Antennas · Volume 31

Regulatory & RF Safety

FCC Part 15 / Part 97 / Part 22, ERP / EIRP limits, ITU regions, MPE exposure tables, OET-65 workflow, lightning, common-mode currents, the legal envelope of every transmit antenna

Contents

SectionTopic
1About this volume
2The three regulatory questions
3FCC Part 15 — unlicensed devices and the ISM bands
4FCC Part 97 — amateur radio
5FCC Part 22 / 24 / 27 / 90 — licensed services
6ITU regions and frequency allocation
7ERP vs EIRP — different references, same idea
8MPE — maximum permissible exposure tables
9OET-65 compliance workflow
10Lightning — codes and protections
11Common-mode currents and RFI to neighbors
12The receive-only carve-out
13Cross-references to other Hack Tools deep dives
14Resources

1. About this volume

This is the regulatory and RF-safety closing volume of the synthesis cluster. Every transmit chapter in this series — the wire-and-air antennas in Vols 6-15, the matching networks and distribution gear in Vols 16-19, the use-case matrix in Vol 29, and the multi-radio sharing volume at Vol 30 — describes what’s physically possible. This one describes the legal envelope that constrains what’s actually operable on the air, plus the safety constraints that determine where you can put the antenna and how close people can stand to it. It exists as a separate volume because regulatory rules cross-cut every band, every antenna, and every radio; folding them into each technical chapter would have duplicated the same material twenty times and obscured the structural pattern.

The treatment is US-centric: FCC is the primary regulator under 47 CFR, and the parts you care about for the Hack Tools collection are Part 15 (unlicensed), Part 22/24/27 (commercial wireless), Part 87 (aeronautical), Part 90 (LMR), Part 95 (personal radio services), and Part 97 (amateur). Where it adds value — band allocations that differ by region, reciprocal-licensing implications for travel, IEEE/IEC standards that the FCC adopts by reference — the volume includes ITU and EU/EAC context. The reader is an FCC Amateur Extra-class operator; amateur-band material is framed peer-to-peer (“the right operating procedure on your authorized bands”). Non-amateur bands keep standard regulatory framing because the Extra ticket doesn’t extend across services.

Two practical anchors. First, the 2021 FCC rule changes (effective 2021-05-03) removed the long-standing categorical exclusion that let most amateur stations skip the MPE evaluation. As of 2026 every amateur installation needs a documented MPE evaluation on file. The free online calculators make this a 10-minute exercise for a typical 100-watt HF dipole, but you have to actually do it. Second, common-mode currents on coaxial feedlines — covered in passing in Vol 16 — are the single most common cause of RFI complaints from neighbors and self-induced RFI in the shack. A current choke at the feedpoint isn’t belt-and-suspenders; it’s how you avoid spending Saturday mornings explaining to the neighbor why their cable TV breaks up whenever you key the rig.

2. The three regulatory questions

Reduce the legal question to three orthogonal checks before any TX key-down.

(1) Is the band one I’m authorized to TX on? This decomposes into “what service does this band fall under” and “do I hold the relevant authorization.” For the amateur bands the answer is yes by virtue of the Extra ticket. For Part 15 ISM bands (902-928 MHz, 2.4-2.4835 GHz, 5.725-5.875 GHz) the answer is yes provided the device holds an FCC certification and you operate it within its certified configuration — the authorization runs with the equipment, not the operator. For Part 22 cellular, Part 87 aeronautical, Part 90 LMR, Part 95 GMRS, etc., the answer is no unless you hold the specific license for that service. Receive is essentially always legal (see §12 below for the ECPA exceptions); transmit is what the regulators care about.

(2) Is my ERP/EIRP within the authorized limit for the band, mode, and license tier? This is a single arithmetic check: transmitter power, plus antenna gain, minus feedline loss, equals effective radiated power. For Part 97 the limit is 1500 W PEP (with band-specific reductions on 30 m, 60 m, and some HF/microwave subbands). For Part 15 the limit is band- and modulation-specific (1 W conducted + 6 dBi antenna for 2.4 GHz spread-spectrum; 36 dBm EIRP for point-to-multipoint 2.4 GHz; 30 dBm for 902 MHz spread-spectrum). The ERP/EIRP arithmetic is covered in §7; the practical implication is that high-gain antennas can push compliant transmitters into non-compliant ERP territory.

(3) Is the antenna safe at the deployment point? This is the MPE evaluation per 47 CFR §1.1310 and OET Bulletin 65 (§8 and §9 below). For amateur HF dipoles at 10 m height running 100 W, compliance is usually trivial. For 1500 W on 6 m into a Yagi at 60 ft, or a 50 W 2 m mobile sitting in a car next to passengers, compliance distances start to bite. Lightning protection per NEC 250/810 (§10) and RFI mitigation (§11) are the secondary safety axes — not technically RF-exposure questions, but they’re the conditions under which a permanent installation is insurable and operable without neighbor complaints.

Get all three to yes and the install is legal. Get any to no and you have a problem the regulators or the insurance company can call you on.

3. FCC Part 15 — unlicensed devices and the ISM bands

Part 15 of 47 CFR is the authority under which essentially every consumer wireless device in North America operates without an individual license. Three concepts make Part 15 readable: the certification model, the intentional/unintentional radiator distinction, and the band-specific power and modulation rules.

The certification model. Part 15 authorization runs with the equipment, not the operator. The FCC certifies a device against the rules for its band and modulation; the operator runs it within the certified configuration. Modify the device (firmware that boosts TX power past the certification, an antenna swap that exceeds certified gain, an external PA) and the certification is void; what was a legal Part 15 device is now an unlicensed transmitter operating outside its authorization, which Part 15 §15.5(b) treats as a Title III violation enforceable by fines and forfeiture. Every device in the Hack Tools collection that operates on ISM frequencies — Flipper Zero sub-GHz, DSTIKE Hackheld and ESP32 Marauder firmware platforms on 2.4 GHz, the AWOK Dual Touch V3, the Nyan Box’s NRF24 stack, the WiFi Pineapple’s Wi-Fi radios, the M5Stick S3, the Ruckus Game Over — runs under a Part 15 certification of either the assembled product or the embedded radio module.

Intentional vs unintentional radiator. Part 15 §15.5 vs §15.15. An intentional radiator (a Wi-Fi card, a Bluetooth chip, a 433 MHz remote) is designed to emit RF as its primary function. An unintentional radiator (a switching power supply, a microcontroller clock, a USB cable, an LED bulb) emits RF as a side-effect. The rules diverge: intentional radiators must meet band-specific emission masks and power limits and require certification; unintentional radiators must keep their emissions below the §15.109 conducted and §15.209 radiated limits and may go through a less-onerous “Declaration of Conformity” or “Verification” rather than full certification. For the Hack Tools collection this distinction matters when a tool generates intentional RF for the user (Marauder’s deauth packet generation) vs incidental RF that the FCC treats as the device’s normal emission profile.

Band-specific rules. The Part 15 §15.247 spread-spectrum and digitally-modulated rules govern 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz. For 2.4 GHz Wi-Fi the headline number is 1 W (30 dBm) conducted transmitter power into an antenna of up to 6 dBi gain — a 36 dBm EIRP ceiling for point-to-multipoint use, with a 1-dB-for-every-3-dB-of-gain power reduction past 6 dBi. Point-to-point links are treated more permissively under §15.247(c): for every 3 dB the antenna exceeds 6 dBi, the conducted power must be reduced by 1 dB. That gives you 1 W into a 6 dBi omni or 0.1 W into a 24 dBi parabolic dish on a fixed P2P link.

BandReg citePowerAntennaEIRP cap
902-928 MHz spread spectrum§15.2471 W conductedup to 6 dBi36 dBm
902-928 MHz frequency-hopping§15.247(b)(2)250 mW (channels >250 kHz)up to 6 dBi30 dBm
2400-2483.5 MHz, point-to-multipoint§15.247(b)(3)1 W conductedup to 6 dBi36 dBm
2400-2483.5 MHz, fixed point-to-point§15.247(c)1 W reduced 1 dB / 3 dB past 6 dBi gainunlimited gainunlimited
5725-5850 MHz§15.2471 W conductedup to 6 dBi (3 dB-for-3 dB reduction past)36 dBm
5150-5350 MHz UNII-1/2A§15.407250 mW indoor, 1 W outdoor (with DFS/TPC)various200 mW EIRP / 1 W EIRP
5470-5725 MHz UNII-2C§15.407250 mW (with DFS/TPC)up to 6 dBi30 dBm
5725-5825 MHz UNII-3§15.4071 Wup to 6 dBi36 dBm

Outside the ISM bands, Part 15 §15.209 sets generic radiated-emission limits in microvolts per meter at 3 m. These are extremely low — a 30-300 MHz limit of 100 µV/m at 3 m works out to about 13 dBµV/m which is on the order of -50 dBm at the test antenna. Anything that radiates above those limits in a band it isn’t certified for is a violation. This is what catches the homebrew amateur who wants to use the HackRF as a 100 mW jammer “just in the lab” — Part 15 doesn’t authorize it, Part 97 doesn’t authorize it (jamming is a separate prohibited mode under §97.101(d)), and §15.209’s residual-emission limits apply regardless of intent.

Equipment Authorization databases at https://apps.fcc.gov/oetcf/eas/reports/GenericSearch.cfm are searchable; the FCC ID on the back of any consumer wireless device looks up its current grant condition and certification scope. If the FCC ID isn’t there, the device isn’t legally sellable in the US.

4. FCC Part 97 — amateur radio

47 CFR Part 97 is the federal authority for the Amateur Radio Service in the US. The Extra-class ticket grants full privileges across all amateur bands HF through microwave, subject to band-specific power and mode restrictions in §97.301 and §97.305. The structure that matters for antenna and station design: license class governs frequency privileges; band class (HF / VHF / UHF / microwave) governs power; mode class (CW, SSB, image, digital) governs sub-band allocation within each band; and §97.313(a)‘s “minimum power necessary” requirement governs everything (you’re supposed to run only as much power as the communication actually needs — the 1500 W ceiling isn’t a target).

License classes and band privileges. Three current US license classes: Technician, General, Extra. Technician gets full VHF/UHF privileges (6 m and up) plus limited HF privileges on 10 m (CW + RTTY + data in 28.000-28.300 MHz; SSB in 28.300-28.500 MHz at 200 W PEP max). General gets substantial HF privileges across all amateur HF bands minus specific Extra-only sub-bands. Extra gets all amateur privileges. The General-to-Extra delta is roughly 25-100 kHz of additional CW/data and 25 kHz of additional phone bandwidth at the bottom of 80/40/20/15 m, plus full privileges on the small Extra-only carve-outs.

For an Extra-class operator the practical question is “what’s my power limit and mode privilege on this specific frequency?” The §97.301 charts (best read in the ARRL FCC Rule Book or the current 47 CFR text) enumerate this band by band. The 200 W PEP limit on 30 m (10.100-10.150 MHz, CW + digital only — no phone) and the 100 W ERP cap on 60 m (five 2.8-kHz channels at 5332/5348/5358.5/5373/5405 kHz USB only) are the two power exceptions Extra-class operators most commonly trip over.

Band allocations. US amateur band table at the headline level:

BandWavelengthFrequency (MHz)Notes
160 m1.8-2.01.800-2.000Phone above 1.800 MHz; LF-influenced propagation
80 m3.5-4.03.500-4.000CW lower, phone upper; daytime regional, nighttime DX
60 m5.3-5.4five discrete channels100 W ERP cap, USB only, secondary status
40 m7.0-7.37.000-7.300Region 2 has full 7.000-7.300; Region 1/3 lose 7.200-7.300 in places
30 m10.1-10.1510.100-10.150200 W PEP, CW + digital only, secondary status, no phone
20 m14.0-14.3514.000-14.350DX workhorse
17 m18.068-18.16818.068-18.168CW + phone + digital; WARC band
15 m21.0-21.4521.000-21.450Solar-cycle DX
12 m24.890-24.99024.890-24.990WARC; sporadic-E and solar peaks
10 m28.0-29.728.000-29.700Solar peak DX; FM repeaters 29.5+
6 m50-5450.000-54.000”Magic band”; sporadic-E, meteor scatter; sub-bands per §97.301
2 m144-148144.000-148.000LOS + repeaters + sat
1.25 m222-225222.000-225.000Region 2 only
70 cm420-450420.000-450.000Heaviest VHF/UHF allocation
33 cm902-928902.000-928.000Shared with Part 15 ISM and Part 90
23 cm1240-13001240.000-1300.000Shared with GPS L2; coordination required
13 cm2300-2310, 2390-2450discontinuousShared with Part 15 (Wi-Fi sits in 2400-2450)
Above 13 cm3.3-3.5 / 5.65-5.925 / 10.0-10.5 / 24.0-24.25 GHz and upvariousMicrowave; some shared with Part 15 / 18

The 4 m band (70-70.5 MHz) is a Region 1 amateur allocation; it does not exist as an amateur band in the US. US operators interested in 4 m operation either travel to a Region 1 country with a reciprocal license or are out of luck.

Power limits — the 1500 W ceiling and its exceptions. §97.313(a) caps amateur transmitter power at 1500 W PEP except where specifically reduced. Three exceptions matter:

  1. 30 m (10.100-10.150 MHz): 200 W PEP max. §97.313(c)(1). The amateur service is secondary on 30 m (US fixed service is primary); the lower power preserves the secondary status.
  2. 60 m (5 channels): 100 W ERP referenced to a half-wave dipole. §97.303(s). This is ERP, not PEP, and the half-wave-dipole reference is unusual. If you use a 0 dBd antenna (a dipole) you can run 100 W. If you use a vertical with -3 dBd performance you can run 200 W to make the same ERP. If you use a 5-element Yagi with 9 dBd gain you must reduce to about 12.5 W to stay under 100 W ERP. The channel list and USB-only restriction add to the constraint.
  3. Beacon stations and certain technician operations. §97.313(d) caps technician-license CW/data operation on 10 m at 200 W PEP.

For everything else the limit is 1500 W PEP. The §97.313(a) language is “the minimum power necessary to carry out the desired communications” — the 1500 W is a ceiling, not a target. Reasonable practice is to run 100-200 W for general HF work and step up when conditions demand it.

Mode and emission privileges. §97.305 defines the emission types authorized in each sub-band. Phone (SSB on HF, FM on VHF/UHF) generally sits in the upper portion of each band; CW is authorized throughout each band; digital modes (RTTY, FT8, JS8Call, PSK31, packet) generally sit in defined narrow segments. The detailed sub-band map by class is the ARRL US Amateur Bands chart at https://www.arrl.org/files/file/Hambands_color.pdf; print and laminate one for the shack.

Spurious emissions and harmonic suppression — §97.307(d) and (e). Below 30 MHz, transmitter spurious emissions must be at least 43 dB below the mean power of the fundamental for transmitters of 5 W or more. Above 30 MHz to 225 MHz, the requirement is 60 dB below mean. Above 225 MHz, the requirement is at least 43 dB below mean (the spec is less tight at microwave because measurement gets harder). These are the harmonic-suppression numbers a TX chain must meet, including PA harmonics, mixer leakage, and any pre-distortion artifacts. Vol 26 covers the bench measurement methodology; Vol 27 covers the spectrum-analyzer setup for verifying compliance. Most commercial amateur HF rigs pass these by 10-20 dB margin out of the box; the time you have to think about §97.307 is when you’re running a homebrew or kit-built PA, when you’ve added an external amplifier, or when a tube-PA’s plate tank is misadjusted and second-harmonic suppression has degraded.

Station identification — §97.119. Identify with your callsign at the end of each communication and at least once every 10 minutes during a communication. Phone uses spoken callsign; CW uses sent callsign. Most digital-mode software handles this automatically.

Volunteer Examiner (VE) process and the question pools. Three license-exam elements: Technician (35 questions, 26 to pass), General (35, 26), Extra (50, 37). Question pools rotate on a four-year cycle, published by the NCVEC (National Conference of Volunteer Examiner Coordinators). The current pool versions as of 2026:

  • Technician pool (Element 2): valid through 2026-06-30 (NCVEC released 2022-07-01); a new pool is scheduled for 2026-07-01.
  • General pool (Element 3): valid through 2027-06-30 (NCVEC released 2023-07-01); replacement pool effective 2027-07-01.
  • Extra pool (Element 4): valid through 2028-06-30 (NCVEC released 2024-07-01); replacement pool effective 2028-07-01.

Verify pool dates against NCVEC at https://www.ncvec.org — pool effective dates are the one regulatory date that absolutely will be wrong if you don’t check the current source.

Exam sessions are administered by VEs accredited by a VEC (ARRL VEC is the largest; W5YI Group and Laurel ARC are major alternatives). The standard exam fee is $15 to the VEC plus the FCC’s $35 application fee for new licenses (the FCC fee dropped from $35 to $0 in 2022 then was reinstated at $35 in 2022-04 — that’s the figure to budget). License processing through ULS is typically 1-2 business days after the session paperwork is filed; the callsign appears in https://wireless2.fcc.gov/UlsApp/UlsSearch and the license is technically valid as of the grant date.

5. FCC Part 22 / 24 / 27 / 90 — licensed services

These are the licensed commercial and government services. Each requires a service-specific license; the amateur Extra ticket does not extend to any of them. The Hack Tools collection touches them only as observation targets (the radios receive in these bands) or as systems to characterize defensively (Rayhunter looks for IMSI catchers operating in Part 22/24/27 cellular bands). Transmit into these bands without the appropriate license is a Title III violation.

Part 22 — Cellular Radiotelephone Service. Legacy cellular: 824-849 MHz (mobile TX) and 869-894 MHz (base TX). This is the original AMPS-era cellular allocation, now hosting GSM and LTE service from licensed carriers. License is geographic (Cellular Market Area, CMA) and held by the carrier; individual handsets operate under the carrier’s authorization. To transmit on Part 22 frequencies you would need to obtain a Part 22 license — practically impossible for individuals and not what they’re issued for anyway. The relevant Hack Tools posture: Rayhunter (Vol 31 cross-link material, see the Rayhunter project) operates strictly as a receive-side IMSI catcher detector; HackRF and similar SDRs can physically receive Part 22 traffic but transmit is enforceable.

Part 24 — Personal Communications Service (PCS). 1850-1990 MHz, the broadband PCS allocation. Same licensing model as Part 22: carrier-held licenses, individual devices operate under carrier auth. Receive freely; transmit requires the appropriate Part 24 license.

Part 27 — Wireless Communications Service. 700 MHz, AWS (1700/2100 MHz), and various other bands that didn’t fit neatly into Part 22/24. Same licensing structure.

Part 87 — Aeronautical Services. 108-137 MHz aircraft VHF (108-118 MHz is ILS/VOR navigation; 118-137 MHz is voice ATC) plus 225-400 MHz UHF military aero. Part 87 is heavily protected — aircraft safety-of-life service. HackRF or any SDR can physically transmit on these frequencies; doing so is a serious Title III violation with criminal exposure, and the FAA tracks interference complaints aggressively. License authorization exists (aircraft station license for aircraft-installed radios; ground station license for FBOs and airports) but is service-restricted to actual aircraft and aviation infrastructure. There is no amateur or hobbyist path to Part 87 transmit authorization.

Part 90 — Land Mobile Radio Service. The big licensed-service catchall: 30-50 MHz, 138-174 MHz, 220-222 MHz, 421-512 MHz, 700/800 MHz. Public safety (police, fire, EMS), business radio (taxi, trucking, utility, construction), and certain government/military allocations. Licenses are by frequency coordination through a coordinator (APCO for public safety, EWA for business, etc.) and issued for specific frequencies, locations, and power levels.

The Hack Tools relevance: Quansheng UV-K5 and similar VHF/UHF handhelds with custom firmware (Egzumer, FAGCI, IJV) can physically transmit on Part 90 frequencies that overlap or sit adjacent to the amateur 2 m and 70 cm bands. Receiving Part 90 traffic is legal (excepting the encrypted-decoding ECPA issue covered in §12). Transmitting on Part 90 frequencies — even on a frequency that’s between two amateur sub-bands — requires the appropriate Part 90 license. The custom-firmware “wide open” UV-K5s do not magically grant Part 90 authorization; they expose the operator to Title III violations.

The 220-222 MHz amateur allocation is adjacent to a Part 90 LMR allocation (216-220 and 222-225 MHz blocks); be careful about VFO drift in homebrew rigs.

Part 95 — Personal Radio Services. This is the consumer-oriented allocation set. Five sub-categories matter:

  • CB (Citizens Band) — 26.965-27.405 MHz, 40 channels, 4 W AM / 12 W SSB PEP, no license required. The original Part 95 service.
  • FRS (Family Radio Service) — 462.5625-462.7250 and 467.5625-467.7125 MHz, 22 channels, 0.5-2 W depending on channel, no license required, integrated antenna only (Part 95E §95.587).
  • GMRS (General Mobile Radio Service) — overlaps FRS channels, up to 50 W on the higher-power channels, requires a $35 license (10-year term, family-sharing — single license covers the licensee plus immediate family).
  • MURS (Multi-Use Radio Service) — 151.820, 151.880, 151.940, 154.570, 154.600 MHz, 2 W, no license required, integrated antenna (Part 95J).
  • R/C and PRS — model aircraft control, narrow allocations on 27 MHz / 50 MHz / 72 MHz / 75 MHz.

The Hack Tools relevance for Part 95: a UV-K5 or similar amateur handheld is NOT type-accepted for FRS, GMRS, or MURS. Even if the frequency and power would be legal for a certified GMRS radio, using a non-certified radio (Part 90 or Part 97 capable) on Part 95 frequencies is technically a Part 95 violation under §95.7 (“equipment authorization requirements”) because Part 95 services require type-acceptance with non-detachable antenna and certified power. This is one of the most-violated rules in casual use; enforcement is rare but the rule is on the books.

GMRS license: FCC ULS application, $35, 10-year term, no exam required (unlike amateur), family-shared. If your buddies and family want long-range simplex on inexpensive radios, the path is one GMRS license + a household of GMRS-certified handhelds (Midland, Wouxun, Btech). Not a UV-K5 with the GMRS frequencies entered into memory.

6. ITU regions and frequency allocation

The International Telecommunication Union (ITU), a UN specialized agency based in Geneva, sets the global framework for radio-spectrum allocation through the Radio Regulations (RR). National regulators (FCC in the US, Ofcom in the UK, BNetzA in Germany, Roskomnadzor in Russia, MIC in Japan, ANATEL in Brazil, etc.) implement the ITU allocations within their own legal frameworks. The interplay is direct: FCC Part 97 implements ITU’s amateur-radio allocations; FCC Part 15’s ISM-band allowances align with ITU footnotes for industrial/scientific/medical use; the spurious-emission limits in §97.307 derive from ITU-R recommendations on spectral purity.

ITU divides the world into three regions, each with its own master allocation table:

  • Region 1 — Europe, Africa, the Middle East (west of the Persian Gulf), Mongolia, and the former Soviet states.
  • Region 2 — the Americas (north, central, south), Greenland, and the eastern Pacific islands.
  • Region 3 — Asia (east of the Persian Gulf), Australia, New Zealand, and the western Pacific.

Region boundaries follow longitude lines (approximately 20°W and 170°E) with specific country-by-country footnotes. The US is firmly Region 2; the UK and continental Europe are Region 1; Japan, China, Australia, and the Asian-Pacific countries are Region 3.

Where the allocations differ. Most amateur HF and VHF bands are consistent across all three regions — 20 m (14.0-14.35 MHz), 15 m (21.0-21.45 MHz), 10 m (28.0-29.7 MHz), 2 m (144-146 MHz core, with Region 2/3 getting 146-148 MHz extension), 70 cm (430-440 MHz core, with Region 2 getting 420-450 MHz). The deltas:

  • 40 m (7 MHz): Region 2 has the full 7.000-7.300 MHz; Regions 1 and 3 have 7.000-7.200 MHz (some Region 1 countries have 7.100-7.200 MHz subject to footnote constraints). Broadcasters in Regions 1/3 use 7.200-7.300 MHz, which is why 40 m DX from a US station can hear strong shortwave broadcasters when working European DX above 7.150 MHz.
  • 60 m (5 MHz): Five discrete channels in the US (Part 97 secondary, 100 W ERP, USB only); various national implementations in other countries. The 2015 World Radiocommunication Conference (WRC-15) added a 15-kHz channelized allocation at 5351.5-5366.5 kHz globally on a secondary basis.
  • 4 m (70 MHz): A Region 1 allocation only. Various Region 1 countries (UK, Germany, Slovenia, Croatia, etc.) implement 4 m amateur access; not available to Region 2 or 3 amateurs.
  • 6 m (50 MHz): Region 2 has full 50.0-54.0 MHz; Region 1 has 50.0-52.0 MHz (some countries with extensions); Region 3 varies country-by-country. The 50.0-52.0 MHz block is the global common segment for cross-region 6 m DX.
  • 1.25 m (220-225 MHz): Region 2 only.

Travel and reciprocal-licensing implications. Three useful regimes for the traveling US Extra-class operator:

  1. CEPT countries (most of Europe, plus some non-European participants). The CEPT Recommendation T/R 61-01 allows visiting US amateurs to operate in CEPT-signatory countries without obtaining a host-country license, at the CEPT-equivalent class level (US General and Extra map to CEPT Class 1; US Technician maps to CEPT Novice/Class 2). You operate using your US callsign with the host country’s prefix (e.g., F/W1AW in France, G/W1AW in the UK). Bring a copy of your FCC license and the CEPT documentation. Operating privileges are the host country’s, not the US — and that can mean fewer privileges than at home (the UK doesn’t have 60 m channels matching the US allocation; Germany caps power at 750 W not 1500 W).
  2. IARP countries — the Inter-American Reciprocal Permit covers OAS member states (most of Latin America plus Canada). Similar structure to CEPT.
  3. Bilateral reciprocal agreements — Japan, Israel, Australia, New Zealand, and several others have direct bilateral reciprocal agreements with the US. Japan (JAIA) requires submitting a reciprocal-license application before operating; the Australian Wireless Institute (WIA) administers Australian reciprocal recognition. Russia and China currently do not have reciprocal agreements with the US for amateur operation; operating from those countries requires a host-country license.

For travel, the canonical reference is the ARRL’s International Operating page at https://www.arrl.org/international-operating and the IARU Region 1/2/3 web sites.

7. ERP vs EIRP — different references, same idea

Two power references appear throughout the regulatory text and your antenna math; getting them straight saves a 10-minute argument every time you compute a compliance number.

EIRP — Effective Isotropic Radiated Power. The power that an isotropic antenna (the theoretical point-source radiator) would have to be fed to produce the same field strength in the direction of maximum gain as the actual antenna with its actual feed. Antenna gain referenced to isotropic is in dBi. The formula is straightforward:

EIRP (dBm) = TX_power (dBm) + Antenna_gain (dBi) − Feedline_loss (dB)

ERP — Effective Radiated Power. The power that a half-wave dipole would have to be fed to produce the same field strength in the direction of maximum gain. Antenna gain referenced to a dipole is in dBd. The formula is identical in form:

ERP (dBm) = TX_power (dBm) + Antenna_gain (dBd) − Feedline_loss (dB)

The 2.15 dB conversion. A half-wave dipole has 2.15 dBi of gain over isotropic (that’s its actual numerical free-space gain). So:

EIRP = ERP + 2.15 dB dBi = dBd + 2.15

Where each is used. The FCC’s high-frequency Part 15 §15.247 limits are in conducted power plus antenna-gain caps (the 30 dBm + 6 dBi structure for 2.4 GHz spread-spectrum); the implicit EIRP cap is 36 dBm. Part 90 license grants typically specify ERP because Part 90’s reference was historically the half-wave dipole. Part 97’s 60 m allocation specifies 100 W ERP referenced to a half-wave dipole (the unusual call-out). Most amateur antenna-vendor specifications give gain in dBi (Cushcraft, MFJ, Hustler, DX Engineering all spec their antennas in dBi); some legacy vendors and the ARRL Antenna Book still use dBd in places.

Worked example. A 100 W (50 dBm) transmitter feeding 50 ft of LMR-400 (about 0.65 dB at 14 MHz, call it 0.7 dB with connectors) into a 4-element 20 m Yagi with manufacturer-quoted 7.8 dBi free-space gain:

  • TX_power: 50 dBm
  • Feedline loss: 0.7 dB
  • Antenna gain: 7.8 dBi
  • EIRP: 50 + 7.8 − 0.7 = 57.1 dBm = 513 W
  • ERP: 57.1 − 2.15 = 54.95 dBm ≈ 313 W

For Part 15 compliance the relevant number is EIRP; for legacy Part 90 grants the relevant number is ERP. For amateur work the operating discipline is to know your station’s worst-case EIRP and verify it against the MPE compliance distance (§9 below).

8. MPE — maximum permissible exposure tables

The RF safety regulation is 47 CFR §1.1310 — Maximum Permissible Exposure (MPE) limits — which the FCC adopted from IEEE C95.1 and ANSI/IEEE standards. The MPE tables specify allowable power densities at various frequencies for two environments:

  • Occupational / controlled environment — people exposed are RF workers who know they’re being exposed and have training. Time-averaged over 6 minutes.
  • General population / uncontrolled environment — people who may not know they’re being exposed and haven’t consented. Time-averaged over 30 minutes.

The general-population limits are typically 5× more restrictive than occupational (because the averaging time is longer and because un-trained un-consenting exposure is held to a higher standard).

MPE table (§1.1310 simplified):

Frequency rangeOccupational E-fieldOccupational H-fieldOccupational power densityGeneral-pop E-fieldGeneral-pop power density
0.3 - 3.0 MHz614 V/m1.63 A/m(100 mW/cm²)*614 V/m(100 mW/cm²)*
3.0 - 30 MHz1842/f V/m4.89/f A/m900/f² mW/cm²824/f V/m180/f² mW/cm²
30 - 300 MHz61.4 V/m0.163 A/m1.0 mW/cm²27.5 V/m0.2 mW/cm²
300 - 1500 MHz——f/300 mW/cm²—f/1500 mW/cm²
1500 - 100,000 MHz——5.0 mW/cm²—1.0 mW/cm²

(*) The low-frequency end is field-strength limited; the power-density figure shown is implied at the field-strength limit.

Where f is in MHz. So at 14 MHz, the occupational power-density limit is 900/14² = 4.6 mW/cm² and the general-population limit is 180/14² = 0.92 mW/cm². At 50 MHz, occupational is 1.0 mW/cm² and general-population is 0.2 mW/cm². At 1 GHz, occupational is 1000/300 = 3.33 mW/cm² and general-population is 1000/1500 = 0.67 mW/cm². The general-population numbers are the ones you compare to when neighbors, family members, or passersby could be in the field — which is essentially every amateur installation.

The 2021 rule change. Before 2021-05-03 most amateur stations were categorically excluded from individual MPE evaluation — the FCC presumed that typical amateur installations didn’t approach the MPE limits and skipped the evaluation requirement. The 2019 FCC rulemaking (effective 2021-05-03) removed the amateur categorical exclusion. Every amateur station, regardless of power level, must now have a documented MPE evaluation on file. The evaluation does not need to be submitted to the FCC — it just needs to exist, in the station’s records, available for FCC inspection on request.

For most typical amateur installations the evaluation is trivial: a 100 W HF dipole at 10 m altitude is well within compliance at all reasonable observer distances. The evaluation paperwork is “I ran the OET-65 calculation, here’s the result, the antenna is in compliance at X meters separation and is in fact located at Y meters from any controlled-access boundary.” For 1 kW+ operation, antennas close to occupied structures, or high-gain VHF/UHF antennas pointing toward the house, the evaluation matters and the compliance distance can be tens of meters.

9. OET-65 compliance workflow

The FCC’s OET Bulletin 65 (Office of Engineering and Technology, Bulletin 65, Edition 97-01 with subsequent supplements) is the methodology document for applying §1.1310. The amateur supplement to OET-65 (Supplement B, “Additional Information for Amateur Radio Stations”) covers the amateur-specific cases.

The OET-65 calculation in five steps.

  1. Determine the EIRP for each band and operating mode. Use §7’s ERP/EIRP formula. The duty cycle matters: CW at 50% duty cycle, SSB at 20% duty cycle (peak vs average power), FM at 100% duty cycle, FT8 at 50% duty cycle (15s TX / 15s RX = 50%). PEP minus duty-cycle adjustment gives average power.
  2. Compute power density at distance r from the antenna. In the far field, S = EIRP / (4π r²). For a 100 W transmitter into a 6 dBi antenna at 10 m distance: EIRP = 100 × 10^(6/10) = 398 W; S = 398 / (4π × 100) = 0.317 W/m² = 31.7 µW/cm² = 0.032 mW/cm². Compare to the MPE limit for that frequency.
  3. Apply duty-cycle averaging. The MPE limits are time-averaged over 30 minutes (general population) or 6 minutes (occupational). A 100 W PEP SSB transmitter with 20% duty cycle is effectively a 20 W average. The CW operator at 50% duty cycle is effectively half-power. The FM repeater operator at 100% duty cycle gets no reduction.
  4. Identify the compliance distance. The distance at which power density drops to the MPE limit. Reverse the formula: r_compliance = sqrt(EIRP / (4π × S_MPE)). For the 100 W / 6 dBi example at 14 MHz (S_MPE_general = 0.92 mW/cm² = 9.2 W/m² and SSB 20% duty = 80 W effective EIRP_avg): r_compliance = sqrt(80 / (4π × 9.2)) = sqrt(0.69) = 0.83 m. The general-population compliance distance is under a meter — trivial.
  5. Verify against the deployment. Is the antenna at least r_compliance away from any uncontrolled-access location (the next-door neighbor’s yard, the family room below the attic dipole, the sidewalk next to the tower)? If yes, compliant. If no, reduce power, increase distance, or redirect the antenna’s main lobe away from occupied areas.

Three worked examples.

Example 1 — 100 W HF dipole on 14 MHz, 10 m elevation, 10 m horizontal compliance check. Antenna gain is 2.15 dBi (it’s a dipole) so EIRP = 100 × 10^(0.215) = 164 W. SSB 20% duty cycle → effective EIRP_avg = 33 W. S_MPE_general at 14 MHz = 180/14² = 0.92 mW/cm² = 9.2 W/m². Power density at 10 m: S = 33/(4π × 100) = 0.026 W/m² = 0.0028 mW/cm². 330× below the limit. Compliant by a huge margin. This is the typical amateur install.

Example 2 — 800 W VHF FM repeater on 145 MHz, 30 m elevation, 6 dBi vertical antenna, observer in next-door yard 20 m horizontal and 30 m vertical (about 36 m slant). EIRP = 800 × 10^(0.6) = 3180 W. FM 100% duty cycle → no reduction; effective EIRP = 3180 W. S_MPE_general at 145 MHz = 0.2 mW/cm² = 2.0 W/m². Power density at 36 m slant: S = 3180/(4π × 36²) = 0.195 W/m² = 0.020 mW/cm². 10× below limit. Compliant. This is what makes high-elevation VHF repeaters safe even with substantial power; the elevation buys distance which buys r² safety margin.

Example 3 — 50 W 2 m mobile, magnetic-mount antenna on car roof, passengers in car at ~1 m from antenna. Antenna gain ~3 dBi for a 1/4-wave whip with car-roof groundplane. EIRP = 50 × 10^(0.3) = 100 W. FM 100% duty cycle (PTT held down) → effective EIRP = 100 W. S_MPE_general at 145 MHz = 0.2 mW/cm² = 2.0 W/m². Power density at 1 m: S = 100/(4π × 1²) = 7.96 W/m² = 0.80 mW/cm². Exceeds the 0.2 mW/cm² general-population MPE limit by 4×. At 1 m the limit is exceeded. Compliance distance: r = sqrt(100/(4π × 2.0)) = 2 m. The driver and passengers cannot be within 2 m of the antenna at full power-during-transmit. In practice this means the roof-mounted antenna over the rear half of a sedan is borderline (the front-seat passenger might be 2 m from the antenna; the rear-seat passenger might be 1.5 m). Reduce to 25 W and the compliance distance drops to 1.4 m, well within typical car geometry. Run high power on a mobile only with the roof antenna positioned over the trunk and people in the front seats — or back off to 25 W for routine operation.

Calculators. Three useful free online MPE calculators:

  • KE0FF MPE Calculator at https://www.ke0ff.org/MPE/ — straightforward web form, hand inputs power/gain/frequency/duty-cycle, outputs compliance distance.
  • ARRL RF Exposure Calculator at https://www.arrl.org/rf-exposure-calculator — ARRL-hosted, OET-65 Supplement B methodology.
  • HamCalc / HamHelper / N5XU calculator pages — multiple amateur-community implementations.

For routine amateur stations the workflow is: use one of the calculators, save the input parameters and the result (screenshot, printed page, plain-text file), keep it in the station log. Done. For high-power operation (>1 kW), commercial installations, or installations close to occupied buildings, a professional RF-safety evaluation is appropriate — there are consultants who do exactly this.

10. Lightning — codes and protections

Lightning protection of amateur and commercial antenna installations is governed by the National Electrical Code, primarily NEC Article 250 (Grounding and Bonding) and NEC Article 810 (Radio and Television Equipment). NEC 810 specifically calls out antenna lead-in conductors, grounding electrodes, antenna discharge units, and the bonding requirements between the antenna ground and the building service ground.

The single-point ground architecture. The canonical lightning-mitigation approach. All antenna feedlines enter the structure at a single point — a metal panel mounted on an exterior wall — and pass through a gas-discharge arrestor (PolyPhaser, Alpha Delta, ICE, Morgan) before entering the shack. The arrestor’s ground terminal is bonded to a copper bus bar that connects via heavy (#6 AWG minimum, #4 AWG preferred) copper conductor to a ground rod immediately beneath the panel, and from there to the building’s main service ground electrode per NEC 250.50. This bonded single-point ground ensures that during a near-strike, all conductors entering the structure rise to the same potential simultaneously, so there’s no differential voltage between the coax shield and the equipment ground — which is what fries equipment.

Why this is the legal requirement, not just a recommendation. Most US homeowner insurance policies require code-compliant grounding for any owner-installed antenna structure. After a lightning strike that damages a non-code-compliant installation, the insurance company can deny coverage on the grounds that the installation violated NEC 250/810. For amateur installations this is more than a hypothetical: a tower struck by lightning that takes out the shack equipment is a routine claim, and the first thing the adjuster asks for is the ground-system documentation.

Components of a code-compliant install.

  • Antenna discharge unit (arrestor) at every feedline entry. PolyPhaser IS-50UX-C0 (DC-pass, 0-700 MHz) is the standard for HF/VHF amateur use; the AL family for higher frequencies; specific microwave units for 2.4/5 GHz. The arrestor’s job is to clamp differential voltages on the coax to harmless levels during a near-strike.
  • Single-point ground panel — copper bus bar mounted on the exterior wall, all arrestors mounted on the panel, ground conductor to the rod.
  • Ground rod — copper-clad steel, 8 ft minimum length, driven into soil immediately adjacent to the panel. Multiple rods bonded together for high-RF-conductivity ground in dry soil.
  • Bonding to service ground — #6 AWG copper minimum from the antenna ground to the building’s main electrical service ground per NEC 250.50. This bond is what equalizes potentials during a strike.
  • Tower grounding — at least one ground rod per tower leg for guyed/freestanding towers; #2 AWG bonding between rods; bond to the single-point ground.

Vol 20 (Grounding, counterpoise, radials, lightning protection) covers the implementation detail; this volume covers the legal framework that makes it required.

FAA tower lighting and notification — 14 CFR Part 77 and FAA Advisory Circular 70/7460-1. The FAA requires notification (FAA Form 7460-1, “Notice of Proposed Construction or Alteration”) for structures over 200 ft AGL, plus certain lower thresholds:

  • Structures of any height that exceed a 100:1 slope from the nearest point on a runway end for distances up to 20,000 ft.
  • Structures within 5 nautical miles of an airport that exceed the airport’s notification surface (typically a 100:1 slope at the nearest runway).
  • Structures over 200 ft AGL anywhere.

For most amateur installations — typical tower heights are 50-100 ft AGL — the notification threshold is not triggered. The exception is amateur installations close to airports. A 100 ft tower 1 mile from a runway end may trigger notification under the slope rule. The FAA’s tool at https://oeaaa.faa.gov evaluates a proposed structure against the notification criteria. Where notification is required, the FAA issues a “Determination of No Hazard” (NoH) or requires specific lighting (red obstruction beacons, white strobes) and marking (alternating bands of orange and white paint).

The good news for the typical amateur installation: the 60-100 ft tower at a suburban residence well away from any airport is below the notification threshold and does not require tower lights or FAA filing. The bad news: if you’re near an airport or in an aviation-corridor area, file Form 7460-1 before construction; doing it after is much more painful.

11. Common-mode currents and RFI to neighbors

Common-mode currents on coaxial feedlines are the single most common cause of RFI complaints and self-induced shack RFI. The mechanism: a coaxial cable carries TX power on the center conductor and the inside of the shield; ideally the shield’s outside surface carries no current. In practice, mismatched antennas, unbalanced feed at the feedpoint (a dipole fed with coax without a balun), or proximity to the antenna’s near-field induces current on the outside of the shield. That outside-shield current makes the coax itself a radiator — a vertical antenna with no pattern control, fed at the radio’s chassis ground.

Why it matters for compliance. Three problems result:

  1. RFI to nearby electronics. The radiating coax couples into telephone lines, CATV cable, baby monitors, intercoms, and audio equipment. The neighbor’s complaint (cable TV breakup whenever you key the rig) is almost always coax common-mode current radiating from the feedline run.
  2. Distorted antenna pattern. Your Yagi’s directional pattern presumes the feedpoint is the only radiator. When the coax radiates as a vertical, you get a vertically-polarized component mixed in with the Yagi’s horizontal pattern, the F/B degrades, and your directional aiming becomes meaningless.
  3. In-shack RFI. The radiating coax couples into the rig’s audio circuits (the “RF in the audio” complaint, where SSB transmit causes the audio chain to motorboat or distort), the computer USB cable (the radio control losing serial communication when transmitting), and the headphone amp.

The cure — current chokes (1:1 current baluns). A 1:1 current choke at the feedpoint is mandatory for every coax-fed antenna, regardless of how well-matched the antenna is. Topologies: ferrite-bead-cluster choke (a stack of 31-mix or 43-mix ferrite cores threaded over the coax), wound-choke (the “ugly balun” — 8-12 turns of coax through a large ferrite toroid), or commercial current baluns (DX Engineering, Balun Designs, Palomar). Vol 16 covers selection and construction; the practical recommendation is a #31-mix or #43-mix ferrite choke rated for the band of interest and the power level — for 100 W on 14 MHz an MFJ-915 or DX Engineering CCB choke at $50-100 does the job.

For runs longer than λ/4 at the operating frequency, additional chokes at every λ/4 break the resonance and suppress remaining common-mode current. For amateur-grade installations 1-2 chokes total usually suffices; for low-noise reception and clean RFI-free transmit, multiple chokes is the standard.

The §15.5 enforcement clause. Part 15 §15.5(b) gives the FCC explicit authority to require any unintentional radiator (or any intentional radiator operating outside its certification) to cease operation if it causes harmful interference. This includes interference to amateur radio operation. Conversely, an amateur station that causes harmful interference to certified Part 15 devices (cable TV, baby monitors, telephone-line audio coupling) — even when the Part 15 device itself is at fault for inadequate shielding — may be required to take corrective measures. The harmful-interference doctrine cuts both ways.

Filing interference complaints — FCC Form 2000C. When a neighbor’s Part 15 device (or any unintentional radiator) interferes with amateur reception, the formal complaint path is FCC Form 2000C (“Notice of RFI to Licensed Radio Services”) at https://www.fcc.gov/general/complaint-handling. The FCC can then require the offending device to be modified, shielded, or removed. In practice, neighbor RFI is usually resolved by direct conversation and a $20 ferrite-core kit (chokes on the offending device’s power cord), but the formal path exists when conversation fails.

Powerline RFI is a major HF noise source — 60 Hz harmonics from arcing-fault distribution transformers, defective insulators, and switching capacitor banks generate broadband noise from 100 kHz through 30 MHz. The “find the noise source” methodology: use a portable HF receiver with a directional Yagi or loop antenna; walk the noise; correlate to the local utility infrastructure. Filing the noise complaint with the local utility usually triggers a line-crew investigation. The utility is legally responsible under §15.5 for fixing emissions that exceed §15.209 radiated limits.

12. The receive-only carve-out

The general rule for receive: it’s almost always legal, in most US jurisdictions, across most frequencies. You can build an RTL-SDR-based wideband receiver and tune anywhere from 24 MHz to 1.7 GHz without any federal licensing requirement. Receive is unregulated under Title III at the federal level — the regulatory authority is over transmission, not reception.

The ECPA exception — Electronic Communications Privacy Act (1986). The ECPA (codified at 18 USC §2511 and §2510) makes it a federal crime to intentionally intercept certain protected electronic communications, even passively. The protected categories that matter for the Hack Tools collection:

  • Cellular voice and data — explicitly protected. Receiving and decoding GSM, LTE, or NR cellular voice or SMS is an ECPA violation.
  • Common-carrier paging and text — explicitly protected. Decoding POCSAG or FLEX paging traffic that’s identifiable as common-carrier service may violate ECPA (though the FCC’s 1994 enforcement guidance carved out non-decoded reception, the line is fuzzy).
  • Encrypted communications — broadly protected. Receiving an encrypted signal is not a violation; intentionally decrypting it without authorization is.
  • Cordless telephone — historically protected (the 1993 amendment); modern DECT cordless phones use built-in encryption that’s itself protection.

What ECPA does NOT protect.

  • Broadcast radio and TV — explicitly unprotected (it’s broadcast for public reception).
  • Amateur radio — unprotected (it’s a public service operating on shared spectrum).
  • CB radio, FRS, GMRS, MURS — unprotected (public services on unlicensed bands).
  • Marine and aeronautical voice — unprotected (safety-of-life broadcasts).
  • Public-safety dispatch (Part 90) — generally unprotected for voice (it’s broadcast over public airwaves; the FCC’s position is reception is legal even if rebroadcast may not be). Encrypted trunked Part 90 systems are protected against intentional decryption under ECPA.
  • ADS-B aircraft transponder data, AIS marine ship data — explicitly published for public consumption.

The Communications Act §605. Independent of ECPA, 47 USC §605 prohibits unauthorized publication or use of intercepted communications — receiving is legal, but rebroadcasting or commercially exploiting intercepted traffic is its own violation.

Defensive monitoring as posture. The Hack Tools collection’s receive-only / monitoring tools — RTL-SDR for general SDR reception, Rayhunter for cellular IMSI catcher detection, PWNagotchi when configured as monitor-only — all operate within the receive-legal envelope. They observe, log, and characterize; they don’t decode protected content. The Rayhunter specifically is defensive — it identifies the existence and behavior of nearby cellular network elements (legitimate and rogue) without decoding any subscriber traffic. The legal framing for these tools is “I’m operating equipment that records the radio environment around me, including signals my devices interact with. That’s lawful.” Decoding the contents of any protected communication crosses a line ECPA punishes.

13. Cross-references to other Hack Tools deep dives

This volume is the regulatory side of the antenna deep dive; it cross-links to every TX-capable radio’s deep dive and to the broader RF tradecraft reference cluster.

Within the Antennas series:

To sibling Hack Tools deep dives:

  • ../Hacker Tradecraft/ Vol 19 (Legal Line & Ethics) — broader-than-RF legal-line treatment for security research; cross-tool ethics baseline.
  • ../HackRF One/CLAUDE.md — the wideband SDR’s posture; HackRF can physically transmit anywhere from 1 MHz to 6 GHz, which means the operator carries the full burden of knowing which band their TX is hitting and what authorization applies. The HackRF deep dive’s regulatory section cross-references this volume.
  • ../Quansheng UV-K5/CLAUDE.md — VHF/UHF handheld with extended-firmware TX capability. The custom firmware’s “TX anywhere” capability does not grant the operator any authorization beyond what they hold (Part 97 on amateur bands; nothing on Part 90 LMR or Part 95 FRS/GMRS).
  • ../WiFi Pineapple/CLAUDE.md and ../ESP32 Marauder Firmware/CLAUDE.md — Part 15 2.4 GHz devices. Operating in certified configuration is Part 15-authorized; modifying firmware to boost TX power or running in non-certified channels (e.g., Japan’s 14 channels when in the US which allows 11) voids the certification.
  • ../Rayhunter/CLAUDE.md — receive-only cellular IMSI catcher detector. Operates entirely in the §12 receive-legal envelope; observing without decoding.
  • ../_shared/legal_ethics.md — cross-tool legal/ethics baseline.

14. Resources

Primary regulatory text (US):

RF safety calculators and references:

License lookup and amateur radio:

International and ITU:

FCC enforcement and interference:

Electrical code (lightning):

  • NFPA 70 (National Electrical Code) — purchase from NFPA at https://www.nfpa.org; Articles 250 and 810 are the relevant sections
  • NFPA 780 (Standard for the Installation of Lightning Protection Systems) — companion to NEC for lightning protection design
  • PolyPhaser application notes (lightning arrestor selection) — https://www.polyphaser.com

Common gotchas and myths — the cheatsheet.

MythReality
”Receive-only is always legal”Mostly true; ECPA (18 USC §2511) makes intentional decoding of cellular voice, paging, encrypted public-safety, and DECT cordless illegal even passively.
”I can transmit FRS on my UV-K5 because no license is needed for FRS”Wrong. Part 95 §95.7 requires type-acceptance with non-detachable antenna and certified power; using a non-Part-95 radio on FRS frequencies is a Part 95 violation regardless of the no-license rule.
”Extra-class lets me transmit anywhere”Wrong. Extra grants full amateur privileges on amateur bands; doesn’t extend to Part 15/22/24/27/87/90/95 services.
”1500 W PEP is the global amateur limit”Wrong. Varies by country (UK 400 W, Germany 750 W, Japan 1 kW, Australia 400 W on most bands) and by ITU region for specific bands.
”Common-mode chokes are belt-and-suspenders if the antenna is matched”Wrong. Coax-shield common-mode current re-radiates as a vertical antenna with no pattern control, distorts the directional antenna’s pattern, and causes in-shack RFI. The choke is mandatory regardless of feedpoint match.
”MPE doesn’t apply to amateur stations”Wrong since 2021-05-03 FCC rules removed the amateur categorical exclusion. Every amateur station needs a documented MPE evaluation, even if the conclusion is “compliant by trivial margin."
"My antenna’s gain is dBi so my ERP is high”Mix-up. dBi is gain vs isotropic; ERP is vs a half-wave dipole. Convert: ERP = EIRP − 2.15 dB.
”FCC won’t enforce ham regs against me”Wrong. The FCC enforces against amateurs for jamming (§97.101(d)), retransmission of non-amateur communications, deliberate interference, and identification violations. Monetary forfeitures of $2-25k are common; license revocation for repeat offenders.

Bottom line for amateur operating (Extra-class, US):

  • Operate within your band privileges per §97.301. Print and laminate the ARRL band chart.
  • Identify with your callsign at the end of every QSO and at least every 10 minutes.
  • Run only the minimum power necessary; the 1500 W ceiling is not a target.
  • Install a 1:1 current choke at every coax-fed antenna feedpoint.
  • Ground the station to NEC 250/810: single-point ground panel, gas-discharge arrestors, bonded service ground.
  • Run your MPE evaluation once for each band-and-mode combination and keep it in the station log.
  • Verify TX harmonic suppression per §97.307: -43 dBc HF, -60 dBc 30-225 MHz, -43 dBc above 225 MHz.

Bottom line for non-amateur testing (Part 15 ISM):

  • Operate certified equipment in its certified configuration. Modifying firmware to exceed certified power voids the certification.
  • Verify FCC ID on the device matches a current authorization in the Equipment Authorization database.
  • Sub-GHz Flipper TX at 100 mW into a quarter-wave whip on 433/868/915 MHz stays in Part 15 ISM territory; don’t TX in adjacent licensed bands.
  • WiFi devices: 36 dBm EIRP cap point-to-multipoint on 2.4 GHz; point-to-point allows higher gain with proportional power reduction.
  • TX into licensed bands (Part 22 cellular, Part 87 aero, Part 90 LMR) without the appropriate license is enforceable. The HackRF and Quansheng UV-K5 are particularly easy traps because the hardware can transmit there.
  • Receive freely; observe the ECPA exceptions in §12 above when targeting cellular, encrypted public-safety, or DECT.