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What Are the Dilemmas

Dilemmas of Electrically Short Antennas (ESAs):

  • We want our antenna to be small
    ..... BUT - we want the small antenna to function like a full size antenna.


  • We may need the antenna to be as small as possible.
    ..... BUT - to be effective, we need it to be as large as is practical.


  • The shorter you need the antenna to be, the more that you will need a good ground system.
    ..... BUT - the more likely that you won't have the room for one!


  • Instead of using grounding radials, you could use a counterpoise system.
    ..... BUT - contemplating the use of elevated radials presents us with another dilemma. Using a counterpoise means that the entire antenna must be raised up and the lower elements spread out, conflicting with the intent of keeping things short and small.


  • Elevated radials also create some safety hazards, including the high voltages present at the tips.
    ..... SO - unless you can keep elevated radials high enough to be out of reach of animals and curious neighborhood children, this might not be a viable option.


  • Capacitive top hats can be utilized to make the antenna look electrically longer and raise the efficiency.
    ..... BUT - a large top hat results in other problems.


  • You can use a loading coil to cancel the capacitive reactance as you make the antenna shorter.
    ..... BUT - the inductance needed introduces coil resistive losses.


  • You can move the loading coil up the antenna to increase the efficiency.
    ..... BUT - you can only move the coil so far up before the increasing inductance required cause the resistive coil losses to overwhelm any potential efficiency gains.


  • A high Q coil can be used to reduce reisistive losses.
    ..... BUT - as you move the coil farther up the antenna, you really need the coil to be small and light, and high Q coils with their larger conductors and wider diameters, tend to be large and heavy.


  • You can use a linear amplifier to make your small antenna's signal bigger.
    ..... BUT too much power can cause problems because of the high currents and higher voltages in ESAs. Click on the links below to see too what much power applied to small antennas can do: wires melted together and arch-over.
    Too Much Power - loop antenna
    Too Much Power - small vertical.


  • We can try a small antenna design that works by some kind of "RF magic".
    ..... BUT - unfortunately, all antenna designs are subject to the laws of physics.


  • These and other dilemmas will arise as you make the difficult choices and compromises that are required to construct and utilize an electrically small antenna.