Posted by
wayne burdick on
May 05, 2007; 5:31pm
URL: http://elecraft.85.s1.nabble.com/Re-filter-selection-tp446972p446973.html
Bill Tippett wrote:
> My point is that you introduce unnecessary complexity with the vast
> number of roofing filters. 400 vs 500, 250 vs 200, etc.
We're providing a range of options so the customer can decide which
they want. We may add supplemental information to the order form to
make decisions easier, but we're not likely to reduce the number of
filters offered.
> As one example here are Elecraft's own specs for the 400 8-pole versus
> 250 8-pole:
>
> Filter 6 dB BW 60 dB BW
>
> KFL3-400K 435 Hz 935 Hz
> KFL3-250K 370 Hz 785 Hz
The reason we offer both of these INRAD filters is that they're both,
historically speaking, very popular. I agree that the frequency spacing
of these filters could be clarified in their literature, but again, we
offer them because our customers asked for them, and we're passing
along the model numbers used by INRAD.
We offer our own narrow filter (200 Hz) for those who really want to
maximize rejection of unwanted signals in CW and data modes. Such
narrow bandwidths have been very popular over the years, including in
the K2.
> In my opinion these filters are redundant and unnecessarily complicate
> the ordering process. 65 Hz difference in 6 dB BW is hardly worth
> bothering with, especially since both are 8-pole and their IMD/BDR
> performance is likely to be identical.
As I explained above, this is a somewhat anomalous historical
situation. If INRAD would like to create alternative filters with
different specs, we're open to offering them.
> It's your decision of course but I'm a believer in "keep it simple".
> I would offer only the best filter for a given BW, predetermined by
> Elecraft and based upon actual IMD/BDR measurements inside the K3.
Eventually we'll have such measurements. For now, we're not about to
limit anyone's personal choice.
We'll also provide great leeway in letting customers change their order
if new information causes them to rethink their filter complement.
73,
Wayne
N6KR
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