Topband: Coping with Noise

[Tree]

On Mon, Dec 08, 2008 at 11:45:07AM -0600, Charles Bibb wrote:

> A good noise blanker works wonders on this pulsed type noise, making 
> the weak signal readable - that is until a strong US station or 
> stations (pileup) starts up nearby. Then the noise blanker might as 
> well be off. And, the strong station(s) doesn't have to be 
> particularly close - 10khz or more at my QTH. Frequently, while 
> listening in the early morning for weak JA's with the NB on, I can 
> hear multiple CQDX's of keyed wideband noise - my noise floor being 
> pumped by STRONG US stations.

There are two issues here.  If there is a strong signal in the passband
of your "roofing" filter then it can desense your noise blanker and it 
can no longer work on the noise.

However, a second problem is that when your noise blanker does blank, it
actually will modulate those same signals with a sharp edge and make the
signals sound clicky.  I proved this to myself once by using two TS850s
and had the noise blanker active on one outside of the band - and had it
triggering the NB gate in the radio tuned to the strong signals.  I had
a bunch of clicks being generated by the NB rapidly turning on and off
the switch.  You need to have some smoothing done to avoid this problem.

I have recently upgraded to a K3 and one of the features that really make
me love this radio is its ability to deal with this type of noise within
the passband of a narrow roofing filter.  I typically use the 400 hertz 
one and this radio can deal with the electric fences around me just fine.
I believe it can also do a good job on power line noise.  

So - if you know someone who has one - you might see if you can borrow
one and try it with your noise.  

73 Tree N6TR
Boring, OR