RF ANALYSIS

Antenna Configuration & SDR Reference Guide

MY CURRENT ANTENNA SETUP

1090 MHz

ADS-B (Aircraft)

Small Dipole

5.5" total

Vertical orientation - both arms in line

     |
     |  ~2.75"
   [SDR]
     |
     |  ~2.75"

Collapsed dipole - 5.5" tip to tip

433 MHz

IoT / ISM Band

Single Whip

Vertical orientation - pointing up

     |
     |
     |  7"
     |
     |
   [SDR]

Single whip antenna - 7" tall

ANTENNA LENGTH FORMULAS

1/4 Wave (Whip) = 300 / freq(MHz) / 4 × 100 = cm

1/2 Wave (Dipole) = 300 / freq(MHz) / 2 × 100 = cm

5/8 Wave (High Gain) = 300 / freq(MHz) × 0.625 × 100 = cm

Multiply cm by 0.3937 to get inches

ANTENNA SIZE QUICK REFERENCE

Frequency	Band / Use	1/4 Wave	1/2 Wave (Dipole Total)
88-108 MHz	FM Radio	~75 cm (30")	~150 cm (60")
144 MHz	2m Amateur	52 cm (20")	104 cm (41")
162 MHz	Marine AIS / NOAA	46 cm (18")	92 cm (36")
433 MHz	IoT / ISM Band	17 cm (7")	34 cm (14")
462-467 MHz	FRS/GMRS	16 cm (6.5")	32 cm (13")
868 MHz	EU ISM / LoRa	8.6 cm (3.4")	17 cm (6.8")
915 MHz	US ISM / LoRa	8.2 cm (3.2")	16 cm (6.4")
1090 MHz	ADS-B (Aircraft)	6.9 cm (2.7")	13.8 cm (5.5")
1575 MHz	GPS L1	4.8 cm (1.9")	9.5 cm (3.7")

ADS-B (1090 MHz) - AIRCRAFT TRACKING

Optimal Antenna Setup

Type: Dipole or 1/4 wave whip
Length: 5.5" dipole or 2.7" whip
Orientation: Vertical
Placement: Outside, clear sky view
Height: Higher = better range

What You'll Receive

Aircraft callsigns

Altitude

Speed & heading

Lat/Long position

Squawk codes

Aircraft type

Range depends heavily on antenna placement. Rooftop antenna can receive 200+ miles. Indoor may only get 20-50 miles.

Software to Use:


                dump1090 --interactive

                # or

                rtl_adsb | grep -v "^$"

433 MHz - IoT & ISM BAND

Optimal Antenna Setup

Type: 1/4 wave whip or dipole
Length: 7" whip or 14" dipole total
Orientation: Vertical
Placement: Outside or near window
Range: ~100-500 ft typical

What You'll Receive

Weather stations

Car keyfobs

Garage door openers

TPMS (tire sensors)

Wireless doorbells

Smart home sensors

Baby monitors

Remote thermometers

Software to Use:


                rtl_433 -f 433920000

                # With more output:

                rtl_433 -f 433920000 -F json -M level

RTL-SDR FREQUENCY COVERAGE (24 MHz - 1.7 GHz)

Frequency	What You Can Receive	Antenna Size (1/4 wave)
88-108 MHz	FM Radio Stations	~30 inches
108-137 MHz	Aircraft Voice (Airband)	~24 inches
137 MHz	NOAA Weather Satellites	~22 inches
150-170 MHz	Pagers (POCSAG/FLEX)	~18 inches
162 MHz	Marine AIS (Ship Tracking)	~18 inches
315 MHz	Car Keyfobs (US)	~9 inches
433 MHz	IoT, Weather Stations, Keyfobs (EU)	7 inches
450-470 MHz	UHF Business Radio	~6.5 inches
462-467 MHz	FRS/GMRS (Walkie-Talkies)	~6.5 inches
850-900 MHz	Cellular (Tower Mapping)	~3.5 inches
915 MHz	LoRa, ISM, Smart Meters	~3.2 inches
1090 MHz	ADS-B (Aircraft Position)	2.7 inches
1575 MHz	GPS L1	~1.9 inches

ANTENNA ORIENTATION GUIDE

VERTICAL (Most Common)

     |
     |
   [SDR]
     |
     |

Use for: ADS-B, 433 MHz, FM, most signals
Matches vertical polarization of most transmitters

HORIZONTAL

  ----[SDR]----

Use for: TV broadcast, some amateur, satellites
Matches horizontal polarization signals

Wrong polarization = ~20dB signal loss! Most IoT and ADS-B transmitters are vertical. Always try vertical first.

ANTENNA PLACEMENT TIPS

Higher = Better
Get antenna as high as possible, especially for ADS-B

Outside > Inside
Walls block signals, especially at higher frequencies

Away from Metal
Keep antenna away from metal objects that cause reflections

Clear Line of Sight
ADS-B needs clear view of sky, 433 MHz needs path to transmitters

Coax Length Matters
Shorter coax = less signal loss. Keep cables as short as possible

Tune for One Frequency
One antenna can't be optimal for everything - prioritize main target