T4A

Station setup and grounding

Wire a station correctly: meters, power, computer audio links, RF bonding, keyers and hotspots.

12 pool questions1 on the exam

Syllabus: Station setup: connecting a microphone, RF power meter, a power source, a computer, digital equipment, an SWR meter; RF grounding; Mobile radio installation

Meters go in the feed line

An RF power meter reads the power going out to the antenna, so it goes in the feed line between the transmitter and the antenna. An accessory SWR meter goes in the same spot.

Meters go in the feed line, not on the power cable.

Pick a meter built for the frequency and power level you'll measure.

RememberMeter: in the coax, between radio and antenna.

13.8 V, lots of amps, short heavy wire

A mobile radio runs on 13.8 V DC. A 50 W FM radio draws about 12 A on transmit. Resistance in thin or long wire wastes voltage as heat: current times resistance.

Illustrative values: 12 A flows when a 50 W FM radio transmits.

Wire (short and heavy to long and thin)0.02 Ω

Voltage lost in wires0.2V

Short, heavy-gauge wire keeps voltage drop low when you transmit.
Connect the negative lead at the battery / chassis ground.

How long a battery lasts:

Runtime in hoursbattery amp-hours ÷ average current (A)

Example: 100 Ah ÷ 10 A = 10 hours.

Remember13.8 V at 12 A. Fat wire, short run, negative to battery ground.

Digital modes need three signals

The computer's sound card does the modem's job. FT8 software runs on the computer.

For FT8 and similar modes the radio's audio goes straight to the sound card of a computer running the software. No terminal or converter box needed.

RememberReceive audio, transmit audio, transmitter keying.

Bond at RF with wide flat strap

Highlighted outline = where RF current flows. The strap has far more of it.

RF current flows on the surface of a conductor, so the more surface, the lower the loss. A flat copper strap is preferred for RF bonding.

RememberBonding at RF: flat copper strap.

Keyers and hotspots

Hotspot = a small personal gateway to the network.

Device	What it does
Electronic keyer	Helps you send Morse code by hand
Digital hotspot	Connects your radio to a digital voice or data network

RememberKeyer = Morse sending aid. Hotspot = gateway to a digital network.

Loading lesson…

Go deeper

Compendium articles on the ideas in this lesson, beyond what the exam asks.

Check what stuck

Practise the 12 pool questions for this group. Answers are shuffled, and every one comes with a one-line "why".

Practise T4A →