572B Tubes

Discussion in 'Amateur Radio Amplifiers' started by AG4RT, Nov 3, 2015.

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  1. W8JX

    W8JX Ham Member QRZ Page

    A MFJ analyzer can only see major/obvious line problems. A TDR (tela digital reflectometer) reads RF echos off line and when you factor in velocity factor of coax it can show you exactly where every bit of damage is and it will see slightest variation in dielectric spacing and every connector. Its a neat tool. We used them to find faulty connections or damaged coax.
     
  2. N8VIL

    N8VIL Ham Member QRZ Page

    I just started a project on building a TDR based off plans from this video. Link I am looking forward to getting the project done and trying it out. I am amazed that you can actually see the echo on a scope for as fast as it travels. The one that I am going to build is not the surface mount design as in the video. The supply is built but I am still figuring how to house the circuit at the BNC connector.
     
  3. W8JX

    W8JX Ham Member QRZ Page

    I have heard them called both Tela Digital Reflectometer and Time Domain Reflectormeter. When we first got them they called them the former. I first used them in 70's and they were pretty pricey then. You could expand sweep on scope readout and expand/pan through it to inspect condition of run. I have not used one for several years now but I have no doubt with todays technology it could be built quite small and use a PC to view results.
     
  4. K4PDM

    K4PDM Ham Member QRZ Page

    Does it have bad tubes ? Seems like another type tube could be put in the Cliperton L ?

    Enjoy your AL-80B.[/QUOTE]

    Actually, the problem with the Clipperton is not the tubes. The bandswitch is flaky, and it won't work on 17 or 160 with any kind of decent power. I know there are mods, but I decided to go with a new amp for the first time in my ham career.

    73, Paul K4PDM
     
  5. KM1H

    KM1H Ham Member QRZ Page

    Time Domain Reflectometer has been the term long before anything with "digital" in it, and as often happens here and on Eham you likely got it bass ackwards again.
     
  6. W8JX

    W8JX Ham Member QRZ Page

    When we were provided a device to test on aircraft in 1975 the contractor called it a "Tela DIGITAL Reflectometer" or TDR . That was first name I heard it called. I was amazed how accurate it was at finding damaged coax or bad connectors back then. If you got velocity factor correctly dialed in it was very accurate on locations of flaws.
     
  7. W9GB

    W9GB Ham Member QRZ Page

    An Optical Time-Domain Reflectometer (OTDR) is mandatory for fiber-optic installation and troubleshooting where a break or fracture has occurred.
    I saw my first OTDR in operation (early 1990s), when SIECOR sent a troubleshooting team to the infrastructure install (their warranty on fiber, free from defects) I was leading.
    Operated virtually the same as a TDR, but with enchancements (LED-multimode; Laser-singlemode) as well as what wavelength (nm) / light color to use for the OTDR tests.
    --
    We had to determine why one of the multi-mode fibers was "dead", if it was manufacturing defect, installation issue with contractors, or other cause.
    The Root Cause was mishandling by the logistics company (dropping spool onto something -- damaging fiber about 0.5 meter from end) delivering the spool to job site.
    Testing records of the spool were invaluable in pinpointing when damage occurred.
    SIECOR paid for repairs (charged back to logistics company), which only required a 1 meter splice from the break to the data-center termination cabinet.
     
    Last edited: Dec 22, 2015
  8. KM1H

    KM1H Ham Member QRZ Page

    I saw TDR's in use on nuclear carriers in the late 60's and much later in 84 on the USS Carl Vinson when I spent 8 weeks on her during the first voyage; it was a mil spec TEK. They all have miles of coax installed.

    These days they come standard in Service Monitors from HP and others.
     
  9. W8JX

    W8JX Ham Member QRZ Page

    TEK rings a bell.

    You would be surprised as to how much coax is in some large USAF aircraft. B52D models used it is fuel quantity system that was based hollow probes in fuel cells that varied in capacitance depending on fuel level in each cell using tube based control modules connected to probes to drive gauges. Damage to cables or connectors could greatly effect it. Water in fuel could also cause big problems with system. Later model 52's and other large aircraft used a different system that was more reliable and less sensitive to water in fuel which was unavoidable at times. Water slugs had no effect on engines but could effect gauges and on a 52 that carries about 150 tons of fuel in wings and body fuel quantity for CG issue, particularly for landing, was a constant concern.
     
  10. AI3V

    AI3V Ham Member QRZ Page

    It takes 12.36 microseconds for a radio signal to travel 2000 yards and back in free space.

    Multiply that by the velocity factor of your feed line, and compare that to the time per division on your oscope to see what kind of resolution you have.

    If possible make the tdr measurement from both ends of the feedline and split the difference. This is particularly important if the coax is very long and buried :)

    Rege
     

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