The Acoustimeter AM-11 is widely regarded as one of the most reliable consumer-grade RF meters available — recommended by Building Biology practitioners, independent EMF researchers, and the team here at EMF Defender. It was designed by Dr Alasdair Philips, founder of Powerwatch and one of the UK's most respected independent EMF researchers. If you are researching the AM-11 before purchase, this page gives you every technical specification you need, a clear explanation of what each spec means in practice, an honest assessment of its limitations, and a direct comparison with the previous AM-10 model.

Quick Specifications At a Glance

Full Technical Specifications

Acoustimeter AM-11 — Complete Specification Table
Frequency Range	200 MHz – 8 GHz
Measurement Type	RF / microwave radiation (electric field strength and power density)
Display — Primary	Dual LED bar graph (16 LEDs): separate Peak and Average columns displayed simultaneously
Display — Secondary	Digital LCD showing V/m and µW/m² readings with peak-hold function
Measurement Units	V/m (volts per metre) and µW/m² (microwatts per square metre)
Minimum Detectable Level	0.001 V/m (approx. 0.003 µW/m²)
Maximum Display Level	6 V/m (approx. 100 µW/m²)
Accuracy	±6 dB across full frequency range (typical ±3 dB at 2.45 GHz)
Response Time — Peak	Captures pulses as short as 1 millisecond
Response Time — Average	Approximately 1 second rolling average
Audio Output	3.5mm headphone socket — demodulated audio of detected signal (allows auditory identification of source type)
Speaker	Built-in speaker with volume control
Antenna	Internal broadband isotropic antenna (omni-directional, responds to all polarisations)
Battery	3 × AA alkaline batteries
Battery Life	Approximately 20 hours continuous use
Auto Power Off	Yes — after approximately 10 minutes of inactivity (can be disabled)
Dimensions	Approximately 155 mm × 70 mm × 28 mm
Weight	Approximately 200 g (including batteries)
Operating Temperature	0°C to 40°C
ELF Measurement	Not included — RF only
Magnetic Field Measurement	Not included
Data Logging	Not included
PC / USB Connection	Not included
Country of Origin	United Kingdom
Designer	Dr Alasdair Philips, Powerwatch (UK)
Compliance / Calibration	Factory calibrated; calibration service available from manufacturer

What Each Key Specification Means in Practice

Frequency Range: 200 MHz – 8 GHz

This is the most important specification for determining what the AM-11 can and cannot detect. The range covers every major domestic RF radiation source except millimetre wave 5G (mmWave, 24–100GHz, which is only deployed in specific dense urban hotspot environments in the UK). In practice, the AM-11 will detect:

• WiFi 2.4GHz and 5GHz — both domestic and public hotspots
• 4G/LTE — 700MHz to 2.6GHz bands
• 5G sub-6GHz — 3.4GHz to 3.8GHz (the primary UK 5G deployment band)
• Smart meters — 868MHz (WAN) and 2.4GHz (HAN/Zigbee)
• DECT cordless phones and baby monitors — 1.88GHz to 1.90GHz
• Bluetooth — 2.4GHz
• Microwave oven leakage — 2.45GHz
• 3G — 850MHz to 2.1GHz

Dual Bar Graph: Why Peak AND Average Matter

The AM-11's dual LED bar graph — showing Peak and Average simultaneously — is one of its most practically important features. Many cheaper meters show only an average or RMS reading. Smart meters, DECT phones, WiFi routers, and 4G base stations all transmit in short, intense bursts (pulsed radiation). An average-only reading misses the peak levels entirely — a smart meter sending a brief high-power burst every 30 seconds would read near zero on average, but show a high peak. The AM-11's peak-hold display captures these instantaneous pulses, which independent researchers consider more biologically relevant than time-averaged levels.

Audio Output: Identifying Source Type by Sound

The 3.5mm audio output demodulates the detected RF signal and outputs it as audible sound. Different radiation sources have characteristic sounds: WiFi produces a rapid chattering sound; smart meters produce intermittent loud bursts; DECT phone base stations produce a regular ticking even at standby; 4G produces a distinctive noise pattern. This audio signature capability allows experienced users to identify the type of source from a reading — not just the level. It is particularly useful when trying to locate and identify an unknown source in a room.

Accuracy: ±6 dB Across Range

±6 dB means the reading could be up to 4× higher or 4× lower than the true value at the extremes of the frequency range. At the centre frequencies where the antenna is most efficient (around 1–3GHz), accuracy is typically ±3 dB or better. This level of accuracy is appropriate for Building Biology assessments and exposure mapping — it is not a laboratory-grade calibrated instrument, but it is significantly more accurate than inexpensive consumer meters that may be off by 10–20× at certain frequencies. For reference, the Building Biology threshold bands span orders of magnitude, so ±6 dB accuracy is entirely sufficient for determining which exposure band applies.

Acoustimeter AM-11 vs AM-10: What Changed?

The AM-10 was the previous generation Acoustimeter, still widely available second-hand and sometimes sold as new old stock. If you are deciding between the two, here is a precise breakdown of the differences:

Specification	AM-10	AM-11	Verdict
Frequency Range	200 MHz – 3.5 GHz	200 MHz – 8 GHz	AM-11 wins
5GHz WiFi Detection	❌ Not covered	✅ Covered	AM-11 wins
5G Sub-6GHz (3.4–3.8GHz UK)	⚠️ Partial (3.4GHz marginal)	✅ Fully covered	AM-11 wins
Digital LCD Display	❌ LED bar graph only	✅ LED + digital LCD	AM-11 wins
LED Bar Graph	✅ 16-LED dual bar graph	✅ 16-LED dual bar graph	Same
Audio Output	✅ 3.5mm jack	✅ 3.5mm jack	Same
Minimum Detectable Level	0.01 V/m	0.001 V/m	AM-11 wins
Battery Type	3 × AA	3 × AA	Same
Physical Size	~155 × 70 × 28mm	~155 × 70 × 28mm	Same
Price (approx.)	£140–160 (secondhand)	£195–220 (new)	AM-10 cheaper

Who Is the Acoustimeter AM-11 Best Suited For?

Honest Limitations of the AM-11

No consumer meter is perfect. The following limitations are worth understanding before purchase to ensure the AM-11 is the right tool for your needs:

• No ELF measurement — if your concern includes ELF magnetic fields from power lines, wiring, or appliances (relevant to the Li et al. miscarriage study), you need a separate gaussmeter alongside the AM-11.
• No data logging — readings cannot be exported or recorded automatically. You must note readings manually or video the display.
• No mmWave 5G coverage — the 8GHz ceiling misses mmWave 5G (24GHz+), though this is a minor limitation given current UK deployment patterns.
• Maximum reading 6 V/m — in very high-exposure environments (directly under a 4G mast at close range), the display maxes out. This is rarely an issue in domestic assessment contexts.
• No directional indication — the isotropic antenna gives no indication of which direction a signal is coming from. To locate a source, walk toward/away from it and watch the reading change.

Reading the AM-11 Against Building Biology Thresholds

The AM-11 displays readings in V/m (primary) and µW/m² (secondary). The Building Biology SBM-2015 sleeping area guidelines, which are widely used by independent EMF assessors, give the following thresholds for RF/microwave radiation:

Building Biology SBM-2015 RF Exposure Levels (Sleeping Areas)
Level	µW/m²	V/m (approx.)
No Anomaly	< 0.1	< 0.006 V/m
Slight Anomaly	0.1 – 10	0.006 – 0.06 V/m
Severe Anomaly	10 – 1,000	0.06 – 0.6 V/m
Extreme Anomaly	> 1,000	> 0.6 V/m

The AM-11's LED bar graph is calibrated to approximately these thresholds — green LEDs broadly correspond to the lower bands; orange and red LEDs indicate severe and extreme anomaly levels. Use the digital LCD for precise numerical comparison against these thresholds.