Recent content by kellogs

  1. K

    First resonate a short antenna, then impedance match it ?

    I m afraid not... Anyway, the clear answer to my clear question is: no, it makes no sense to first resonate an antenna by means of adding a lumped element in series (capacitor or inductor); just match it as it is. It would have made sense to first resonate it by operating on the antenna itself...
  2. K

    First resonate a short antenna, then impedance match it ?

    Not sure why it makes no sense. Let me give my simple reasoning: small antenna are not resonant on the intended frequency, otherwise they would not be small. Their reactance can be cancelled by means of one series element - eg. an inductor for the short monopole antenna, or a capacitor for the...
  3. K

    First resonate a short antenna, then impedance match it ?

    Or incorporate the reactive resonator component (one capacitor or one inductor) into the impedance matching network, any difference besides lower component count ?
  4. K

    Long differential pair to balanced antenna

    The helix dipole is in 3D while the diff pair is 2D with a ~ lambda / 10 length.
  5. K

    Long differential pair to balanced antenna

    Thank you for the interest, 315 MHz, picture attached
  6. K

    Long differential pair to balanced antenna

    Hello, If I understand correctly, a differential PCB trace pair feeding a balanced antenna will not radiate much. Of course, there will be no ground plane above or below the diff pair. So then the antenna's radiation pattern will also not suffer much ? Can the diff pair + antenna piece...
  7. K

    Cause for TX frequency difference

    I have adjusted the frequency from software, problem persists. What about the two feed inductors used, how much of an effect can they have ? A: SRF = 1050 MHz DCR = 0.15 ohm Q = 15 B: SRF = 1400 MHz DCR = 1.5 ohm Q = 32 Thank you
  8. K

    Cause for TX frequency difference

    Oh yes... do you think this amount, 6 kHz, would be enough for a black box 433 MHz receiver to always process the signal vs never process the signal over a 50 deg C range ?
  9. K

    Cause for TX frequency difference

    i have an ISM band transmitter device based on the MAX41460 chip. It expects a 16Mhz, 12 pF crystal. Switched from set A of parts: - crystal: https://www.tme.eu/ro/en/details/16.00m-smdxt224/smd-quartz-crystals/yic/ - PCB antenna feed inductor...
  10. K

    thermal issues: surface mounted on 1" x 1" FR4 board

    Got some answers: https://electronics.stackexchange.com/questions/664950/thermal-issues-surface-mounted-on-1-x-1-fr4-board
  11. K

    thermal issues: surface mounted on 1" x 1" FR4 board

    A number of parts are rated at certain thermal impedance with a note, something along the lines of like in this datasheet for instance - https://www.tme.eu/Document/8ae9fea82a7cb44d4c881a980e95a2fe/siss05dn.pdf Does this mean that in order to achieve the stated thermal impedance (63C/W in this...
  12. K

    How will a car 10A circuit deal with double load?

    And for incadescent filament bulbs: https://www.allaboutcircuits.com/textbook/direct-current/chpt-2/nonlinear-conduction/
  13. K

    Automotive ISO 7637-2 transients dealt with by MCU ?

    The ISO is talking about +150V / -220V fast transients. Aside from these, there is also the dreaded load dump 400 ms, 79V and 0.5 ohm Does this design stand a chance to protect a large resistive load drawing up to 10A ? Q1, Q2 = 250V N channel MOSFETs Q3 = logic level N MOSFET D1 = standard...
  14. K

    Swapping diode for P-MOSFET: reverse spike protection

    Hey, could you, or anyone else, comment on this diagram ? How will R1 affect the TVS clamping voltage here, if at all ? And a side question, is there any difference between D2 above and two identical unidirectional TVS arranged like below (disregard the text around them and consider D1 and...
  15. K

    Swapping diode for P-MOSFET: reverse spike protection

    Err... please excuse my noobness. I surely would not want any resistor in series with it all. Is the second diagram going to do the job ? I did lay out 3 points where i am having uncertainty. And a 4th one - that MOV, I really don't like. It will likely not withstand 10 - 15 years of service.
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