The Watt's New articles serve to keep you abreast of what has been going on around the C.A.R.L.A. Network. Feel free to browse our archive of past Watt's New articles as well.
On this page:
PAVE PAWS and its effect on the C.A.R.L.A. Network
Last updated on February 27, 2009 by The C.A.R.L.A. Team | This article is Archived | Permalink
Some of you may already know what PAVE PAWS is and some may not. It is not a new running shoe or tracks left by a bear in the woods. Basically, it is a radar system that utilizes around 1,700, 325W transmitters and antennas in a phased array with spread spectrum technology and is used in the 420-450 UHF band by the USAF/Department of Defense. They use it to track incoming water based ICBM's and also track the space shuttle amongst other things. There are a couple of them working in the U.S. and one is at Beale AFB near Marysville, CA which is North of Sacramento and the other in the Cape Cod area in Massachusetts.
You might say to yourself, "Hey that's in the Amateur Radio band" and you would be correct. However, contrary to popular belief, we are NOT the primary user in that band but rather secondary to the military. That means we must not cause interference to them and can be ordered off the band by the FCC if they insist. Most people don't realize this and it hasn't been too much of an issue until recently. We do experience interference from their system generally in the form of random "popcorn" popping sound under someone's signal with mobiles that are less than fully saturating the repeater's receiver and various link paths. This is prevalent on certain repeaters that are in closer proximity to the source like C.A.R.L.A. 6 & 16 and lots of others in the greater Sacramento Valley area and beyond.
The DoD recently approached the FCC and ARRL regarding increasing interference to their receivers on the system and have targeted over 100 repeaters in the greater Sacramento Valley, San Joaquin Valley & Bay Area as "allegedly" being a potential source of interference. A person in the ARRL has been made the point person for us and the ARRL has been the single source for the DoD to work with in relations with the Amateur Radio community and interfacing with the FCC.
The ARRL has come up with an interim plan for ALL targeted repeaters to turn their power down to 5W. The max limit has always supposed to have been 50W within a 150 mile radius of certain included military bases like Beale AFB and is what C.A.R.L.A. repeaters have always abided by. There are other steps that the ARRL will do to try and test repeater signal strengths, coverage patterns, etc., and make further recommendations in conjunction with the DoD/USAF. Some systems may have to change antenna patterns, heights, power output, location or just simply cease operations permanently.
In certain circles there has been quite a bit of chatter going back and forth regarding the situation and especially, but not limited to:
- Why all of a sudden is there an issue after ~30 years of peaceful coexistence?
- Where did they get their source of information on repeaters as it seems to be way out of date?
- How have they determined which repeaters do make the list and which ones don't?
- What is their criteria for "interference" and what levels would be acceptable to them?
- What does the changing of their PAVE PAWS system contractor have to do with all this?
- Did they make changes to their system that would affect the alleged problems and how many millions were spent?
- Are there other sources of interference out there besides what they allege is coming from Amateurs?
- This problem has been going on for a few years so why are they doing something about it now?
- If the Amateurs could potentially cause them interference, what could a determined adversary do to them?
- 5W transmitter output does not create a level playing field for everyone when considering varying system gains & losses.
- Why haven't they targeted anything in the 420/430 sub bands?
- If it really and truly has been disruptive then why didn't they do something more severe, long ago?
The irony is that the repeaters they are messing with are the ones that would help in the aftermath of a real attack.
There are a whole lot more discussion topics and revealing insight to the issue that would at the very least open one's eyes just a bit more.
When asked questions to clarify certain things their answer has been that its "classified" When you look at some of the information they gathered (call sign, location and frequency) it doesn't all make sense and is full of holes. But again, "its classified".
The first deadline was June 15th 2007, for turning down the power. The DoD wants all interference to be gone by August 1. Will this happen? Who knows, especially when they won't be as forthcoming with information as we need them to be. It may not solve their problem and they may look deeper into the Amateur band or other sources for the "real" reason(s).
C.A.R.L.A. has complied with the requests from the ARRL that were sent via certified letter recently. This means that C.A.R.L.A. 6 & 9 have been lowered in power to 5W. For C.A.R.L.A. 9, it is a bigger drop in power than C.A.R.L.A. 6 which is already turned down well below 50W due to co-channel neighbors. What this means to the user is that the footprint will obviously not be as great and things will sound noisier than normal especially in marginal areas and non line of site situations. The repeater should still hear as well as it did (maybe better) and the transmitters should run cooler but it will certainly reduce the effective range of the systems. For those that are close to the repeaters you may not notice a thing except, perhaps its not full scale on the S-meter. By reducing the power from 50W to 5W it will effect about a 10db reduction in power which could equate to 1-2 s-units on a radio depending on various circumstances and relative signal strength, etc.
As things significantly change and affect C.A.R.L.A. we will try to update this page. We truly hope that these changes will show them that the Amateur Radio community is not the sole or primary cause for their problems but we're also not so naive as to think they'll be satisfied with these changes alone. All we can do is to wait and see what else happens and hope for the best.
Below are some links that we gathered from other sources and files that may be of further interest in explaining the PAVE-PAWS system, the intentions of the DoD/ARRL/FCC, and other related issues.
Letter from the ARRL