[Elecraft] K3/100 input voltage and TX IMD

[Ian Maude]

Don Wilhelm wrote:
> Jim,
>
> You mention that the TX IMD gets worse when run at 120 watts.
> The K3 is specified at 100 watts.  If you run at 120 watts, it is 
> entirely possible  that the TX IMD will then not be as specified.
>
> I don't understand why hams expect performance when a transmitter is 
> pushed beyond it specifications. 
>
> Why should I expect a transmitter specified for 100 watts to operate 
> within its other specs at 120 watts?  I don't because that is 
> unreasonable!  Trying to squeeze the last drop of power from a 
> transmitter has long been known to create splatter and distortion 
> products.  Please don't do that.
>   
This was what I was saying in my post the other day Don.  If the rig 
does not have good IMD over 100W and Elecraft say we should not run it 
over 100W, why does the radio allow me to turn it up?  IMHO, the power 
level on SSB should stop at 100W.  It is fine probably on CW to run 120W 
but on SSB and possibly datamodes, it should stop at 100W.  It is only 
software.

73 Ian
> 73,
> Don W3FPR
>
> Jan Erik Holm wrote:
>   
>> Rick, and others
>>
>> Just to clarify things a bit.
>> First of all when I did get the "bad IMD" report on the
>> air I was at a different QTH and used a another PS, in
>> this case I do not know exactly what voltage K3 got or
>> voltage drop.
>> Then I did bring K3 home to a PS that had 13.9V RX and
>> 13.5V at TX, didn´t reflect much about this. I then started
>> to measure IMD on the K3 and it didn´t look all that
>> bad up to 80W but at 120W it was much worse.
>> After that I started to "rant" about different things here
>> on the reflector, did get more or less zilch help from
>> Elecraft sorry to say.
>> Received some good ideas from some nice people here on the
>> reflector. That together with some studies of my own
>> led to bias adjustment on the KPA100 and also I did
>> turn up PS voltage to 14.9V at RX. Also made area of cable
>> between PS and K3 much much larger, at TX I now have
>> 14.6V at the K3 display. My IMD measurements now looks
>> very good up to 100W and at 120W only slightly slightly
>> worse.
>> Since I didn´t get much help from Elecraft I don´t feel I owe
>> them anything but still to be fair to Elecraft it actually
>> looks slightly better now compared to the "known good"
>> FT-1000D. You can look at these analyzer pictures,
>> Ft-1000D at 200W and K3 at 100W. It actually looks very
>> good.
>>   
>>
>>     
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>   


-- 

Ian J Maude, G0VGS
SysOp GB7MBC DX Cluster
Member RSGB, GQRP, FISTS
K2 #4044 |K3 #455
http://www.amateurradiotraining.org