I tried this on my R4B and found that while it worked it didn't make the NB any more effective on noise other than ignition noise. Ignition noise is rare these days, about the only time I hear it is from the gardener's mower. The threshold of the NB is such that it will prevent pulse noise from raising the AVC level, which is what is expected of it. Lowering the threshold much begins to produce distortion. There are more elaborate blankers that are more effective on power line noise but the best ones seem to be the digital processing ones that are external to the receiver.
?? The theory of the noise blanker is not as simple as it may appear. The idea is that the blanker will cut off the RF path during the pulse but the effect of the bandwidth on the noise wave form at both the sensing and control points is critical plus you don't want the blanker to cut off desired signals.
?? As a matter of comfort in listening a simple clipper on the audio may be helpful. While its best to have it on the input to the audio stage even a simple solid state diode clipper on the audio output may help with some types of power line noise. My experience with many old fashioned receivers with both series and shunt clippers is that they are at best illusory.
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On 4/11/2021 10:45 AM, Robert Berg via groups.io wrote:
David,
You can try a mod to permit an adjustment to the NB threshold, as per this suggestion: <>
This allows an adjustable threshold, as per the original R-4 configuration. Might help.
Bob
K7CY
On Apr 11, 2021, at 10:10 AM, AC9PA via groups.io <byroncordes@...> wrote:
?Don¡¯t expect miracles with the NB ! It works on some noise and some it just don¡¯t care! I would eliminate all noise in and around house first!
I run a Timewave dsp599 ( works on audio ) which makes the radio much better to listen to.
My R4C I don¡¯t have a NB in it the first IF is to narrow for stock NB to work but using the Timewave ?, lightning isnt to bad ?and I don¡¯t make any rf noise in house or if I do I can turn that light off Hihi
73s Byron AC9PA
On Apr 11, 2021, at 11:20 AM, wb6ogd <garywinblad@...> wrote:
?The Drake blanker is very effective... ?Like Richard says it works great on ignition noise.
Back in the day it made the difference between being able to hear a station or not.
Now a days, there isn't much ignition noise anymore so it really doesn't do much.
73,
Gary
WB6OGD
On 4/11/2021 7:36 AM, Richard Knoppow wrote:
??I can talk about the R4B. The blanker works fine on ignition noise, which was what it was mostly designed for but does nothing for the grinding line noise that is much more common. I tested it using a Tektronix pulse generator. It does work but is not like the blankers found in some more modern receivers. The idea of the blanker is to prevent pulse noise like ignition noise from causing the AVC to reduce sensitivity. It also does not affect the sort of noise a conventional noise limiter of the sort found in boatanchor receivers will take out but the usual series valve limiter does not work for CW or SSB. I think there are after market noise removers that work pretty well.
On 4/11/2021 5:09 AM, David Lipson via groups.io wrote:
Hi
I,ve been trying to use my r4a recently. The pulse noise has been strong, and the blanker does not seem to be helpful. IS the experience of others similar?
73s
David
N9pvf
--
Richard Knoppow
1oldlens1@...
WB6KBL
