Thursday, June 3, 2010

Digitally Linking Analog Repeaters

Those from Wisconsin might be familiar with the Wisconsin Interstate Network. It's a wide area coverage UHF linked repeater system, composed of nearly 20 systems throughout the state. It is all RF linked, so from an emergency commutations standpoint it's very handy resource.

Now imagine if you can if it was all linked digitally, but still using RF, not the internet.

It would not be very expensive to convert the analog audio to digital at each site and run inexpensive outdoor ethernet cable up the tower instead of a hardline line for linking. Since each analog repeater site is at significant heights, achieving line-of-site linking on 3 GHz or 900 MHz should be possible.

If you did this, you would have a high-speed statewide digital RF backbone independent from the internet, that not only connects all the analog sites, but has plenty of bandwidth left over.

ARES / user LAN access could be on 440 or 900 MHz. I'm talking about sending 20 MB of pictures from your ARES incident across the state in seconds. Or hooking an IP phone up and having a fairly secure conversation if the situation warrants it.

All this is possible, all fairly inexpensively. You just have to think different.

Wecomm is a smaller linked repeater network project going on in the state, that I have blogged about before.

They are building data networks into their site deployments.

What I am showing above is a very inexpensive way to stream audio digitally. Wecomm (so far) has been using expensive JPS Ratheon ARA-1 radio interface devices to accomplish this.

USB server adapters are fairly new. They allow you to use USB devices as network devices... cheaply.

When you are dealing with many sites, far away, the idea of having a computer at each site is less than ideal. Fairly inexpensively you could build a computer with no moving parts using flash drives to increase reliability..... But can you do this for under $50?

If a plug and play solution is what you seek, check out the CAT CL-100 Internet/802.11/HSMM Linking Controller.

Tuesday, June 1, 2010

Ham Radio in KA9Q's eyes

It took me a while to find this snippet of comments from Phil Karn, KA9Q in WT Docket No. 97-12 from about 10 years ago:

....amateur frequencies are still occasionally involved in emergency communications despite being almost completely eclipsed in recent years by cellular phones, portable satellite links and the like. But the amateur service has always been primarily an experimental, technically-oriented service. It is not a critical operational safety-of-life service like public safety or aviation, nor is it a common carrier utility like cellular telephones....

For those of you who aren't familiar with the Phil Karn, KA9Q:

He is an engineer that worked for Bell Labs in the 70-80's. He was on the ARRL future systems committee/Technology Task Force for nearly a decade. He had had his fingers involved with many Amateur Satellite Service projects.

Has helped develop the Internet as he as been a strong contributor to its architecture. (His name is on at least 6 RFCs, as a member of the Internet Engineering Task Force)

He is well know for his work with digital communications specifically with DSP and forward error correction (FEC) and spread spectrum.

Since 1991 Phil was been with Qualcomm, a wireless telecommunications research and development company, as well as the largest cellular chipset supplier in the world.

Simply put: Your cellphone works on CDMA technology that Phil Karn helped develop. Phil is the best example I can think of where ham radio served as an "experimental, technically-oriented service" that served(s) as a breeding ground for technological development that later the rest of the world greatly benefited from.