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 January 07, 2011, 05:52:39 PM
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Super Member
Posts: 2338
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And you're sure all this engineering was in place in 1963?
Herbert, do you know:
-which DPD sirens, if any that day, were mechanical, rotary sirens, and if so, what make and model(s) they were?
-which of them were electronic, which would put them at the very infancy of the electronic vehicle siren altogether, and again if so, what make and model they were?
The answers to these questions would be EXTREMELY important to know, in regard to anything that you might be thinking about presenting as further information of this topic.
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"you're the cop, you figure it out"
-Lee H. Oswald to Dallas Police detectives, weekend
of 11-22-63.
"Part of the reason why we avoided talking about this thing, because every time you say something, somebody misinterprets what you say."
-James. J. Humes, excerpt of ARRB statement, 2-13-96
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January 07, 2011, 07:11:23 PM
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Super Member
Posts: 2201
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And you're sure all this engineering was in place in 1963?
Herbert, do you know:
-which DPD sirens, if any that day, were mechanical, rotary sirens, and if so, what make and model(s) they were?
-which of them were electronic, which would put them at the very infancy of the electronic vehicle siren altogether, and again if so, what make and model they were?
The answers to these questions would be EXTREMELY important to know, in regard to anything that you might be thinking about presenting as further information of this topic.
I made no statement about the sirens being mechanic, rotary or electronic. So where do you get the idea that the design of the siren affects the way that engineers suppress the sounds in sirens in the presence of voiced sounds? The Dicatbelt shows that the sirens on the emergency vehicles had constant frequencies that feel into two separate groups. One group had fundamental frequencies that were effectively filtered by the notch filters in the transmitter and receiver. These sirens yielded spectrographs showing the second and third harmonics. The other group of sirens had a fundamental frequency slightly above the notch frequency and produced spectra with a substantially attenuated fundamental and harmonics. These notch filters gave all the sirens their unusual shrillness. Do you think ----- has too many notch filters? Herbert
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January 07, 2011, 07:33:53 PM
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Super Member
Posts: 2338
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In my former life Herbert, I spent quite a few years involved in Fire/Rescue. There are electronic sirens, and mechanical sirens, and for each of them there are several different makes and models, each with different decibel levels, etc. They are not all the same, not even close. Electronic sirens were just hitting the market in 1963, they were just starting to get used in vehicle applications. There weren't yet a lot of choices in 1963 if you wanted to install 1 on a fire truck or a police car. It used to be I used radios and sirens every day I was at work, and this includes very primitive, mobile radio types, right out of the late 1950s and early 1960s. And I don't mean familiar, as simply because I keyed microphones and spoke in to them. What I know is well beyond that level Herbert.
There are also different types of 2 way radios, and you'll need to make sure that anything you might be proposing for filters and noise suppression technology existed at all for the application in 1963. And for the type of radio. You'll need to know what police cars and motorcycles were equipped with what radio/mic combinations, as well as radio brand and type. AM, FM, high band, low band, solid state or analog (tube amps)? It would be a miracle if they were all equipped with the same units, something I would bet my life against. And, not always is/was the case, that a technology that could be applied to a solid state radio could also be applied to an analog type of radio. I know a bit about radio technology back then, and I know about sirens and how they work. Both types.
If you start hypothesizing something that is from the outer limits, I am going to be right here pestering you the whole way along....but if you do your homework and get it right, I will agree with you most likely. Where do you get the idea that any kind of noise suppression technology for sirens existed at all in 1963 Herbert? Be careful out there.
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January 07, 2011, 08:02:18 PM
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Super Member
Posts: 2201
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In my former life Herbert, I spent quite a few years involved in Fire/Rescue. There are electronic sirens, and mechanical sirens, and for each of them there are several different makes and models, each with different decibel levels, etc. They are not all the same, not even close. Electronic sirens were just hitting the market in 1963, they were just starting to get used in vehicle applications. There weren't yet a lot of choices in 1963 if you wanted to install 1 on a fire truck or a police car. It used to be I used radios and sirens every day I was at work, and this includes very primitive, mobile radio types, right out of the late 1950s and early 1960s. And I don't mean familiar, as simply because I keyed microphones and spoke in to them. What I know is well beyond that level Herbert.
There are also different types of 2 way radios, and you'll need to make sure that anything you might be proposing for filters and noise suppression technology existed at all for the application in 1963. And for the type of radio. You'll need to know what police cars and motorcycles were equipped with what radio/mic combinations, as well as radio brand and type. AM, FM, high band, low band, solid state or analog (tube amps)? It would be a miracle if they were all equipped with the same units, something I would bet my life against. And, not always is/was the case, that a technology that could be applied to a solid state radio could also be applied to an analog type of radio. I know a bit about radio technology back then, and I know about sirens and how they work. Both types.
If you start hypothesizing something that is from the outer limits, I am going to be right here pestering you the whole way along....but if you do your homework and get it right, I will agree with you most likely. Where do you get the idea that any kind of noise suppression technology for sirens existed at all in 1963 Herbert? Be careful out there.
I have never been a CIVIL engineer so pardon my bluntness. I wrote, “The Dicatbelt shows that the sirens on the emergency vehicles had constant frequencies that feel into two separate groups. One group had fundamental frequencies that were effectively filtered by the notch filters in the transmitter and receiver. These sirens yielded spectrographs showing the second and third harmonics. The other group of sirens had a fundamental frequency slightly above the notch frequency and produced spectra with a substantially attenuated fundamental and harmonics.” Now do I need to post the spectrographs derived from the Bowles tape of the Dictabelt to prove to you that notch filters were used in the DPD radio system? Herbert
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January 08, 2011, 05:10:20 AM
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Super Member
Posts: 6711
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And you're sure all this engineering was in place in 1963?
Herbert, do you know:
-which DPD sirens, if any that day, were mechanical, rotary sirens, and if so, what make and model(s) they were?
-which of them were electronic, which would put them at the very infancy of the electronic vehicle siren altogether, and again if so, what make and model they were?
The answers to these questions would be EXTREMELY important to know, in regard to anything that you might be thinking about presenting as further information of this topic.
We have discussed it several times on alt.conspiracy.jfk. Some of the Web page reference are no longer working, but here is one mesage which might clear it up. Well I think this issue is finally dead Dr. Martin Rosenblum of Harley Davidson just gave us the difinitive answer on the sirens: Rosenblum did give us the specific part numbers for the Sirens used back then. 1) Rear Siren, Foot Controlled....91126-59 2) Front Siren, Hand Controlled...91130-58 3) Front Siren, Foor Controlled...91131-58 He told me you can find these in various parts catalogs used today for vintage collectors. He also stressed the sirens were indeed NOT Electronic, in any way, shape, or form. They were mechanical only. Rob Spencer RIP Siren issue And of course Steve Barber has studied it in depth. I think there are some photos showing the sirens which you could blow up to see it in more detail.
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January 08, 2011, 12:57:19 PM
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Super Member
Posts: 2201
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In my former life Herbert, I spent quite a few years involved in Fire/Rescue. There are electronic sirens, and mechanical sirens, and for each of them there are several different makes and models, each with different decibel levels, etc. They are not all the same, not even close. Electronic sirens were just hitting the market in 1963, they were just starting to get used in vehicle applications. There weren't yet a lot of choices in 1963 if you wanted to install 1 on a fire truck or a police car. It used to be I used radios and sirens every day I was at work, and this includes very primitive, mobile radio types, right out of the late 1950s and early 1960s. And I don't mean familiar, as simply because I keyed microphones and spoke in to them. What I know is well beyond that level Herbert.
The theme of my original post pertained to notch filters and said nothing of the noise blanker technology used during the fifties or the early sixties. They used a bridged-tee RC-circuit and one active stage to implement a notch filter. Typically the employed negative feedback to widen the notch at the expensive of the otherwise excessive sharpness of the filter. Your claim that I need to know whether they used a solid-state or a vacuum tube amplifier for the active device is nonsense on par with the assertion that knowledge of the mode of modulation, either amplitude or frequency, is required to filter an audio signal. You have demonstrated that your knowledge of radio technology is on level with an appliance operator.
There are also different types of 2 way radios, and you'll need to make sure that anything you might be proposing for filters and noise suppression technology existed at all for the application in 1963. And for the type of radio. You'll need to know what police cars and motorcycles were equipped with what radio/mic combinations, as well as radio brand and type. AM, FM, high band, low band, solid state or analog (tube amps)? It would be a miracle if they were all equipped with the same units, something I would bet my life against. And, not always is/was the case, that a technology that could be applied to a solid state radio could also be applied to an analog type of radio. I know a bit about radio technology back then, and I know about sirens and how they work. Both types.
If you start hypothesizing something that is from the outer limits, I am going to be right here pestering you the whole way along....but if you do your homework and get it right, I will agree with you most likely. Where do you get the idea that any kind of noise suppression technology for sirens existed at all in 1963 Herbert? Be careful out there.
You have ignored my original post that calculated the attenuation of the fundamental frequency required for the regulatory 20-db margin of the voice over the siren. Now you declare my sound calculations as something from the outer limits. On this point, I challenge you to defend your derogatory remark. Herbert
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January 08, 2011, 01:26:27 PM
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Super Member
Posts: 2338
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Herbert You really need to get a grip on this stuff. On yourself too. Before you make an  out of yourself. The sort of specs I pointed out are very relevant in terms of the sort of radio noise(s) being filtered. In addition to this Herbert, sometimes the equipment in a dispatch center itself-radio transmitters, dictabelts and other recorders, can and will put forth considerable noise on to the recordings of the events, noise that didn't exist at all when it all went down in real time. Or noise that gets filtered off is replaced by other noises that the filtering and then the recording devices put in place. Since you don't know what the DPD dispatch center had in place within their consoles that day, your thread here is going to quickly swirls down the commode. You are going to make a HUGE mistake if you think that you can make some sort of blanket statement about the noise cancelling/filtering technologies available in 1963 compared to a typical system of today, or the 1980s. Bottom line Herbert, until you can bring forth the information I have noted, you are going to be blowing smoke out of a body orfice. Again, I'd add. I have spent quite a bit of time with the web, trying to find out the answers to what I am saying in this thread, which regardless of what you think you know Herbert, matters quite a lot. You either don't know all you think you do, or you are forgetting some things you need to not forget. I have been very interested in what the DPD had in place for their dispatch center that day, for radio consoles, recording devices, and more. Background noises have figured very prominently in previous debate here, as you obviously know Herbert. But so far, I have been unable to get very far, and if you know and can prove what was actually there in place, I'd be very interested in knowing this sort of information. The very last thing I will add here Herbert, is that it was not uncommon back then for there to be 2 or more entirely different systems in place, in use at the same time, within the same dispatch center, if there were multiple channels and/or multiple consoles. Think about it Herbert, and I hope that if you are going to make conclusions about radio noises and filters and RF interferences and more, that you can document exactly what the DPD had installed-and was operating correctly mind you-on that day when these radio transmissions were initially made. Plenty more I could add at this time Herbert, but I think for now I will just sit back for a while and see where you go with this.
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January 08, 2011, 01:29:12 PM
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Super Member
Posts: 2201
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And you're sure all this engineering was in place in 1963?
Herbert, do you know:
-which DPD sirens, if any that day, were mechanical, rotary sirens, and if so, what make and model(s) they were?
-which of them were electronic, which would put them at the very infancy of the electronic vehicle siren altogether, and again if so, what make and model they were?
The answers to these questions would be EXTREMELY important to know, in regard to anything that you might be thinking about presenting as further information of this topic.
Quoting the guy who thought that a notch filter meant that sirens were electronic does not help your case. This is especially true when I have the spectrographs of the sirens that show dominance of the second harmonic. I post a sample.  The 600 Hz fundamental frequency of the siren fell below the notch centered around 700 Hz and is still visible on the spectrograph. However, the second harmonic at about 1200 Hz has larger magnitude and dominates the signal. Despite a high-frequency cut-off of around 1 kHz, the third harmonic of approximately 1800 Hz is also seen at about half the magnitude of the filtered fundamental. I have presented my proof that those who calculated the distance between the open microphone and the sirens made a fundamental error by ignoring the notch filters in the DPD radio system. So what does your side have? Herbert We have discussed it several times on alt.conspiracy.jfk. Some of the Web page reference are no longer working, but here is one mesage which might clear it up. Well I think this issue is finally dead Dr. Martin Rosenblum of Harley Davidson just gave us the difinitive answer on the sirens: Rosenblum did give us the specific part numbers for the Sirens used back then. 1) Rear Siren, Foot Controlled....91126-59 2) Front Siren, Hand Controlled...91130-58 3) Front Siren, Foor Controlled...91131-58 He told me you can find these in various parts catalogs used today for vintage collectors. He also stressed the sirens were indeed NOT Electronic, in any way, shape, or form. They were mechanical only. Rob Spencer RIP Siren issue And of course Steve Barber has studied it in depth. I think there are some photos showing the sirens which you could blow up to see it in more detail. Quoting the guy who thought that a notch filter meant that sirens were electronic does not help your case. This is especially true when I have the spectrographs of the sirens that show dominance of the second harmonic. I post a sample. The 600 Hz fundamental frequency of the siren fell below the notch centered around 700 Hz and is still visible on the spectrograph. However, the second harmonic at about 1200 Hz has larger magnitude and dominates the signal. Despite a high-frequency cut-off of around 1 kHz, the third harmonic of approximately 1800 Hz is also seen at about half the magnitude of the filtered fundamental. I have presented my proof that those who calculated the distance between the open microphone and the sirens made a fundamental error by ignoring the notch filters in the DPD radio system. So what does your side have? Herbert
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« Last Edit: January 08, 2011, 01:29:56 PM by Herbert Blenner »
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January 08, 2011, 03:06:29 PM
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Super Member
Posts: 2201
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Herbert You really need to get a grip on this stuff. On yourself too. Before you make an out of yourself. The sort of specs I pointed out are very relevant in terms of the sort of radio noise(s) being filtered. In addition to this Herbert, sometimes the equipment in a dispatch center itself-radio transmitters, dictabelts and other recorders, can and will put forth considerable noise on to the recordings of the events, noise that didn't exist at all when it all went down in real time. Or noise that gets filtered off is replaced by other noises that the filtering and then the recording devices put in place. Since you don't know what the DPD dispatch center had in place within their consoles that day, your thread here is going to quickly swirls down the commode. You are going to make a HUGE mistake if you think that you can make some sort of blanket statement about the noise cancelling/filtering technologies available in 1963 compared to a typical system of today, or the 1980s. Bottom line Herbert, until you can bring forth the information I have noted, you are going to be blowing smoke out of a body orfice. Again, I'd add. You are “blowing smoke out of a body orfice” by pretending that the discussion is about filtering noise, a far more difficult problem than the elementary task of filtering a narrow-band sinusoid from the harmonic signal generated by a siren.
I have spent quite a bit of time with the web, trying to find out the answers to what I am saying in this thread, which regardless of what you think you know Herbert, matters quite a lot. You either don't know all you think you do, or you are forgetting some things you need to not forget.
If you did your web homework then you would have found about 100,000 hits for the bridged-tee or bridged-t notch filter. This circuit was widely used in communications equipment since being introduced during the forties.
I have been very interested in what the DPD had in place for their dispatch center that day, for radio consoles, recording devices, and more. Background noises have figured very prominently in previous debate here, as you obviously know Herbert. But so far, I have been unable to get very far, and if you know and can prove what was actually there in place, I'd be very interested in knowing this sort of information.
The following spectrograph showing the prominent sinusoids from a siren with a three to two-ratio of frequencies and the attenuated fundamental proves that the DPD radio system used notch filters to reduce the volume of the sirens relative to voices. The 600 Hz fundamental frequency of the siren fell below the notch centered around 700 Hz and is still visible on the spectrograph. However, the second harmonic at about 1200 Hz has larger magnitude and dominates the signal. Despite a high-frequency cut-off of around 1 kHz, the third harmonic of approximately 1800 Hz is also seen at about half the magnitude of the filtered fundamental.
The very last thing I will add here Herbert, is that it was not uncommon back then for there to be 2 or more entirely different systems in place, in use at the same time, within the same dispatch center, if there were multiple channels and/or multiple consoles. Think about it Herbert, and I hope that if you are going to make conclusions about radio noises and filters and RF interferences and more, that you can document exactly what the DPD had installed-and was operating correctly mind you-on that day when these radio transmissions were initially made.
You just do not get it, mister. The Bowles tape of the Dictabelt documents exactly how the radio system altered signals. Herbert
Plenty more I could add at this time Herbert, but I think for now I will just sit back for a while and see where you go with this.
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