CW roofing filters for the K3

[Joseph Trombino, Jr]

My K3 will be in the 2nd production run so I have some time to make a
decision regarding CW roofing filters for the K3 as well as the 2700hz stock
SSB filter .

Am wondering though if the Elecraft lab has made any measurements in
comparing the performance of the 5 pole  500hz CW filter as opposed to the 8
pole 400hz CW filter.

Believe I read that the DSP will make up for any loss caused by the 8 pole
CW filter.

The Ten Tec Orion had a problem with the optional 500hz roofing filter in
that when that filter was selected an amp was turned on to make up for the
additional loss the filter caused....in turn the IMD performance of the
receiver suffered.  I went to an Inrad filter (believe it is 5 pole) 600hz
filter and plugged it into the 1000hz filter socket to get around this
problem.

My hope is that going to the 8 pole CW filter over the 5 pole CW filter
won't cause a similiar problem in the K3 (I'm betting it won't but I would
sure like to hear more about these filters to aid in my decision on which
one to buy with the rig)

Similiar info regarding replacing the stock 2700hz SSB filter with the 8
pole 2800hz filter would be most appreciated as well.

Since there probably aren't too many K3's out there yet to get feedback on
the above questions I would hope that the Elecraft lab folks could provide
some qualitative information with numbers to allow comparisons to be made.

                                    73, Joe W2KJ
                                    K2 owner and soon to be K3 owner

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[KK7P]

> Believe I read that the DSP will make up for any loss caused by the 8
> pole CW filter.

When installing a crystal roofing filter in the K3, you enter a gain
compensation amount in dB.  The compensation is done by the DSP when
that filter is in use.

73,

Lyle KK7P

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[Joe-aa4nn]

>> Believe I read that the DSP will make up for any loss caused by the 8
>> pole CW filter.
-------------------
> When installing a crystal roofing filter in the K3, you enter a gain
> compensation amount in dB.  The compensation is done by the DSP when
> that filter is in use.
-------------------
Wait a minute.  Does the act of putting in a specific filter tell DSP
what compensation to do OR must we dumb operators try to
guess at what compensation number to enter?  And how would
that number be entered?
de Joe , aa4nn

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[Ed Muns, W0YK]

> >> Believe I read that the DSP will make up for any loss
> caused by the 8
> >> pole CW filter.
> -------------------
> > When installing a crystal roofing filter in the K3, you
> enter a gain
> > compensation amount in dB.  The compensation is done by the
> DSP when
> > that filter is in use.
> -------------------
> Wait a minute.  Does the act of putting in a specific filter
> tell DSP what compensation to do OR must we dumb operators
> try to guess at what compensation number to enter?  And how
> would that number be entered?

This is covered fully in the K3 User Manual, available on the Elecraft web
site.  Refer to the crystal filter configuration section where it gives
detailed instructions for adding a specific gain compensation value for any
individual filter via the CONFIG menu.  No gain compensation is needed
except for the narrow filters, e.g., 400 Hz and 250 Hz.  I use +2 dB and +3
dB respectively on those filters.  I think the manual suggests 2-4 dB in
general for the narrow 8-pole filters.  Just set the compensation so there
is no change in level as you switch through the wide and narrow filters.

73,
Ed - W0YK

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