[Elecraft] K3 :: slightly reduced TX power output noticed

[Steef PA2A]

When I make keydown at the 120 Watt level on 20 meters, the message HI CUR 
appears after about 10 seconds and the power goes to 106 watts. I did not 
see that before.

73 's Steef PA2A
k3 #1184

----- Original Message ----- 
From: "Steve Jackson" <kz1x at yahoo.com>
To: <elecraft at mailman.qth.net>
Sent: Friday, July 25, 2008 5:51 AM
Subject: [Elecraft] K3 :: slightly reduced TX power output noticed


>
> Hello
>
> I noticed CW output power on 40M was off by a small amount, 7-10%.  (Was 
> set to 100W.)
>
> Meters are Bird 43 and LP-100.  2 kW dummy load has mondo return loss (26 
> dB).
>
> So, I went to see what the 40 meter HP TX gain setting was, and it seems 
> like it was topped out.
>
> K3 didn't quite make the same power it did before, maybe 8% low.  Odd, so, 
> I cranked the TXG setting to 60, which is max.
>
> Still didn't quite make 50W.  Then I noticed that the gain setting 
> reverted back to 58 without my input.  Huh?
>
> Turned the TX ALC back on, then checked TX out on 40M at 50W ... and got 
> 50 watts.  Cool.  But ~7 watts low at 100W setting.
>
> HP TX gain setting, for comparison, on 20M is 24.  It's like it has no 
> headroom on 40M.  My K2 was hottest on 40, IIRC.
>
> Checked power on 20M at 50W, right on the money.  At 100W, 7-10% low, and 
> much the same on other bands.
>
> Internal voltmeter shows 13.6V on RX and 12.9V on TX @ 100W setting, 
> drawing 17.7A for 94W out on 7050.
>
> 50W out setting yields 50.4W RF at 13.15A @ 13.1V.
>
> Power source is an Astron RS-35M across three 105A-h AGM batteries, and 
> nothing smaller than 10AWG in between.
>
> West Mountain Radio crimper tool assembled PowerPoles, the shack standard 
> here for years.
>
> Probably have 100s of them.  I don't think this is an I^2R problem.
>
> All 3 RF wattmeters agree at 50W.
>
> FWIW I just upgraded to the new firmware this evening.
>
> Since 92 watts equals 100 in my book and because at 50W the set makes 50W, 
> this isn't too much of a concern.  However, I thought I'd bring it up in 
> case the observation is indicative of something else that actually does 
> matter.
>
> Steve KZ1X/4
> K3 #1209
>
>
>
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