Showing posts with label antenna. Show all posts
Showing posts with label antenna. Show all posts
Monday, November 17, 2014
Wave antenna 5 8 pro VKV FM
Wave antenna 5/8 consists of a vertical radiator which is fed at the base of the antenna. A suitable device of some sort should be added between the antenna and feedline if you want to eat with coax. Adding a coil in series with the antenna on the base is one of these methods are suitable.
So why would anyone use an antenna 5/8 wave if they have to go through all that extra work? After all, a ground plane antenna provides a good match. There are several answers. The first is GAIN. The computer shows that the antenna (mounted 1 foot above the ground) has a margin of about 1.5 dBd higher than a dipole (also installed 1 foot above the ground.)The second reason you might want to use the wave 5/8 vertical is to get a lower angle of radiation. Peak radiation angle A half-wave antenna is 20 degrees. You will find that the angle 5/8 wave antenna radiation is only 16 degrees so it is better dx antenna.
You may have noticed a pattern developing here. A quarter-wave ground plane antenna has a radiation pattern that produces the maximum gain at about 25 degrees and half-wave antenna drops to 20-degree angle, and wave antenna 5/8 further drops to 16 degrees angle. So why not just keep extending the antenna to one full wave? Well it would be nice if it worked, but unfortunately the wave patterns begin to create a very high angle of radiation waves exceed 5/8. So weve reached the maximum gain at this point and extend the antenna further reduce profits only where we want it (low angle).
Of course if you are interested in a very short jump, extend the antenna will produce a nice profit on the dipole.All the length of the antenna depends on various factors. Some of these factors are: height above ground, the diameter of the wire, nearby structures, the effects of other antennas in the area and even the conductivity of the soil.This page allows you to calculate the wavelength for the antenna 5/8. It uses the standard formula, 585 / f (178.308 / f for metric) MHz to calculate the length of the element. If you have experimented with 5/8 wave antenna before and know a better formula for your QTH, feel free to change the formula accordingly. This formula is for the antenna wire.
Of course if you build your antenna out of the tube, total length of the antenna will be shorter, for example I have found that 21.5 feet seems to provide maximum benefit to the frequency of 28.5 MHz when using a 1 "tube, and 22.5. Foot seems be the best long-wire at the same frequency. Since the formula to calculate the antenna to be about 2 feet shorter, be sure to experiment and maybe add a little for your final term.
Saturday, October 5, 2013
Up Down Timer For A Power Antenna
This up/down timer was designed to control a power antenna on a late-model vehicle. Normally, this vehicle uses a body computer to control the antenna. However, the person who owned the vehicle wanted to install his own high-powered audio stereo system. The original stereo system was tied in with the body computer and this meant that a separate antenna controller was required for the after-market sound system. Also, the power antenna fitted did not have limit switches inside, hence the need for a timed control circuit. Heres how the circuit works. first, assume that the radio antenna control output is not switched on - ie, the radio is switched off.
In that case, relay RLYC will be off and so relay RLYA will also be off, as is the motor. Conversely, when the radio is switched on, the radio antenna control output line switches to +12V. And when that happens, RLYC closes its contacts and applies power to the circuit. As a result, C2 (330OF) quickly charges via D4, while Q4 is biased on via D5 and R5. This ensures that Q3 and relay RLYB remain off. At the same time, Q2 is is turned on, thus turning on RLYA and applying power to the motor. This drives the antenna in the up direction. During this time, C1 charges via R2.
When the voltage across the capacitor reaches +8.1V, Q1 turns on via ZD1 and so Q2 turns off and switches off the relay - ie, this gives the "up" timeout. Using the values shown for C1, R2 and ZD1 gives an "up" duration of approximately 6 seconds - long enough to fully extend the antenna. D1 discharges C1 (via resistor R1) when the +12V supply is later removed. When the radio is switched off (or a CD placed into the stereo unit), the radio antenna control output switches back to 0V. This does several things: first, it turns Q4 off and this allows Q3 to turn on due to the stored charge in C2. Q3 and RLYB now turn on for about six seconds - ie, while C2 discharges via R4 - and this switches power to the motor in the opposite direction to drive the antenna down. Diodes D4 and D5 are there to prevent C2 from discharging back via the circuitry around on Q1 and Q2.
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In that case, relay RLYC will be off and so relay RLYA will also be off, as is the motor. Conversely, when the radio is switched on, the radio antenna control output line switches to +12V. And when that happens, RLYC closes its contacts and applies power to the circuit. As a result, C2 (330OF) quickly charges via D4, while Q4 is biased on via D5 and R5. This ensures that Q3 and relay RLYB remain off. At the same time, Q2 is is turned on, thus turning on RLYA and applying power to the motor. This drives the antenna in the up direction. During this time, C1 charges via R2.
When the voltage across the capacitor reaches +8.1V, Q1 turns on via ZD1 and so Q2 turns off and switches off the relay - ie, this gives the "up" timeout. Using the values shown for C1, R2 and ZD1 gives an "up" duration of approximately 6 seconds - long enough to fully extend the antenna. D1 discharges C1 (via resistor R1) when the +12V supply is later removed. When the radio is switched off (or a CD placed into the stereo unit), the radio antenna control output switches back to 0V. This does several things: first, it turns Q4 off and this allows Q3 to turn on due to the stored charge in C2. Q3 and RLYB now turn on for about six seconds - ie, while C2 discharges via R4 - and this switches power to the motor in the opposite direction to drive the antenna down. Diodes D4 and D5 are there to prevent C2 from discharging back via the circuitry around on Q1 and Q2.
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