K1 NB Modification

[Mike Morrow-3]

>I remember somewhere on the net reading about some mods to make the
>K1-NB a little bit more aggressive.

I've never come across anything like that in the almost nine years that I've
had my K1.  I've found the KNB1 to be effective on spark-type noise, but
not at all effective on local power line noise.  The NB on my old TS-50S is,
in contrast, very effective on that same power line noise.

The KNB1 has only the OFF, HI, LO noise threshold settings.  Obviously,
the blanking is *least* effective in the HI setting since the noise magnitude
has to exceed a higher value to trigger the noise gate, compared to when
the LO threshold is selected.  The only construction option provided is
changing D2 from the normal 1N4148 to an LED to raise the threshold in HI
to require an even *higher* noise pulse magnitude before the the noise gate
will trigger.

The early KNB1 is identcal to the current KNB1, except that it wasn't
provided with a 0.01 uF cap between U1 pin 1 and pin 8.  Without that
cap, gosh-awful noise is generated on some frequencies in the 20m
band (at least) as the K1 transitions between transmit and receive.
Anyone whose early KNB1 is without this cap should install it.

Of course, that cap has no effect on setting the noise gate trigger threshold.
That's determined only by RP1(9-10), RP2(5-6), and D1 when on LO, plus
D2 when on HI.

BTW, the K1 Quick Reference has for almost a decade now said that the
KNB1 menu selections are OFF, NB1, NB2 instead of the correct OFF, HI, LO.

Mike / KK5F
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[Brett Howard]

hrm...

I could have swore that there was a set of mods that would allow one to
modify the blanking time and what not a bit...  

I'm finding it ineffective in power line noise and would like to try and
make it more so.  However if I end up with the time to do it I'll
probably not have enough time nor repeatable enough condx to test a
whole lot.

~BTH

On Sat, 2009-09-19 at 12:00 -0400, Mike Morrow wrote:

> >I remember somewhere on the net reading about some mods to make the
> >K1-NB a little bit more aggressive.
>
> I've never come across anything like that in the almost nine years that I've
> had my K1.  I've found the KNB1 to be effective on spark-type noise, but
> not at all effective on local power line noise.  The NB on my old TS-50S is,
> in contrast, very effective on that same power line noise.
>
> The KNB1 has only the OFF, HI, LO noise threshold settings.  Obviously,
> the blanking is *least* effective in the HI setting since the noise magnitude
> has to exceed a higher value to trigger the noise gate, compared to when
> the LO threshold is selected.  The only construction option provided is
> changing D2 from the normal 1N4148 to an LED to raise the threshold in HI
> to require an even *higher* noise pulse magnitude before the the noise gate
> will trigger.
>
> The early KNB1 is identcal to the current KNB1, except that it wasn't
> provided with a 0.01 uF cap between U1 pin 1 and pin 8.  Without that
> cap, gosh-awful noise is generated on some frequencies in the 20m
> band (at least) as the K1 transitions between transmit and receive.
> Anyone whose early KNB1 is without this cap should install it.
>
> Of course, that cap has no effect on setting the noise gate trigger threshold.
> That's determined only by RP1(9-10), RP2(5-6), and D1 when on LO, plus
> D2 when on HI.
>
> BTW, the K1 Quick Reference has for almost a decade now said that the
> KNB1 menu selections are OFF, NB1, NB2 instead of the correct OFF, HI, LO.
>
> Mike / KK5F
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

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