Posted by
VK7JB on
Nov 09, 2010; 9:42am
URL: http://elecraft.85.s1.nabble.com/K2-ALC-and-power-control-on-40m-SSB-in-K2-100-tp5719064p5720219.html
Don,
The KPA100 is new -from Elecraft in September 2010 - and it therefore is the new
design with the blue toroids @L16/RFC1. The shield is installed as instructed,
using the 2 solder lugs to the SO-239 socket.
I took the KPA100 off the top of the rig, as you suggested, but there is no
difference in SSB mode running into the dummy load with the KPA100 attached or
flipped off beside the K2.
Looking more systematically, I see the overdrive is most noticable on 40m, but
is also present on 80 and 30m. It's not a problem on 20m and up. Reducing
requested power to 50W (or less) and the power out remains close to 100W on
peaks and the ALC indicator shows 6-7+ bars in ALC mode. Seems the ALC is
working hard but not reducing the drive sufficiently to maintain the requested
output??
Mic is the MH-2 which I run SSBA = 1, SSBC = 2. The audio sounds very good.
The problem reduces on the low bands with the compression setting @1:1, but then
there is insufficient drive for 20m and up.
Does this mean my TX chain has a lot of gain on 80/40/30 - too much for the ALC
to manage?
Thanks for your help,
John
VK7JB
Quoting Don Wilhelm <
[hidden email]>:
> John,
>
> Is this a relatively new KPA100, or did you purchase an older kit from
> someone who never built it?
>
> The reason I ask is because the older T/R switch design had elements
> that could cause parasitic oscillations near 40 meters, and often was
> most noticeable on SSB.
>
> If your KPA100 has blue toroid cores for L16 and RFC1, then it is the
> new design.
>
> If you have the new design, then did you fasten the shield directly to
> the SO-239 jack using the two solder lugs as instructed? These are
> important.
>
> Make a check - remove the KPA100 from the base K2, but keep it connected
> - in other words turn the KPA100 upside-down on a book or box to the
> right of the K2. Then try your SSB operation again (into a dummy load
> please, antennas are not consistent). If it works OK with the KPA100
> upside-down, then look for causes of coupling from the KPA100 into the
> base K2, but if it still mis-behaves, we can look at other things.
>
> 73,
> Don W3FPR
>
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