KNB2 - Electric fence QRN

[Allan Duncan-4]

Hi to all on list,

Last weekend I went to a nice QTH out in the country, which belongs to a
friend, for the RSGB 80M AFS CW contest, here in the UK.

I had intended to use my K2 in the contest but S9+20db QRN from a
neighbouring farmer's electric fence put and end to that hope. Using the
KNB2's NB1 and NB2 and both Hi and Lo threshold had a negligible effect.

I don't have a KDSP2 or a KAF2 fitted but I suspect they would not have been
a good solution anyway, as the RX AGC was being badly affected by the very
loud QRN.

Thankfully, my faithful Kenwood TS940S noise blanker killed the noise
completely using either its NB1 or NB2 irrespective of the NB level control
setting. I used the TS940S throughout the contest although I missed the K2's
superior RX strong signal performance.

I see that on the LA3ZA modification pages there are some capacitor changes
that change the time constants in the KNB2. Unfortunately the links to the
mods themselves seem to be broken.

My questions to the list are, will changing C11 and C12 (value unknown)
likely to help with the electric fence QRN and, if so, will this compromise
the KNB2 with other types of noise? Has anyone else performed some other
modification which may help with this type of QRN?

Any help would be much appreciated.

73

Allan
GM4ZUK

K2 S.No. 4946


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[Don Wilhelm-3]

Allan,

C11 controls the width of the NB1 gate and C12 changes the width of the NB2
gate.  You may want to experiment with the values to find what will work
with your particular noise.  I can't say if you will find any improvement.

The best help would be to ask permission from your neighbor to trim the
vegetation that is touching the electric fence wire, or better yet, have him
volunteer to do that (or he may have a faulty insulator).  If you convince
him it will increase the effectiveness of his electric fence, perhaps he
will be quite cooperative.

73,
Don W3FPR

> -----Original Message-----
>
> I see that on the LA3ZA modification pages there are some
> capacitor changes
> that change the time constants in the KNB2. Unfortunately the links to the
> mods themselves seem to be broken.
>
> My questions to the list are, will changing C11 and C12 (value unknown)
> likely to help with the electric fence QRN and, if so, will this
> compromise
> the KNB2 with other types of noise? Has anyone else performed some other
> modification which may help with this type of QRN?
>
> Any help would be much appreciated.
>
> 73
>
> Allan
> GM4ZUK
>

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[Deni F5VJC]

Allan Duncan wrote:

>
> I see that on the LA3ZA modification pages there are some capacitor changes
> that change the time constants in the KNB2. Unfortunately the links to the
> mods themselves seem to be broken.
>
> My questions to the list are, will changing C11 and C12 (value unknown)
> likely to help with the electric fence QRN and, if so, will this compromise
> the KNB2 with other types of noise? Has anyone else performed some other
> modification which may help with this type of QRN?
>
> Any help would be much appreciated.
>
> 73
>
> Allan
> GM4ZUK
>
> K2 S.No. 4946
>  

Yes Allan the mod does help in this respect, I found when I moved to a
nice quiet location in France, I was also plagued by QRM from a local,
badly installed and maintained electric fence. However my modified noise
blanker certainly helps, but doesn't completely cure my problem,  it
seems to vary from day to day and with wet weather of course. The mod
certainly makes a difference to this type of qrm and is worth doing.

73, Deni

F5VJC K21188

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