[ICOM] Icom 7000 noise blanker

[Frank N. Haas KB4T]

I use an Icom IC-7000 as the principal RFI location tool in my company
truck. The Noise Blanker (NB) will reduce but not usually eliminate strong
power line noise. 

I work for a large electric utility as a power line interference
investigator. In most cases, I can locate an offending pole by driving
around while listening to the interference on the 7000 (7K) in AM mode at
the same frequency at which the customer reports hearing the interference. I
usually leave the NB ON, yes, ON while listening for RFI at lower
frequencies. The NB does a good job of reducing (not eliminating) the
ignition noise of the truck engine while allowing me to clearly hear the
power line interference signal. 

I'm not sure why the NB is more effective on the engine ignition noise than
the power line noise. Perhaps the ignition noise is more periodic than the
power line noise and the NB is able to more easily lock on the engine noise
as a result.

As I get closer to the source, I increase the frequency at which I'm
listening, often going to 144 MHz in AM mode. If I can hear the RFI at 144
MHz, I turn the NB OFF because it is no longer needed and I can more clearly
hear the RFI. With VHF copy, I can usually drive right up to the source, be
it a pole, house, barn, office building...whatever. 

If I can't hear the RFI at VHF frequencies, the 7K is still a great tool to
get very close to the source. I have other handheld tools to effectively
pinpoint the source on foot. 

When not tracking down RFI sources, the 7K serves me well for Mobile CW &
SSB contacts, Shortwave Listening and getting "Smokey" reports on the super
slab. The extraordinary frequency range and infinitely variable selectivity
are a huge benefit on the road in my business.

The only thing I don't like about the NB, and this is true of any recent
Icom HF rig, the level setting is critical to avoiding the spurious junk
that can be produced by the NB. The NB Level setting has to be set to a
point where you get decent NB action but a minimum of spurious junk in the
passband. 

The junk to which I refer is the thumping hash one hear's in the receiver
caused by the noise blanker's action in the presence of strong adjacent
frequency signals. The Icom noise blanker will produce this hash even with
narrow selectivity settings where the adjacent strong signal isn't even in
the passband to which one is listening. 

Generally speaking, I try NOT to use the NB if I can avoid doing so. The
hash produced by the NB can be worse than the interference it's trying to
reduce (not eliminate.) I wonder how expensive the next generation of Icom
HF rig will be when they finally figure out how to make a noise blanker that
doesn't add to the problem and only solves it. 

I would say that the artifiacts produced by the Icom NB in nearly all HF rig
models is Icom's Dirty Little Secret. Fortunately, there are so many pro's
to outweigh this con, that I still like all of the Icom rigs I own. And I
couldn't do my job as efficiently each day without the 7K, flawed NB and
all. 

73, 

Frank N. Haas KB4T
Utility Interference Investigator
Florida

=======================================
Original message:

Date: Fri, 15 Jul 2011 22:14:42 -0000
From: "John Geiger" <aa5jg at fidmail.com>
Subject: [ICOM] Icom 7000 noise blanker
To: "ICOM Reflector" <icom at mailman.qth.net>

How does the Icom 7000 noise blanker do on taking out line noise?

73s John AA5JG