[K2] K2/100 power out on 10m SSB...

[VK7JB]

Just noticed that power out on 10m (28490) CW and in TUNE mode is 85W, but maximum PEP on SSB is 30W.

All other bands, I get 100W out in CW/TUNE & SSB.  I'm checking this by running K2/100  into a 50 ohm dummy load.  Wattmeters are a WavenodeWN-2 and Autek WM1. Same  PO PEP recorded with both.

I've done the mod replacing K2 R98 with a 1k0 resistor to reduce the ALC dithering on 40m. This did reduce the power out on 10m in CW and TUNE from 100W to 85W, but I was happy with that compromise for the more stable ALC action.

Any explanation why is the output SSB is so much reduced compared with CW and TUNE modes?

73,

John
VK7JB

[Don Wilhelm-4]

  John,

As a quick check, reduce the value of R98 back to 270 ohms (put a 360 or
390 ohm resistor in parallel with your 1k0 resistor).
That will quickly tell you if the cause is due to the increased value of
R98.
If that is the problem, you may have to compromise further on the
damping of the power control loop by reducing R98 below the 1k0 value.

The fact is that the K2 RF Gain is lowest on 10 meters (and highest on
40 meters), so some compromises in the damping of the power control loop
may have to be made.

There is an alternative - increase the SSB RF gain by installing the
KI6WX Increased SSB RF Gain Mod.  If you do that, be certain to change
the ALC components on the KSB2 board to handle the greater gain with the
KPA100 installed.
I can email the instructions for the original KI6WX mod with the KSB2
ALC modifications included upon request.

73,
Don W3FPR

On 11/5/2010 11:51 PM, VK7JB wrote:

> Just noticed that power out on 10m (28490) CW and in TUNE mode is 85W, but
> maximum PEP on SSB is 30W.
>
> All other bands, I get 100W out in CW/TUNE&  SSB.  I'm checking this by
> running K2/100  into a 50 ohm dummy load.  Wattmeters are a WavenodeWN-2 and
> Autek WM1. Same  PO PEP recorded with both.
>
> I've done the mod replacing K2 R98 with a 1k0 resistor to reduce the ALC
> dithering on 40m. This did reduce the power out on 10m in CW and TUNE from
> 100W to 85W, but I was happy with that compromise for the more stable ALC
> action.
>
> Any explanation why is the output SSB is so much reduced compared with CW
> and TUNE modes?
>
> 73,
>
> John
> VK7JB

... [show rest of quote]

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