[Elecraft] Re: K3 Filter IMD numbers

[Don Wilhelm]

Toby,

I believe you have stumbled onto something that should be carefully 
defined when testing with wide roofing filters when the DSP IF is set to 
the more typical testing bandwidth of 500 Hz.   The K3 has both IF shift 
and narrow passbands available in DSP and they can be effectively used 
together.  Then we hear about the 'narrow filtering with wings' in a 
recent post and that would further complicate matters.

It seems to me that a lot of the DSP setup characteristics must be 
defined for any test to assure test repeatability.  I can envision test 
setups to make the 2 kHz spacing 'numbers' for the wide filters look 
good or bad depending on the rest of the parameters.  That may be why 
the list posted by Eric had 'n/a' for the 2 kHz number for the wide 
filters.  For instance when both signals are within the roofing filter 
bandpass, the results will depend only on the DSP and based on the 
number of bits used in the input DAC, the BDR should be in the vicinity 
of 90 dB, but very different (and better) numbers can be obtained by 
placing one signal inside and the other outside the roofing filter - so 
I conclude that the receiver setup details must be better defined for 
any test using 2 kHz spacing.

73,
Don W3FPR

dj7mgq at muenchen-mail.de wrote:
> Good Morning/Day/Evening/Night,
>
> While the numbers which Eric posted a few days ago are interesting, not to
> mention very good... Congrats! ...I am still wondering about the 2100Hz and
> 1800Hz filter figures and the 2kHz numbers for 2700/2800Hz would also be rather
> interesting, because they would "look deeply into the IF chain".
>
> I suppose we will have to wait for somebody to do some "heavy" testing.
>
> vy 73 de toby
>
>