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Radio Frequency Bridges

Bridge networks, DC to RF: Principles and overview .
+ downloadable references, manuals, etc.
Part 1: Wheatstone-Christie Bridge. Generalising the bridge. Voltage-splitting networks.
Part 3: Practical impedance bridges. Admittance bridge. The universal bridge. Vector and scalar addition. Impedance magnitude bridge. Monitoring Bridges.

Silvertown telegraph indicator galvanometer

6.2 Current transformers for RF bridges and ammeters
Part 1
: Intro. Equivalent circuit. Models. Transfer function. Output impedance. Insertion impedance.
Part 2: LF response. Core selection. Propagation delay. Secondary capacitance.

RF current transformer
Part 3: Multiple secondaries.

6.3 Transmission bridges.
Part 1
: Current transformer bridges: Low frequency compensation. Douma-Buschbeck (capacitive voltage sampling) bridge.

6.4 Reflectometry.
Part 1: <writing in progress>.

6.5 Magnitude-Difference Bridges.
Part 1: Intro. Prototype current-transformer magnitude-bridge. Insertion defect. Load-side voltage sampling. Port balancing. RVS. CVS. Detectors and summing networks. Absolute measurements.
Part 2: The bridge as an analog computer. Resistance bridges.
Part 3: Phasor theorems. Conductance bridges. <writing in progress>.
The G3GFC M50 Match Meter: Details of the original prototype units.

Impedance and admittance measurement using scalar voltage samples.
+ spreadsheet YZ_scalar_sim.ods (8 worksheets, + macros. 1 MiB).

Transmission bridge and Z-matching patents.




Background theory and experiment

Evaluation and optimisation of current-transformer bridges .
The Faraday shield, through-line mismatch; compensation for parasitic inductance; propagation delay and phase neutralisation.

A self-evaluating precision reference bridge.
A 50 Ω transmission bridge with phase accuracy better than ±0.1° and magnitude accuracy better than ±0.2% over the 1.6 MHz to 30MHz range.

HF reference bridge

Current transformer efficiency factor .
  + spreadsheet Itr_effy.ods (v 1.01).

Analysis of Herzog's current-transformer LF-compensation method.
  + spreadsheet Herzog_LF.ods . + Herzog's patent US 4739515 (1988).

The maximally-flat current transformer .
  + spreadsheet maxflat_sim.ods .

Amplitude response of conventional and maximally-flat current transformers.
  + spreadsheets Maxflat_test1.ods & Maxflat_test2.ods .

The maximally-flat transmission bridge .
  + spreadsheets maxflat_prelim.ods , maxflat_mtpri.ods & maxflat_brgd.ods .
  + LT SPICE files maxflat_v_i.asc & maxflat_brg.asc .
  LTspice - free SPICE simulator from Linear Technology.

Analysis of Douma's generator power-factor correction scheme.
  + Douma's patents US 2734169 (1956) & US 2808566 (1957).




Antenna and Network Analysers
AIM 4017, MFJ 269 and HP8753B comparison by Larry Benko W0QE
.
Measuring High Impedances with VNA, by Larry Benko .
Shunt capacitance of 1206 SMD resistors, by Jeroen Belleman .


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