unlimited
most radio supply outfits will provide an antenna mast to 78 inches, but you can get your machine shop to make a longer mast for a few $$$ extra
The principle of the lens antenna is THE EQUALITY OF THE PATH LENGTH.
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Answer: An antenna is a tuned circuit, so it have to be tuned to the wavelength of the signal that it will transmit. If the antenna is not tuned properly some of the transmitted power will be feed back to the transmitter and will damage the output stage, SWR (Standing Wave Ratio) is very important, that is the ratio between the power that is transmitted by the antenna and the power that is fed back to the transmitter a zero is ideal but not always possible.The lower the frequency the longer the wave length and a 1/4 wave length is the minimum length that will give one a good SWR. The formula to use when one design a antenna is 300/frequency in MHz, if the frequency is 30 MHz then it is 300/30 = 10 Meter divide it by 4 to get the length of the 1/4 wave antenna that is 2,5 meters.Note: The antenna have to be multiples of a 1/4 wavelength like 1/2 wave or full wave, a 5/8 length can be used but it will need a L/C circuit at the input of the antenna to tune it to the frequency.
yagi udda antenna has only one reflector...but it has many directors...depending upon gain and efficiency...the length of reflector is normally...more than one-half of wavelength... and directors have a length less than one-half of wavelength...
Capacitive hats are used to alter the distribution of the current on a short antenna so that the antenna current is not concentrated near the ground. A whip or short antenna can be modeled as a series of LC circuits in which the capacitance per unit length is highest near the base and the inductance per unit length is highest near the top. A capacitive hat simply adds capacitance to the antenna. It basically makes the antenna seem longer, but maximum current is still at the base.The reason why you'd want to make your short antenna longer, is to obtain the antenna's resonance frequency. The length required to do this is a quarter or a half of the wavelength of the radio wave that it's receiving. At resonance, the electrical resistance of the antenna drastically drops, which effectively increases the Q factor, or quality factor, of the resultant output signal. The term Q factor is simply a measurement of how good the clarity and stability of the output signal is, the higher the better when dealing with radios and televisions.Of course, instead of using a capacitive hat on your antenna, you could always physically lengthen the antenna itself. However, considering that commonly-used radio waves can be up to 10 m (33 ft) long, your antenna would have to be about 8 feet long, which would make using your radio a bit awkward.
The size of the dish isn't as important as the length of the antenna. The antenna is INSIDE the little can at the focus of the dish. The length of the antenna is tuned to the wavelength of the frequency being received.
The principle of the lens antenna is THE EQUALITY OF THE PATH LENGTH.
Modern digital cordless phones use high frequencies - the length of the antenna is so short at these frequencies that its whole length can be incorporated inside the casing of the phone. The length of the antenna is 300 divided by the frequency.
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A short antenna causes higher than normal current to capacitive reactance and a long antenna causes higher than normal current to inductive reactance; a correct length antenna is free of reactance and appears as a resistance. Change the length of the antenna in small increments until you obtain the lowest (resistive) current.
You can extend an antenna wire, but the added length will reduce amplitude of received signal. You may need an in-line amplifier depending on the application and length of antenna wire.
how to measure the length of elements and spacing of elements
A thin antenna has nothing to do with the physical size of the antenna. Any antenna whose length is less than (1/10) of the wavelength of the signal is thin antenna. A linear antenna is one in which the current distribution is linear or bears a linear relationship with some parameter, say voltage of the antenna...... Mukesh
In the trunk ,on the right side there is a 3"diameter at the base of the antenna wheel that carries the nylon string or rope that winds up the antenna. That has to be replaced... Measure the length and replace with a length of grass trimming nylon .. Crimp it and it should work In the trunk ,on the right side there is a 3"diameter at the base of the antenna wheel that carries the nylon string or rope that winds up the antenna. That has to be replaced... Measure the length and replace with a length of grass trimming nylon .. Crimp it and it should work
[ (234) divided by (station frequency in MHz) ] feet, hanging vertically.
For every frequency there is an antenna that is perfect for radiating at that frequency. Unfortunately, it would be unrealistic to carry a separate antenna for every frequency that a communications center is capable of radiating. To overcome this problem, we use ANTENNA TUNING to lengthen and shorten antennas ELECTRICALLY to better match the frequency on which we want to transmit. Simply put, the antenna does not physically change length; instead, it is adapted electrically to the output frequency of the transmitter and "appears" to change its physical length. Antenna tuning is done by using antenna couplers.
A good material for an antenna is copper wire. For perfect reception, the antenna should be cut to a length determined by the frequency you want to receive. length = 468/frequency in megahertz.