[Elecraft] [K3] Perfect for Field Day S&P ... Limited Production 700 Hz 8-Pole Filters

[Joe Subich, W4TV]

Fred,

In general you are correct.  However, there is one other effect that
the narrow roofing filters are not going to resolve - garbage from
your neighbors in the form of key clicks, transmitted phase noise and
IMD.  I see it every time my neighbor (.66 mi) comes on a band with
his Icom POS ... phase noise an clicks +/- 20 KHz.  The K3 handles his
fundamental just fine as little as 500 Hz away but the phase noise and
clicks make any band almost unusable.

73,

    ... Joe, W4TV


On 3/1/2014 7:59 PM, Fred Jensen wrote:
> If you can, help me out here Don ...
>
> These are roofing filters.  From my perspective, which is likely wrong,
> their job is to restrict the bandwidth presented to the 2nd mixer [and
> downstream ADC].  They are of most value when you have very strong [i.e.
> geographically close] signals adjacent to the desired signal [That would
> be WX6V for me :-)].  The ultimate BW is set by the DSP of course, but a
> really strong adjacent signal can begin to activate the HW AGC in the K3
> which affects the signal inside your DSP BW, or I think that's true. So,
> it follows to me that, if you are plagued by KW neighbors, narrower
> roofing filters can reduce that problem.  This could be true on FD or
> any other closely spaced HF operations ... IF you have two stations on
> the same band/mode.
>
> If you are not so plagued, I can't figure out why it really matters.  I
> have the filter that came with the K3 and I bought one [2.7 and .5, I
> don't remember which was which], I've had no difficulties.  Jim [WX6V]
> and Jack KF6T [equally close] became non-problems when I got my K3 ...
> even more so now that Jim has a K3 and phase-noise has disappeared. :-)
>
> I've got to be missing something here, and sadly, it wouldn't be even
> close to the first time.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 2014 Cal QSO Party 4-5 Oct 2014
> - www.cqp.org
>
>
> On 3/1/2014 4:03 PM, Don Wilhelm wrote:
>> Eric has permitted such announcements, but limits them to one a month.
>> You will see offers to build a K2 that come in that same category.
>>
>> Personal comment -- I particularly like the 700 Hz CW filter in my K3. I
>> got used to tuning the bands using a 700 Hz filter width in my K2, and
>> opted for the 700 Hz roofing filter when it was offered. Yes, I find it
>> nice for 'scouring the pileup' before switching to the narrower 400 Hz
>> filter when listening to a pileup.  YMMV, but it is an available option.
>
>
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