[Elecraft] [K2] KNB2 vs. electric fence.

[Dale Putnam]

My K2 has a KNB2, that works very well on my electric fence and on my neighbors. I can hear his fence shorting to the steel post, every pulse, mine is rather quiet that way, both are noisy at times to the radio.. until I turn on the NB... works better than any of the other NB that I have. Maybe the effectivness is the settings of the rx? 

--... ...-- Dale - WC7S in Wy


 
> From: brett at livecomputers.com
> To: don at w3fpr.com
> Date: Tue, 7 Jul 2009 21:43:26 -0700
> CC: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] [K2] KNB2 vs. electric fence.
> 
> Are there a set of mods for the KNB1 similar to this? My TS450Sat had a
> very effective noise blanker and the K3 works wonders on the noise at my
> home QTH but the K1 blanker could really use a bit more work. Not sure
> what it needs ATM but it could be fun trying to find it.. 
> 
> ~Brett
> 
> 
> On Wed, 2009-07-08 at 00:17 -0400, Don Wilhelm wrote:
> > Steve,
> > 
> > I suggest that you build the KNB2 first and see if it is effective for 
> > the noise you have to deal with. Normally, the gating level is not the 
> > problem, but the blanking pulse width can be varied (G3ULB mod) to 
> > handle other noise pulses.
> > 
> > The stock KNB2 is quite effective for impulse noise of the automotive 
> > ignition type. Yes, if you have other types of noise sources that you 
> > must deal with, try either (or both) of these mods to see if it helps in 
> > your situation. Similarly, your proposed change for Q3 may make a 
> > difference too, so try it out. There is nothing wrong with a bit of 
> > experimentation. What I am encouraging you to do is build the KNB2 as 
> > "stock" first, and then experiment from there. The actual beta of 
> > several 2N2222As that I have measured is in the range of 100, so your 
> > proposed transistor change may make no difference.
> > 
> > 73,
> > Don W3FPR
> > 
> > NU7B wrote:
> > > Joe:
> > >
> > > I just ordered a KNB2 and looked at DL7MAJ's modification. In looking at the
> > > schematic, it seems like the shortest time constant for the one-shot is
> > > above 10 µs. The DL7 mod noted that Q2 was being loaded by the base of Q3 -
> > > possibly there is a load transient associated with charging C11,12. The
> > > 2222A has a fairly low beta, and Q3 has no RE, so its base current could be
> > > fairly high. Raising the beta seems like it would reduce the loading on Q2.
> > >
> > > I'll measure the beta on what comes with the KNB2. I've got 2n3904 (B=100)
> > > and 2n5089 (B=400), so I may substitute. The 5089 has a lower fT of 50 MHz,
> > > but for a 10µs pulsewidth, it should be fine.
> > >
> > > Steve NU7B
> > > 
> > >
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