[Elecraft] Re K2/100 Flat Topping on 30m

[Brendan Minish]

At 14:54 31/10/2002 +0000, peter barville g3xjs wrote:

>I'd be interested to know if others can set up a two tone test on 30m
>and look at the output on a monitor 'scope.


I have just finished having a look at my K2/100 (in my case the KPA100 is 
mounted externally in an EC2 case with the 270 Ohm resistor mod)

My rig looks textbook perfect @ 100w SSB on 30 with a 2 tone test, (unless 
of course I overdrive the input on purpose!)

I also have a spectrum analyzer, it doesn't have tight enough filtering to 
do close in monitoring of SSB signals but it did uncover another oddity

I found low level switching (sounded like popping) noise +- ~500 Khz each 
side of my SSB output. The worst of these under the worst provocation) was 
more than 70Db down from the fundamental and they fall off fairly rapidly 
each side of the transmit frequency. The level of these spurs increased 
with a reduction in power out of the K2 but at all times remained low 
enough that they would not cause problems meeting (by a good margin!) all 
relevant standards

they were only present when the PA was engaged and could be heard on a 
nearby receiver as well as be seen on the analyzer.
they weren't present in CW mode at all and were only present in SSB mode 
when the ALC was showing some activity so I suspect that they are related 
to the ALC on the KPA100

Anyone any ideas ?

A well screened Dummy load was of course used during all tests

73
Brendan EI6IZ K2 1642