Merv's Brain Dump

This guide outlines a cheap, homebrew method to calibrate or verify a Screwdriver without any pre-calibrated equipment. It relies on known physics (wavelength, impedance, resonance) and public references (WWV, GPS, broadcast carriers).

What you will build

• A simple reference or fixture based on known dimensions or components.
• A repeatable setup for measurements and comparisons.

Calibration compares the Screwdriver response to a known reference. For antennas, the reference comes from physical dimensions (wavelength), known impedance standards, and repeatable measurement setups. For supporting gear, the reference comes from basic circuit physics and stable sources.

1. Use measured cuts based on wavelength formulas.
2. Use common copper wire or tubing.
3. Include a feedpoint structure that allows adjustment.
4. Use a simple support structure to keep geometry consistent.

1. Cut elements to calculated length.
2. Assemble the feedpoint with a connector and strain relief.
3. Mount the structure in its intended orientation.
4. Verify continuity and no shorts before measurements.

1. Use a stable reference signal (WWV, beacon, or known local carrier).
2. Measure resonance, SWR, or gain pattern.
3. Compare against expected values from calculations.
4. Apply corrections or document offsets.

1. Sweep across the target band.
2. Shorten or lengthen elements in small steps.
3. Record resonance shift per adjustment.
4. Lock the final configuration.

Confirm performance at several frequencies or positions. Keep a log of environment, height, and orientation so future checks are comparable.

Wavelength relationships

• Wavelength (meters) = 300 / Frequency (MHz)
• Quarter-wave length = Wavelength / 4
• Half-wave length = Wavelength / 2

Impedance

• V = I * R
• Power (W) = V^2 / R

Example

If target frequency is 7.1 MHz: - Wavelength = 300 / 7.1 = 42.25 m - Half-wave = 21.1 m