"Thierry" wrote in message
If such a modification exists for that TS570D or for any mic, can a ham do
it himself or can he ask his dealer to make the modificationcan
Where on the Internet can we find this procedure ?

Thanks in advance

Another note...Most all radios are set up from the factory to have the
mike controls match the stock mikes. So if you use the stock hand
mike, or stock desk mike, the mike gain controls "should" end up
being set in the middle range of the mike gain control. I know on my
706, if using the stock mike, I end up with the mike gain about on
"5", which is halfway. This is the way you want your mike set up. So
if you add on extra mikes, you want to adjust the gain to match what
you have, and let the radio be in the middle of it's range for gain.
How to adjust mike gain while talking? I have a method I use, which
seems fairly accurate. Set up the radio into a dummy load, and set
power output for 100w "full power". Use an average meter, or if peak
reading, set to "average".
Then set the mike gain at it's lowest setting. Then speak into the
mike in your normal volume, and say x-ray a couple of times at the
lowest mike setting. Then adjust the mike gain up a notch at a time,
and say x-ray a couple of times while on each increasing setting of
mike gain. When you get to the point where increasing the gain makes
no change on the indicated watt meter reading, you have full mike
drive. I bet if you try this on your radio, you will end up near the
half way mark on your mike drive when using a stock mike. When you get
to the point where you have no change, set it back to the first
setting that gave max reading, and you are pretty dang close to the
proper setting. Watching a scope while doing this is even better, but
this method is intended for non-scope users. And yes, being this is an
average meter being used, you will likely only see voice peaks of
25-35 watts or so. Depends on the voice. If you add a pre-amp to a
normal mike circuit, you will overdrive the radios own circuit, and
end up at "1" as far as your mike setting. Will make it real touchy,
and easy to overdrive.
If you did the "x-ray" test, and could go all the way to the end of
the mike gain, and were still seeing increasing average power, and
show no signs of clipping at all, it's then possible you would need a
preamp. It will be fairly obvious power is down from normal, once you
get used to what normal should look like on your particular meter. You
can also do a hard whistle test...I have to use a preamp for my audio
technica mike when going to the 706. I only get about half drive
without it. But thats a case of an aftermarket low Z "200 ohm" mike.
BTW, that same mike element drives my TS-830 with no preamp needed, so
radios vary to their mike gain requirements. Many old icoms needed
outboard mike preamps. "IE: 730,740, etc.. Also be aware that radios
will read different due to audio freq differences also. The bottom
line...If you see a point of no increase when adjusting, as when
normal, there is no point in adding any preamps. And also no point in
worrying what a particular meter reads on voice peaks unless it's
radically off from normal. The meter movements just can't keep up. MK