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SX-117 noise limiter behavior
It IS periodic, not random. Each noise pulse has a definite
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signature. It is well above average random noise. A noise blanker of any sort desensitizes the signal channel during the noise pulse. In fact, the pulse can be singular. It is important that the timing is correct, that is, if the blanker or the channel it blanks, has too much time delay the pulse and hole do not coincide. Mostly they do and digital circuits can provide delay where necessary to synchronize them. Perhaps I should not have said periodic but there is a better term for non-random which I am not thinking of at the moment (blanking on it). The kind of noise that you can't cancel is random noise generated in two different places, such as in the receiver vs: from space via an antenna. They don't cancel, they combine. On 6/9/2024 6:26 PM, Mike Feher wrote: Rich – Ignition noise is far from periodic. It may approach that at a -- Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
开云体育OK – have fun. 73 – Mike ? Mike B. Feher, N4FS 89 Arnold Blvd. Howell NJ 07731 908-902-3831 ? From: [email protected] <[email protected]> On Behalf Of Richard Knoppow
Sent: Sunday, June 9, 2024 10:23 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? It IS periodic, not random. Each noise pulse has a definite
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开云体育Richard , do you drive your engine at one speed? ? From: [email protected] [mailto:[email protected]] On Behalf Of Richard Knoppow
Sent: Sunday, June 9, 2024 9:16 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? Well, you are speaking of _random_ noise, like natural radio noise It seems to me, that since noise is neither correlate-able or -- _._,_._,_ -- don??? va3drl |
开云体育Mike and all, there must be quite a different scheme when trying to reducing Lightning storm “static” as opposed to very local noise or nearby bad power line noise, or your own light dimmer noise. More later tomorrow.. maybe..don ? From: [email protected] [mailto:[email protected]] On Behalf Of Mike Langner
Sent: Sunday, June 9, 2024 9:16 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? 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. ? Mike Langner ? From: [email protected] <[email protected]> On Behalf Of Mike Feher ? 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 ? Another technique for reducing or eliminating noise was to introduce _._,_._,_ -- don??? va3drl |
The operation of a noise antenna and associated circuitry are
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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 On 6/9/24 17:11, Mike Feher wrote:
It seems to me, that since noise is neither correlate-able or |
开云体育Maynard, your theory sounds mostly good, but we need some details on what is called an antenna; will it work with my 10 feet of haywire antenna? ? From: [email protected] [mailto:[email protected]] On Behalf Of Maynard Wright, P. E., W6PAP via groups.io
Sent: Monday, June 10, 2024 2:22 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? The operation of a noise antenna and associated circuitry are -- don??? va3drl |
The reverse phase cancellation is not how I understand the blanker
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to work although I think there are noise eliminators that do work this way. My understanding is that the signal from the noise antenna is detected and converted into a DC pulse which is applied to a gate in the signal path which cuts it off momentarily for the length of time the pulse lasts. Since both the detection and gating can be done where the bandwidth is fairly wide the rise and fall times of the gating signal can be made quite short. The device must be such that there is not an excessive time delay between the noise pulse in the receive chain and the muting or gating signal. Presumably, there is some delay in both signal and noise channels and they can be matched by careful design. The advantage of this system over the type of noise gate that picks up the signal from the IF is that the bandwidth of the noise pulse can be narrower and the rise and fall times of the pulse are shorter thus reducing the amount of time the signal channel is cut off. I am pretty sure Collins used this system, perhaps in its first mobile transceivers. Also, since the kind of noise pulse the blanker is supposd to work on is very short it will have a spectrum well into the the HF or VHF range so that a short antenna antenna can be used and desired signals will not get into the blanker. Again the blanker works by shutting off the signal path briefly during the noise pulse. On 6/10/2024 11:22 AM, Maynard Wright, P. E., W6PAP via groups.io wrote: The operation of a noise antenna and associated circuitry are -- Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
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 |
Don Read the enclosed excerpt from TM 11-310.? The first page shows the noise antenna circuit and lists all design changes to the series of receivers.? I would think that the noise antenna would be short so as to only pick up ignition noise.? Anything longer would subtract form the signal of interest. Regards, Jim Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Monday, June 10, 2024 at 01:55:22 PM CDT, don Root <drootofallevil@...> wrote:
Maynard, your theory sounds mostly good, but we need some details on what is called an antenna; will it work with my 10 feet of haywire antenna? ? From: [email protected] [mailto:[email protected]] On Behalf Of Maynard Wright, P. E., W6PAP via groups.io
Sent: Monday, June 10, 2024 2:22 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? The operation of a noise antenna and associated circuitry are -- don??? va3drl |
Hi, Richard,
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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 idea is to collect a signal contaminated by noise from one antenna and just the noise from the second and then combine the two to cancel the noise. The two antenna inputs on the BC-342 family are "SIGNAL ANTENNA" and "NOISE ANTENNA." In the BC-342, the circuitry is internal to the receiver but, if used, is inserted between the antenna and the first RF stage. Other implementations are in separate boxes that connect to two antennas and the input to the receiver. To your question, Don, it depends on where the noise originates. If the noise is local to your home, a short antenna that minimizes pickup of the desired signal but receives the noise might be just the right thing. You would then twiddle the amplitude and phase adjustments of the combiner to minimize the noise in your receiver. If the noise is from some distance away, you might have to fiddle with positioning of the noise antenna so that the signal is minimized while the noise is maximized. If you are receiving a signal from the same direction from which the noise is coming, this may be difficult. 73, Maynard W6PAP On 6/10/24 12:33, Richard Knoppow wrote:
A further note: The purpose of the blanker is more to prevent pulse |
I see, since the two noise signals are coherent its possible to
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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, --
Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
True: my BC-342, BC-312, etc. manual suggests routing the noise antenna
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near the engine of the vehicle whose ignition noise is troublesome. Maybe when the receivers weren't used in vehicles where that was convenient, the noise suppression wasn't very useful and that's possibly why it was discontinued, even to the point of not supplying spare parts for the existing circuits. 73, Maynard W6PAP On 6/10/24 13:31, Richard Knoppow wrote: I see, since the two noise signals are coherent its possible to |
开云体育Thanks jim, but first, is/has this topic swung to dealing with ignition noise only?? For an SX-117 ??? . interesting discussiuons, but what is the scope of it? Help..I’M lost??? …. again. don ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Monday, June 10, 2024 3:58 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? Don Read the enclosed excerpt from TM 11-310.? The first page shows the noise antenna circuit and lists all design changes to the series of receivers.? I would think that the noise antenna would be short so as to only pick up ignition noise.? Anything longer would subtract form the signal of interest. Regards, Jim ? Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy ? ? On Monday, June 10, 2024 at 01:55:22 PM CDT, don Root <drootofallevil@...> wrote: ? ? Maynard, your theory sounds mostly good, but we need some details on what is called an antenna; will it work with my 10 feet of haywire antenna? ? From: [email protected] [mailto:[email protected]] On Behalf Of Maynard Wright, P. E., W6PAP via groups.io ? The operation of a noise antenna and associated circuitry are
-- don??? va3drl |
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 Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Monday, June 10, 2024 at 07:04:29 PM CDT, don Root <drootofallevil@...> wrote:
Thanks jim, but first, is/has this topic swung to dealing with ignition noise only?? For an SX-117 ??? . interesting discussiuons, but what is the scope of it? Help..I’M lost??? …. again. don ? From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Monday, June 10, 2024 3:58 PM To: [email protected] Subject: Re: [HallicraftersRadios] SX-117 noise limiter behavior ? Don Read the enclosed excerpt from TM 11-310.? The first page shows the noise antenna circuit and lists all design changes to the series of receivers.? I would think that the noise antenna would be short so as to only pick up ignition noise.? Anything longer would subtract form the signal of interest. Regards, Jim ? Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy ? ? On Monday, June 10, 2024 at 01:55:22 PM CDT, don Root <drootofallevil@...> wrote: ? ? Maynard, your theory sounds mostly good, but we need some details on what is called an antenna; will it work with my 10 feet of haywire antenna? ? From: [email protected] [mailto:[email protected]] On Behalf Of Maynard Wright, P. E., W6PAP via groups.io ? The operation of a noise antenna and associated circuitry are
-- don??? va3drl |
Drake R4B and some other models. Also, Collins used a blanker with
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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 -- Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
开云体育Noise blankers in Amateur Radio and in commercial sound installations – two very different animals! Mike Langner |
I always heard them called "duckers" although a ducker is really a
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special application. I agree, a different animal. On 6/10/2024 5:37 PM, Mike Langner wrote: Noise blankers in Amateur Radio and in commercial sound installations – --
Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
See the Collins 136B-2, used with the KWM-2 for details. This uses a
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separate antenna such as the broadcast receiver whip, as a noise antenna. FWIW, for the other meaning, i.e. a squelch, while they are mostly found on FM receivers there are some HF communication receivers that have them. These are used to eliminate noise between periodic communications. On 6/10/2024 5:34 PM, Richard Knoppow wrote: Drake R4B and some other models. Also, Collins used a blanker with --
Richard Knoppow Los Angeles WB6KBL SKCC 19998 |
The use of a noise antenna and associated circuitry is independent of
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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 On 6/9/24 17:11, Mike Feher wrote:
It seems to me, that since noise is neither correlate-able or |
开云体育The ANC-4 by Timewave is a very effective device for limiting local noise. ?I get more than 40dB reduction, sometimes more, so that weak signals stand out against an almost silent background. ?MFJ makes a similar device. ?These devices use an active RF circuit to amplify the offending noise from a separate antenna, and then beat it against the same noise in your main antenna. ?They really work. I see some used ones online around 125 bucks. ? Preston WJ2V
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