Fw: Noise Blanker Observations?

[K7TV]

----- Original Message -----
From: "Erik N Basilier" <[hidden email]>
To: "Ignacy" <[hidden email]>
Sent: Friday, March 20, 2009 11:09 AM
Subject: Re: [Elecraft] [K3] Noise Blanker Observations?

>I agree that the K3 NB, like any other Noise Blanker I have used, works
>mostly on impulse noise. Indeed, the general design (at least in most
>radios) is to briefly block reception for the short duration of a noise
>pulse, which means that if the noise power is there constantly it can't be
>blanked out. Adjustments are helpful in matching the blanking duration to
>the width of noise pulses. The K3 seems to provide two dimensions of NB
>adjustment; I don't know what they do, but experimentation is helpful when
>dealing with a particular noise source.
>
> I have a few blocks of older single-family housing north of me,
> essentially a forest of power-line-related noise sources. (I have spent
> much time locating these with a portable AM receiver and working with the
> power company for repairs, but new sources pop up constantly.) Taken
> together, these act more like a continuous source of radiation than as an
> impulse noise source. Using a Noise Blanker helps but only marginally. The
> K3's Noise Reduction is much more effective because it removes noise
> continuously, but you have to experiment with settings and the audio is
> negatively impacted. I have just purchased a BHI audio noise reduction
> module to see if that works any better. I haven't hooked it up yet.
>
> Ignacy, you caught my interest with your comment on the MFJ-1026. Several
> months ago I got an MFJ-1025, which is the same unit minus the short
> antenna on top of the box. (The circuit board inside is the same; it has
> the point of connection for the short antenna, should you want it, and
> apparently also the amplifier for the short antenna. Since most people
> seem to find that a large noise pickup antenna is needed, it makes sense
> not to pay the extra $$ for the 1026 model.) For anyone not familiar with
> this kind of unit, the idea is that you feed your regular receive (or
> RX/TX) antenna though the box to the TRX, and you also feed a separate
> receive antenna to the box. The box matches the two received noise signals
> in amplitude (using two potentiometers on the front panel) and also
> adjusts the phase of the two noise signals for cancellation (using one
> potentiometer and one pushbutton).
> Since the phasing of the noise signal is different for individual noise
> sources, in general only one noise source can be phased out at any given
> time.
> (Alternatively, a single amateur or broadcase signal can also be phased
> out, but less effectively because the constantly changing ionosphere
> affects phase.) Here is my experience with this unit so far. It is not at
> all effective against the power line noise on 20 using my R5 vertical as
> the noise pick-up and my horizontal beam as the main antenna. This makes
> sense with so many individual power noise sources. It was very effective
> against funny noises on particular frequencies, and even on multiple such
> signals. However, most such signals recently went away when we replaced
> the TV set in the living room. My WI-FI access point/router doesn't seem
> to create noise, but I would guess that the MFJ unit may help in cases
> where you have noise from WI-FI. Someone has said that it is better to
> have the same polarization for the noise antenna and the main antenna, and
> I want to try that in the future. Maybe I will find some improvement
> w.r.t. the power line noise, maybe not. The power line noise is much worse
> on 40 than on 20, but I haven't been able to try the MFJ on 40 for lack of
> a noise pickup antenna. I have tried a 10 ft wire, and I have tried the R5
> with a tuner. Neither provides enough noise signal for the MFJ unit to
> work with. My plan is to put up a 40 m dipole under the eaves of the house
> for noise pickup duty. At this point I don't have high hopes that it will
> enable the MFJ to help with the power line noise, though.
>
> 73,
> Erik K7TV
>
> ----- Original Message -----
> From: "Ignacy" <[hidden email]>
> To: <[hidden email]>
> Sent: Friday, March 20, 2009 10:02 AM
> Subject: Re: [Elecraft] [K3] Noise Blanker Observations?
>
>
>>
>>>From time to time I have a very strong powerline or other impulse noise
>>>or
>> noises. K3 sometimes takes care of it sometimes not. I general, I have a
>> feeling that NB is IC-7000 is a bit better although K3 does well with
>> some
>> types of noise that IC7000 cannot bite with the DSP NB.
>>
>> NB takes care of short impulse noises from a single location very well.
>> When
>> the noise is from multiple locations or of a very complex type, NB does
>> not
>> do much. In such a case, a device like MFJ-1026 does wonders; you will
>> need
>> a second antenna.
>>
>> Ignacy
>>
>

... [show rest of quote]

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