Discussion in 'Mobile Radio' started by K7POC, Oct 1, 2014.
Could explain it. Did you try just turning down the gain before you did all that?
I didn't on the FT-857 mobile setup, because as soon as I became aware that there was an issue, I knew that it was RF getting into something (I just didn't know that it was the mic specifically). It would be relatively easy to remove most of the ferrite cores and try it; I might try that if I get a chance. The exception is the core(s) in the mic, as it was a royal pain to remove each contact from the internal connector to thread each wire through the core(s). I say core(s) because I tried various configurations in my MH-59 as well as two MH-36s; some got one core for all wires and some got several, and I don't remember how many are in that one. Also, the cores were initially installed in the previous vehicle, and have always been present in the current one. The installations are very different (front mounted radio and antenna on top of metal roof originally, and remote mounted radio in vehicle with soft top currently). Logic would dictate that the current installation should be far worse, considering the long, unshielded extension cable on the mic, the soft top, and the fact that the antenna is much closer to the rest of the system. I doubt that the antenna is even 6 feet away from the mic!
On the FT-817, prior to adding the cores to the mics, there was often terrible RF feedback (depending on antenna, frequency, and other variables). At its worst, it was present at any mic gain setting which passed any audio at all. It was sometimes so severe that it completely swamped the microphone audio, transmitting nothing but an audio tone. Adding the cores helped, and oddly enough, switching the MH-36 keypad backlight on (it is not switchable on the MH-59) reduces the feedback even more.
On my second FT-857D - only because I lost the first one in a fire. (a non-electrical fire, thank you) No issues. No problems with RF - but I've always used with properly choked antennas, properly managed common mode current, etc - I think if someone is having severe RF issues, then either something is wrong with the radio or the installation needs another eye. Never had an issue like that. I use a cheap computer headset, mic biased directly from the radio through a 512 Ohm resistor, and blocked to the mic input by a 1uF electrolytic cap. I run the mic cord for the headset through a 43 mix toroid 7 turns or so near the input to the radio - although I never had a problem at 100W, its just something I tend to do by habit. The stock mic is very decent. Audio at home was improved using a better quality mic. I tune the offsets a bit on SSB - I don't use the EQ, I do use the processor. I frequently get compliments on the audio - with a "disposable" computer headset that was given out by an online training seminar.
About the only criticism I have of the FT-857D is that the receiver isn't very good with strong adjacent signals. There is no comparison to my TS-590s on receive - but its not a fair comparison. It was my only HF radio for quite a while, and I've used it for everything from 160m dx'ing to working the birds SSB/CW. I really love it. Great little radio, lots of fun, lots of stuff packed into a neat package at a great price.
Oh yes - the optional filters are excellent. Get them from w4rt.com - well worth the money.
I lied - I did have one RF problem, but I was running 800W on 160m into a difficult vertical - it was a high common mode current on the USB cable causing the issue. Ferrite core on the USB cable solved that problem. Not a design issue or flaw with the FT-857D.
Likewise, I've never taken any special care of mine. Spilled all kinds of stuff on my old one, including half a bottle of orange soda - had to take the head apart and clean it all out. Then, good as new.
I have had a 857D for 2 years. No problems so far.
I've had my 857D for over 1 1/2 years. It's been both in shack and mobile, with mobile being 2m/70cm. Works great with good reports.