Question on Purchase of K2

[frank-142]

I'm getting close to order a K2 but I have a few questions.    
The K2 would be for CW operation only.  
Like many others, I prefer to tune the band using wide bandpass of
over 2khz and only use narrow CW filter operation when band
conditions require it.  My understanding is that if you equip the K2
with the SSB module, that you can use the SSB filter on CW and that
works better than operating the CW filter on wide setting. Is that
true?  If so it would be worth the extra cost of the ssb option.

I have decided not to order the DSP filter but perhaps the passive
audio filter.   The passive audio filter appears to be set up for
80hz bandwidth which is way too narrow for my liking.    Is there
any easy way to change that for 250hz bandwidth?   If not I'll have
to go with an outboard audio filter.  

 


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[wayne burdick]

On Feb 21, 2005, at 11:39 PM, frank wrote:

> I'm getting close to order a K2 but I have a few questions.
> The K2 would be for CW operation only.
> Like many others, I prefer to tune the band using wide bandpass of
> over 2khz and only use narrow CW filter operation when band
> conditions require it.  My understanding is that if you equip the K2
> with the SSB module, that you can use the SSB filter on CW and that
> works better than operating the CW filter on wide setting. Is that
> true?  If so it would be worth the extra cost of the ssb option.
>
> I have decided not to order the DSP filter but perhaps the passive
> audio filter.   The passive audio filter appears to be set up for
> 80hz bandwidth which is way too narrow for my liking.    Is there
> any easy way to change that for 250hz bandwidth?   If not I'll have
> to go with an outboard audio filter.
>

Hi Frank,

The SSB filter is much more pleasant to use than the CW filter set for
a wide bandwidth. The SSB filter has a flat passband, whereas the CW
filter, being varactor controlled, develops a lot of ripple by the time
you widen it out. We experimented with variations on the filter
topology before releasing the K2 to production, but it was getting too
complex.

A 2 kHz filter is especially useful on quiet bands or if you're working
a contest where you may get called up/down significantly from your
carrier frequency. I use it much of the time. And heck, you might just
want to listen to AM or SSB sometime :)

As for the audio filter: you can change the components in the op-amp
circuit to make it more like 250 Hz if you prefer. But the time when
the 80 Hz filter is really useful is when you're trying to pick a weak
one out of atmospheric noise and/or nearby QRM. Most of the time you'll
probably just leave the audio filter in its OFF position. But that
still keeps in-circuit the KAF2's passive (L-C) low-pass filter, which
removes the small amount of residual hiss from the product detector. It
also improves roll-off of high-pitched QRM, and thus enhances the
ultimate rejection of the I.F. filters. It's very effective for those
who sometimes use headphones with the rig.

The DSP filter is quite flexible, and adds stochastic noise reduction
as well as notch filtering. But if you don't live in a very noisy area
or use SSB, you may find the KAF2 just as useful (and at lower cost).

I hope you enjoy using the rig if you do decide to buy one. Eric and I
are both serious CW ops, and we designed the rig from the ground up to
be a great home/portable CW rig. (Keying is state-of-the art with the
latest circuit changes, too.)

As the principle designer of the K2, I'd be happy to answer any further
technical questions.

73,
Wayne Burdick
N6KR


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[KK7P]

> I'm getting close to order a K2 but I have a few
>questions.    
> The K2 would be for CW operation only.  
>...
> I have decided not to order the DSP filter but perhaps
>the passive
> audio filter.   The passive audio filter appears to be
>set up for
> 80hz bandwidth which is way too narrow for my liking.
>   Is there
> any easy way to change that for 250hz bandwidth?

One of the neat things the DSP can do is if you run the
radio with the widest filter (CW filter set at its widest
is OK since you aren't concerned much with passband
ripple) and set the DSP to denoiser, then the radio is
generally quiet.  When a signal appears in the passband,
the DSP passes it, still suppressing most of the band
noise.

If the band gets crowded, you can tighten both the IF
filter (a great feasture of the K2) as well as the DSP
filter.  Set them both to 250 Hz if that is your prefered
bandwidth...

Enjoy!

Lyle KK7P/VK6
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[Steven Pituch]

Hi Frank,
I have an early unmodified K2 #402 and it is gangbusters on 5W CW with one
of the unmodifieed early KSB2s.  I would not change a thing on mine as the
performance is so good, but with the filter improvements on the newer KSB2s
I think you should just get the K2 and the KSB2 as far as filtering goes.
Forget the audio filter for now, and maybe consider the DSP far into the
future.

I do have the KAT2 and its is wonderful.

Using the K2/KSB2/KAT2 with a 40 meter dipole about 12 feet average off of
ground and a manual tuner I have gotten 29 out of 32 Foxes this season in
the Foxhunts.  Most of the contacts were 329-229, something I could not have
managed with other (some expensive) radios I have used.  What I do is tune
the antenna with the MFJ tuner until it is close and then use the KAT2 for
perfect SWR.  I should probably try the KAT2 alone as this may work even
better.

Regards,
Steve, W2MY/5
http://users.ev1.net/~spituch/, Corpus Christi, TX, ELl7
QRP/ARCI 8351, FPQRP 1025, NJQRP 25, QRP-L 269, FISTS 3150, ARS 142, NEQRP
281, NWQRP ??, 10-10 61720, NORCAL 691, K2 #402


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[James1787]

I prefer to use my K2 on CW only as well. I bought the SSB Module in case I would like to try other digital modes such as RTTY or PSK. I haven't heard the K2 without the SSB module so I'm not sure how to compare the filters, but the filters with the SSB module do sound nice and I've never had a complaint.
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[Dave Lowenstein]

Is the K2 unsuitable for listening to SSB if the KSB2 isn't installed?

73,
Dave
N7AF

> The SSB filter is much more pleasant to use than the CW filter set for
> a wide bandwidth. The SSB filter has a flat passband, whereas the CW
> filter, being varactor controlled, develops a lot of ripple by the time
> you widen it out. We experimented with variations on the filter
> topology before releasing the K2 to production, but it was getting too
> complex.

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[Don Wilhelm-3]

Dave,

The variable filter is not completely unsuitable for SSB listening, it just
has a high passband ripple which can become tiring after a time to some
people's ears.  I use the variable filter as a narrow SSB receive filter to
combat high pitched QRM (1.8, 1.7 or 1.6 kHz widths), but it does OK out to
about 2.2 or 2.3 kHz.  The passband is relatively flat up to about 1.2 kHz
and above that the ripple becomes progressively greater as the width is
increased.

73,
Don W3FPR

> -----Original Message-----
>
> Is the K2 unsuitable for listening to SSB if the KSB2 isn't installed?
>
> 73,
> Dave
> N7AF
>
> > The SSB filter is much more pleasant to use than the CW filter set for
> > a wide bandwidth. The SSB filter has a flat passband, whereas the CW
> > filter, being varactor controlled, develops a lot of ripple by the time
> > you widen it out. We experimented with variations on the filter
> > topology before releasing the K2 to production, but it was getting too
> > complex.
>
>

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[Dave Lowenstein]

Thanks for the replies Don, David, & Philipe.  Sounds like it ought to work.
I'm a CW man on the verge of ordering a K2 but like to just listen to SSB
while I'm puttering around the shack.

73,
Dave
N7AF

----- Original Message -----
From: "W3FPR - Don Wilhelm" <[hidden email]>
To: "Dave Lowenstein" <[hidden email]>; <[hidden email]>
Sent: Tuesday, February 22, 2005 10:12 AM
Subject: RE: [Elecraft] Listening to SSB on K2 without KSB2


> Dave,
>
> The variable filter is not completely unsuitable for SSB listening, it
just
> has a high passband ripple which can become tiring after a time to some
> people's ears.  I use the variable filter as a narrow SSB receive filter
to
> combat high pitched QRM (1.8, 1.7 or 1.6 kHz widths), but it does OK out
to

> about 2.2 or 2.3 kHz.  The passband is relatively flat up to about 1.2 kHz
> and above that the ripple becomes progressively greater as the width is
> increased.
>
> 73,
> Don W3FPR
>
> > -----Original Message-----
> >
> > Is the K2 unsuitable for listening to SSB if the KSB2 isn't installed?
> >
> > 73,
> > Dave
> > N7AF
> >
> > > The SSB filter is much more pleasant to use than the CW filter set for
> > > a wide bandwidth. The SSB filter has a flat passband, whereas the CW
> > > filter, being varactor controlled, develops a lot of ripple by the

time
> > > you widen it out. We experimented with variations on the filter
> > > topology before releasing the K2 to production, but it was getting too
> > > complex.
> >
> >
>
>

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[Bill Coleman-2]

On Feb 22, 2005, at 11:41 AM, Dave Lowenstein wrote:

> Is the K2 unsuitable for listening to SSB if the KSB2 isn't installed?

No, but it ain't pretty....

SSB sounds a little funky through the wide CW filter. And each sideband
sounds different.

Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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[k6dgw]

And then there are those of us who gave much of our hearing away many
years ago and now can't tell the difference between my stock CW K2 on
SSB and a really tricked out K2 with all the bells.  In a low noise, no
QRM, strong signal environment, my K2 sounds great on SSB. In a noisy,
QRM'ed, weak signal environment, I can't understand SSB on ANY
receiver.  I think it's all in the ears of the behearer.

Fred K6DGW
Auburn CA CM98lw

W3FPR - Don Wilhelm wrote:

>
> Dave,
>
> The variable filter is not completely unsuitable for SSB listening, it just
> has a high passband ripple which can become tiring after a time to some
> people's ears.  I use the variable filter as a narrow SSB receive filter to
> combat high pitched QRM (1.8, 1.7 or 1.6 kHz widths), but it does OK out to
> about 2.2 or 2.3 kHz.  The passband is relatively flat up to about 1.2 kHz
> and above that the ripple becomes progressively greater as the width is
> increased.
>
> 73,
> Don W3FPR
>

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