filter offsets question

[David F. Reed-2]

I am confusing myself, so I thought I'd ask this helpful forum for some
advice and help.

I note the filter settings in the K3 Utility; I further note that for
most of my filters, the offset is 0.00 but for the 2.7 KHz filter it is
-0.85.

So why is it that, and no offset for the 2.1 KHz filter or the 250 Hz
filter?

Just hoping to better understand my rig...

Thanks and 73 de Dave, W5SV
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Bruce Beford-2]

The 5-pole filters require an offset value, the 8-pole filters are
(nominally) a zero offset.
73,
Bruce, N1RX

> I note the filter settings in the K3 Utility; I further note that for
> most of my filters, the offset is 0.00 but for the 2.7 KHz filter it is
> -0.85.

> So why is it that, and no offset for the 2.1 KHz filter or the 250 Hz
> filter?



______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[David F. Reed-2]

Ron (& Bruce, who also replied),

thanks so much for an understandable explanation.

73 de Dave, W5SV

On 2/19/12 5:46 PM, Ron D'Eau Claire wrote:

> David, there are both 5 pole and 8 pole filters available from Elecraft. The
> 8-pole filters have a somewhat flatter passband and steeper skirts than the
> 5-poles. (These are crystal filters and the "poles" refer to the crystal
> poles in each filter - more poles means better filtering but more complex
> matching of the crystal elements required for correct performance, hence
> greater cost).
>
> Because the specs on the 5-pole filters are a little looser their exact
> center frequency may shift slightly. The "offset" is a value entered to
> center up a 5-pole filter on the K3's intermediate frequency. The 8-pole
> filters are extremely consistent and need no offset correction.
>
> The "standard" 2.7 kHz filter is a 5-pole filter, hence a correction value
> is provided. The 2.1 KHz and 250 Hz filters are both 8-pole types and the
> "correction" is zero.
>
> 73,
>
> Ron AC7AC

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html