What does TDR mean?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KE0CU, May 17, 2020.

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  1. WD0BCT

    WD0BCT Premium Subscriber QRZ Page

    Turbo-encabulator Drive Reversal

    It only works while the turbo-encabulator is engaged but that's the only way to fly with this transceiver.
    KA9JLM likes this.
  2. K8JD

    K8JD Ham Member QRZ Page

    In two way radio work , you use a TDR (Time Domain Reflectometer) to find breaks in the coax going up a tower and bad connections to the pigtail coax going to the antenna, Gives you a pretty good idea where (in feet up the line) the .22 slug is stuck in the 7/8 inch lines.
    AJ4WC likes this.
  3. KB0MNM

    KB0MNM Ham Member QRZ Page

    Yep, and I just got through looking at a book by Joseph Carr regarding RF which had a 'poor man's TDR' using the 4024 chip as a base. It also had the 'poor man's spectrum analyzer'. I bet a few others have this green book on the shelves. Unfortunately, some TDRs ( like those built for LANS ) will not double very well for two-way radio work. I once found a resonant line that looked good to an SWR meter ( LDF4 or similar, around 200+ feet ). My supervisor did not believe me that the technician before me had signed off on the system, yet the customer called my attention to poor propagation. The antenna had been disconnected for other work at the top, yet the SWR showed good. The supervisor brought along the LAN TDR to see if it might have detected the issue.
  4. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Give me a digital storage oscilloscope, a battery and some wire and I'll show you how to make a very poor man's TDR.
    K7TRF likes this.
  5. KB0MNM

    KB0MNM Ham Member QRZ Page

    Yes, "Secrets of RF Design" allows one to build a stand-alone Time Domain Reflectometer ( albeit nowhere near as good as a Tek 1503 ) with a chip, a few discrete components, and a regular oscilloscope. The chip pretty much just acts as a signal generator. A more expensive DSO, switch, wire, and battery would do that with storage- in some cases better than the chip circuit. The LAN tester had a '50 ohm' coax port, the problem for others was that the open line was quite a climb. I understand that they goofed around with trying to use that LAN tester with the antenna and at least one other 'load'. The MASTRII base station was later replaced with a BK mobile, controlled remotely. That probably saved the folks enough money on power bills to make up for their previous inconveniences caused by lack of range. It took a bit of programming, and then they could also access more than one frequency. Sometimes a fail can lead to a victory.
  6. K2WH

    K2WH Premium Subscriber QRZ Page

    Time Domain Reflectometry.

    Its used to measure the distance to a faulted cable.
    AD7DB likes this.
  7. K6CLS

    K6CLS Ham Member QRZ Page

    Ah sooo... Man with two radios, never really knows which one to talk on.... (gong sound)
  8. KA2RRK

    KA2RRK Platinum Subscriber Platinum Subscriber QRZ Page

    Time Delayed Resume, maybe?

    Used in scan mode.


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