Leaky Coax Perimeter Security + Propeller

kochevnik

There is a method of perimeter security using 'leaky' coax cable - either specially designed (like the attached Trad datasheet) - or even standard coax (RG-58 and such).
If you look at the Wong paper, this is a college student who did a basic system a few years back, it is the best amateur attempt - actually the ONLY attempt I have been able to find on the net.

What I would like to do is to experiment with this, but I am probably out of my depth - I see this as :

1) a (RF Power) signal generator - the Wong paper uses a 150Mhz signal @ 5 watts which is totally illegal from an FCC standpoint right ?
2) Radiax leaky coax - $6 a foot at that time
3) National Instruments PCI DAQ (data acquisition) card & BNC 2110 box - I see this on ebay for $100 to $350 :
http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&_nkw=bnc-2110&_sop=15
4) LabView

So you shoot a 150Mhz signal down the first leaky coax and do data acquisition on the second cable and when a person comes near the first cable the signal is altered (amplitude increases) and when you measure this you have a perimeter intrusion device.

And yes there are cheaper and less complicated options (like a dog) but what's the fun in that ? LOL

So since all this equipment is old (some of it from the 70's) what would all you experts recommend as modern day alternatives ?

My primary goal is RELATIVELY EASY to program - I don't see any point in spending thousands of dollars on labview - that signal change that he was looking at was a simple amplitude spike - that's all I want to detect (not measure) beyond some threshold - I'm thinking a DSP can do this ? Something like a Blackfin ?

I'd like the DSP/DAQ to send a signal to a Propeller because I already have a lot of work done getting the Propeller to talk to a PC.

I'd guess the real key is it is going to be the signal processing that is 90 percent of the work ?

Again, I am pretty much clueless here, but I have a decent budget for this and I'd really like to hear any advice suggestions etc.

kwinn

A DSP like the Blackfin should be more than adequate, however if you just want to detect the spike you could probably do so by demodulating the RF signal and use an op amp and comparator or ADC for the demodulated signal.

kochevnik

So if the original signal is a 150 MHz sine wave, I'm not sure what you mean by demodulating the RF signal ? (Sorry beginner question I know).

What would be the least expensive way to generate that sine wave and then monitor it for testing purposes (oscilloscope ? digitizer ?)

Circuitsoft

To generate the sine wave, use something like the FXO-HC736R, and to detect it, you really just need a diode and a capacitor. If the signal level is too low for that, there are plenty of LNA modules you can get that will amplify the signal to the point that a basic AM detector (same circuit as a classic "crystal radio") will see it.