Drake R4B and some other models. Also, Collins used a blanker with
separate antenna in some transceivers, have to look at the specs to jog
my memory.

On 6/10/2024 5:20 PM, Jim Whartenby via groups.io wrote:

I've looked and have not found a radio that uses a noise blanker.
All I
have seen is clippers which remove noise spikes above a set level.? The
guitar guys mention it but it is a squelch gate which is open below a
set value and closes above this set level.? So audio is muted for very
low passages; one assumes to remove background hiss.
Regards,
JIm

Noise blankers in Amateur Radio and in commercial sound installations –
two very different animals!

Yes, noise blankers, typically called audio noise gates, are quite
common in performed music and in broadcasting.? I’ve built a number of
studios for talk radio that use several microphones feeding a mic mixer
that automatically mutes any mic that nobody’s talking into at the
moment.? Here’s a typical example:

<> of one kind I’ve
installed with great success.? There are also individual mic processors
that perform the same task along with compression, equalization, and
other voice enhancements:

<> .? I would expect to find some of these among the AM aficionados that use converted AM broadcast transmitters and inhabit 3885 and vicinity.

In PA systems they’re great at stopping feedback when a person stops
talking and a compressor might otherwise raise the gain to the point of
feedback “howling.”

These are completely different from noise blankers that we use on HF for
receive signal noise reduction.? The kind of noise blankers that reduce
ignition and similar noises typically cut off the IF or RF signal in the
receiver when a separate receiver and antenna receives the impulse noise
that we desire to be reduced.

Is there a version that works within a single receiver?? Yes, although
its effect isn’t quite a great as the two antenna and receiver version.
Info on the single on-frequency version, sometimes called a noise
silencer, can be found here:
<> .

Incidentally, they also work well for lightning static.

For typical background hiss, atmospheric static, and the like, they’re
practically worthless.

And now I’ll just fade back into the background noise!

Interesting stuff!

Mike/
K5MGR
___________________________

Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901

(505) 898-3212 home/home office
(505) 238-8810 cell
mlangner@... <mailto:mlangner@...>

I've looked and have not found a radio that uses a noise blanker.? All I
have seen is clippers which remove noise spikes above a set level.? The
guitar guys mention it but it is a squelch gate which is open below a
set value and closes above this set level.? So audio is muted for very
low passages; one assumes to remove background hiss.
Regards,
JIm

?

?

Just wanted to say thank you to Jim K9AXN, Walt and the rest who helped me along the way!? ?The radio is finished and really runs and looks great!

It was a massive amount of work to get the rig back to factory specs:
New caps in radio and PS
20 something resistors changed in radio and PS
Mica Caps and caps in VFO changed.
Carrier Null circuit had to be rebuilt with all new parts.
Ceramic band switch BLOWN to bits. Had to take it apart, drill rivets and replace contacts (NOT FUN)
Impossible to find NPO trimmers located and replaced.
Mechanical gears on VFO off alignment (another fun job)
Annoying 40 cycle offset on TX fixed
FULL alignment.
Cleaning of chassis, panel, knobs.
Tubes replaced
Fan serviced
Cabinets stripped and powder coated.
All new SS hardware.
Had new P2000 rear panels made at a sign shop.

Its very stable. It does not require adjustment of VFO in an evening of use.? If turned on and left to run 20 minutes its back exactly to the cycle it was when you turned it off.? Remember, I have two SR2000s. The second one should be finished this week. I am waiting on parts. It had the exact same treatment.? One will be sold.? I don't care which one I keep. They are the same. If you want one please let me know.? Its in PHX AZ and I would hate to ship the PS. I guess it could be done somehow.

Some videos of it running:

?

?

I see, since the two noise signals are coherent its possible to
cancel it by phasing. Would work on man made noise where the signal and
noise can be separated.

On 6/10/2024 1:12 PM, Maynard Wright, P. E., W6PAP via groups.io wrote:

Hi, Richard,

The system I described is not the same as the noise blanker internal to
the receiver. The circuitry that the Signal Corps used, and that has
been implemented by MFJ and others, works prior to the first RF
amplifier of the receiver and collects signals from two antennas. The

--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998

Hi, Richard,

The system I described is not the same as the noise blanker internal to
the receiver. The circuitry that the Signal Corps used, and that has
been implemented by MFJ and others, works prior to the first RF
amplifier of the receiver and collects signals from two antennas. The

A further note: The purpose of the blanker is more to prevent pulse
noise from desensitizing the receiver by being seen by the AVC as
signal. Although the noise pulses may be very short their amplitude can
be very high. The AVC system tends to integrate these pulses and causees
the AVC to desensitize the receiver. Also, and important, the presence
of these high amplitude pulses in the IF path can cause intermodulation
which can significantly exaggerate their effect. Also, narrow bandwidth
IF filters tend to stretch out the pulses, causing ringing and further
exaggerating their effect. Actually, the "holes" from the blanker may
also be stretched, also causing some strange effects.
In general, this type of noise eliminator works mostly for impulse
noise like ignition noise (does it exist any more?) and not for lower
level noise from arcing or of the sort generated by electronic circuits.
There are digital noise eliminators which do work pretty well for these.
I have some more but am blanking on a couple of names I need,
researchers into communication theory at Bell Labs. They showed that the
conventional idea of the effects of _random_ noise are not quite true.
So maybe more in a a while.



--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998

?

The operation of a noise antenna and associated circuitry are
independent of the nature of the noise, whether or not it's periodic and
whether or not it's random.

Ideally, the signal antenna would receive the signal plus the offending
noise and the noise antenna would receive just the noise. The combining
network would be adjusted to combine the two signals so that their time
domain noise components would be equal in amplitude but opposite in
polarity so that they would cancel and leave only the desired signal at
the input to the receiver.

There are several potential difficulties that make this system less than
perfect in most, if not all, implementations, but it may reduce the
noise enough to be useful in some situations.

73,

Maynard
W6PAP

The operation of a noise antenna and associated circuitry are
independent of the nature of the noise, whether or not it's periodic and
whether or not it's random.

?

The operation of a noise antenna and associated circuitry are
independent of the nature of the noise, whether or not it's periodic and
whether or not it's random.

Ideally, the signal antenna would receive the signal plus the offending
noise and the noise antenna would receive just the noise. The combining
network would be adjusted to combine the two signals so that their time
domain noise components would be equal in amplitude but opposite in
polarity so that they would cancel and leave only the desired signal at
the input to the receiver.

There are several potential difficulties that make this system less than
perfect in most, if not all, implementations, but it may reduce the
noise enough to be useful in some situations.

73,

Maynard
W6PAP

It seems to me, that since noise is neither correlate-able or
stochastic, elimination is not possible. Also the multiple antenna
theory is out the window since RF generated noise travels at the speed
of light. 73 – Mike

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

*From:* [email protected] <[email protected]>
*On Behalf Of *Maynard Wright, P. E., W6PAP via groups.io
*Sent:* Sunday, June 9, 2024 7:31 PM
*To:* [email protected]
*Subject:* Re: [HallicraftersRadios] SX-117 noise limiter behavior

Another technique for reducing or eliminating noise was to introduce
local noise to the front end of a receiver from a local "noise antenna."
The amplitude and phase of that noise could be adjusted to, hopefully,
cancel the noise received by the signal antenna.

Early BC-342 and BC-312 receivers featured a noise suppression circuit
of this type. War Department TM 11-850 states that the noise antenna
was intended to eliminate ignition noise when the receiver was mounted
in a vehicle.

By the time my BC-342-N was born (1942), the noise antenna and
associated circuitry were omitted, so that circuit may not have worked
well. The September, 1946 revision of the TM notes that spare parts
were no longer available for the noise suppression circuit and
recommends removing it if any of the components fail.

MFJ has featured at least one similar unit, the MFJ-1026, which is now
listed as sold out. There are other such units available but I have no
experience with them.

73,

Maynard
W6PAP

?

True, but a good approximation of the noise in the vicinity of the receiver antenna can be sampled and used to reduce the noise coming in along with the desired signal from the main antenna.? The noise from the secondary system, must, as you point out, be as close as possible to the noise being picked up by the primary antenna.? Cancellation is, of course, incomplete, so elimination is not possible, but quite significant reduction is indeed possible and has been proven in the field.? Needless to say, the noise receiving system must not pick up much of the desired signal.? This can be effected both by operating the two receive systems on dissimilar frequencies, and also by utilizing a receive antenna location that will pick up the closest possible envelope to the noise the primary antenna receives but picks up a minimal amount of the desired signal.

How much improvement is available?? Results vary widely with the nature of the noise and the environment in which the noise is being received.? Still, the reduction is often very, very worthwhile!

As always, your mileage may vary!!

Mike/
K5MGR
_____________________________________________

?

?

?

It seems to me, that since noise is neither correlate-able or stochastic, elimination is not possible. Also the multiple antenna theory is out the window since RF generated noise travels at the speed of light. 73 – Mike

?

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell NJ 07731

908-902-3831

?

?

Another technique for reducing or eliminating noise was to introduce
local noise to the front end of a receiver from a local "noise antenna."
The amplitude and phase of that noise could be adjusted to, hopefully,
cancel the noise received by the signal antenna.

Early BC-342 and BC-312 receivers featured a noise suppression circuit
of this type. War Department TM 11-850 states that the noise antenna
was intended to eliminate ignition noise when the receiver was mounted
in a vehicle.

By the time my BC-342-N was born (1942), the noise antenna and
associated circuitry were omitted, so that circuit may not have worked
well. The September, 1946 revision of the TM notes that spare parts
were no longer available for the noise suppression circuit and
recommends removing it if any of the components fail.

MFJ has featured at least one similar unit, the MFJ-1026, which is now
listed as sold out. There are other such units available but I have no
experience with them.

73,

Maynard
W6PAP

?

Well, you are speaking of _random_ noise, like natural radio noise
but blankers are intended to work on periodic signals such as ignition
noise.

On 6/9/2024 5:11 PM, Mike Feher wrote:

It seems to me, that since noise is neither correlate-able or
stochastic, elimination is not possible. Also the multiple antenna
theory is out the window since RF generated noise travels at the speed
of light. 73 – Mike

Mike B. Feher, N4FS

--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998