[Icom] MARS xmt for 756ProII

[Ray, W2EC]

I've been to the www.dk.mods page for the 756ProII MARS mod and notice
that it is a little different than the 756Pro version in that a diode
removed on the Pro is not removed on the ProII. I've done the indicated
mod on my ProII and find some strange range conditions occurring. One of
these seems to impact the potential new 60 meter band.

First, I'm aware that Icom indicates that only the programmed ham bands
are supported so the specs on other freqeuncies may not be valid, so no
need to tell me that I shouldn't expect full performance out of the ham
band range. I'm just wondering what others might have seen.

After performing the mod, I went and checked my main MARS frequencies,
mostly in the 2mc to 3mc range, 4mc to 5mc range, 5mc to 6mc range and
15mc to 16mc range. I was interested to see how the 5mc to 6mc range
worked due to the possible new 60 meter band. I used a 50 ohm 1kw
dummyload for initial testing.

2 to 3mc and 4 to5mc worked fine with full output. But the 5 to 6mc
range showed a significant power reduction into the dummy load. The
power started out at over 100 watts at 5.0 mc but dropped to 80 watts at
5.2, then 50 watts at 5.4. By the time I got to 5.9mc, where my MARS
frequency is, max power was down to 20 watts. SWR still showed less than
1.1:1 into my dummy load. I switched to 6mc and power then returned to
over 100 watts. It would seem that the bandpass filter used in the 2mc
to 6mc range has a real sharp cutoff starting around 5.2mc thru 5.999mc. 

I then went thru the entire frequency range from 2mc up and found
several places where power dropped off considerable, several of which
are, surprisingly, in the ham bands.

On 17 meters, at 18.068mc, when you first key the transmitter power
rises to 105 watts, but then almost instantly drops down to 85 watts. At
18.163, power rises initially to 105 watss then drops to 80 watts.  

Likewise, on 15 meters, anywhere in the band, power initially rises to
105 watts then drops almost instantly to 75 watts.

12 meter (24.940) maintains full 105 watts out while 10 meters (28.010)
maintains almost 100 watts out but it drops to 60 watts out by the time
the frequency has changed up to 29.0mc

Has anyone else checked their power out at these various frequencies?
Does any know if the third diode (from the 756Pro mod) also has to be
removed for the MARS frequency mod on the 756ProII?

By the way, consistent with all these power drops is that the backlight
for the LCD also goes noticably dimmer when the power drop occurs.

Ray  W2EC