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How to detect the transmitter frequency ?

Discussion in 'Electronic Design' started by Rodo, Mar 10, 2007.

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  1. Rodo

    Rodo Guest

    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 ?

  2. Phil Allison

    Phil Allison Guest


    ** 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

    ........ Phil
  3. DaveM

    DaveM Guest

    Assuming that the Tx power is in the milliwatt range, just connect the antenna
    to the input of a sensitive frequency counter.
    No antenna lead? Get a smallish coil of a few tens of uH and place it in close
    proximity to the Tx module. Connect the coil leads to the counter input. You
    might have to play with position and orientation of the coil, but it should give
    you a solid count somewhere around the module.

    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

    Life is like a roll of toilet paper; the closer to the end, the faster it goes.
  4. Something like this: Precision_103
  5. Phil Allison

    Phil Allison Guest


    ** Shame if the RF signal is pulsed or out of range of the counter ....

    ....... Phil
  6. Jim Yanik

    Jim Yanik Guest

    Or use a spectrum analyzer and antenna.
    Optoelectronics used to make low-cost receiver/counters for this sort of
    thing;are they still in business?
  7. Rodo

    Rodo Guest

    I'm sorry I didn't make it clear that the Tx/Rx modules are not the one
    reading the water level. That system is an ultrasonic meter. The Tx/Rx
    modules are connected to the output of the ultrasonic meter and transmit the
    info to the base unit.
    Someone suggested a BK Precision counter. This sounds like a pretty good
    option. I think the model 106 will need to be because I'm almost certain the
    info is digital (on-off stuff)

  8. Rodo

    Rodo Guest

    This looks good. Thanks
  9. Phil Allison

    Phil Allison Guest

    ** NO - you posted the opposite in fact:

    " We have a Tx/Rx system at work that measures water level in a huge tank. "

    Top posting Dickhead !

    ** Counters cannot count what is not there.

    A transmission must be * 100% continuous * to use a counter obtain the

    A radio scanner is still your best, low cost bet.

    ....... Phil
  10. ISTR there's a way to use a grid dip meter to get close.
  11. Guest

    This may not be an engineering issue. If you cannot guarantee that
    you can reverse-engineer the mfgr's specs _including safety margins_,
    whose ass is on the line if the system goes tits-up and the tank
    fails; just yours, or the owner's?

    I know it sounds like a fun problem, but the phrase "CYA, remove and
    replace" exists for a reason.

    Mark L. Fergerson
  12. It's not his fault you misunderstood him. The rest of us didn't have that

    You are wrong. The B&K 106 only needs a 250uS burst to measure.
    Yeah right. Stick with audio Phil.
  13. Phil Allison

    Phil Allison Guest

    "Anthony Fremont = Asinine **** "

    ** It is entirly his fault for posting the wrong info.

    ** What an idiotic bloody lie.

    ** Nope - it is true of the vast majority of counters.

    ** Cite ?

    ** Thanks for the vote.

    Now, go shove you pointy, totally fuckhead head back up you slimy arse.

    ......... Phil
  14. NO, it's entirely your problem for jumping to the wrong conclusion and
    thinking it's the OP's fault.
    Well, most didn't.
    That isn't all of them. At any rate, it only has to last for a maximum of
    two gate times on "the vast majority of counters".
    _I_ just gave you one. If you need a confirmation, look it up.
    I guess you cut the rest out and put it up on your bathroom mirror.
    Can't you be more clever than that? If you don't like being treated like a
    dick, stop acting like one.
  15. Phil Allison

    Phil Allison Guest

    "Anthony Fremont = Asinine ASD Fucked **** "

    ** It is entirly his fault for posting the wrong info.

    ** Another idiotic bloody lie.

    ** Yawn - more asinine ASD fucked drivel.

    ** Cite the info.

    ** Yes - go get your arse fucked by a dead donkey.


    ....... Phil
  16. Phil Allison

    Phil Allison Guest

    "Anthony Fremont = Asinine ASD Fucked **** "

    ** Shame that is not the same counter you suggested earlier.

    Shame if the pulses are shorter than 250uS.

    The OP already has a radio scanner with no such limitation.

    Piss off - you vile, autistic donkey fucker.

    ........ Phil
  17. I never said it was. I suggested the cheap one first. I'm sure it will fit
    his needs just fine. I referenced the other one just to set you straight.
    Different problems, different tools.
    What kind of baud rate do you think they're using Phil? Maybe it's DSS?
    Fat lot of good that will do him with transmissions <250uS, huh?
    Come back again when you need some more learnin'
  18. ehsjr

    ehsjr Guest

    Yes. AT the low end of their line, the "Cub" covers
    1MHz - 2.8 GHz. On sale for $129. They have other
    units, the "Cub" is the only one I'm familiar with.

  19. Phil Allison

    Phil Allison Guest

    "Anthony Fremont = Asinine ASD Fucked **** "

    ** I was never wrong.

    Sampling frequency counters are rare items.

    ** Shame if the UNINTERRUPTED RF pulses are all shorter than 250uS.

    ** The repetition rate of data bursts is audible in the speaker.

    Piss off - you vile, autistic donkey cock sucker.

    ........ Phil
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