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.

https://hamstudy.org/extra2012 (the “Read Questions” link) is very helpful. Many of the questions have explanations associated with the answers.

- Reminder: micro and mega both deal with a million (10
**6). Pico is million million (10**12). **Circulator**- a three- or four-port device, in which an RF signal entering any port is transmitted to the next port in rotation (only).- Receiver performance measures
- 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

- i.e. On the exam, calculate

- 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).

- 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)

- One time constant = all but 37%.
- 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.

- Half_Power_Bandwidth = Frequency / Q. [B = F/Q]
- 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

- A
- 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= I
*I*R- 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 m
**E**teor 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
**R**ight 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)

- R is to the
- Impurity atom that adds holes to a semiconductor = “Acceptor impurity”. (Mnemonic
**A**tom and**A**cceptor.) - Filter types:
- Jones Filter - a type of crystal lattice filter