My Flexradio RFI problems manifested itself in a couple of areas.First off
I had owned my existing shack and antennas, ground system for 10 years before I invited the Flexradio 5K into my shack. Never did I have any RFI problem until the Flexradio. In that 10 years I had 2 Yaesu radios a Kenwood 2000 and 4 different Icom Radios. Most of these were $2K plus radios. None of them had any RFI problems. None. Before the Flex I did not even own a ferrite except the ones that were already formed on cables.
Enter the Flexradio 5K. The first RFI I noticed was xmit audio in the external powered speakers. Unlike other radios, Flexradio cut corners and does NOT provide a speaker amplifier in their radios. You must provide an external speaker and amplifier. The first speakers I used was an old pair I had laying around. Terrible xmit audio thru them. I perused the Flex Reflectors and found that everyone recommended a pair of powered Bose speakers available at Sam's Club for under $100. I bought them. The RFI with them was about the same and I hated the RX audio. Even after putting ferrites on ALL the Bose speaker cords (both ends) the RFI persisted. I got my $$ refunded.
I then went to BB and demoed and looked at every powered speaker they had in stock. I bought a pair of M-Audio powered speakers at $100. With ferrites this speaker setup worked perfectly. No more RFI from xmit audio and they sounded and looked much better than the Bose speakers.
Next I was getting SSB audio reports of "stuttering"SSB audio. This was at the 100 watt level, no amp on.These reports came from different bands and antennas - but not always. Sometimes the Flex worked without issue. Sometimes it stuttered. Once I started getting in pileups and using my Ameritron Al-1500 that changed. RFI in stuttering SSB xmit audio happened almost all the time. It is interesting to note I never had any RFI problems with CW even at high levels of RF power.
I tried about everything to rid myself of the dreaded Flex Stuttering audio. Ferrites on everything including my German Shepherds tail.
Also I tried at least 4 or 5 different microphones fully ferrited.
After a couple of months I finally got rid of the stuttering SSB audio. If this was the only problem I experienced with the Flex 5K I would probably still own it. Alas. the Flex 5K had many other warts - things I could not and would not live with. I got rid of the Flex 5 K after only 11 months, the shortest time I have ever owned a radio. I took a big $$$ loss, it was worth every penny of loss to get rid it.