Recent content by w5dxp

  1. W

    I Are EM fields clouds of photons?

    Thanks, I already read that paper and I am not saying that photons are anything like birds. I know that photons are pure energy with no rest mass and the only reason they are called particles is that they possesses momentum when traveling at the speed of light. The question remains: Do EM fields...
  2. W

    I Are EM fields clouds of photons?

    Personally, I have trouble visualizing a flock of birds without the birds. I have the same trouble trying to visualize an EM field without the photons. More than once, I have been hounded off of the ham radio forums for mentioning the word "photon". As one ham radio operator put it, "We don't...
  3. W

    Electronics Building a Radio: Basics for the High Schooler in Australia

    Lots of radio info here: www.arrl.org, www.qrz.com, www.eham.net Also try a google search for "software defined radio" and "SDR kits".
  4. W

    Insights The What and Why of Circuit Analysis Assumptions - Comments

    From the thread on helical antennas: How about the fact that between its 1/4WL self resonant frequency and 1/2WL self resonant frequency, an inductor exhibits capacitive reactance? So much for inductance being proportional to the square of the turns. :eek:
  5. W

    How can I calculate the necessary inductance for a half wave helical antenna?

    There are a number of references at the bottom of this page: http://hamwaves.com/antennas/inductance.html "The calculator returns values for the axial propagation factor β and characteristic impedance Zc of the n=0 (T0) sheath helix waveguide mode for any helix dimensions at any frequency." The...
  6. W

    How can I calculate the necessary inductance for a half wave helical antenna?

    In 80m mobile antenna shootouts, helical antennas have proven less efficient than center loaded bugcatchers using high-Q loading coils. Here's a useful site: http://hamwaves.com/antennas/inductance.html
  7. W

    Zero Group Velocity: What Does it Mean?

    To see why a pure standing wave has a zero phase velocity, let's look at the equation for the current, I, in a standing wave. I(x,t)=Imax[sin(kx)][cos(wt)] ;where w is omega=2*pi*freq and 0 < kx < 180 degrees At any time, t, the phase of the current is a constant, i.e. the phase of the...
Back
Top