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Old Nov 11, 2012, 12:02 AM
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Here are some pictures of a 433MHz transmitter and receiver. The transmitter is a pine board with door bell buttons to control the robot. Two forward and reverse for the left side and the same for the right side. These are controlled by the thumbs. There are two weapon buttons on the bottom of the board controlled by the index fingers. The board was sized to fit the drivers hands so he could maximize control speed. The electronics are mounted in a pocket in the board. The antenna is a quarter wave length and mounted so it is vertical when the board is held normally. The back side is covered with copper foil to make the ground plane. The operator also adds to the ground plane through capacitive coupling.

The receiver also has a vertical quarter wave antenna and the outside of the receiver box is foil covered to make a small ground plane. The receiver also has a gyro to make the two wheeled robot controllable. The picture also shows a receiver with a helical antenna which is much smaller.

Note that the foil ground planes are hidden to confuse the other drivers.

The last picture is a receiver from an automotive remote door lock system. It uses a dipole antenna that does not need a ground plane.
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Old Nov 11, 2012, 04:47 AM
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Quote:
Originally Posted by mjsas View Post
Here are some pictures of a 433MHz transmitter and receiver. The transmitter is a pine board with door bell buttons to control the robot. Two forward and reverse for the left side and the same for the right side. These are controlled by the thumbs. There are two weapon buttons on the bottom of the board controlled by the index fingers. The board was sized to fit the drivers hands so he could maximize control speed. The electronics are mounted in a pocket in the board. The antenna is a quarter wave length and mounted so it is vertical when the board is held normally. The back side is covered with copper foil to make the ground plane. The operator also adds to the ground plane through capacitive coupling.

The receiver also has a vertical quarter wave antenna and the outside of the receiver box is foil covered to make a small ground plane. The receiver also has a gyro to make the two wheeled robot controllable. The picture also shows a receiver with a helical antenna which is much smaller.

Note that the foil ground planes are hidden to confuse the other drivers.

The last picture is a receiver from an automotive remote door lock system. It uses a dipole antenna that does not need a ground plane.
Perfect !! exactly what i looking for . How about the range ? power ?
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Old Nov 12, 2012, 06:01 PM
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The transmitter I used was the cheapest one possible and the receiver was also a cheap super-regen type. Also I used 5 volts on the transmitter instead of 12 volts. In addition we used a crude encoding which also cuts range. The transmitter was a one transistor oscillator and we used OOK (on-off-keying), not even AM modulation. The range was about 500' but worked very well in the steel battle cage. I think we had one of the most reliable radios, much better then the 75MHz radios as our short wave length fit in the battle cage.

The power level was maybe 1/10mw.

I found with 12 volts on the transmitter and with a super-het receiver the range was out of sight for a ground robot.

To get that range requires good antennas, proper encoding and ground planes. Also the antennas were both vertical for best range.
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Old Nov 13, 2012, 05:14 PM
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The Netherlands, OV, Almelo
Joined Nov 2010
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Mjsas, I read your posts and IMO you under estimate radiosystems. An example!

The proven distance for my amplitude modulated 27 MHz (transistor) transmitters and super regenerative receivers at ground level is more than 1000 m (3280 ft).
Recently I have tested a new 4 channel receiver to combine with an old transmitter. The distance at which the system was still fully functional (double simultaneous) was 857 m (+2800 ft). The system could not be tested for full range, it was limited by local conditions, we would enter private property. In the past distances of more than 1000 m were measured with the use of this transmitter and super regenerative receivers.
See this thread: http://www.rcuniverse.com/forum/m_11202553/tm.htm#

The transmitter is equipped with vertical CLC antenna and powered by 12 volt battery and an input power of 240 mW at the RF amplifier (MOPA). The receiver is of super regenerative type, has a horizontally positioned antenna (wire) of about 75 cm (30 inches) length and positioned 60 cm above ground level . The receiver doesn’t have an rf amplifier but the antenna is directly coupled with the (low power) regenerative detector.
During these tests there is no visual contact, we did use a Twintalker set to communicate.

Of course these measured distances are far more than out of sight range because the bridgeable distance for airplanes is more than double the distance measured on ground level so 1700m a 2000m at least, that’s 1 mile (5280 ft) and more.

One more note. For systems with a super regenerative receiver, a less sensitive receiver and powerful transmitter is a better combination than visa versa to prevent interruption by foreign inputs (transmitters). For this reason the measured distances still can be enlarged by use of a antenna preamplifier in the receiver but that probably has more disadvantages these days. Of course these amplifiers still can be used to prevent rf radiation if needed and to make a shorter receiver antenna fully functional!

Taurus Flyer
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Last edited by Taurus Flyer; Nov 13, 2012 at 05:23 PM.
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Old Nov 13, 2012, 07:55 PM
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The type of radios I was using was more like key fobs, garage door openers, baby monitors, cordless phones, etc. All these are very short range, in some cases a few meters.

In the US we have something called 'part 15' which allows all kinds of very low power stuff at many frequencies. The key is low power and short range. As a hobbyist, one person can build 5 low power transmitters at just about any frequency.

At the standard radio control frequencies, 27Mhz, 72Mhz and 75Mhz (US) the transmitted power is limited by the goverment. The transmitter antenna is not critical as even a paper clip could be driven hard enough to radiate at the legal limit.
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