[Elecraft] SSB output overshoot

[Mike Harris]

G'day,

I have now done the resistor mod to no effect and will probably revert 
'cos I don't like how I had to add the 1K0 in series with the base of Q1.

Driving the K2/100 into a dummy load and just using the bar led display I 
see the following:

Set requested power to 30W.  Mode SSB.  SSbA = 2,  SSbC = 2-1, Mic Kenwood 
MC-43C.  Mic jack grounding mod done.

On 80M I see up to three bars ALC.  Set to RF, regular peaks of 50W.

On 40M I see up to seven bars of ALC.  Set to RF, regular peaks of 50W and 
occasional peaks of 70W or more.

On 30M I see up to six bars of ALC. Set to RF, regular peaks of 50W, 
occasional peaks to 60W.

On 20M I see one bar of ALC.  Set to RF, regular peaks to 40W.

18M - 10M, one bar of ALC.  Set to RF, peaks to 40W.

Set mode to CW.  Request 30W.

All bands power peaks to 30W, no overshoot.

I dropped the requested power to 5W thus switching out the KPA100 and 
similar SSB overshoot problems presented.

Conclusion, in it's present state my K2/100 is unusable on 40M SSB with an 
amp.

If this is a common problem then it looks like the KSB2 is in need of some 
serious work unless the excess TX path gain in the 7 - 10MHz spectrum can 
be tamed.  Maybe it also gives a clue to those reasonably frequent Hi 
Current warnings when running barefoot at 100W

Regards,

Mike VP8NO


| Thanks Steve.. I was hoping there was something I could do.
| Do you (or anyone) have the details of the necessary resistor changes?
|
| Don K7FJ
|
|
|
| ----- Original Message ----- 
| From: "Steve Kavanagh" <skavanagh72 at yahoo.ca>
| To: <Elecraft at mailman.qth.net>
| Sent: Wednesday, November 01, 2006 5:55 AM
| Subject: Re: [Elecraft] SSB output overshoot
|
|
| >I think Don's observations sound like the problem I
| > and a few others have had. See, for example the
| > symptoms described here:
| >
| > 
http://www.ac6rm.net/mailarchive/html/elecraft-list/2005-03/msg00676.html
| >
| > 
http://www.ac6rm.net/mailarchive/html/elecraft-list/2005-12/msg00408.html
| >
| > These two, at least, were due to the KSB2 ALC circuit
| > having insufficient attenuation range to control the
| > output of K2/100's which have above-average overall
| > transmit gain on the lower bands.  The fix involves
| > adding a resistor and changing another in the KSB2.
| > Gary Surrency at Elecraft was able to provide me the
| > necessary details.
| >
| > But Mike's problem sounds much less severe.  It might
| > be a marginal case of this effect, I suppose.
| >
| > 73,
| > Steve VE3SMA