TA-0344: Yaesu FT-891 TX Delay on AM and FM - Fixed - Improved

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Fixing the Slow TX on AM and FM, step by step.
**The effects on SSB Mode are untested, do this only on Bands you use FM/AM.
The Values: www.tonyplaza.nl/download/YT0344/FT891TXG.pdf
Yaesu Line : www.tonyplaza.nl/download/YT0321/YaesuLine.jpg
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FT-891 Firmware Upgrade : ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MAF3V7CTJmo.html
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#yaesu #ft891 #ft-891

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Опубликовано:

19 мар 2023

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Комментарии : 35

@g4vft Год назад

By doing these changes you are affecting the ALC response of the radio. The most likely outcome is you will drive the PA out of its linear region in SSB mode and have a wide, splattering signal.

@TonyAlbus Год назад

Thanks you, good point, i put a disclamer on the messages t do this only on Bands you use FM and the affect on SSB is untested

@M0XFXUK Год назад

@@TonyAlbus Hi Tony / Jonathan, I have taken a look at the technical supplement for the 891. It's a little unclear to me what exactly the TXG adjustment is doing, it certainly looks like it has something to do with the ALC. However the FALC setting in the menus looks to me like the main ALC adjustment as this is where the RF power is set and controlled. The TXG looks like it controls the raise timing of the RF power which would make sense to tie into the ALC. So I really don't think this will effect the linearity of the PA. That being said I have a sneaky suspicion that Yaesu deliberately set the radio like this to protect the PA from adverse SWR conditions. There may be a PTT reaction time issue from the SWR detection to the ALC being throttled back under adverse SWR conditions so they may of set the TXG to combat this. I really do think it was set like this from the factory to lower the likelihood of blowing the PA keying up on really bad SWR conditions. I.e. Yaesu did not want to see them back during the warranty period. There is a complete PA alignment procedure detailed in the technical supplement it may be worth following this and see how the radio behaves. Just a guess but would be interested in your thoughts.

@glaros0 Год назад

@@M0XFXUK ''Yaesu deliberately set the radio like this to protect the PA from adverse SWR conditions'' in the beginning I had exactly the same suggestion. But, why then this slow response isn't observable as well on digital or CW modes, as bad mismatch (accidental or else) can happen anytime, Yaesu's logic is so confusing... 🤔 TNX, 73

@g4vft Год назад

@@M0XFXUK @Tony Albus I was trying to be succinct (or blunt ?!). If you look at the block diagram, the FALC setting controls the TX IF level before the mixer. TXG sets the drive level just before it leaves the main unit. I just feel that messing about with values rather than setting them as detailed in the Tech Bulletin is probably inadvisable.

@M0XFXUK Год назад

@@glaros0 Hi Kostas, very interesting comment. Regarding the delayed RF raise time I am only guessing as I don't have one of these radios to test however; I think it may only cause delay when the the radio initially switches from RX to TX mode and I would imagine that there would be a reset time period for digital, CW modes. One thing is for sure the delay is being controlled by the micro controller and I think we will never know the logic behind how Yaesu wrote the program to control this radio. I am still leaning towards protection of the PA from high SWR or a software solution to combat a hardware design issues (The PA is probably one of the highest points of failure and most expensive to fix in most rigs so it would make kind of sense but who really knows). Yaesu obviously knew about it but released the radio anyway. I totally agree Yaesu's logic sure is confusing. thank you for the reply and food for thought. 73 M0XFX

@killerbites3963 Год назад

Thanks for the video showing how to remedy this, as much as I would like to fix it by this method I dint think it’s for me

@TonyAlbus Год назад

Thanks, yes its not for everyone, also its unknown what it will do on longterm and consequense on SSB. i just opened a door and hopefully some others continue to perfect it, at least there is a start now

@grerlab2777 Год назад

Thanks Tony... always interesting...✌

@TonyAlbus Год назад

Always nice to see your comments Grer!. Thanks

@Edisson. Год назад

Hi, this is a Spanish village for me, as they say here - so it's completely beyond me, I don't have any radios and I don't broadcast. I'll be happy to watch the video anyway as it will at least broaden my general knowledge a bit - thanks Tony But the load is luxurious, I have to make something similar to load AC circuits, because my load can only handle DC 150V 60A or 300W Nice day 🙂 Tom

@TonyAlbus Год назад

Thanks for your comment Tom, nie to read. i have a few videos about electronics DC load, a cheap kit and a Kunkin.

@Edisson. Год назад

@@TonyAlbus Hi Tony, I have a good DC load, I originally wanted a 600W but it was 50cm deep and it wouldn't fit anywhere, so I took the 60A 300W version. Now I have to solve the AC load, I have some large ceramic resistors, that's why I wrote that I like the cooler you have on the power load for the radio. I saw the video with your load, I didn't understand the switch at the back, I also have a few such devices and solved it with switchable sockets.

@TonyAlbus Год назад

@@Edisson. Resistir are prob the best for AC indeed, or a 1000Watts old lightbulb with a variac :)

@Edisson. Год назад

@@TonyAlbus Without a light bulb, variac and isolating transformer, it is impossible to work efficiently 😁

@TonyAlbus Год назад

@@Edisson. Yes :)

@phils2180 Год назад

I've just watched this video and, you guessed it, I went straight to my 891 and tried it!😂 I think mine is around 5 years old now and currently running one firmware version below the latest but there is no discernible delay on either FM or AM, the response is virtually instantaneous. I've never had any issues using the radio so never thought of looking at this, nor have I ever gone into the service menu. Maybe this was something done by Yaesu on newer examples for whatever reason?

@TonyAlbus Год назад

Thats great Phil!... you are one of the few.. most have this 'problem' i had it on the first firmware and the last. i did not check it on yours (the middle version you run) but many run that firmware too.

@phils2180 Год назад

@@TonyAlbus After checking the receipt I found I bought mine new in March 2017 so turns out it's 6 years old and probably one of the first batch after being launched in July 2016. It's been/still is a great radio, especially for mobile and really punches above it's weight for it's size.👍

@TonyAlbus Год назад

@@phils2180 Yes great radio! enjoy! 73

@glaros0 Год назад

Very interesting video, thanks for this, as this slow output response has been around for long time now. Without questioning the validity of the method, however, if the solution would require only a straightforward change of some values through the service menu, I am wondering why didn't Yaesu simply incorporate these changes in the new firmware? I am pretty sure that Yaesu is aware of this 'slow' response on AM/FM modes. Also, how's the response of the ALC value following your change? Previously, the slow PO response was followed by a 'peak' in the ALC and then a gradual drop-off (i.e. in effect the opposite effect of the PO, as this is the ALC's purpose, to contain the power). Is the ALC faster now too in AM and FM modes? TNX, 73

@M0XFXUK Год назад

Very good point regarding the firmware update.

@TonyAlbus Год назад

Thanks yes we need to investigate what else are the consequences of this changes... its a start

@M0XFXUK Год назад

@@TonyAlbus Hi Tony, I hope you don't mind me jumping into this as I have a suggestion. As you certainly have no shortage of test equipment it might be a good idea to take some measurements in order to get to the bottom of what is happening here. The first thing I would suggest is to understand what the TXG is actually doing. The TXG level can be measured at test point TP1001 which looks like a DC control voltage for Q1009 a dual gate field effect transistor that in turn controls the RF levels passing to the PA and ultimately to the antenna socket. If you use a storage scope or a logging volt meter to measure what is happening at TP1001 during the delayed power up time it would be interesting to see if it's a delayed on state or a ramped on state. The voltage swing at this point is most probably below 5v DC. It would also be interesting to see what adjusting the TXG in the menus is actually doing at TP1001. If we can understand what is happening at this point I think we are half way to understanding what the knock on effect problems are or if any actually exist at all. I think it would also make an interesting video too. Please let me know what you think.

@TonyAlbus Год назад

@@M0XFXUK Hi John, thanks great idea....

@M0XFXUK Год назад

Hi Tony, interesting video. I wonder if it's a delay for the output RF to switch on OR it's a delay for the RF to reach desired power. In other words is the issue a gradual power up or a delayed power up? I'm completely guessing at this but I have a feeling that Yaesu may have done this deliberately to combat other issues possibly with PA reliability. Just a guess but not out of the ordinary for Yaesu.

@TonyAlbus Год назад

Thanks John, yes unknown why Yaesu did this, and indeed the effects in SSB are not tested.