[Kenwood] TS930 SSB Umph

Tue, 18 Mar 2003 06:22:27 +0700

Agreed, 50% is not so bad for SS of this type. Certainly I think that
the heatsink and power supply are the two areas where most concern would
lie. In my own 930 the power supply has been significantly modified with
the result that it would handle a significant extra load. At least I'm
not expecting a psu failure in the near future. The PA heatsink is
something that really cannot be changed though and is, together with the
stock power supply probably the real reason for the stated limits.

I'm still not happy with the way mine works on SSB though. The 940 and
930 do use the same ALC circuits but I haven't yet looked at the
individual component values to see if there were any changes done.

73's
Martin, HS0ZED

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Dr. Gerald N.
Johnson, electrical engineer
Sent: 17 March 2003 23:12
To: Martin Sole
Cc: [email protected]; [email protected]
Subject: Re: [Kenwood] TS930 SSB Umph

50% efficiency is good for a solid state PA.

One issue of power capability besides linearity getting worse at higher
power output is the size of the heat sink. The 930/940 may not have the
heat sink size as used in the FT1000, nor the RF feedback to correct for
the distortion at higher power.

Since 930/940 power supply meltdown leads to PA meltdown from excess
voltage, it should be clear that the power supply can't support excess
RF power output without a major redesign and probably a larger
transformer, better pass transistors and more pass transistor heat sink.
All for 1 or 2 dB is never worth the effort.

73, Jerry, K0CQ

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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