Amateur Radio Antenna & Feedline Math: Wavelengths, Dipole & Vertical Lengths, SWR & Mismatch Loss, Coax Loss, ERP and Logbook Statistics

What you'll build

What you will be able to do

Each lab ends with a concrete result that you build yourself and the checker confirms, cell by cell.

• Turn nine practice frequencies into wavelengths and half waves, count the channels whose wavelength is above 10 m and work back from a wavelength to the frequency of the club beacon.
• Cut a half-wave dipole and a quarter-wave vertical for five channels with an end-effect factor, then trim a dipole that resonates too low: new total length and the piece to cut off at each end.
• Compute the reflection coefficient and the SWR for six resistive loads on a 50 Ω line, flag the loads above the fictional radio's limit and turn a meter reading back into |Γ|.
• Turn five SWR values into |Γ|, the reflected power share, the mismatch loss in dB and the watts the load accepts from 100 W forward power.
• Look up the loss per 100 m for five cable runs in a two-way table, add the connector losses and work out how many watts reach the antenna and what share is lost.
• Convert five transmitter powers to dBm, combine cable loss and antenna gain into a net gain against a dipole and calculate the effective radiated power in watts and dBm.
• Decode six-character grid locators into longitude and latitude with MID and a letter table instead of CODE, then compute the great-circle distance from the club with the haversine formula and ATAN.
• Summarise Nell's 20 October contacts by band, count the evening contacts per band with COUNTIFS, find the station of the longest contact with INDEX/MATCH and chart the contacts per band.