What Delta Markers Do
A delta marker (Δ marker) reads the difference between two marker positions: ΔFreq = f₂ − f₁ and ΔLevel = S21(f₂) − S21(f₁). This is essential for measuring bandwidth, stopband rejection relative to passband, and group delay ripple without manual subtraction.
Setting Up Delta Markers in RF View
- Place Marker 1 at the reference point (e.g., S21 peak, −1.8 dB at 1815 MHz)
- Activate Marker 2 in Δ mode (delta, relative to Marker 1)
- Move Marker 2 to the point of interest
- RF View displays: Δfreq = f₂−f₁ and ΔdB = level₂ − level₁
Use Case 1: Measuring Filter Bandwidth
Marker 1: at S21 peak (1815 MHz, −1.8 dB)
Marker 2 (Δ): move left until ΔdB = −3.0 dB
→ Reads: Δfreq = −18 MHz (lower edge at 1797 MHz)
Move Marker 2 to right side until ΔdB = −3.0 dB
→ Reads: Δfreq = +20 MHz (upper edge at 1835 MHz)
Total 3 dB BW = 18 + 20 = 38 MHz
Use Case 2: Measuring Stopband Rejection
Marker 1: at passband IL (1815 MHz, S21 = −1.8 dB)
Marker 2 (Δ): move to TX band (1750 MHz)
→ Reads: ΔdB = −52 dB
Actual stopband S21 at 1750 MHz = −1.8 + (−52) = −53.8 dB
Relative rejection = 52 dB (passband to stopband difference)
Use Case 3: Group Delay Ripple Measurement
Switch to Group Delay view Marker 1: at maximum group delay in passband (1835 MHz, τ = 182 ns) Marker 2 (Δ): move to minimum group delay (1800 MHz, τ = 165 ns) Δτ_g = 182 − 165 = 17 ns (group delay ripple over passband)
Use Case 4: Cable Electrical Length
Load cable .s2p → S21 phase Marker 1: at 1 GHz Marker 2 (Δ): move to 2 GHz ΔPhase = −360° over 1 GHz → electrical length = 1 ns propagation delay Physical length = 1 ns × c/√εe = 1e-9 × 3e8/√1.5 = 245 mm
RF View Delta Markers: Tap any marker to switch to Δ mode. Reads frequency difference and level difference simultaneously. Works on all plot types: dB, VSWR, phase, group delay, Smith chart. Free on Android.