More talk power on SSB from your Icom 706Mk2/Mk2G and Alinco
DX70TH
The following adjustments are
to increase the average talk
power on SSB for the above
radios. If your radio is still under
warranty, check with your
supplier to ensure warranty will not
be invalidated
Do not proceed if you are unable to verify
that the modification is not overdriving your radio! A CLEAN SIGNAL IS MORE
IMPORTANT!
Alinco DX70TH: Turn up the
microphone gain as detailed in the manual. This should be set to maximum. The adjustments
described here is concerned with the ALC control. ALC action is indicated by the TX light
which should glow brighter when speaking into the microphone.
Remove the top cover and locate the high
power/50w switch (this switch location is detailed in the manual, it is the only switch
visible under the top cover). To the left of the switch there should be a small pot which
is for the ALC. Just above the pot printed on the circuit board is 100w. Set the radio to
28Mhz and while speaking into the mike turn the pot counter clockwise until the TX light
just fails to glow brighter. Back off slightly to restore the increase in brightness of
the TX light while speaking into the microphone. Replace the top cover.
This adjustment increases talk power
considerably and for local contacts on SSB the compressor should be switched off.
Icom 706Mk2/Mk2G: The
Icom 706 series are notorious for low talk power on SSB. A simple tweak of the ALC can
solve the problem. This procedure was published in Radcom July 1999 but is updated here to
include the IC706Mk2G. As far as I can ascertain, the later model 706MK2G seems not to
suffer from the problem of low talk power and this mod may not be necessary. Remove the
top cover. At the front edge of the main circuit board (to the left of the crystal filter
slots, with the front of the radio facing you) should be a small pot. In the 706Mk2 this
is R511 and in the 706Mk2G it is R579 (the number is not actually printed on the board!).
The pot may be obscured by printed ribbon. This pot needs to be turned clockwise while
speaking into the microphone, with power set to high and microphone gain at 6 (compressor
should be switched off). Adjust for maximum talk power.
circuit layout showing location of pot R579 (click
on image for full size)
The article in Radcom claims that this
adjustment will bring the 706Mk2 up to 100w pep without the need for the compressor. For
the 706MK2G (early models), adjusting R579 can give a dramatic increase in talk
power although you will find that you will still need to have the microphone
gain turned up to 10 and the compressor switched on. On my own set I have noticed that
some bands give more talk power than others. On 160, 80 and 2 meters I get nearly full
power by speaking into the mike (gain at max and compression on). However on other bands
the increased talk power is not so dramatic particularly on 10, 20 meters).
Another way to boost the talk power on the 706
series is to use a preamplified microphone. If you do decide on a preamplified microphone
reset R511/R579 back to it's original position or distortion may result. |