[Elecraft] K2 phase noise

[G3VVT at aol.com]

In a message dated 18/03/05 01:27:47 GMT Standard Time, g4bjm at hotmail.com  
writes:

I don't  expect the K2 to have lab grade 
performance, nor to outperform high price  rigs.  My sole reason for looking 
into this (believe me I've got  better things to do) is due to complaints 
about my signal on air.   These have been from respected and technically 
competent  amateurs.


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>From a later posting by S55M-Adi it may appear there is  some distortion 
reported from the K2's KSB2, SSB adapter under certain  circumstances. Rather than 
resorting to "shotgun troubleshooting" a rather more  thorough examination of 
the problem seems necessary.
 
Firstly the basic QRP CW K2 TX is reported to be clean. Is it?
 
Check that it is by removing all the additional boards from the K2, install  
the necessary straps/capacitors to return it to basic and test with a known 
good  spectrum analyser that has the resolution capability or other test 
equipment as  deemed appropriate. The spectrum analyser *must* be connected via 
suitable  external attenuators to protect it's input and prevent the generation of  
non existent spurii within the instrument due to overload. Many an unwitting  
technician has been led astray with this point and can also result in the  
spectrum analyser having to be returned for repair to a burnt  out front end and 
recalibration. An expensive process.
 
If the K2 passes this test, install the KSB2 and start again with the  
testing. Follow this through board by board until the culprit for  the perceived TX 
distortion is found. This would then be a good time to  contact Elecraft 
Support or post on the Elecraft reflector for assistance with  known specifics. 
Blanket criticism of the K2 is unlikely to succeed, only  generating hostility 
from the satisfied users. It may be something as simple in  some cases as wrong 
bias levels on the K2 PA transistors when that stage is used  as part of the 
system. The K2 will still work on CW with no bias at all, but  does sound 
extremely poor on SSB. This should show up in the testing and simple  DVM tests 
will pin down the cause if this is so. Any non linearity in  the TX signal path 
will degrade SSB where it has little if any effect  on CW.
 
Sensible testing with the knowledge of how to correctly use the test  
equipment should localise the problem. However having the best test equipment  that 
money can buy still is no good if the person that is operating it does not  
know how to use it!
 
In my latter years at work was involved in commissioning/acceptance testing  
of new communication sites that contained SDH digital microwave, SDH fiber  
optics plus all the various power systems and other support needed to run  these 
systems. Due to the complex nature of the testing, the design engineers  had 
thoughtfully documented precisely what test equipment should be used and all  
the settings for the various tests. Without this the job could have been 
rather  chaotic with the engineers and technicians from many nations involved in 
the  testing process.
 
In my original posting I used the term "slagging". Fred, K6DGW pointed out  
to me quite rightly that the non UK members of the list may not  understand 
this UK slang term. The nearest translation for this would be  "castigate".
 
Will follow the outcome of the reported problem with interest.
 
Bob, G3VVT
K2 #4168