Amateur Radio Quiz: Way-back Wireless
1) What electrical function was performed by a "slop jar"?
a. Accumulate grid leaks
b. Rectify ac
c. Artificial ground
d. Transient clamping
2) Poulsen invented what device used in early transmitters?
3) What type of device was the "audion"?
a. Vacuum tube
4) To what was the nickname "Old Betsy" given?
c. This was the term for "Murphy" before Murphy's Law was popularized.
5) Who is most widely credited with first describing vacuum-tube rectification?
6) Who invented the "single-signal" crystal filter?
c. de Broglie
7) A "TRF" is a type of what?
c. Early coaxial connector family
8) In a spark transmitter, what determined the strongest wavelength of the transmission?
a. Antenna system
b. Rotational speed
c. Gap spacing
d. All wavelengths were of equal strength
9) What was the original name for radio waves?
a. Cathode rays
b. Ethereal waves
c. Alpha particles
d. Hertz or Hertzian waves
10) Who discovered the electron and in what year?
a. J J Thomson (later, Lord Kelvin) in 1897
b. Dimitri Mendeleev in 1859
c. Ernest Rutherford in 1915
d. Albert Einstein in 1904
Bonus: What was the first solid-state device used in wireless communication?
1. b -- Consisting of strips of dissimilar metals in a caustic lye solution, you can see where the rectifier got its name.
2. c -- A Poulsen arc, also called an arc converter, converted dc into RF.
3. a -- A triode amplifier, manufactured by Lee DeForest.
4. a -- Old Betsy was Hiram Percy Maxim's rotary spark-gap transmitter, on display at W1AW.
5. c -- Fleming made use of the Edison Effect to create the first electronic device, the thermionic diode.
6. b -- Lamb applied the quartz crystal as a filter to limit receiver bandwidth.
7. d -- Tuned Radio Frequency receivers preceded the superheterodyne.
8. a -- The combination of the antenna's natural resonance and the coupling circuit from the spark gap acted formed a low-Q tuned circuit.
9. d -- For the physicist Hertz who conducted the first experiments with electromagnetic waves in 1887.
10. a -- Only four years later, Marconi spanned the Atlantic, 14 years before the discovery of the atomic nucleus!
Bonus: The Branly coherer consisted of an insulating tube filled with fine metallic particles -- usually iron filings -- squeezed between an electrode at each end. When a radio wave passed through the filings, their conductivity increased, allowing an external circuit to respond, creating a radio wave detector. Interestingly, vacuum tubes quickly replaced the coherer as a detector, delaying an understanding of the physics of its operation until 2005! The full story is told in the September 2009 issue of IEEE Communications Magazine by Jean-Marie Dilhac.
H. Ward Silver, N0AX
ARRL Contributing Editor