Flex 6xxx series is advertised as having a powerful transmit audio because of CESSB implementation. This is one of the reasons I bought the radio. A regular speech processing with IF clipping produces some peaks that need to be suppressed. CESSB is a technique that avoids those peaks leading potentially to a 2 db improvement. See an article in Nov 2014 issue of QEX.
When operating Flex in contests, I frequently had to repeat my signal report, something I did not have to do with my older radios (TS850, FT1000 MkV Field, K3). Listening to my signal on another radio, the signal was muffled. More with higher mic gain. Soon I could recognizing Flex signals on the air. A good case of that was the contest audio of K9CT. Weak and mediocre.
I made my findings known on the Flex group on groups.io. Most people responded like I was an idiot criticizing a divine product.
Some time later Flex released a new firmware. It drastically reduced the lag when remote under Windows ( from almost a second to a fraction of a second) and the audio was nicer. Not muffled although not crystal clear like FTDX101.
In subsequent contests I did pretty well in CW but still poorly in SSB. Despite phased Yagis and 1.5 KW, my signal was not competitive. I was losing run frequencies, and the success in pileup for multipliers was so so. I thought that something is wrong with my antennas. Updating to a new tower with larger beams would cost > $20k.
With speech processing , the antenna power meter shows an average around 30-40W for 100W radios. I attached an analog meter to the Flex and could not believe what I saw. Without speech processing the meter was barely moving. With speech processor the meter was moving but not much.
I did an A/B test with FT991. Without speech processing, the average power of FT991 was 5 W and of Flex 6600 was 1 W. With processing, the readings were 30 W in FT991 and 5 W in Flex. When cranking the mic gain to the max, the average power of Flex went up to 10W with a busy but acceptable signal for contesting.
So Flex was at least 3-6 times weaker in SSB than FT991. Probably 4-8 times with contest radios like K3/4, 7610, FTDX101. Weak Flex audio explained why my SSB contesting was worse than expected. At least 3 times power deficit compared to the competition.
I posted my findings on the discussion group. I got support from a few other contesters, who found Flex uncompetitive in contests and IC7300 beating Flex handily. The feedback from the Flex guys was different. They claimed everything was fine and I was the troublemaker. They also came with a test that revealed ignorance of speech processing. Why Flex was defensive instead of fixing the problem? Apparently things are not going well over there.
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