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I have a couple of questions about voice inversion. Of someone can please dm me.
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Voice inversion
- Thread starter rescue674aa
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jim202
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The simple function of speech inversion is to use a fixed tone, mix the audio against it , filter out one of the mixes and send the remaining audio to the transmitter. The simple way of listening to it is to have a tone generator on the receive end and then mix it with the received audio.
This speech inversion units came out way back in some time like the 80's. They didn't last long after it was found out how simple it was to make a simple jury rig up to make it understandable.
Hope this might answer your question. I don't know of anyone still using this method to mask their communications.
This speech inversion units came out way back in some time like the 80's. They didn't last long after it was found out how simple it was to make a simple jury rig up to make it understandable.
Hope this might answer your question. I don't know of anyone still using this method to mask their communications.
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I was just wondering how it works and how to listen to it on my Kenwood 2180k. I found out its an ltr vhf trunking system with analog enc.
teufler
Member
In reviewing the manual on the tk 2180, there are 6 keys that are programmable for use. The two little side buttons then s,a,b,c,. s, and a have defaults of none. I would check those two out. In scranble mode , you get a diamond shape on the led screen that indicates scramble mode. It may have not been turned out when the radio was programmed. Did you get a program sheet that shows how the radio is set up? how it works, basically lows in the voice become highs and highs become lows. In a basic voice inversion. Now you have an auxillary board installed. yOU MAY HAVE A ROLLING CODE,
RayAir
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Inversion Based Scrambling
Finding a rolling code inversion scrambler already installed in a radio is pretty rare. Transcrypt was probably the most common boards in use and they had several models. They ceased operation a few years ago.
Transcrypt models:
400: Fixed inversion
410: Inversion hopping ( 1 time per second)
430: Medium rate rolling code inversion
460: Fast rate rolling code inversion
DES (sc20-DES/also SC20-500): Not really DES but a DSP based spectral rotation scrambler with the scramble code set with a 56 bit key.
For any decent level of security something like the Transcrypt 460 or better would have to be used as there are many weaknesses of inversion based scramblers which could be exploited using a handful of techniques. In fact, they ALL can be broken so the actual level of security is hard to quantify. Some of the rolling band splitters (DSP) were pretty good and they operated by splitting the 300Hz-3000Hz voice spectrum up into 4 or 5 separate bands and then would swap the bands around up to 10 times per second . But again, if one could match just the two lower band divisions for each swap, some intelligibility was possible.
As far as plain Jane voice inversion, it just inverts the signal spectrum so the lower frequencies are moved to the upper part of the band while the higher frequencies are moved to the lower part of the band. Generally inversion scramblers will have an inversion frequency somewhere between 2600Hz-4100Hz. Most are centered around 3KHz - 3.3KHz to avoid loss. Ex- Take an inversion carrier of 3700Hz, then say the speech band to be inverted around that carrier occupies 400Hz-3400Hz. Some of the signal that occupies 300-400Hz is lost because it now occupies 3300-3400Hz. If a carrier of 4000Hz is used the original band will occupy 700-3400Hz resulting in the loss of signal occupying 3300-3700Hz.
If someone wanted to try to descramble a fixed inverted signal, running a scrambler set somewhere between 3KHz and 3.3KHz will work. With this type of scrambling you don't have to match the actual inversion perfectly. Close enough is good enough. "Close enough" again cannot be quantified as it varies depending on the listener.
The main disadvantage of inversion scramblers is they retain speech like rhythm and residual intelligibility mostly because voice components around 1500Hz remain undisturbed by the inversion scrambling process.
I haven't heard inversion used in quite a while, but I have it on my PD782's and used an Android app that allows you to select 8 different inversion carriers. Running the inverted speech from my Hytera through the app I you could make out the voice using any of the 8 inversion carriers. I think the actual inversion carrier used in the Hytera is around 3.1KHz.
Finding a rolling code inversion scrambler already installed in a radio is pretty rare. Transcrypt was probably the most common boards in use and they had several models. They ceased operation a few years ago.
Transcrypt models:
400: Fixed inversion
410: Inversion hopping ( 1 time per second)
430: Medium rate rolling code inversion
460: Fast rate rolling code inversion
DES (sc20-DES/also SC20-500): Not really DES but a DSP based spectral rotation scrambler with the scramble code set with a 56 bit key.
For any decent level of security something like the Transcrypt 460 or better would have to be used as there are many weaknesses of inversion based scramblers which could be exploited using a handful of techniques. In fact, they ALL can be broken so the actual level of security is hard to quantify. Some of the rolling band splitters (DSP) were pretty good and they operated by splitting the 300Hz-3000Hz voice spectrum up into 4 or 5 separate bands and then would swap the bands around up to 10 times per second . But again, if one could match just the two lower band divisions for each swap, some intelligibility was possible.
As far as plain Jane voice inversion, it just inverts the signal spectrum so the lower frequencies are moved to the upper part of the band while the higher frequencies are moved to the lower part of the band. Generally inversion scramblers will have an inversion frequency somewhere between 2600Hz-4100Hz. Most are centered around 3KHz - 3.3KHz to avoid loss. Ex- Take an inversion carrier of 3700Hz, then say the speech band to be inverted around that carrier occupies 400Hz-3400Hz. Some of the signal that occupies 300-400Hz is lost because it now occupies 3300-3400Hz. If a carrier of 4000Hz is used the original band will occupy 700-3400Hz resulting in the loss of signal occupying 3300-3700Hz.
If someone wanted to try to descramble a fixed inverted signal, running a scrambler set somewhere between 3KHz and 3.3KHz will work. With this type of scrambling you don't have to match the actual inversion perfectly. Close enough is good enough. "Close enough" again cannot be quantified as it varies depending on the listener.
The main disadvantage of inversion scramblers is they retain speech like rhythm and residual intelligibility mostly because voice components around 1500Hz remain undisturbed by the inversion scrambling process.
I haven't heard inversion used in quite a while, but I have it on my PD782's and used an Android app that allows you to select 8 different inversion carriers. Running the inverted speech from my Hytera through the app I you could make out the voice using any of the 8 inversion carriers. I think the actual inversion carrier used in the Hytera is around 3.1KHz.
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voice inversion is basically taking the voice and phase shifting it (180 degrees) within the FM signal. Kenwood uses the frequency of the inversion to make it shift anywhere from 45 degrees to 300 degrees out of phase. MotoTRBO is able to do that now as well I believe, but the only thing I say was 2 options of phase.
scotttish
Member
Kenwood TK 8180 "descrambler"
I will be getting the Kenwood TK 8180K this week. From what I hear, you only have to listen to the inverted voice sound and then select between 1-16 to get a clear sound. Once I find it, I should be up and running. I haven't seen the programming software for it yet, but God willing the programming process will be uncomplicated enough.
I will be getting the Kenwood TK 8180K this week. From what I hear, you only have to listen to the inverted voice sound and then select between 1-16 to get a clear sound. Once I find it, I should be up and running. I haven't seen the programming software for it yet, but God willing the programming process will be uncomplicated enough.
mmckenna
I ♥ Ø
Kenwood programming is pretty easy to figure out. It's also got some excellent "help" documents built in.
Whatever you do, before you do ANYTHING, do the following:
1. Read the radio as it is out of the box.
2. Change ABSOLUTELY ___NOTHING___
3. Save that file in a couple of places. On your computer, on a USB thumb drive, and somewhere else.
4. Only then should you start changing anything with the radio programming.
While it's difficult to really screw up a modern radio these days, it's very helpful to have a "fall back" place where you can go. Being able to restore the radio to the "known good" setting can be a lifesaver if you run into issues.
I always take a new radio out of the factory packaging and read the blank file first. I'll save that as a "factory default" file. That was I can always roll back.
Good luck with the new radio.
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