Military radiolocation system to operate on 70 cm

[G4TUT]

Military radiolocation system to operate on 70 cm

As described in Schedule I of RBR-4, amateur usage of the 430-450 MHz (70 cm) band is on a no-protection, non-interference basis. Amateurs may not cause interference to nor be protected from interference from stations licensed in other services operating in that band. The same is true in the United States, and amateur operations on this band in a number of areas of the United States have power limits imposed on them in order to avoid interference to radiolocation services operated by the US military.

Industry Canada has informed Radio Amateurs of Canada (RAC) that it has authorized the Department of National Defence to use a digital system called Enhanced Position Location Reporting System (EPLRS) on these frequencies. The EPLRS system consists of mobile, fixed, transportable and airborne stations that use 5 MHz-wide spread spectrum channels to provide strategic telemetry information for military platforms. This authorization is on a no-protection, non-interference basis, which means that no new restrictions will be imposed on Canadian amateur operations in this band as a result.

Industry Canada has informed RAC that there is a slight potential for interference to amateur radio systems, typically in the form of a minor audible clicking noise. If Canadian amateurs encounter such interference, they are requested to report it to RAC at regulatory @ rac.ca. The information reported should include the geographical location, date, time, frequency and mode being used by the amateur station, and a description of the interference.

Questions or concerns regarding the planned implementation of EPLRS may be sent to regulatory @ rac.ca.



Richard Ferch, VE3KI
Vice President
Regulatory Affairs
Radio Amateurs of Canada






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[AK7AR]

We have experienced the spread sprectrum signal of this system in the repeater areas of the band. It is quite the irritant for analog 70cm repeater owners.

It does not seem to bother the D-STAR repeaters at all.

The military has indicated nothing about any interference from the amateur side of the equation. The Tucson area has been "enjoying" this signal for about two-ish years now.

Tnx,
AK7AR

[W4JE]

There's a similar system operating in the Washington DC area. Just as Industry Canada noted, the effect is a lot of frequent "clicking" in a typical FM passband. If you put a spectrum analyzer into peak hold mode over the 420 - 450 MHz band, it will build up a good picture of the individual wideband carriers after 15 minutes or so. The noise is definitely annoying when trying to monitor amateur satellites and other weak signals. Amateurs are secondary to military radiolocation in this band, but there's no allocation for military comm links, so if this system is being used for communications, then we may have some potential protection (in theory at least...).

73 de W4JE

[WA3VJB]

Oh, and beware the mystery garage door opener.

With DOD’s deployment of the new radios and increased use of the 380 MHz-399.9 MHz range of spectrum, some users of garage door openers have experienced varying levels of inoperability that has been attributed to interference caused by the new radios.


http://www.gao.gov/new.items/d06172r.pdf

[KA5S]

It might be interesting to make use of time difference of arrival, plotting against the known locations of repeaters, to identify the location of the emitters from the retransmission of clicks by those repeaters.

Cortland
KA5S

[W6EM]

Oh, and beware the mystery garage door opener.

With DOD’s deployment of the new radios and increased use of the 380 MHz-399.9 MHz range of spectrum, some users of garage door openers have experienced varying levels of inoperability that has been attributed to interference caused by the new radios.


http://www.gao.gov/new.items/d06172r.pdf

LOL. Well, Paul, one hand doen't know what the other is doing. Where's all that surplus TV spectrum that nobody wants?

The poor garage door crowd had to move from the PAVE PAWS spectrum, now what are they going to do? Perhaps the answer is a cellular modem so you can dial-open the garage door....

[K5OKC]

It's a Frequency Hopping (FH) Spread Spectrum signal. They just went from 57 kbps to 486 kbps on a 5 MHz bandwidth per hop. Very fast hopping. This system is really pretty neat, and Amateurs would do well to duplicate it and get off the old analog systems. The analog repeaters are just a waste of bandwidth on this spectrum.

The other neat thing about the EPLRS is you can use other stations in the net to communicate over the horizon. So you get high speed and long range.

This stuff worked very well in Iraq, all the way down to sniper teams with a backpack. I'm jealous...

20 MHz is not that wide to do brute-force jamming though. Also FH type signals are easy to triangulate. I expect to see jamming equipment out of Eastern Europe, and Iran :-)

[AA5TB]

For those that haven't heard it before, see the following:

http://www.aa5tb.com/sig13.html

I need to update the page but it's all there.

73,
Steve - AA5TB

[W6EM]

It's a Frequency Hopping (FH) Spread Spectrum signal. They just went from 57 kbps to 486 kbps on a 5 MHz bandwidth per hop. Very fast hopping. This system is really pretty neat, and Amateurs would do well to duplicate it and get off the old analog systems. The analog repeaters are just a waste of bandwidth on this spectrum.

The other neat thing about the EPLRS is you can use other stations in the net to communicate over the horizon. So you get high speed and long range.

This stuff worked very well in Iraq, all the way down to sniper teams with a backpack. I'm jealous...

20 MHz is not that wide to do brute-force jamming though. Also FH type signals are easy to triangulate. I expect to see jamming equipment out of Eastern Europe, and Iran :-)

I guess you must think that we have the ability to do synching of radios to some form of protocol to effect synchronized 'hopping.' Well, considering that this stuff is point to point, the concept sort of defeats the idea of high level repeaters and wide area coverage from one location. Essentially, it is a secure simplex system. And, the simplex repeating is akin to packet.

No, it doesn't fit rag chewing and it doesn't fit emcomm. In a crisis, we need maximum communicability, not security, which spread spectrum is all about. Imagine what would happen to a person trying to summon help if the radio they used didn't have the right hopping protocol? Nothing heard from them and nothing heard from anybody else.

Like I tried to joke about, there is ample spectrum that has been freed from UHF TV for the FCC and NTIA to put this "high priced spread" junk on. And, if they can't manage to do that, then perhaps they should underwrite the cost of new garage door opener receivers and transmitters for the general public to use to replace what is now in use by everyone. The Canucks can do what they please, of course, while we Yank around.

[K5OKC]

...In a crisis, we need maximum communicability, not security, which spread spectrum is all about.

I disagree. The main advantage of SS is that it virtualizes the spectrum. Instead of having 40 frequency channels (repeaters are channelized, and I know amateurs like to say we are against channelization, but there it is) in the frequency domain, we can have 10,000 channels in the frequency and time domain.

Spread Spectrum is like a Multitasking Real Time Operating system on top of raw hardware. Repeaters are like using the raw hardware and accepting the limitations. Sort of like DOS versus Java, or DOS versus .NET.

The reason the U.S. Military could care less about obsolete TV spectrum, is they need spectrum that they can use in any part of the world. We all remember what happened when the B-2 bomber decided to use any frequency they wanted for the radar. Yes, cost billions in tax dollars to start over again, and put the radar in the right spectrum.