Testing the FT-991A on FT-8

As some  of you may know I have been having an issue with “hearing” people while using MSK144 on  6 Meters for Meteor Scatter. The number of decodes I would get was lower then whale crap at the bottom of the ocean. After many different people gave me many different, often conflicting (but helpful) words  of advice I took matters into my own hands.  I knew that on my FT991a there were three main areas that was affecting my ability to hear:

The AGC: Automatic Gain Control. This has X settings: AUTO, FAST, MED, SLOW. There is also an OFF setting, you choose this by pressing and holding the AGC box. The others you choose by just tapping the box.

The IPO: Intercept Point Optimization: I’m not sure that this really is, but I think it is some sort of PreAmp. The possible settings are: IPO, AMP1 and AMP2

The DNR: Digital Noise Reduction: Settings are from OFF to 1 though 15.

There isn’t enough MSK144 traffic to do some standardized testing, so I went with the FT8 protocol on 20 meters. I assumed that this would at least give me a baseline that the settings would be close to the MSK144 protocol. I also understand that antenna I am using is terrible to say the least. That is the reason for the terrible DB levels, even on the best results.

I spent one Sunday afternoon figuring out what was best from the AGC and the IPO. What I came up with was that the AGC = AUTO, and the IPO =AMP2 was the best combination. This was based on decodes per minute and best average DB level. See this chart.




The following weekend I decided to test which DNR (Digital Noise Reduction) would be best or if it was even helpful. I was surprised to learn that in some cases the DB went way up and the decodes per minutes also went up. But I also learned that some of the options on the DNR were less then helpful. As you can see from the attached chart. The DNR options 9 and 10 seem to be the best for FT8.




I understand that there is a bunch of variables that I may have missed or not thought about, but I was only going for a place to start on MSK144. The results that I see here, were similar to what my gut (not including the DNR) was telling me.


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