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  1. zappedagain

    thin film resistor for TIA

    I'm looking into changing a transimpedance amplifier (TIA) from a thick film gain resistor to a thin film resistor. I see a thin film resistor shows -20dB on their datasheet (MIL-STD_202 method 308), but I haven't seen this spec on a thick film datasheet. I see MIL-STD-202 has the noise...
  2. zappedagain

    IP washers and earth continuity

    Earth rings are good for low frequency connections (bonding), but fairly worthless if you need the connection for an RF shield. Z
  3. zappedagain

    cone vs step FC connectors

    Thanks. One of those 'you get what you pay for' situations. We're finding higher insertion loss on these too, after a vendor switched from step to cone. That's still hard for me to comprehend, unless there are other tolerance issues coming into play. Z
  4. zappedagain

    cone vs step FC connectors

    What is the advantage of cone shape APC (angle polished connector) in the FC series over step shape? I see lots of info where step is easier to polish and easier to work with (our own experience included). Why would someone chose cone shape? Z
  5. zappedagain

    IP washers and earth continuity

    If the fiber washers are there for IP protection to keep fluids out, then you probably need a conductive gasket around the washer to make the electrical contact, or a counterbore ring for the washer so you can compress the washer adequately for IP protection, and then compress it a little more...
  6. zappedagain

    7805 / 7905 Power supply problem

    "There are no protecting diodes. Not across the output and not backwards across the regulator. The designer of the board has long retired, unfortunately. " If the output of a positive voltage regulator gets pulled below ground because a negative supply (the LM7905) starts up first, it can...
  7. zappedagain

    Difference Between Lock-In Amplifiers and other Coherence methods

    A lot depends upon your frequency range. When we used lock-ins 20+ years ago it allowed us to basically shift our low frequency data onto a carrier to move away from the 1/f noise at low frequencies, and then use the carrier to convert it back down to low frequencies (baseband) with a quieter...
  8. zappedagain

    CP SAR?

    Thanks!
  9. zappedagain

    CP SAR?

    Is it possible (plausible?) to use Circularly Polarized (CP) antenna in a Synthetic Aperture Radar (SAR) array? My initial study is showing my smallest CP antenna has outer dimensions of lambda/2, and my SAR processing constraints need the antenna placed at lambda/2 intervals (pitch). That...
  10. zappedagain

    ATEX certification - Associated Equipment

    I found the answer, and that I had a few things misidentified. For Class I Zone 0 the Associated Apparatus definition stops at the safety barriers that are regulated under ATEX. The circuitry powering the barriers is 'other equipment' covered by the applicable standards. So for ATEX in the...
  11. zappedagain

    Near field antenna to tell if radiated emissions are better or worse after modification to circuit?

    "It fails EMC at the moment. " - that's good, you have the first step, as long as you know how badly you are failing (X dB). I often use a near field probe to do before and after comparisons before I take a unit back to the test lab ($$$). If your mod shows an X + 3 dB or better improvement...
  12. zappedagain

    EMC filtering for real situations?....not the usual ideal setup

    Good questions. Again - https://www.emiguru.com/books/edn-designers-guide-paypal/ (I am not affiliated with emiguru.com, they just taught me a lot of valuable knowledge that I've used for my entire career) Z
  13. zappedagain

    Radiated EMC test with chassis earthed or chassis floating?

    The answers is "it depends..." If Enclosure A is 'totally enclosed', how do the wires exit? Via filter caps? A shielded cable? If neither of those your cabling is probably going to be a strong antenna that will swamp any other issues. With proper filtering on the PCBAs or maybe the cables...
  14. zappedagain

    ATEX certification - Associated Equipment

    Our equipment is certified for Class I Division 1 usage in the USA via UL 913/60079-11. The Associated Apparatus has a CE Mark and we self certify via the Low Voltage Directive (2014/35/EU), with supporting documentation from recognized test houses. We are looking to upgrade from UL 913 to...
  15. zappedagain

    What would you call this diagram?

    https://www.researchgate.net/figure/Blocker-and-Signal-levels-along-the-Receiver_fig4_261234760 I'd swear back in the early '90s I learned this as a Signal Flow Diagram (SFD). It is useful to track the noisefloor, headroom, and dynamic range in a receiver. If you Google SFD, you see the...
  16. zappedagain

    Criteria for defect rate of Junction boxes of PV modules

    No takers, eh? Maybe a post in the 'Engineering Codes, Standards & Certifications' section might get answered. Should the OP link to this message from that board, or is a week without a response long enough to not be considered double posting? Z
  17. zappedagain

    Looking for ideas on a DC disconnect.

    Have you checked out Stock Drive Products? - http://shop.sdp-si.com/catalog/?cid=p727 They have all sorts of little cams and things that can push your little red button (or give you ideas to 3D-print your own). #6 wire under high deceleration is pretty good at pushing those too (some know this...
  18. zappedagain

    Traxxas Charger Blown Up.

    With the big inductor (circle thing) right next to it on the bottom I'm thinking it might have been a voltage/current regulator before the magic smoke leaked out. What model charger was this? Z
  19. zappedagain

    Ethernet length estimate via software

    We need the length for absolutely nothing to do with Ethernet communication! (even though the PHY is calculating it for equalization and error correction) We run an optical fiber along with the Ethernet cable. This pair can have various lengths and are changeable in the field. If a customer...
  20. zappedagain

    Ethernet length estimate via software

    I finally found a non-TDR example for length estimation. Texas Instruments 'AN-1508 DP83849 Cable Diagnostics' (snla085a.pdf) gives on oversight of how a 100Mb link calculates cable length: 100MB cable length is a linear function of the Analog (AEQ) and Digital (DEQ) equalization coefficient...

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