What is a high Z antenna?
The High Z Antenna Amplifier is designed to match shortened high impedance antenna elements to a 50 or 75 ohm feeder for excellent reception in the medium wave, 160 and 80m amateur radio bands with good reception from 100 kHz to 30 MHz.
A standard recommendation (see QST, March 1936, p. 32, "An Unorthodox Antenna") is an 84' long end fed and a 17' long counterpoise (6.5' for 20m). While these lengths have been shown to work well on many bands, which is helpful if you're in a hurry to get on the air, read up on the topic and experiment.
The wire may be straight or it may be strung back and forth between trees or walls just to get enough wire into the air. Due to the great variability of the (unplanned) antenna structure, effectiveness can vary wildly from one installation to another.
While the below described antenna does not fit the criteria for a true long wire antenna on the lower bands it will on the higher band above 20m and certainly meets the definition at 10m. Technically a true "longwire" needs to be at least one wavelength long.
Z is the input impedance of your system (for example, the impedance of the antenna you are trying to match). The value Z usually contains real and reactive components. As an example, the antenna impedance may be 30+j56. Z0 is the characteristic impedance of the measurement system such as a network analyzer.
The reading should be low, usually under 5 ohms; that means a good electrical connection between the tip of the antenna and the radio pin. TEST 2. Connect one meter lead to the cable and the other to the antenna base. A reading below 5 ohms indicates a good ground connection.
Longer antennas have lower frequencies and higher bandwidths. This means signals can travel over longer distances. Radio stations operate at lower frequencies and their signals can easily connect to longer antennas.
Length of counterpoise should be approx. 20-30 feet but NOT resonant. If possible, run the counterpoise away from or perpendicular to the antenna wire. You can also use the unun with no counterpoise or ground if your feedline is at least 25+ feet long.
In practice the impedance at the end of an end fed half wavelength antenna is on the order of 1800 to 5000 ohms. It is often commented that the End Fed Half Wavelength Antenna needs no "counterpoise" or radials to work.
The toughest and most flexible of all the wire tested was the thin stainless-steel cable, making it the best overall choice of antenna wire for all conditions.
Can any wire be used as an antenna?
Since most antennas are used outdoors, you must use outdoor-rated wire. You can use uninsulated wire, but it is much better to use insulated wire for safety purposes if there is any chance that someone could come in contact with the wire while you are transmitting.
A height of 120 feet or even higher will provide even more advantages for long-distance communications. To a distant receiving station, a transmitting antenna at 120 feet will provide the effect of approximately 8 to 10 times more transmitting power than the same antenna at 35 feet.
In fact, it looks more like an end-fed 1/4 wave 160 meter antenna (130 ft or 39.624 m long) which goes up some 25 feet (7-8 m), then over horizontally, at an average of 25 feet (7-8 m) above ground, to a tree at the far end of my property.
The antenna has a limited bandwidth on the 80 meter band because the antenna is shortened for this band. The 10/(15)/20/40/80 End fed Antenna Kit has a total length of about 23 meters.
The 10/20/40 End fed Antenna kit has a total length of approximately 11.9 meters.
The EFHW antenna will work without any grounding too but it is recommended for protection of your equipment.