[Elecraft] Filters and Configuration Questions

[Bill W4ZV]

P.B. Christensen wrote:
> 
> Since keying bandwidth is a function of the RF envelope shape, I'm not
> sure 
> why anyone would want to narrow the K3 filter on CW transmit.
> 

Because most rigs have spurs and I wanted to make my signal as clean as
possible.  Typically these may be <80 dBc but still readable if the
transmitter is using high power and the receiving station has good antennas
(e.g. on 160m in particular).  I often hear +/- 1 kHz -80 dBc spurs from
FT1000 series rigs and of course the 2.4 kHz -60 dB spur from the Flex 5k
(recently fixed thanks to W5ZN and others' persistence).  

If you look carefully at Figure 2 in ARRL's original K3 product review, you
can see a few suspicious blips which I wanted to clean up.  Unfortunately
using 1 kHz to TX in the K3 caused other problems so I abandoned the idea.  

I'm not aware of any spur reports on the K3 since the VCO stiffener and KPA3
mods were implemented, so I agree there's probably no need now.  

http://www.elecraft.com/manual/ELECRAFT%20KSYN3%20Stiffener%20Mod%20Rev%20D.pdf
http://www.elecraft.com/K3/mods/K3%20Technical%20Alert%201.pdf

For any interested in assuring clean signals you should also consider the
chirp mod (if applicable):

http://www.elecraft.com/K3/mods/KSYN3%20DDS%20Gain%20Modification.pdf

73,  Bill

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