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| MPT-1327? http://interceptradio.com/bbs/viewtopic.php?f=26&t=2108 |
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| Author: | Wilrobnson [ Fri May 16, 2008 10:16 pm ] |
| Post subject: | MPT-1327? |
So, I'm getting what sounds like an MPT-1327 control channel on 217.6125, which is of course not licensed in Washington. I can't even find where it would be a system, as it appears to be a freq solely used for AMTS, i.e. data and whatnot for shipping. I can't seem to get Trunkview to decode it; this probably has something to do with audio levels and exhaustion levels. Ideas? |
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| Author: | Rich [ Sat May 17, 2008 3:12 pm ] |
| Post subject: | Re: MPT-1327? |
Wilrobnson wrote: So, I'm getting what sounds like an MPT-1327 control channel on 217.6125, which is of course not licensed in Washington. I can't even find where it would be a system, as it appears to be a freq solely used for AMTS, i.e. data and whatnot for shipping. I can't seem to get Trunkview to decode it; this probably has something to do with audio levels and exhaustion levels. Ideas? Its probably under a nationwide license for a company named AccessSpectrum. Unitrunker might decode it. |
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| Author: | Wilrobnson [ Sun May 18, 2008 3:22 pm ] |
| Post subject: | Re: MPT-1327? |
Rich wrote: Its probably under a nationwide license for a company named AccessSpectrum. Unitrunker might decode it. unitrunker manual wrote: There is a variation of MPT1327 found on 220 Mhz in North America that uses ACSSB modulation inside a 5khz channel. The FFSK parameters also differ from the standard narrow-FM MPT1327 mode. UniTrunker does not support this format. :( |
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| Author: | Vizwar [ Mon May 19, 2008 12:24 pm ] |
| Post subject: | Re: MPT-1327? |
I swear, the most secure protocol is an obscure protocol. |
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| Author: | Wilrobnson [ Mon May 19, 2008 2:16 pm ] |
| Post subject: | Re: MPT-1327? |
217.7725 was also passing MPT1327 traffic. |
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| Author: | unitrunker [ Tue Jun 10, 2008 4:47 pm ] |
| Post subject: | Re: MPT-1327? |
Sorry for the late reply. I just noticed this. I do not have any such 220 Mhz systems in my area so I've had no practical (decoding) experience. Could someone make a recording - perhaps a WAV file or even MP3? Ideally, I would like to see "hi-fi" recordings of speaker audio taken from a receiver in the appropriate SSB mode (upper or lower). The resulting FFSK audio waveform should have a very sinusoidal look to it. Please send email if you're interested. |
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| Author: | Wilrobnson [ Tue Jun 10, 2008 6:12 pm ] |
| Post subject: | Re: MPT-1327? |
http://www.kb9ukd.com/digital/mpt_1327.wav from http://www.kb9ukd.com/digital/ |
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| Author: | unitrunker [ Tue Jun 10, 2008 8:04 pm ] |
| Post subject: | Re: MPT-1327? |
Hi Wil; The link is to a plain vanilla MPT system which uses narrow FM modulation. Unitrunker can decode ordinary MPT1327. I'm interested in the SSB variant on 220 Mhz. In other words, if someone can provide samples - I may be able to adapt the program to accept this alternate form. |
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| Author: | Wilrobnson [ Wed Jun 11, 2008 5:45 am ] |
| Post subject: | Re: MPT-1327? |
unitrunker wrote: Hi Wil; The link is to a plain vanilla MPT system which uses narrow FM modulation. Unitrunker can decode ordinary MPT1327. I'm interested in the SSB variant on 220 Mhz. In other words, if someone can provide samples - I may be able to adapt the program to accept this alternate form. I have no idea how to do that, but I'll work on it later in the week. I may be able to record it off the disc tap/output of the PSR500; we'll see. Of course, I also have to be in an area I can hear it better than 2x5. |
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| Author: | Rich [ Wed Jun 11, 2008 6:56 am ] |
| Post subject: | Re: MPT-1327? |
Wilrobnson wrote: Rich wrote: Its probably under a nationwide license for a company named AccessSpectrum. Unitrunker might decode it. unitrunker manual wrote: There is a variation of MPT1327 found on 220 Mhz in North America that uses ACSSB modulation inside a 5khz channel. The FFSK parameters also differ from the standard narrow-FM MPT1327 mode. UniTrunker does not support this format. :( 220mhz doesn't necessarily mean its ACSSB. Down here I can decode sysid 4021 on 217.625. One easy way to tell ACSSB is by listening for extremely narrow bandwidth SSB on the voice channels. My AOR3000 could receive it in Washington but your radio alignment has to be dead-on frequency to hear it clearly. Of course the audio level sounds low since the radio isn't designed to receive companded audio. I don't seem to recall needing to notch the pilot tone probably due to its level being so low. Yours is probably ACSSB since a frequency like 217.7725 is a narrow allocation. |
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| Author: | Wilrobnson [ Wed Jun 11, 2008 8:52 am ] |
| Post subject: | Re: MPT-1327? |
Rich wrote: 220mhz doesn't necessarily mean its ACSSB. Down here I can decode sysid 4021 on 217.625. One easy way to tell ACSSB is by listening for extremely narrow bandwidth SSB on the voice channels. My AOR3000 could receive it in Washington but your radio alignment has to be dead-on frequency to hear it clearly. Of course the audio level sounds low since the radio isn't designed to receive companded audio. I don't seem to recall needing to notch the pilot tone probably due to its level being so low. Yours is probably ACSSB since a frequency like 217.7725 is a narrow allocation. I have yet to find a location to hear it where it's sufficient strength for decoding. It's been no better than 2x5 in Puyallup, Tacoma, Seattle, and Port Townsend. |
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| Author: | unitrunker [ Wed Jun 11, 2008 7:10 pm ] |
| Post subject: | Re: MPT-1327? |
MPT1327 decodes better with speaker or headphone audio rather that discriminator audio. A receiver that supports SSB in that band would be ideal for recording (and eventually decoding). If the signal is narrow FM - Unitrunker should decode it just fine. Some rare system use a non-standard frame sync - but that's another story. Again, you want speaker audio - not FM discriminator audio. |
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| Author: | Wilrobnson [ Wed Jun 11, 2008 8:43 pm ] |
| Post subject: | Re: MPT-1327? |
OK, I've got Trunkview, the MPT utility, decoding the system now after tweaking the settings. The control channel is on 217.6125, and the sysID is 40E1. Now what? |
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| Author: | unitrunker [ Thu Jun 12, 2008 9:59 am ] |
| Post subject: | Re: MPT-1327? |
May I presume your radio is set to FM or narrow FM? |
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| Author: | Wilrobnson [ Thu Jun 12, 2008 11:56 am ] |
| Post subject: | Re: MPT-1327? |
unitrunker wrote: May I presume your radio is set to FM or narrow FM? Auto mode. |
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