Hi all,We have a Tx/Rx system at work that measures water level in a huge tank. The system works but all the documentation got lost somehow. I tried to open the Tx and Rx modules to see the parts inside but they are potted solid. I need to document the system because the info is missing and the design engineer left a few years back. Is there an easy way to detect the transmitter frequency ?We don't have any fancy spectrum analyzer but we have a scanner (scope and the like). I tried a few of the common freqs (900, 315, 310, 433MHz, etc) but I couldn't find it (I was told is below 900MHz). If the Tx has shifted a bit I could be close but .... well ... the possibilities are endless so ... I wonder if there is an easier way ?Thanks

"Rodo"** How does it do this ??Non contact systems typically use X- band microwaves - ie 10 GHz.Could it be ultrasonic instead of RF ?In both the above, you ain't gonna see it on a scope or hear it on any scanner........ Phil

Phil Allison idiot savant wrote:

How to detect the transmitter frequency ?

Mar 10, 2007 23 Replies

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Anthony Fremont 19 years ago

You implied they didn't exist. Well actually it was a bit more than an implication.

If you could now kindly cite something that makes your straw-grasping fantasy a reasonable assumption, I'm willing to look at it. I could certainly be wrong, but I can't think of any reasonable protocol that wouldn't transmit for at least a couple of mS. I mean I can think of silly schemes to keep the transmissions below 250uS, but why? Just so this counter can't lock onto it? Just so you can be right?

A scanner, even a good one, is NEVER going to lock on to intermittent bursts that are

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Anthony Fremont 19 years ago

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Anthony Fremont 19 years ago

Cite an example of one remote logger that would be.

I guess you think the OP can just wait for the squelch to open too instead of having to listen to all that noise? Show me one scanner with specifications indicating that it can lock onto a burst that small. Give it up phil. You don't even have the decency to answer the questions you don't like, you just snip them away. Try acting like an adult for once.

I don't want to here any more garbage from you phil. I only want to see some references to back up your pig ignorant claims.

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Frank Raffaeli 19 years ago

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The drawing in the link above illustrates how you can build your own frequency measuring system with a frequency generator, a mixer, and an oscilloscope. With a little ingenuity you could build it for about $200.

You will need to tune the generator until you see a low-frequency signal on the oscilloscope from the IF output of the mixer. The closer you get to the transmit frequency, the lower the IF signal frequency will be.

There are a few 1 GHz generators for sale on eBay for under $150

Frank Raffaeli

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