[Elecraft] KNB2 - Electric fence QRN

[Allan Duncan]

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