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Showing posts with label wire. Show all posts
Showing posts with label wire. Show all posts

Shortwave Antenna

Horizontal wire dipole antennas are popular for use on the HF shortwave bands, both for transmitting and shortwave listening. They are usually constructed of two lengths of wire joined by a strain insulator in the center, which is the feedpoint. The ends can be attached to existing buildings, structures, or trees, taking advantage of their heights. If used for transmitting, it is essential that the ends of the antenna be attached to supports through strain insulators with a sufficiently high flashover voltage, since the antenna's high-voltage antinodes occur there. Being a balanced antenna, they are best fed with a balun between the (coax) transmission line and the feedpoint.

These are simple to put up for temporary or field use. But they are also widely used by radio amateurs and short wave listeners in fixed locations due to their simple (and inexpensive) construction, while still realizing a resonant antenna at frequencies where resonant antenna elements need to be of quite some size. They are an attractive solution for these frequencies when significant directionality is not desired, and the cost of several such resonant antennas for different frequency bands, built at home, may still be much less than a single commercially produced antenna. 

Source: https://en.wikipedia.org/wiki/Dipole_antenna#Shortwave_antenna

Random Wire Antenna


A random wire antenna is a radio antenna consisting of a long wire suspended above the ground, whose length does not bear a relation to the wavelength of the radio waves used, but is typically chosen more for convenience. 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. Such antennas are usually not as effective as antennas whose length is adjusted to resonate at the wavelength to be used. Random wire antennas are a type of monopole antenna and the other side of the receiver or transmitter antenna terminal must be connected to an earth ground.

They are widely used as receiving antennas on the long wave, medium wave, and short wave bands, as well as transmitting antennas on these bands for small outdoor, temporary or emergency transmitting stations, as well as in situations where more permanent antennas cannot be installed. 

Source: https://en.wikipedia.org/wiki/Random_wire_antenna

Par EndFedz EF-SWL


The Par EndFedz ® EF-SWL is an end-fed short wave antenna optimally designed for 0-30 MHz reception.  The radiator is 45 feet of #18 black polyethylene coated Flex-Weave wire.

The radiator wire is custom made for us.  It is a stranded #18 copperweld with a slippery polyethylene jacket.  Breaking strength is 280 pounds. Very flexible yet small diameter. The black polyethylene jacket is also very abrasion resistant. The UV resistant matchbox houses a wideband 9:1 transformer wound on a binocular core.  Unlike other transformers, external stainless studs on the matchbox allow the user to configure the primary and secondary grounds for best noise reduction at their particular location.

Specifications:

Design Frequency: 0-30 MHz
Transformer: 9:1 ratio
Grounding: User configurable
Radiator length: 45’ of #18 black polyethylene coated Flex-Weave wire
Connector: silver/Teflon SO-239
Hardware: Stainless steel
Polarity: User configurable

Source: http://www.vibroplex.com/contents/en-us/p3415.html