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  • Users: TWW
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  1. TWW

    waveguide beyond cut off

    The lowest mode of propagation is TE01 with a cutoff of 1.64*diameter therefor your waveguide is cut off. 1/4 wavelength of cut-off waveguide is enough to extinct all of the evinescent energy.
  2. TWW

    S-Parameter Measurement with Network Analyzer

    If you establish your reference plane at the IC pin, you can use a 50 ohm load at that point (with no IC). use three standards O-S-L at that point for the s11,s22 calibration. the thru will have some line length (from pin to pin) and some impedance that you will have to calculate for the thru...
  3. TWW

    RF output power vs. Frequency

    My humble attempt to answer these deep questions. Question 1: Electrical Limitation: Fundemental material parameters effects such as saturated drift velocity, mobility, gate length or base thickness, various resistive and reactive parasitic elements. Thermal Limitation: Junction temperature...
  4. TWW

    RF output power vs. Frequency

    BTW. 1/f is electronically limited, 1/f^2 is thermally limited.
  5. TWW

    RF output power vs. Frequency

    Pmax is typically proportional to the inverse of 1/freq, or 1/freq^2 depending on the device. Threrefor you could expect 25-50W of optimized power.
  6. TWW

    Mechanical Eng. with 2450 MHz Microwave question

    How about a two interlocked two door scheme, 1-open, 1-closed and visa-versa. with RF gasketed doors. The chickens would need to be spaced approptiately to keep from getting the doors jambed though.
  7. TWW

    Mechanical Eng. with 2450 MHz Microwave question

    The carburundum?? spl? can take the heat I have seen less than an inch used in 500W mmw loads. (however a heat sink is needed)
  8. TWW

    Mechanical Eng. with 2450 MHz Microwave question

    A quick reality check would indicate that your "waveguide" is operating in a higher mode (I am use to TE10 only) Yours may be TE6,2? in this case you would need an array of the ferrite rods 6 top and 6 bottom (evenly spaced), arrayed at a longitudinal spacing on the order of 1.2&quot...
  9. TWW

    Mechanical Eng. with 2450 MHz Microwave question

    It sounds like you want to build a waveguide attenuator with probably a high level of attenuation. There are various sources of information available. The rods are probably high temperature lossy ferrite material such as emersons mf-500. I would place them at 1/4 guide wavelengths apart such to...
  10. TWW

    10 kW 60/50Hz MG or invertor

    Any sources for motor generators or invertors that will convert 208 or 480v 60Hz to 220V 50Hz (single phase or 3-phase) Motor generators are prefered (from our 60/400 hz experiences) Power output in the 10KW range. Thanks
  11. TWW

    Type of starter and its rating

    One major large user of pumps and drives only consider soft starters for 75 hp and above, below that it is DOL.
  12. TWW

    GPIB/HPIB 488 control software

    HP Basic always worked well for me. The GPIB card can get setup using an autostart script, that you can select the options for your GPIB card (the hardest part). However HP basic has gone the way of latin it would appear, a dead languange.
  13. TWW

    Isolated Grounds

    I personally do not think that the isolated grounding is that important today (if ever). Since the isolated grounding conductor is ran in the same conduit as the rest of the conductors, common-mode noise will still be induced upon it, Plus the inductance of the single wire (isolated ground) is...
  14. TWW

    AFD emergency disconnect

    The US navy no longer trust (most) microproccessor AFD drives on crane hoist motors to be shut down (ie upper limit switch) using the AFD's built in logic/ discrete input. Therefore I am faced with the prospect of opening the three legs of the input or output of the AFD. I am worried about...
  15. TWW

    How do you measure the impedance of a balanced transmission line?

    depending on your frequency band, you could calibrate into standard 300 ohm twinlead using a off-the shelf 75-to 300ohm balun & using a short, 1/6lambda, 1/3 lambda shorts or 300 ohm load and open cal standards whatever you prefer, or using tsd etc. then using the measured reflection coefficient...
  16. TWW

    Are there any SiC transistors available?

    Search the web for CREE research. They have enjoyed a wealth of gov't funding for wide bandgap research.
  17. TWW

    Variable Frequency Drive

    As a side bar, the US Navy no longer considers microproceesor based AC drives trustworthy enough for emergency stop operations (with some exceptions). Per CSA 121 (crane saftey advisory 121), the microprocessor based controls are to be bypassed for emergency stop.
  18. TWW

    Circuit breaker sizing for DC loads

    Squared sells DIN mounted QOB circuit breakers that are dc rated.
  19. TWW

    replacing panel board interiors

    In cases of retrofits (grouted in panelboards, panel boards connected to many RGS conduits with seals etc.) , We have often specified replacing the interiors of old obsolete panel boards with new interiors and covers. The new interiors are much smaller than the old so clearance is not an issue...
  20. TWW

    PANEL SIDE FED MAIN BREAKERS

    Ok, so bolt on circuit breakers are easy to get. However, say, squared QOB circuit breakers appear to be UL listed for many things however no UL listing for "back fed operation". The purpose of this was look and cost. These restrictions drive me to a seperate disconnect and regular...

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