I have been using the little FlexRadio FLEX-1500 for many years, mainly for WSPR operation. I am posting this because I recently ran into an FT8 issue and could find almost no information about it. The FLEX-1500 may be old, but it is still a very capable radio, and I suspect there are many of them still in use today. I would not recommend it for CW operation. The latency is simply too high. However, I believe this is a limitation of many SDR transceivers from that era. I am used to the CW performance of the Elecraft K3, which sets a very high standard. The receiver itself is excellent. With dedicated switched band-pass filters on both receive and transmit, the FLEX-1500 is truly a hardware masterpiece. I owned the radio long before FT8 even existed. For WSPR, operation was straightforward since only about 200 Hz of bandwidth is required. When FT8 became popular, I widened the USB filter to approximately 3 kHz so I could receive all signals across the normal FT8 passband. However...
K3 repair - deafness after HI RFI warning M0VFC Thanks for sharing! This was 3 years ago I also found the K3 total deaf after HI-RFI warning. Need to have the K3 service manual opened with PDF reader ( I prefer Sumatra for PDF) In my case, D25 was fine, but the signal is stopped in the KXV3 by D5, which is a BAP64-4 . The issue was caused by transmitting on an antenna very close to the K3 antenna on the same band. After checking the RX preamp on the main board, I found that preamp Q4 and the post-preamp were undamaged and still sensitive to hand effects. Connecting a temporary antenna to the 80m band filter produced normal expected signals, and receiving through the sub-receiver AUX port was also fine. However, the rear SO239 antenna inputs were completely dead. The antenna signal travels a long path in the K3: entering via SO239 1/2 at the KAT3 ATU, passing through to P70 on the main RF board, going through the SWR bridge where the ANT signal is grounded ...