of the clipping introduced by ALC, your average power is twice as high with the same peak power? If that's the case, then how does that work if the signal is purely "FM" ?

Measured how? By the signal report that WSJT generates? Then I'm curious how do you tell that the signal reports are "better". Better than what? Have you done an A/B comparison in contact with the same station?


Just trying to make sense of it all. Not just the "what" you're doing, but the WHY ?

I've been watching FT8 and have been thinking about trying it out. I want to not only make sure I'm doing it "right", but I like to understand what "right" is and WHY it's "right"; i.e. understand what I'm doing and not just be an appliance operator just because some internet video said to set the ALC to 30%.

 

Pretty "typical"comments by owners of an entry level rig, but, it sure is purdy.

BTW. prices of used 7300 continue to fall, they can easily be purchased for <$900.

 

Thank you for your comment and interest. I can see you're passionate about this.

The video and article just show a method to adjusting power output and maintaining a consistent ALC. You choose what % ALC to run. Even if you choose no ALC (o), you don't have to use a software slider to adjust your Po. Many choose to use the knob on the radio, myself included.

As I see it, it is not all black or all white, cut and dry. There are a lot of variables. Amateur Radio is an art form, not just science. We apply intuition, ingenuity and creativity.

I am not sure about right, but you'll be doing a good job if you follow the WSJT-X manual. There's another nice write up about operating FT8 and it is here: FT8 Hinson Tips for HF DXers

Now, 15 watts and I was using 30 watts (peak) max on FT8. I am going by what signal reports I receive from QSO partners. As I said in the video, it could have just been propagation at that time. However, I am more convinced today that there is a difference and it wasn't just conditions.

I have not heard or been shown that running ALC causes poor signal quality in these radios, unless you go way out there. Use your best judgement.

As far as PSK31 goes, I am now running less power. 20 watts (peak) instead of 30 watts. Received signal reports on PSK31 are still basically the same.

This is my experience. Don't just take my word for it, visit other forums on the topic.

If you decide to try it, use your best judgement and as I have said, "your mileage may vary".

Thank you and I hope to hear you on the air.

Best 73,

 

I always adjusted the ALC on my FT-950 for ZERO deflection on the ALC meter. One thing I noticed was that power out would vary depending on what frequency within the passband I was transmitting...not because the software had adjusted the drive levels.

 

N6YFM is correct.

Moderate amounts of ALC action in modern rigs will help stabilize power output and will generally have no impact on signal quality for FT8, JT65, JT9, etc., because they are constant amplitude modes where each symbol transmitted is simply a different tone. About as simple as FSK/FDM gets.

PSK31 is phase shift keying where signal amplitude is rolled off to zero at phase transitions to avoid the spurs generated by sudden, abrupt phase jumps. Depending on attack/release time constants, ALC action may compensate for amplitude drop off and thereby increase transmitted spurs. Audio compressors are designed to do exactly this and will cause significant widening of the TX signal.

Different strategies for different modulation modes.

Brian - K6BRN

 

Thanks Stephen,

Good point. Especially in PSK31 mode, when getting out of the sweet spot, power will drop.

WinWarbler has a neat button to "optimze" the transceiver frequency and I use it frequently. Of course adjusting the VFO does the same.

I find the Split Operation (Rig) in WSJT-X works extremely well in my setup. Although "Fake It" for Split Operation is probably the most common among Hams I've talked to.

Thank you for commenting and I hope to hear you on the air.

73,

 

Hopefully you will in a few weeks. I've been off the air for the last two and a half years after my wife had an affair and bailed. I close on my first house since the divorce next week and plan on getting my station on the air as quickly as I can.

73,
K7CB

 

I can relate. After my divorce I bought a brand new Kenwood 570D with accessories and really, really enjoyed the alone time, hi!

Best 73,

 

I've done it the same way ever since I got into digital modes which is probably about five thousand Q's ago. Never had a problem making a contact. I also run the monitor on the PROIII, so I will immediately hear if there is a problem.