[Elecraft] Tight Skirts...

[Eric Swartz WA6HHQ - Elecraft]

Hi Larry,

OP1 is the KSB2's SSB fixed b/w filter, which has been optimized for 
minimum ripple at one SSB b/w. In SSB it is always used for transmit, 
but it or any of the CW filter bandwidths can be used for receive. Looks 
like you are using one of the CW settings at 1800 Hz..

Any of the variable CW filter settings (1800 Hz etc.) use the varactor 
tuned CW filter on the motherboard. This variable CW filter is really 
optimized for user settings below 700 Hz. (You can chose what b/w to use 
in each of the four filter memories for each mode..) Wider CW filter 
settings will have more ripple and poorer out of filter rejection. We 
allowed the variable CW filter to be set wider to facilitate quickly 
tuning the band in CW mode and for simple SSB reception in K2s that do 
not have the SSB adapter. We recommend using the OP1 filter for most SSB 
reception.

One interesting side note: The SSB OP1 filter can be used with different 
BFO settings in each of the four SSB filter memory settings, creating 
low and high cut settings. See the filter calibration section of the K2 
and KSB2 manuals for information on setting up the filters.

73, Eric  WA6HHQ
-------------

Larry Phipps wrote:
> 
> You may have just sold me on a KDSP2 down the road Eric. I just ran some 
> tests on my "new used" K2 (#568), and to cut to the chase... I measured 
> ultimate rejection out 5 kHz as 80dB with the KSB2 OP1 filter in, better 
> than you indicated. But with FL2, which is set for 1.8 kHz, I measured 
> 115dB. Is this a result of the KSB2 being outboard?
> 
> Larry N8LP
> 
> 
> 
> Eric Swartz - WA6HHQ, Elecraft wrote:
> 
>> We designed the KDSP2 to improve ultimate SSB filter ultimate 
>> rejection in the K2.
>>
>> The KDSP2, with its brick wall SSB filter settings, when cascaded 
>> after the KSB2 filter, totally eliminates any residual leakage from 
>> strong signals outside the passband.