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Author Topic: Rigs with good noise blankers  (Read 3663 times)
W8JX
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Posts: 6045




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« Reply #15 on: March 13, 2013, 08:51:20 AM »

The NB button on my Kenwood TS-570 does nothing at all. It is the exactly the same with it on or off. That is my only complaint with my 14 year old 570.
Jim. 73. W5JJG

It is only effective against certain type of noise pulse. Try the NR1 as it has 10 levels. The 480 has excellent noise reduction/blankers. It has a DNL, a NB  and two NR's and all are adjustable and DNL and NB can be used with NR1 or NR2.
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All posted wireless using Win 8.1 RT, a Android tablet using 4G/LTE/WiFi or Sprint Note 3.
W1JKA
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Posts: 1765




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« Reply #16 on: March 13, 2013, 08:51:33 AM »

Re; AF5CC  Reply #11

Yes, and as others have said the parameters are adjustable and results are dependent on any particular EMF or other electrical noise issues at your QTH.Definitely rugged with moisture resistant membrane behind all panel controls.Nice mid priced all round rig with simple no hassle menus and operation.
« Last Edit: March 13, 2013, 09:00:28 AM by W1JKA » Logged
WB2WIK
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« Reply #17 on: March 13, 2013, 09:23:43 AM »

I'd always spend the time and effort to find the noise source and see if I can kill it at the source.

Of course, nowadays it's very possible for there to be numerous noise sources.  Anything with electronics in it can be a noise source.

If it peaks on 17m, that may be because your antenna works best on 17m.  Although there are exceptions, most noise sources are at lower frequencies but generate a lot of harmonics so by the time you get up to HF or above, they appear to be just broadband sources.  Sometimes, they're periodic in nature which can make them easier to pin down.

Blankers can be helpful, but not nearly as nice as eliminating the source -- and eliminating the source might be cheaper!
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AD4U
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« Reply #18 on: March 13, 2013, 09:50:41 AM »

Since I am a boat anchor ham I cannot comment on the newest DSP based noise blankers.  However the older and most effective noise blankers actually "blank" the entire receiver (including the desired signal) for the duration of the noise pulse(s).  On the other hand noise limiters "clip" the noise peaks instead of blanking the receiver.  IMO they are about as useless as a screen door on a submarine.  

If you have lots of noise pulses, your receiver will be blanked a lot which will reduce the intelligibility of the desired signal as well as creating distortion and introducing phantom signals within the receiver passband.  It is a trade off.

As posted by many, by far the best approach is to identify and reduce or eliminate the noise source(s).  Maybe one day there will be a smart noise blanker that can distinguish between noise and the desired signal.  But I don't think that day has arrived.  Today there is no free lunch.

Dick  AD4U
« Last Edit: March 13, 2013, 10:23:13 AM by AD4U » Logged
K1TWH
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Posts: 103




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« Reply #19 on: March 22, 2013, 12:45:40 PM »

__If you cannot find the noise source, I'd vote IC-7000, then IC-7200.  Of the radio's I've used, these two were able to address a large number of differing noises while impacting the desired signal as little as possible.  Being able to configure both noise amplitude and blanking width seems to help.  The IC-7000 has a wider "roofing" filter which would allow the DSP a better view of pulse noise as it has not been stretched by a 'narrow' filter.   Of course a wider filter also means strong signals within +/- 10 to 15KHz may impact your reception, but I don't see this all that often on my IC-7000.
__If there is one primary noise source , a noise phasing device like the ANC-4 or MFJ-1026 can be very helpful, but if you are plagued by many sources this is a dead end street.
Best wishes on less QRM,    Tom WB1FPA
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K6AER
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« Reply #20 on: March 25, 2013, 08:54:12 AM »

Some folks have problems with noise blankers and don’t realize that not all noise sources are removable. Pulse noise is relative easy to remove with the new DSP functions in the radio. This is because the noise source has a signature that repeats itself and has a relative long interim of audio between the narrow pulse width.  White Gaussian noise has no signature and is very broad in band width. AS a result it seems that the high frequency is reduced and add little to the recovered audio.

If your noise is from a specific source you can use RF interference noise cancellation but it requires sampling the RF source in some way. This is phase/amplitude inversion and can reduce the noise up to 30 dB. It is frequency sensitive and will have to be adjusted for each frequency.

Getting your antenna as high and far as possible from the noise source is also helpful. In addition using an antenna with a pattern null in the direction of the noise location will also reduce the noise level.
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N6AJR
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« Reply #21 on: March 25, 2013, 12:22:55 PM »

ten tec does well, and on the lower bands a magnetic loop is great for rx.  (Like the pixel technologies loop) also see if you can locate and fix the noise.
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WB9YCJ
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« Reply #22 on: March 27, 2013, 06:58:02 PM »

VERY IMPRESSIVE IC-7700 Noise Blanker ......

http://www.youtube.com/watch?v=KnBkr_Io3KE


Dont cry, see if this NB is offered in lower priced Icoms.
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AF5CC
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« Reply #23 on: March 28, 2013, 11:44:30 AM »

That is impressive. Wonder if the same NB is in the Icom 7200, I hear it is supposed to have a good noise blanker as well.

John AF5CC
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K6AER
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« Reply #24 on: March 28, 2013, 01:15:10 PM »

I just thought of another thing to realize about noise blanker operation in many older and newer radios.

Older radio mostly have only a single level of noise blanker operation and when applied, like a hammer, can provide as much artifact as the noise they are removing.

New blanker circuits can also adjust the timing, width and depth of the blanking signal. When combined with a good DSP system they can not only make the noise disappear but will also aid the RF gain in setting the proper level for the incoming signal.

My current SUV has coil over plugs and a nonmetal hood. The ignition noise was very intense.  My IC-706MK II G and the FT-100D did a reasonable job of removing the ignition noise but it was far from perfect.  On advice from other hams using the IC-7000 I bought the radio at HRO and installed into the SUV.

The ignition interference disappeared completely. I was able to adjust the depth of the blanking for minimum effect on the recovered audio.  In addition the ANR (Automatic Noise Reduction) also reduced the background hiss withy out reducing the audio highs. I was dumbfounded how far the DSP in these little radios have come.

Bottom line is you can have mobile operation without turning your engine wiring into a shielded airplane ignition system
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AF5CC
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« Reply #25 on: March 28, 2013, 02:58:11 PM »

So of the older rigs did have adjustable NBs.  I know the Icom 740 and 745 did, as well as the Kenwood TS140/680. It does seem, though, that newer radios are using digital based NBs which might work better.

John AF5CC
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