Level 4 · Lesson 4.2

Advanced antennas and feed lines

Jimmy Bob, a friendly cartoon mountain man in a trucker cap and overalls

“The antenna is where the magic happens, and the feed line is where it leaks out if you are careless.”

You'll be able to

compare antenna gain figures, feed line loss, and matching.

Antenna gain is given in , compared with a theoretical antenna, or in , compared with a dipole; 0 dBd equals 2.15 dBi. Feed line loss increases with frequency and length, so good coax matters most at VHF and UHF. Phased arrays steer signals electronically. Matching networks transform impedance so the transmitter sees 50 ohms.

Tap an underlined word for its meaning.

Try it

On-air activity

compare coax loss for 100 feet of RG-58 and LMR-400 at 146 MHz.

This one happens on the air in The Shack, which opens in a later phase.

Quick check

Get 2 of 3 right to complete the lesson.

1. 0 dBd equals…
2. Feed line loss increases with…
3. A matching network makes the transmitter see…

Words from this lesson

Phased array