2.3kHz KSB2 feedback

[John Rader]

I recently built a KSB2 with the now standard 2.3Khz filter configuration. I
have been recieving compliments on the TX audio quality. Some have said the
SSB audio is the best they have heard from a K2. The filter sweeps on
Sectrogram show less ripple and more symmetry then my previous 2.5kHz KSB2.
John K5XTX

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[Don Wilhelm-2]

Folks,

I didn't know that the 2.2 (or 2.3) kHz SSB filter had become the
'standard', but it does get my vote.  I have long advocated the KI6WX 2.2
kHz filter bandwidth as my choice for a great compromise between 'punch' for
QRP operation and good SSB fidelity.  It does offer a flatter passband than
the original 2.0 kHz SSB filter.  To my mind, the 2.5 kHz bandwidth is a bit
too wide, but many folks favor it for the increase in fidelity.

I do recall there was a time when the Collins 1.8 kHz  mechanical filter was
considered the ultimate for communications effectiveness - at least in the
receive part of things - my how times and values have changed!!!

73,
Don W3FPR

----- Original Message -----

> I recently built a KSB2 with the now standard 2.3Khz filter configuration.
I
> have been recieving compliments on the TX audio quality. Some have said
the
> SSB audio is the best they have heard from a K2. The filter sweeps on
> Sectrogram show less ripple and more symmetry then my previous 2.5kHz
KSB2.
> John K5XTX
>


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[G3VVT]

In the original build of my K2 #4168 decided that a greater SSB bandwidth  
filter in the KSB2 SSB option than the normal 2.0kHz was needed. John,  KI6WX
recommended to go for 2.2kHz, so that was done.
 
Sourced the extra capacitors needed in the UK and used 2.5mm lead  spacing cer
amic plate 2% tolerance capacitors. 10 capacitors are  required, 2 x 27pF and
6 x 39pF. The 2 x 100pF can be  recovered from the original KSB2 kit.
 
The response when checked with Spectrogram was pretty flat with  minimal
ripple compared to the original K2 filter. The bandwidth came out in my  case with
the components used at certainly greater than 2.2kHz, though less than  
2.4kHz, so this is where the 2.3kHz figure may be accurate for some  builders.
 
Perhaps other K2 builders could comment on their results?
 
I did a comparison against my main station receiver the JRC NRD-515  which
has a nominal 2.4kHz bandwidth, Kokusai 455kHz mechanical filter. The  results
of the two receivers were very comparable in the Spectrogram traces with  the
NRD-515 coming out as slightly wider than the modified K2. This puts  the K2 in
good light as I would rate the NRD-515 against most receivers on the  market
despite it now being manufactured 23 years back.
 
For the K2 owners that use SSB TX, I find good results with an Altec  Lansing
AHS-201 computer headset when used with the K2. This is a cheap PC  headset
with a noise cancelling electret boom microphone and a single earpiece  
probably costing about $10 in the USA. The operating voltage for the microphone  can
be supplied by the K2 or as mine was originally for a handsfree mobile use  
with another radio, a single AA 1.5V cell provides the necessary power. A PTT  
switch can be added as a footswitch or as in my case with the small plastic  
battery box.
 
Seems to work very well and particularly works with my voice on SSB. Took  30
years trying different microphones on SSB before I hit the jackpot with  
electret microphones. The North American voice is much more suited to SSB it  
would seem that the European one for use with standard microphones.
 
Bob, G3VVT
K2 #4168
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[John, KI6WX]

The new standard version of the KSB2 filter is the same as my 2.2 kHz
design.  Elecraft measures the bandwidth to the 6 dB points, so they quote
the bandwidth as 2.3 kHz.  If you want to use my 2.5 kHz bandwidth design,
you now only have to change 4 capacitor values.
-John
 KI6WX

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>


> Folks,
>
> I didn't know that the 2.2 (or 2.3) kHz SSB filter had become the
> 'standard', but it does get my vote.  I have long advocated the KI6WX 2.2
> kHz filter bandwidth as my choice for a great compromise between 'punch'
for
> QRP operation and good SSB fidelity.  It does offer a flatter passband
than
> the original 2.0 kHz SSB filter.  To my mind, the 2.5 kHz bandwidth is a
bit
> too wide, but many folks favor it for the increase in fidelity.
>
> I do recall there was a time when the Collins 1.8 kHz  mechanical filter
was
> considered the ultimate for communications effectiveness - at least in the
> receive part of things - my how times and values have changed!!!
>
> 73,
> Don W3FPR
>
> ----- Original Message -----
>
> > I recently built a KSB2 with the now standard 2.3Khz filter
configuration.
> I
> > have been recieving compliments on the TX audio quality. Some have said
> the
> > SSB audio is the best they have heard from a K2. The filter sweeps on
> > Sectrogram show less ripple and more symmetry then my previous 2.5kHz
> KSB2.
> > John K5XTX
> >


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