1. Transmission Line Considerations
WZ4O

2. Types of Common Transmission Lines

3. Impedance of Transmission Lines

4. Impedance of Transmission Lines

5. Impedance of Transmission Lines
Properly balanced line will not radiate

9. Note:
Larger coax diameters generally have less loss
Loss goes up with frequency
Question: At Field Day, we have two 100 foot sections of coax that we need to connect together to get to our antenna, both with 2 dB/100 feet of loss on 10 meters. What will be our total loss?
Question: We need a 50 foot length of coax to get to our antenna. The loss is rated at 4 dB/100 feet at 70 cm. What is the loss in 50 feet of this line?

10. Sources of Loss in Transmission Lines (Current)
Current in transmission 100 watts:
P = I*E = I*I*R > P = SQRT(P/R)
50 ohms: I = amps
300 ohms: I = amps
600 ohms: I = amps

11. Sources of Loss in Transmission Lines (Dielectric)

12. Sources of Loss in Transmission Lines (VSWR)

15. Sources of Loss in Transmission Lines (VSWR)

17. Parallel Wire Balanced Line

21. Notes:
Don’t bend coax too sharply
Seal all outdoor connections…braided shield acts like a wick to moisture
Coax CAN be taped to tower legs
Coax runs CAN be taped together
Window line can change characteristics in rain
Keep balanced line balanced – NEVER run next to metallic objects
Do NOT tape to tower legs – use standoffs