[Elecraft] Variable bandwidth crystal filter

[HowardZ]

It appears that the only way the K3 achieves its high test scores in dynamic
range is when the noise is outside the roofing filter's bandwidth.  Only the
roofing filter yields this high performance.

For example, if your roofing filter is 2.8Khz, but you hear an unwanted
nearby signal, and you use DSP to narrow it to 2.0khz, the reduction of the
unwanted signal will not be as great as if you switched to your 2.0khz
roofing filter (which you had not purchased yet).  This is because the
offending signal is within the roofing filter's 2.8khz bandwidth.

Thus following this example, the Flex 5000 has the same dynamic range
regardless of the DSP filter bandwith khz, and will outperform the K3 when
the offending signal is within its DSP bandwidth.  So with the Flex, you'll
have 96db of dynamic range regardless of the DSP bandwidth selected.  But
with the K3, such high dynamic range is only achieved when the offending
signal is being blocked by a roofing filter.

(When the offending signal is 20khz, 50khz, etc away - the K3's dynamic
range will be superior to the Flex, since the Flex is always 96db regardless
of how far away the offending signal is.)

Loading up the radio (and second receiver) with roofing filters makes the
expensive K3 radio even more expensive.

Thus the interest in the "variable bandwidth crystal" roofing filter as a
major money saver - if it ever comes to fuition.

Howard



Chuck Guenther wrote:
> 
> J.R. Groeger wrote:
> 
> "I seem to remember talk some time ago about a variable bandwidth 
> crystal filter becoming available for the K3 at some stage. Anyone know 
> the status of its development?"
> 
>  With the upoming 10 Hz resolution DSP upgrade (Firmware 3.23 being 
> talked about), I certainly wouldn't see much need for a variable BW 
> roofing filter.
> 
> 73,
> Chuck  NI0C
> K2, K3
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> 
> 

-- 
View this message in context: http://n2.nabble.com/Variable-bandwidth-crystal-filter-tp3394075p3400928.html
Sent from the Elecraft mailing list archive at Nabble.com.