· Today I was preparing to take my radio out to the back country to do some Astronomy work and some portable FT-991 work… So I pulled out the hand mike that was stored away a year ago and plugged it in..
· I should mention that I never had HUM reports with theMD-100..
· With all the talk about the ALC setting of late, I just happen to have the meter set to display ALC. Mic gain was STILL set to the factory default of 50…
· When I transmitted into my dummy load I had a nice 95 watts but I than noticed that the ALC meter was peaking severely into the RED zone….
· So I began to decrease the MIC gain, and to get the ALC to settle down into its sweet zone I had to reduce the MIC gain down to 13.. I checked all bands and everything was right on both ALC and power output…
· I was thinking about the fact that new owners of the FT-991 using the supplied microphone and the gain set to 50, (Like I Did For The First Day) might be operating the radio incorrectly because they may not have selected the ALC meter to observe its operation (I did not). Most people feel RF power output and low SWR are key operating parameters and that is a true statement..
· To be honest with you, I never worried much about over peaking the ALC on many radios of the past… BUT?????? Could this be a leading cause of RF failure on the 991???
· We hear things like BIAS adjustments and the like for units going into the factory for repair, well ALC is sort of an indirect way of measuring bias…
· So it appears that the factory stock microphone with the rear switch in the “A” position plus a mic gain of 50, will give you clean audio, a full 100 watts, but that ALC meter is saying NOT GOOD
I would love to hear from other hams with similar findings, like a MIC gain of 13 for the hand microphone, the dangers of that ALC going into the red zone, and could this be the culprit… You would think a radio, out of the box, with factory defaults would not put the radio into a danger ALC zone!!
Yaesu FT-991(A) Users Group (groups.io)
https://groups.io/g/Yaesu-FT-991
www.FT991a.com
I wasn't "affected" at all by any response to my posting. It became obvious some phone guys were unduly alarmed by the excessive ALC issue and thought it applied to SSB. It doesn't since it is controlled by the MIC gain. It was also obvious some were not reading their manuals.
ReplyDeleteI'm sorry if it affects you that other that CW/ ALC is discussed in your thread.
ReplyDeleteIt's not stated in the thread subject (CW) and its quite normal that there developes some twists in the thread.
Interesting observations on ALCS is what we still discuss.
We understand you talked about CV, but since we also notice strange behavor of ALC in FM, I thoght that was ok to mention and discuss, but I could have started a new thread if thats what you mean.
(Mine also show over full scale in CW, just checked that now on. Never use that mode.)
As the one who started this thread on the ALC levels, remember that I was drawing attention to the ALC level only on CW, not on SSB. The ALC level is fixed on CW, it is adjustable on SSB.
ReplyDeleteRegardless of the ALC setting when you first received your radio, the proper ALC setting on SSB is somewhere in the blue zone (but not above the blue zone) on voice peaks as adjusted by the MIC gain. Yaesu has a habit of shipping radios with a lot of settings at the mid-point range. This is NOT to be understood as a "factory default" setting if the manual says to set it otherwise. Judging from the recent flurry of ALC postings that say "my radio came that way and that's the way I'm leaving it" tells me a lot of new owners are not reading their owner's manual.
In that regard, the printed manual we all received with our rigs may or may not be the latest version. Mine was not. The latest version can be found on Yaesu's website, and is worth down-loading, 3-hole punching, and putting in a binder.
Now to the real issue . . .
On CW (read, "CW"), my FT-991 showed an ALC reading that was full-scale plus 3 red bars. Lacking a drive control, the FT-991's ALC level is not adjustable on CW. In emails with Yaesu, the tech I corresponded with indicated that such an ALC reading was "excessive" and authorized return of my rig for warranty service. It was scheduled to arrive in Cypress, California, yesterday. Because more than one posting has indicated the same excessive ALC setting (again, on CW), I'll let you know what they do to the rig if, in fact, they still report their findings and fixes.
Again, if you are a phone operator this discussion does not affect you or your rig. It is relevant only to the CW mode.
Recently I have been concerned with the high ALC reading of the my FT-991 during CW operation. At 100 watts into a 50 ohm dummy load, and with no peripherals or cables attached, my ALC meter goes past the end of the blue zone and shows 3 bars of red. The ALC should fall somewhere within the blue zone. Discussions with Yaesu's technical department confirm that the ALC is set too high, and today they authorized returning it for warranty service.
ReplyDeleteMy suspicion is that the blown finals problem in the FT-991 may be related in some fashion to the high ALC indication. Since ALC is a factor in controlling drive to the PA circuitry, the high ALC reading might be an early indicator of misaligned bias to the PA board.
I recently stumbled across this thread and having the ALC meter at "S9+10" in CW is actually the way to set it according to the service manual. If that is good or not is another story, but my Icom IC-7300 behaves the same.
ReplyDelete