I’m studying for the Amateur Extra Class license exam. I want to pass, but I’m not seeking a perfect score. (Perfection is not an effective use of my time.) I’m willing to memorize facts but not answers. The difference is that a fact is something useful after the exam.

However, I will memorize an occasional answer or write-off a question if the amount of learning is enormous just to answer a few questions.

These are just the things I have to learn. I’m not capturing things I already know, such as Ohms law.

• Reminder: micro and mega both deal with a million (106). Pico is million million (1012).
• Circulator - a three- or four-port device, in which an RF signal entering any port is transmitted to the next port in rotation (only).
• MDS = Minimum Discernable Signal
• Dynamic range = space between weakest signal radio can receive and strongest it can handle w/o excess distortion.
• Desense (a.k.a. blocking) = close frequency at strong level drives RF amp to compression (non-linear behavior).
• Narrowing receiver bandwidth reduces this because “close” means within the receiver passband.
• Cross-modulation = modulation of a close frequency superimposes on desired frequency.
• Phase noise in the local oscillator of a receiver can mix with nearby frequencies to interfere with the tuned frequency. (It creates a signal that mixes with the nearby frequency.)
• Blocking Dynamic Range = dB between noise floor and incoming signal level which will cause 1 dB of gain compression. In effect, it is the signal strength range the receiver can handle.
• Intermodulation
• Intermodulation products are the emissions at frequencies generated by the combination of two or more frequencies in a non-linear device, such as the output stage of a transmitter, or the input stage of a receiver (or corroded connections). E.g. (f1 - 2*f2). Mixing often occurs in a non-linear RF amp.
• A circulator reduces intermod by preventing signals received in the transmitting antenna going back into the transmitter amplifier and mixing.
• 3rd order intercept
• a 3rd order intercept of x db means that a pair of signals will theoretically generate a third-order intermodulation product with the same level as the input signals
• 3rd order intermod products created within a receiver are of interest because the 3rd order product of two signals in the band of interest is also likely to be within the band
• Resonance
• At resonance, the L and C components of an RLC circuit go to zero, leaving only R.
• In series, when L and C cancel, you have lower total RLC impedance, so more current flows. (This is like removing 2 of 3 resistors that are in a series. R goes down.)
• In parallel, when L and C cancel, you have higher impedance between the two rails, so less current flows. (This is like removing 2 of 3 resistors that are in parallel. R goes up.)
• L and/or C shift the phase between voltage and current in opposite directions. Ergo, at resonance, there is no shift because AC circuits that are resistive have no phase shift.
• F = .159 / sqrt(LC)
• Note: This is true when the units on L and C are similar. (e.g. Farads and henries, or micro-farads and micro-henries.) On the exam, they mix micro-henries with pico-farads, so you use: F = 1000 * .159 / sqrt(LC).
• i.e. On the exam, calculate F = .159 / sqrt(LC) without regard for units, and then multiply by 1,000
• Time constant
• One time constant = all but 37%.
• e.g. Discharging to 37% in one time constant.
• e.g. Charging to all but 37% (meaning charged to 63%) in one time constant.
• Calculating a time constant: T = RC
• On the test, if you forget, pick the answer that is closest to the microfarad value (for all calculate-the-TC questions)
• Q
• Half_Power_Bandwidth = Frequency / Q. [B = F/Q]
• e.g. If Q = 10, and Frequency = 10 MHz, then Bandwidth = 1MHz.
• e.g. If Q = 95, and Frequency = 1.8 MHz, then Bandwidth = 1.8 / 95 = 0.0189 MHz = 18.9 KHz.
• Gates
• The symbol for the AND gate is rounded. • The symbol for the OR gate looks like AND with a pointy rounded end. • A triangle is a no-op.
• The symbol for Nxxx is a little circle at the tip of AND / OR / no-op
• XOR (and XNOR) have a double line at the input side. e.g. • Phase-locked Loop = An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator.
• If no antenna reference is specified for gain, assume a dipole. (Otherwise, EIRP = Effective Isotropic Radiated Power.)
• ERP:
• Add up the dB gain and loss for total dB. Call that TDB.
• TPO = Transmitter Power Output
• ERP = InverseLog(TDB/10) * TPO
• On a TI-36X Pro Calculator, Double-tap [ex 10x] for InverseLog
• Double-tap “ex 10x”
• Open paren, TDB / 10, close paren
• x TPO
• e.g.
• If watts is 50 and gain is - 4 dB - 2 dB -1 dB + 6 dB = -1 dB
• press InverseLog (-1 / 10) * 50
• press Enter
• On XY RLC charts, Resistance is to the right; inductance is up; capacitance is down. Pure L or C is way up/down; mixed is near mid-line.
• A sawtooth wave is made up of a sine wave plus all its harmonics. A square wave is made up of a sine wave plus its odd harmonics.
• -174 dBm/Hz = The theoretical noise at the input of a perfect receiver
• Matches:
• A delta match feeds at two places, each side of center.
• A gamma match feeds at the center and off one side (like my Arrow VHF Yagi).
• A stub match runs feed line and radiator in parallel near the feed point
• P-type uses holes; n-type uses electrons. P = positive, so it has holes (which are anti-electrons); N = Negative, so it has electrons (which are negative).
• VCC is supplied to MMIC (monolithic microwave integrated circuit) via resistor or a choke on the amplifier output.
• Spurious emissions must be down 43 dB
• A hot-carrier (Schottkey) diode is often used as a VHF/UHF detector/mixer.
• Digital protocols
• JT65 is designed for moon-bounce
• PSK31 is narrowest bandwidth. 31 baud and 31 Hz bandwidth. It uses variable-length characters.
• MFSK16 is FSK with 16 tones; about 300 Hz bandwidth.
• 120V RMS is 170V peak-to-peak. It is 120V * sqrt(2).
• An op-amp has high input impedance and low output impedance. (This is what you want. Low-drain input, and low-resistance output.)
• A marker generator can be used to calibrate a receiver. (Send at a known frequency and see what frequency the receiver thinks it is.)
• a FET has gate, drain, and source
• A point-contact diode is a “cat’s whisker” diode.
• P= IIR
• This can be derived from P=EI and E=IR
• Deviation Ratio:
• Modulation index = DeltaCarrier / Modulation
• Deviation ratio = MaxDeltaCarrier / MaxModulation
• Highest allowed modulation index for angle modulation = 1
• Space stations, Satellites, and Moon:
• HF - not allowed on 30m (because that’s CW-only)
• VHF - only allowed on 2 meters
• UHF - allowed on 70, 23, and 13 cm
• Mode x/y - uplink before downlink. (Must get TO the satellite before the signal comes FROM the satellite.)
• Moonbounce at 144.0 to 144.1 (First 100 KHz of 2 meter band). Also at 432.0 to 432.1 (100 KHz, but not at bottom of 70 cm.)
• Meteor from 10 to 2 meter (28 to 148 MHz).
• Aurora and mEteor strike happens at the E-layer
• PSK31 - (Phase Shift Keying, 31-baud) has data rate close to typing speed, and has extremely narrow bandwidth
• Spread spectrum is permitted above 222 MHz
• Line-A takes a chunk out of the BOTTOM of the 70 cm band (400 MHz)
• (“A” is the beginning of the alphabet; Line-A loses the beginning of the band; 400 MHz is the only band in the answers with multiple, close answers.)
• dB = 10 Log (x/y)
• Log is base 10
• e.g. 400x increase in power = 10 Log (400/1) = 26 dB
• A noise blanker briefly switches off the receiver when a broadband spike occurs. (Not “broadband white noise” and not a narrowband spike.)
• X,Y graphing of RLC:
• R is to the Right of the vertical axis.
• L is up
• C is down
• Reactance of an inductor is 2pi * FL
• Reactance of a capacitor is 1/(2pi * FC)
• Impurity atom that adds holes to a semiconductor = “Acceptor impurity”. (Mnemonic Atom and Acceptor.)
• Filter types:
• Jones Filter - a type of crystal lattice filter