[Elecraft] 250 Hz and 400 Hz Filter Measurements

[Dick Dievendorff]

RF Gain calibration has separate calibrations for main and sub. It's a DSP computation, and the K3 Utility has code that invokes these DSP computations in main and then sub  The wizard has more pages if you have a sub installed

Dick, K6KR


Sent from my iPhone

On Jul 16, 2010, at 1:07 PM, "Joe Subich, W4TV" <lists at subich.com> wrote:

> 
> Jim,
> 
>> There's something different about the K3 Sub-RX, and the Roofing
>> filters seem to fall apart below about -25dB. Makes a guy wonder
>> what's going on!
> 
> I would bet the subreceiver has excess gain in the IF and you're
> seeing amplified IF noise (particularly since the bandwidth is
> about 1 KHz).  I don't see any way for the K3 Utility to calibrate
> main/receiver gain separately (Dick?) but I'd suggest checking the
> gain calibration of the subreceiver or measuring all of the filters
> only in the main receiver.
> 
> 73,
> 
>    ... Joe, W4TV
> 
> On 7/16/2010 3:28 PM, Jim Brown wrote:
>> On Fri, 16 Jul 2010 14:38:24 -0400, Guy Olinger K2AV wrote:
>> 
>>> Each to his own, just don't start a ban the 250 campaign.
>> 
>> Both you and Ed raise good points. No intent there -- I agree that
>> the so-called 250 Hz filter is slightly more useful than the 400
>> Hz. My real objective is to get Inrad to clean up their act!  BUT
>> -- take a look at the data in this link. Lots of food for thought.
>> There's something different about the K3 Sub-RX, and the Roofing
>> filters seem to fall apart below about -25dB. Makes a guy wonder
>> what's going on!
>> 
>> http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf
>> 
>> 73, Jim K9YC
>> 
> 
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