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

Fri, 9 Jan 2004 12:47:04 -0700

I guess I am a 'purist enough' to want the details of your modification. I
have been reluctant to use the W8JI or Inrad mod.
I am certain that I can live with limiting myself to 40 wpm transmitted
speed.

I would have sent this direct, but there is no email address given for you
in the message.

Tod Olson, K0TO

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of juha
> Sent: Friday, January 09, 2004 11:47 AM
> To: [email protected]
> Subject: [1000mp] Key Click Mod for MP with the 3rd keying stage
> included
>
>
> 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.
>
> 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.
>
> 73
>
> Juha  OH1NOR
>
>
>
>
>
>
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