Greece AM Theory common mistakes
Greece AM Theory · Understand the traps and how to avoid them.
Adding or comparing RMS and peak voltages directly, for example answering that a 230 V RMS mains supply has a 230 V peak, or computing power as V_peak²/R instead of V_RMS²/R.
Candidates memorise 'V_RMS = V_peak/√2' as a formula but never internalise which quantity a meter or a supply rating refers to, so under time pressure they treat all voltages as interchangeable.
What to do instead
Drill a fixed checklist before any AC calculation: identify the quantity given (RMS, peak, peak-to-peak), convert once to RMS for power work (V_RMS = V_peak/√2 ≈ 0.707·V_peak), and state the quantity in the answer. Practise with 230 V RMS → 325 V peak → 650 V peak-to-peak so the ratios become automatic.
Computing the resonant frequency of an LC circuit with the formula for a series circuit while the components are in parallel, or forgetting to convert inductance in µH and capacitance in pF to henries and farads before substituting.
The single formula f = 1/(2π√(LC)) is remembered without the unit discipline, and candidates do not realise that µH × pF gives 10⁻¹⁸, which must be handled explicitly.
What to do instead
Always write units next to every substitution and use the shortcut that f(MHz) = 159/√(L in µH × C in pF) for the same formula, then cross-check the order of magnitude (a 100 µH/100 pF circuit must land near 1.6 MHz, not 1.6 kHz). Do three or four such problems in both units until the conversion is reflex.
Treating a 50 Ω transmitter, a 50 Ω feed line and a 50 Ω antenna as automatically matched, and answering that the SWR must be 1:1 without considering the antenna's resonant frequency and impedance at the operating frequency.
Candidates conflate 'nominal impedance' with 'actual impedance at frequency', so they miss that a 50 Ω antenna is only 50 Ω resistive at resonance and presents reactance elsewhere.
What to do instead
Learn the definition SWR = (1+|Γ|)/(1−|Γ|) with Γ = (Z_L − Z_0)/(Z_L + Z_0), and practise with reactive loads (for example 50 + j50 Ω) to see that SWR rises even when the resistive part equals 50 Ω. Always state the frequency at which an impedance is quoted.
Assuming an SWR meter inserted anywhere in the feed line reads the true antenna SWR, or reading forward power on an SWR/power meter without checking the meter's calibration, frequency range and power range.
Candidates have used a meter in one setup and generalise; they do not know that lossy coax between meter and antenna masks a high antenna SWR, and that meters are calibrated for a specific characteristic impedance and power band.
What to do instead
Place the SWR meter as close to the antenna as practical (or account for feed-line loss) and verify the meter is rated for the frequency and power used. Learn that a 3 dB cable loss halves the reflected power seen by the meter, so a 3:1 antenna can read near 1.5:1 at the transmitter.
On an oscilloscope, measuring amplitude with the vertical scale but forgetting the probe attenuation (×10) or the vertical position offset, and reading time with the horizontal scale without counting divisions correctly.
Candidates focus on the waveform and not the instrument settings; the ×10 probe factor and the zero reference are easy to overlook when the trace is off-centre.
What to do instead
Before reading, state aloud: probe attenuation, volts/div, time/div, trigger source and zero position. Compute amplitude as (divisions peak-to-peak) × (volts/div) × (probe factor), and period as (divisions per cycle) × (time/div), then verify against a known signal such as a calibrator square wave.
Classifying a spurious emission from a neighbouring transmitter as receiver overload, or blaming the transmitter when the interference is actually caused by a nearby receiver's front-end being desensitised by a strong signal.
The symptom (distortion, blocking, intermodulation products) looks the same at the listener, and candidates do not systematically distinguish transmitter-side spurious outputs from receiver-side effects.
What to do instead
Use a structured diagnosis: switch the suspect transmitter off and confirm the interference stops; insert a band-pass filter or attenuator at the receiver to see whether the problem is receiver overload; check for intermodulation by testing whether the frequency matches 2f1 − f2 products. Document each test before changing hardware.
Ignoring the distinction between PEP and average power when answering questions about licence power limits, and quoting a linear amplifier's output as if it were the permitted figure.
Candidates see 'maximum power' in the licence and assume it refers to whatever the amplifier's meter shows, without checking whether the regulation specifies PEP, carrier power or average power, and at what point in the chain it is measured.
What to do instead
Learn that amateur power limits are normally expressed as PEP at the transmitter output (antenna terminal), that PEP is measured at the peak of the modulation envelope, and that average power for SSB is much lower. Re-read the Greek licence conditions and the ITU Radio Regulations for the exact wording on power measurement before answering any limit question.
Confusing the ITU regions and the IARU regions, or assuming that a frequency allocation valid in Region 1 applies unchanged in Region 2 or 3, when answering questions about band edges.
The three ITU regions and the three IARU regions have different boundaries and the amateur allocations differ between them; candidates memorise one table and apply it everywhere.
What to do instead
Memorise the ITU region boundaries (Region 1: Europe, Africa, Middle East west of the Persian Gulf; Region 2: the Americas; Region 3: Asia-Pacific) and Greece's position in Region 1, then learn the Region 1 amateur bands and the Greek national limits separately. When a question mentions a band edge, check which region and which document is being cited.
Writing a call sign incorrectly in an answer, for example omitting the prefix or the district indicator, or assuming a Greek call sign's structure is the same as a visitor's CEPT-style call.
Candidates learn call signs by sight rather than by structure, and they do not know how the Greek prefix, the numeral and the suffix are assigned, nor how a foreign visitor operating in Greece under CEPT is identified.
What to do instead
Learn the Greek amateur call sign structure explicitly: the prefix for Greece, the numeral indicating the licence class or district, and the suffix letters, plus how a visiting CEPT licence holder adds the Greek prefix and their home call. Practise by writing out three example call signs and explaining each element.
Underestimating RF exposure by considering only the transmitter's rated power and not the antenna gain, distance, duty cycle and frequency-dependent limits, or treating an indoor antenna as if it were in free space.
Candidates apply a single 'safe distance' figure they have heard, without accounting for EIRP, near-field effects or the fact that exposure limits vary with frequency and are averaged over time.
What to do instead
Work through the exposure assessment chain: transmitter power → feed-line loss → antenna gain → EIRP → power density at the operator's position → comparison with the reference levels for that frequency. Learn that limits are averaged over six minutes and that indoor operation, balconies and roof-mounted antennas change the geometry, then keep a written assessment for each station configuration.