[Elecraft] Want to Buy a K3

[Joe Subich, W4TV]

>> The words "would seem" suggests that you have not actually used the
>> 250 Hz filter, or have not used it much. I HAVE used both 250 Hz
>> and 400 Hz 8-pole filters extensively, and I do NOT feel that the
>> 250 Hz filter is too narrow or that it requires "rather critical
>> tuning."

No, I have not used the specific INRAD "250 Hz" filter in the K3.  I
have, however, used 300 - 370 Hz filters in other transceivers, the
Elecraft 200 Hz filter, and operated the K3 with DSP bandwidth set
to 300 Hz +/- and the INRAD 400 Hz filter ... all of which provide a
strong basis for understanding the behavior of cascaded IF/DSP filters
at various bandwidths.

I find that composite bandwidths much below 400 Hz make it difficult
to tune an RTTY signal.  Narrowing the bandwidth to as little as 300
Hz does help with strong adjacent QRM once a signal is tuned but it
is nearly impossible for me to to tune a new signal at that bandwidth.

>> The -6dB bandwidth is roughly 330-350 Hz, so if you use it as K6LL
>> has suggested (that is, tell the K3 it's a 400 Hz filter), it's
>> nearly ideal for crowded band CW and RTTY contesting. If you want
>> to listen wider, simply use the width control.

Using the width control is not a good solution as going wider than
400 Hz with the "250 Hz" (350 nominal) selects the next wider filter
which can result in the loss of IMD and overload protection.  The
400 Hz filter is, in my opinion, a better compromise for CW and RTTY
than the "250 Hz" filter.  If more selectivity is needed for CW,
adding the 200 Hz filter becomes worthwhile for CW only.

73,

    ... Joe, W4TV


On 2/7/2011 3:24 PM, Jim Brown wrote:
> On 2/6/2011 7:28 AM, Joe Subich, W4TV wrote:
>> The 400 Hz INRAD is probably the best compromise.  Wide enough for
>> tuning the band but good skirts/reasonable selectivity.  The 250
>> would seem to require rather critical tuning.
>
> The words "would seem" suggests that you have not actually used the 250
> Hz filter, or have not used it much. I HAVE used both 250 Hz and 400 Hz
> 8-pole filters extensively, and I do NOT feel that the 250 Hz filter is
> too narrow or that it requires "rather critical tuning." The -6dB
> bandwidth is roughly 330-350 Hz, so if you use it as K6LL has suggested
> (that is, tell the K3 it's a 400 Hz filter), it's nearly ideal for
> crowded band CW and RTTY contesting. If you want to listen wider, simply
> use the width control.
>
>> I find the 1.5 KHz filter to be too tight (I have a couple).  It
>> requires too much adjustment to be useful, particularly in the
>> "heat of "battle."  The overall difference between 1500 and 1800
>> in the IF doesn't mean much when using a more narrow DSP setting
>> but it is significant in ease of use when tuning.
>
> I haven't used the 1.5 kHz filter, but I use the 1.8 kHz filter
> virtually all the time for SSB contesting.  I find it rather tweaky to
> tune "just right," and I definitely would NOT want anything narrower for
> SSB.  I tell the K3 that it is a 2 kHz filter.
>
> 73, Jim K9YC
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