Tech Talk Pictures, Discussion, and Links

This page is for posting drawings, pictures, and links related to tech talk. I have to put the data up manually. No pictures above 800KB size! The ideal size for a drawing is in the 100-300KB range if properly formatted. The ideal photo file size is likely 200-800KB if normal size and detail.

TechTalk is Sunday and Monday nights at 9PM EDST.

Thanks!
W8JI Tom

Antenna Terms

Please help add to these terms with suggestions:

Antenna the radiating structure

Balun a device to make sure the antenna radiates and receives rather than the feedline

Cable  a thick, strong rope made of wires that are twisted together, or  a group or bundle of wires, glass fibers, etc., covered in plastic or rubber and used to carry electricity or electrical signals

Coax a concentric conductor cable with a single central conductor. Both the shield inside and the center conductor carries equal and opposite currents. Any common mode which includes (most lightning current) flows over the shield outside

Counterpoise a floating or connected artificial ground system that an antenna references against

Dipole antenna unless specified otherwise a center fed half wave antenna fed with low impedance coax

Elements independent parts of a system

Radials wires or conductors that extend radially from a point, generally used as an RF ground system

Resonance much like how a tuning fork or guitar string works, a system tuned to have no reactance. This does NOT make an antenna work better and it does not make the SWR low. Resonance in an antenna system simply means it has no reactance.

Tech Talk 3/31/2024 (revised)
Download PDF link


Tech Talk for 10/23/2023

Tech Talk for 12/21/2020

Antenna modeling,

Tech Talk for 12/13/2020

We need to talk about transmission line loss, resonance, and the effects of standing waves on the systems we have. Please look at this calculator

https://owenduffy.net/calc/tl/tllc.php

I’m proposing we look at two or three installations and calculate the effect of standing waves in those systems. I’m trying to find details on a couple installations.

11/9/2020 balun for a fan (or any coax fed) dipole

This is a screen shot of my fan dipole feedpoint. My fan dipole is about 120-foot in the air. It has been hanging in the air a few years now.

Droopy dipole or “Inverted Vee dipole” about 70 feet high. The black pattern is with legs straight in line and the blue pattern is with 90 degree angle in legs.

This shows how little importance it is to be “fussy” about leg angles on a low dipole antenna.