While setting up for WSPR ops- the first time in a long time- I noticed a lot of "racket" (noise) just before and after the WSPR program transmits its audio tones.

Some further observation found that; regardless of the WSPR program, my FT-857D (s/n 4J31...) makes a great deal of audio noise in transmit mode. The noise is obvious, when all audio input is turned off or unplugged. With the mic gain turned down to zero, or mic unplugged etc., and the RF power output tried at various levels, the noise is heard in a nearby monitoring receiver. (Even XMITR turned right down to its lowest output setting of 5 Watts still produced the noise)

This has me worried and puzzled. The last time I noticed this behaviour, I suspect the 6-metre oscillation problem, common with these rigs. That time, I sent it in to Yaesu under warranty, and it was repaired. (It still cost me $125 shipping and broker fees!). Also repaired at that time, were the blown UHF/VHF output power transistors. I blew them while testing PSK-31 at 5 watts. An intermittent antenna connector was later found to be bad. Why the SWR protection cct did not save the rig is beyond me, but I suspect the 5W level affects its ability to work. But I digress….

Back to the noise problem:
Further experimenting and reading lead me to think the noise may not be caused by the FT857D alone, but rather by the radio I was using to monitor. Its close proximity on the table to one another may be causing oscillations, or strange I.F mixing etc. I thought I had figured it out, until I tried monitoring on some other radios nowhere near the FT857D. The noise was still present. Granted, these radios are still in the same house and with antennas close-by. I guess the only way to tell is to ask for another distant station's help. Or looking at the FT857D’s output on a scope.

THE NOISE: The "idle" noise is heard in SSB. It sounds like the "background noise" of a crowded room. You know… lots of rumbling and general "breathing” hash. In AM, it’s even worse. It has very noticeable hum with terribly weak voice audio when I speak into the mic, (after I turn its gain back on). FM seems OK. I changed Power Suppies too, and that made no difference.

Does anyone have any advice or ideas? There has been some material found on the web regarding this rig (and the identical cct of the FT897D) and a noise problem. But that was found on the earlier S/N rigs. The fix on DK MODS shows a ground revision. It is no longer required, or possible, on my S/N and later. Tightening the CCT board mounting screws etc, was not required- they were tight. The only other test would be for the various transistors BIAS settings, which I have read, can change drastically with rig age and use.

Interestingly, when I sent the rig to Yaesu in California, I specifically asked them to do a full bench realignment. When I got it back, checking the Service Menu settings, it was obvious they had been changed. But not all for the better! The SSB offset had the LSB and USB sounding much different from one another. Some other values seemed different too. I wonder if they did a rush job. To be so far off with USB/LSB and have it obviously bad sounding, make one wonder how the BAIS got treated.

Please let me know what YOU have found after testing your rig for “Idling Xmit noise” and BIAS.

This has me wonder if something has become defective, if my testing method is causing the problem and it really does not exist, or if it is normal for this rig... and your opinions would be appreciated.

73
Greg
VA3VFO
FN04