[1000mp] Key Click Mod for MP with the 3rd keying stage included

[juha]

I noticed that W8JI and Inrad modifications change the keying at two =
stages. There is a third one, transistor Q1019 at RF-board, that causes =
some click at falling edge. I eliminated the keying of Q1019 by short =
circuiting the cap C1129 at transistor base to ground. Carrier leakage =
during TX mode increased a bit but was about 90dB that is good enough. =
Now the rising edge was faster and not so rounded as in original MP. My =
MP is a vintage version from -95. Maybe later series are different at =
Q1019.

The two remaining stages I modified with rather simple RC filters one =
series resistor away from FET gates and not directly at gates. The RC =
filters have different rise and fall times with diode circuits.  I =
prefer not to connect any additional capacitors parallel to an existing =
capacitor at FET gate. This is to avoid parallel resonance of the =
capacitors combination. Note that 100nF cap with legs is inductive at =
high frequencies. However, this seems to be no problem in this case =
because the modified rigs work ok. =20

The modified rise and fall times are about 5ms.  This is a bit slow but =
seems to be fast enough for 40WPM.

I  connected MP TX to TS850 via dummy load with attenuator and tested =
the modification by listening with TS850 having 500Hz filters on both =
IFs. I adjusted attenuator to get S9+60dB at TS850 RX and started to =
transmit dots and to change RX frequency. I could not hear any clicks on =
USB or LSB sides on any offset. The only thing to hear was my keying as =
TS850 phase noise. MP phase noise is much better that TS850. So, I can =
not say how much I reduced the clicks because the testing was phase =
noise limited. Probably the clicks are now more that 90dB attenuated at =
500Hz offset.  The difference to unmodified MP is easy to hear on MP own =
monitor also. Using that monitor and SSB filter is a nice way  to =
demonstrate original MP clicks.

I do not write the exact modification here. If someone is purist enough =
and wants the details I can give a description later.=20

73

Juha  OH1NOR