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383.5500 ??

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#1
I have been hearing what sounds like a steady data stream on 383.5500. I am in the central U.S. Anyone have an idea------mil-air is not my strength. It's pretty strong between 3-4 bars on the 396xt. Update, I listened for 20mins. no idea how long it had been going on, it slowly faded out too nothing but dead air, static. Mike
 
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rmcgowan

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#2
383.550

Northstar C3 Wideband Multiplexed System:
The system onboard the E-6B TACAMO, Air Force 1, The E4B NAOC and other aircraft that provides
connectivity into the Northstar network via Ground Entry Points (GEP) is the UHF frequency division
multiplexed (FDM) command, control, and communications (C3) system. Both commercial and military
networks can be accessed. The onboard components consist of three UHF AN/ARC-171-1H transceivers,
five UHF antennas, three MD-1172 modems, three multiplexers, and associated hardware. Currently, the
equipment provides three of any combination of the following four services:
- UHF FDM (up to three full-duplex groups of up to15 channels each)
- Airborne Launch Control System (ALCS) data links
- Conventional UHF AM line-of-sight (LOS) (up to three half-duplex channels)
- UHF SATCOM phase shift keying (PSK) receive-only channel (TACAMO broadcast)
A UHF LOS air-to-ground configuration is used in conjunction with the ALCS for communications to
intercontinental ballistic missiles. In peacetime, the ALCS is used only during exercises in certain
geographic regions within LOS of missile silos. The 75 baud UHF SATCOM data (TACAMO broadcast) is
simultaneously broadcast on HF and can be received via that medium. Therefore, much of the time, the
third ARC-171 is available for other missions or functions. Nominally, at 25,000 feet, connectivity is
provided at an aircraft distance of up to 180 nmi from a GEP. GEP stations are usually located at elevated
sites for maximum unobstructed view. Towers are used to elevate antennas in flat areas. Separate transmit
and receive omnidirectional antennas are used. All sites are terrestrially connected via AT&T T-1 lines.
The current Air-to-GEP interface is a full duplex UHF FDM link that provides up to 1000 Watts of power
and 12 full duplex voice channels per FDM group. GEP sites have at least two radios and two compatible
multiplexers. The channels are frequency multiplexed into a 60 kHz baseband group consisting of twelve 3
kHz full duplex voice channels and three orderwire channels plus guard bands and then frequency
modulated for transmission on a UHF channel.
Principal sites at Waldorf, MD, Omaha, NE and Lamar, CO are connected via multiple T-1 lines. The
primary ground control site for the entire network is the Special Government Operations Center (SGOC) at
Waldorf, MD. The secondary ground control site is at Offutt AFB, NE
 
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#3
Northstar C3 Wideband Multiplexed System:
The system onboard the E-6B TACAMO, Air Force 1, The E4B NAOC and other aircraft that provides
connectivity into the Northstar network via Ground Entry Points (GEP) is the UHF frequency division
multiplexed (FDM) command, control, and communications (C3) system. Both commercial and military
networks can be accessed. The onboard components consist of three UHF AN/ARC-171-1H transceivers,
five UHF antennas, three MD-1172 modems, three multiplexers, and associated hardware. Currently, the
equipment provides three of any combination of the following four services:
- UHF FDM (up to three full-duplex groups of up to15 channels each)
- Airborne Launch Control System (ALCS) data links
- Conventional UHF AM line-of-sight (LOS) (up to three half-duplex channels)
- UHF SATCOM phase shift keying (PSK) receive-only channel (TACAMO broadcast)
A UHF LOS air-to-ground configuration is used in conjunction with the ALCS for communications to
intercontinental ballistic missiles. In peacetime, the ALCS is used only during exercises in certain
geographic regions within LOS of missile silos. The 75 baud UHF SATCOM data (TACAMO broadcast) is
simultaneously broadcast on HF and can be received via that medium. Therefore, much of the time, the
third ARC-171 is available for other missions or functions. Nominally, at 25,000 feet, connectivity is
provided at an aircraft distance of up to 180 nmi from a GEP. GEP stations are usually located at elevated
sites for maximum unobstructed view. Towers are used to elevate antennas in flat areas. Separate transmit
and receive omnidirectional antennas are used. All sites are terrestrially connected via AT&T T-1 lines.
The current Air-to-GEP interface is a full duplex UHF FDM link that provides up to 1000 Watts of power
and 12 full duplex voice channels per FDM group. GEP sites have at least two radios and two compatible
multiplexers. The channels are frequency multiplexed into a 60 kHz baseband group consisting of twelve 3
kHz full duplex voice channels and three orderwire channels plus guard bands and then frequency
modulated for transmission on a UHF channel.
Principal sites at Waldorf, MD, Omaha, NE and Lamar, CO are connected via multiple T-1 lines. The
primary ground control site for the entire network is the Special Government Operations Center (SGOC) at
Waldorf, MD. The secondary ground control site is at Offutt AFB, NE
Thanks for all that info! As I am typing, it's back on. Faded back in , and gaining in strength again. I normally listen to the HF network, but today I was just pulling out some of my older scanners, and letting them search. Guess I should be doing it more often. Thank's again for the help Mike
 
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#4
Do you have any federal or military installations near by? 380-400 was realigned for LMR use years ago, it could be the control channel of a trunk system.
 

nd5y

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#5
Do you have any federal or military installations near by? 380-400 was realigned for LMR use years ago, it could be the control channel of a trunk system.
I hear it a lot. It doesn't sound anything like a trunking control channel. The 380-400 band isn't 100% exclusively LMR either.
 
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#6
Do you have any federal or military installations near by? 380-400 was realigned for LMR use years ago, it could be the control channel of a trunk system.
Actually, the closest would be at least 200 miles. This sounds quite a bit different than a control channel, at least any types I have ever heard. Mike
 
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#7
I hear it a lot. It doesn't sound anything like a trunking control channel. The 380-400 band isn't 100% exclusively LMR either.


For sure----much different. Just like a digital data stream type signal. Sounds quite a bit like some of the HF utility stuff I have heard. At least to me----I am no expert in this area for sure though. Mike
 
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#8
Is there any frequency besides 383.55 I should add to my scanner that is part of this system?
 
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#10
Read through the whole thread, lot's of good information in there. 383.5500 has been active for the last hour, non-stop here today. Finally faded out about 10 mins. ago. I have a question, I parked my 396xt on it, and ran a Uniden 125at, and Uniden 330t non-stop through the Mil-Air band, nothing anywhere, at my location. Would that be normal? Or would other freq. be active at the same time?

I checked 11.175, 8992.00, and 15.016 usb on a few of my HF radio's also, nothing. Just for the heck of it, I put a Pro-106 on 383.5500 also, just as loud and clear (my wife really like's this sound). Anyway guess i am curious is that normal? I realize location, and equipment limitations may come into play also. Mike
 
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#11
Hi, first off, 383.55 is common to a lot of US mil bases, likely around the world, for trunked land mobile repeater activity. If you have a base within uhf range, your strong signal may be trunked repeater activity, but the tacamos and naocs still have that freq in their radios for northstar use. Also, the geps and abcps will be running a few thousand watts of output power, the trunked repeaters will be running much less. Also, if you're within uhf range of a gep, ground entry point, not always but can be a US mil base, you'll be able to hear the aircraft and ground sides of the full duplex radio link. Non mil base gep's are commercial telco setups, sprinkled around the US where the tacamos and naocs are wont to roam, ie middle of nowhere in a lot of cases.

If you enter all the suggested freqs into your scanners you should become very familiar with what is day to day routine for the abcp's in your area. Keep in mind the northstar system is frequency agile and can go about anywhere in the 200 to 400 range whenever they please and no one other than potus is going to stop them from using a frequency, so having a scanner set to sweep the band is a good idea when hunting abcps. If you don't hear them at the same time every day - that is normal, they operate 24/7 and can roam several thousand miles if they wanna, but usually they pick a spot and orbit the chosen gep by a few hundred miles.

If they traverse from one gep to another or exit the net, they will setup the link ahead of time and coordinate the drops and acquisitions as they qsy or drop the link altogether. They may or may nor use HF but often do, for the tacamos you can find them on the hfgcs entering and exiting the net as well as injecting traffic (eams), however the USN has a dedicated tacamo net where eams are passed;
13155
11244
8776
6697
4372

Another USN hf freq with tacamo activity is 9031. They can be found on hf ale but I don't have the freqs at hand.
 
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#12
I am guessing the one I am hearing is a non-military ground entry point for tacamos and noacs. Because of my location. Thank you for all the knowledge, and help------you have sparked a new interest in my radio hobby.I now have 3 scanners pretty much dedicated to mil-air, so I will see what pop's up. Thanks again, Mike
 
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#13
You have it made if near a gep, if you hear the gep you know the naoc is around and is talking to the gep. If the signal never fades or changes otherwise until it drops completely - you likely have a gep, if it fades out briefly, the fade may have been caused by a wing or the fuselage blocking the rf path to your antenna as they are constantly circling up there, waaaay up there, trying to keep a few miles of vlf antenna wire as vertical as possible, it's also routine for them to come in strong, then fade out for a few minutes, and then come back in as the naoc completes its loop near you. If you can hear a gep you absolutely will hear the naoc too, unless the gep was doing maint on the system of course. I'm about 50 miles or more to the nearest mil base that would support a gep, so barring a closer commercial gep about the only way I'm going to hear a gep is by ducting, and that is very seasonal, like those few days when you can get a fm radio station from a few states away.. It all makes for interesting listening, more of a challenge, really.
 
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dlwtrunked

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#14
Hi, first off, 383.55 is common to a lot of US mil bases, likely around the world, for trunked land mobile repeater activity. ...QUOTE]

I have monitored dozens of the trunked US mil systems. All I have seen use 380-382 and 385-390 for the repeaters with 382-385 always unused for those systems.
 

Airboss

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#15
Do you have any federal or military installations near by? 380-400 was realigned for LMR use years ago, it could be the control channel of a trunk system.
383.550 is still a Northstar wideband downlink frequency.

After DoD reorganized the 225-400 MHz spectrum in 2004, they carved out several subbands devoted exclusively for wideband operations (bandwidths greater than 25 kHz, such as the Northstar freqs). My April Milcom column in The Spectrum Monitor has a complete breakdown of the 225-400 spectrum including these new wideband subbands.

383.2375-384.4375 MHz is the wideband subband that your 383.550 rest in.

If you missed my April column you get order it ($3 single copy or $24 1 yr sub) on the TSM website at The Spectrum Monitor.

73 and good hunting

Chief
 
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#16
383.550 is still a Northstar wideband downlink frequency.

After DoD reorganized the 225-400 MHz spectrum in 2004, they carved out several subbands devoted exclusively for wideband operations (bandwidths greater than 25 kHz, such as the Northstar freqs). My April Milcom column in The Spectrum Monitor has a complete breakdown of the 225-400 spectrum including these new wideband subbands.

383.2375-384.4375 MHz is the wideband subband that your 383.550 rest in.

If you missed my April column you get order it ($3 single copy or $24 1 yr sub) on the TSM website at The Spectrum Monitor.

73 and good hunting

Chief


Been listening to them all weekend------rarely fades out here. Using the signal indicator on my 396xt, I am pretty sure I was able to actually see the EB6, or EB4. The signal strength changed as it flew in and out of my sight. It started getting stronger again after a 1/2 hour or so, and again ,it looked to be the source of my signal , this time flying a further South route. Looked like an East-West loop. Still going strong 5 bars for the better part of 6 hours (minus intermittent fade in and outs).

Larry--------I really miss Monitoring Times, I never subscribed, but bought every issue I could ever find! I always read your column first. Still have them, even still refer to them. I will check out the Spectrum Monitor site for sure! Thanks for the info, Mike
 

K4FLB

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#17
I wouldn't discount 380-400 Mhz for ground-to-air or air-to-air comms. I have still heard a few in recent years. airnav.com still shows 381.3 as the command post for Shaw AFB, Nellis AFB and Davis Monthan AFB. 383.0 is also another common command post frequency. Seems I saw that one recently too. I have heard comms on 381.3 in recent years visiting some of the bases I listed.
 
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#18
I didn't want to start a new thread. I know "Global Thunder" is going on, and I am hearing a ton of traffic. And as usual I am hearing 383.550 loud and clear today so far , for over 6 hours, since I turned the radios on. My question is I am hearing the usual steady data stream on 383.550, BUT I was outside killing time with my C.Crane Skywave (SSB version) , I had Brother Stair on (I know, but I was REALLY bored) a freq. of 9395 (totally normal), but I was hearing the steady data stream from 383.5500 , very prominently in the background (just using the whip) . Is that even possible?? The signal is VERY strong here. I have video from my phone from both radios , I am just having trouble getting them posted.


Little update, inside now hearing it in the background on 9395 still----but on my Tecsun PL880 off the whip also. Same data stream on 345.60 now.
 
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