TxID Transmitter FingerPrinter

Discussion in 'Discussions, Opinions & Editorials' started by KC9JIQ, Jul 8, 2007.

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  1. KC9JIQ

    KC9JIQ QRZ Member QRZ Page

    Anyone out there has this, seems cool, could you use this on your radio, like for example have your fingerprint in there, and only your finger print will key up the repeater, or prevent certain individuals from using your equipment.

    Eham has no reviews, but this seems very interesting for a particular use that I cannot say here. [​IMG]
  2. N5FOG

    N5FOG Ham Member QRZ Page

    The transmitter finger printer has nothing to do with limiting access to your radio or human fingerprints.

    Every radio's transmitted signal is somewhat differnt from others in very minor ways from its deviation,spurious emissions and other characteristics that are measurable/visible on a spectrum analyzer.

    What a transmitter finger printer does is it allows the user to save the "fingerprint" of known transmitters/stations to a database and when an unknown station is causing problems it can search the database to see if that fingerprint matches a known station.

    There was a group of hams down here in Houston that used one to quickly identify who was jamming a local repeater back in the mid-90's.

  3. VA3SAX

    VA3SAX Ham Member QRZ Page

    I was going to say it would be good for interference complaints...also might be useful if you stored the data from your transmitters...that way if they were stolen and fenced you'd know who had it...course it's not their fault if they didn't know that the seller didn't buy the rig
  4. N5PVL

    N5PVL Ham Member QRZ Page

    Does it work for HF too?
  5. N4AUD

    N4AUD Ham Member QRZ Page

    At $800 a pop, it will go on the long list of "things I'll just have to live without."
  6. KA5PIU

    KA5PIU Guest


    At $800 is is something you have the police buy and than borrow, like what was done in Houston.
    The cellular carriers also use this along with most military.
    Nothing new, just expensive.
  7. N5PVL

    N5PVL Ham Member QRZ Page

    There has been some free soundcard software around for this, for a very long time. It was one of the earlier soundcard-related ham radio programs. If I remember correctly it was a DOS program I played with years ago, but there may be later versions for Windows.

    I'd look around for a software solution before I coughed up 800 bux, no doubt.
  8. K5OKC

    K5OKC Ham Member QRZ Page

    It is designed for FM radios with a raw discriminator output, or a modified rig with the discriminator brought out to a jack.

    AM and SSB don't have all the markers that FM does.

    It's just audio, so a soundcard could be used to sample and display the output.  Basically you want to capture and expand the first couple of hundred milliseconds as the rig keys-up.  That's the only part that is different between rigs. 16 bits should be enough dynamic range to capture everything.
  9. NE5H

    NE5H Ham Member QRZ Page


    When an offender and his transmitter is identified, and you request FCC enforcement action, and an offender takes you to task or to Civil Court, does one have to qualify equipment as being "certified/calibrated/accepted" by the FCC, Courts, etc.? And, must the operator receiving and recording the electronic fingerprint be "certified" as an expert in any way, or, by the courts, in order for the electronic fingerprint to be introduced into a FCC Enforcement Hearing or Court of Law as evidence? Does the offender have legal recourse against you in a Hearing or Court of Law should you fail to prove your case? I don't know, I'm just asking the "what ifs".
  10. K8MHZ

    K8MHZ Ham Member QRZ Page

    I have used Audacity to do basically the same thing. It's sure easier to rule out a signal than match one, though.

    It's also easier to do on simplex than through a repeater.
  11. K8MHZ

    K8MHZ Ham Member QRZ Page

    Actually, an agent of the FCC is the only one that can collect such data if it is expected to be admissible in court.

    Usually a friendly note from the FCC mentioning the fact that someone has made a complaint and if offensive actions do not cease it would be possible to have an agent come to the area and monitor the transmissions is all it takes.

    If the FCC does come out and gather needed evidence to prosecute they will attempt to go after very stiff penalties in the form of fines, or force you to drag out the issue in court for years.

    The FCC does encourage recordings to be sent to them, but that is usually just to get a case started with at least some form of evidence.
  12. N5PVL

    N5PVL Ham Member QRZ Page

    I think you get the samples by listening on the input frequency. - I'm not sure if it will ID sigs that are repeated.... Maybe so, I dunno.
  13. N4CD

    N4CD Ham Member QRZ Page

    finger printing

    You can use several different techiques.

    Rigs when they key up have very specific key up sequences - power rise, frequency shift as they key up, any other 'glitches'. While you are keyed up, you have frequency offset (very few rigs are 'exactly' on frequency to within 0.0001 Hz), and most rigs have some hum on them or synthesizer products. If you have a CTCSS tone, you can measure the exact frequency of it, and the rise and wobble if any in it - digital artifacts.

    While you transmit, your signal likely has some drift or shift. Were talking about very high power DSP analysis of a strong signal.

    It won't work well on HF because of the effects of reflection off the ionosphere distorting the signal, and multi-path effects, but on CW and digital modes, it can be used to define transmitter types..and for those services on 'channelized' frequencies, you obviously once again have offset, drift, digital artifacts, and other things to look at. For SSB, it's much harder to get information out of the signal.

    You can tell the type/manufacturer of most transmissions by the way the FM radio keys up.

    It's not 100% able to differentiate all, but it sure can lead the FCC to your doorstep, and if you have a model Y, type Z radio, and you are screwing up something, then you are 'toast' at that point.
  14. WA2ZDY

    WA2ZDY Guest

    Back in the 70's we used an all-mode or SSB rig to listen just to the chirp of a rig on key-up on the repeater input. Very basic but usually enough back in those days to "fix" ptoblems.
  15. W6IRE

    W6IRE Guest

    It's been my experience that signal fingerprinting is highly unreliable.
  16. AI3V

    AI3V Ham Member QRZ Page


    I noticed that every time the FCC publisishes a NAL (notice of apparent liability) That there is a blurb to the effect of:

    On 1 dec 77, agents Smith and Jones, Acting on complaints to interference with communications with the ACME dogwashing company, tracked a radio transmission to 123 Main st,Anytown, Pa. A Mr. green answered the door, and agents gained access to a second floor room where we observed a Transmitter model "Rubber Duck 1000" capable of operating on frequency 123.456mhz. Mr Green admitted that he does not have a liscence to operate on that frequency.Furthermore, The "Rubber Duck 1000" Is not type accepted for use on this frequency. In accordance with rule 987 of paragraph ABC we issued a NAL for $$$

    Seems that a visual is required for many FCC actions- At least with bootleggers.

    Disclamer- I am not an attorney, and I slept in my own bed last nite!:D

    Last edited: May 8, 2009
  17. AI3V

    AI3V Ham Member QRZ Page

    Yep, Input it is.

    Doesn't do much good to fingerprint or D/F the repeater!

  18. K8MHZ

    K8MHZ Ham Member QRZ Page

    The more evidence, the better if the offender decides to fight the charges.

    I helped on a case where a telephone system was interfering with a licensed amateur across the street. The FCC had sent an agent from Detroit who determined that a telephone system from an insurance company was the culprit. It was nearly two years before the situation was resolved and that was with full cooperation on both 'sides'.

    The entire 'NAL' thing is strange to me. NAL stands for Notice of Apparent Liability. An NAL is NOT a fine. Take note of the K1MAN case. A 20 thousand dollar NAL was issued YEARS ago and has nothing has been paid. K1MAN still has his license.

    I am not at all impressed with the FCC as of late. The FCC is a shadow of it's former self. During the FCC's heyday we had hams like W8FLA (sk:() and W2DU manning the controls while a fleet of white vans awaited instructions from the monitoring station.

    Like it or not, the FCC is all we have. I will have to say that at least the FCC has been approachable over the last few years. I have shot off several e-mails with questions and have gotten some good responses. Even with an e-mail from the FCC in my hand, there are still people that will keep arguing a side that research has shown to be incorrect. :confused:

    In real life, if you took on the role of scoundrel and decided to start screwing with a repeater and an FCC agent showed up at your door and told you to knock it off, what would you do? Evidence or not, you got caught. Is messing with a repeater worth having the FCC drag one through the entire legal mess and risk prosecution?

    A few, however, take the fight to the finish......if there ever really is one with the FCC. I know of a case right now that has been going on for a couple years now involving an attorney. It's very interesting watching the case proceed. The attorney is a hoot and is having a great time with the case. It's better than any reality show I have ever seen!
  19. K8MHZ

    K8MHZ Ham Member QRZ Page

    If you can't get a signal from the input, every radio has an 'un-key' signature. Background noises can also be matched easily.

    Our group is pretty technical, has access to some great equipment and we pride ourselves with being great fox hunters.

    We seldom have problems and when we do they are so far and few between that a few of us actually enjoy it.
  20. N5PVL

    N5PVL Ham Member QRZ Page

    I was thinking that the known characteristics of the repeater could be filtered out, perhaps leaving enough information about the original signal to ID.

    I do not know of any software that does this, but - maybe someday, as software developers are wont to say.
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