A radio transmitter is an object that makes it possible to transform a signal into a radio wave powerful enough to go to the receiver. The signal that is transmitted by these waves can be a radio program, a conversation (radiotelephony) or even information (army).
Establishment of a radio transmitter
A radio transmitter is made up differently depending on its use: a broadcasting transmitter is a single frequency, and it is multi-frequency in radiotelephony and broadband for military radio communications. The single-frequency single transmitter contains a frequency source which will be the carrier frequency that is to say the one carrying the information from an oscillator. The transmitter used in broadcasting, an amplifier for amplifying the modulated signal (the information) so that it can be broadcast through the antenna at the end of the circuit. the transmitter contains an oscillator generating the carrier signal that will convey the information, the modulator that will allow the modulation of the carrier signal and therefore the sending of the
Explain the main functions of a radio
This radio exists in different versions, with more or fewer model memories, with or without LCD screen, but still the same receiver and the same features. It is precisely these features that we will detail, knowing that we find the same on virtually all radios in the market (including some dating a few years). Sometimes, some functions may have a slightly different name, probably from the fruitful mind of a marketing “engineer,” but the function will always work in the same way. On the most basic radios, only the REV and TRIM functions will be present: there is hardly any valid argument to buy this type of communication nowadays because much more evolved models exist at an equal price or often cheaper. Also, many modern models include a memory to store the individual settings of several models: it is particularly useful when you have more than one model to control, but also economical because you just have to buy an additional receiver and pair it on the radio to control a new model.
The functions are presented in the most logical order, that is to say, according to the most probable sequence that we follow when we equip a model. Depending on the radio, channel one can also be called ST (Steering: direction) and channel 2 TH (Throttle: gas): in all cases, channel 1 is always that of direction and channel two that of gases.
A function that determines the direction of rotation of the servo: REV or INV for Reverse or Reverse, or NOR for Normal. Specifically, depending on the direction of mounting the steering servo in the model, it may be that the response of the servo is reversed compared to the command sent by radio. This function allows rectifying this parameter if necessary.
Note that this function can be applied independently to the two channels. Most often, channel two should be set to REV mode for brushless controllers.
Important: in the case of an electronic dimmer (brushed or brushless), do not use this function to remedy the fact that the model backs up while accelerating with the radio. In this case, if the model moves backward instead of forward (and vice versa), the drive must be reprogrammed. In the opposite case, the brake control will be applied to the reverse gear and not to the forward gear (which will have the effect of directly switching on the reverse gear when it is desired to brake: the gear of the model will not like at all).
TRIM or Sub-T
Trim could result in “balance”: this command is used to adjust the neutral position of a servo finely. When you install the servo saver on the head of the servo (previously set to neutral), you must position it following the grooves of the servo head: these grooves cause most of the time a slight shift of the servo-saver by relative to the neutral position of the servo. The trim control of the radio allows fine correction of this shift to shift the neutral servo to reposition the servo-servo neutral. This function can also be applied to the lane two servos exclusivelyin the case of a mechanical vibrator (or a model with a thermal engine). In any other case, if the wheels of the model do not remain perfectly still when the throttle is in neutral, it is the electronic variator that must be reprogrammed (to redefine its neutral position).
EPA or E. Point
End Point Adjustment: this setting is 100% by default, i.e., it allows the servo to give all the range of motion it is capable of in both directions. However, depending on the architecture of the management, this can be a problem: in fact, it is common for an element of the management to find itself in abutment (at the end of the race) before that the servo has reached its movement stop. The servo can still turn while the wheels are already turned to the maximum. In this case, to command the servo to turn to its maximum from the radio will have the effect of forcing on the elements of the direction which they can not steer more. As a result, once the elements of the steering have reached their stop, the servo will continue to rotate: it is the backup-servo that will cash this constraint, which will generate premature wear on both the servo-saver and on the servo itself.
The end-of-travel adjustment, therefore, indicates on the radio what is the endpoint of the servo: physically, the steering wheel or the level of the radio will continue its course until its physical stop, but the command of rotation sent to the servo will have reached its maximum before reaching the maximum physically allowed by the radio.
Tip: Always set the EPA to the same value on the left and right. The value to use will be the one on the side that reaches its stop first. Balancing the values in both directions of rotation of the servo makes it possible to obtain the same steering angle on the left as on the right.
D / R or D-Rate
Dual Rate: This function is different from the previous one, even though it seems to have the same effects. The EPA must be considered as defining the mechanical limits of the steering range of the model. The Dual Rate should be considered as the overall adjustment of the steering angle of the steering according to the course of the track and the preferences of the pilot.
On a very winding track with very tight turns, use the full mechanical steering potential of the model (which is defined by the EPA). However, on a fast track whose turns are not very pronounced, we can afford to use only a percentage of the turning radius: the lever or the wheel of the radio can be turned to its maximum, but the model n will obey at 80% of its potential (for example). The interest is to have a less sensitive direction to the controls of the radio, thus better stability (in particular in a straight line).
I hate to have too sensitive a direction on my models, so I use the Dual Rate a lot by adapting it to each model and each plot. Other people prefer a compassionate direction because it allows, in particular, to finely adjust a trajectory during a turn. Also, note that we can have the feeling that the direction is slower by activating the Dual-Rate: technically, the servo always rotates at the same speed, however, with a D / R set at 50%, the movement given by the pilot on the steering wheel of the radio is reproduced only 50% on the model. It’s a matter of preference, you determine yours.
Let’s pause: we have reached the moment when I no longer touch the other functions of my radio.
This does not mean that the rest of the functions are useless, only that the ones we have detailed so far are generally quite sufficient for the vast majority of pilots. In my opinion, the following functions are intended for pilots who want a finer and more personalized response according to their habits and preferences. This also implies that they already master their model perfectly with the first set of functions we have seen. I’m not at this point in my driving, like many other drivers I think. Nevertheless, it is always interesting to know the effects of other functions, even if they are not necessarily useful for improving our driving.
EXP or Expo
Exponential: exponential. Applies to the direction and gases. The principle is as follows: at 0% (default setting), the radio controls are linear. If you put 10% of gas or steering (i.e., 10% of the trigger or flywheel stroke), the model will respond with a 10% gas or steering angle; if you order 20%, the model will respond by 20% of his abilities and so on.
However, you may want higher precision at low speeds or conversely, higher accuracy at high speed (this applies to the same for steering). Typically, on a very slippery surface, a motor with a lot of torque will be very difficult to control: so we want a great fineness in the gas dosage at low speed, even lose precision once the model is well launched, so more stable. In this case, we will put negative expo on the gases, which will affect that the first 50% of the race of the trigger will control only the first 25% of the power of the engine (for example). On the other hand, the last 50% of the trigger race will have to manage the remaining 75% of the engine speed (because we always start from 0% radio and model side to finish at 100%).
Same principle for management: the positive expo will make the model extremely lively and sensitive around the neutral while the negative expo will make the direction lazy (it will be necessary to turn the steering wheel for the model to answer).
In green, the default expo setting is 0%: any point on the line implies a radio control level and a model response that is proportional.
In red, of the positive expo (enormously): the servo (or variation) is immediately at 80% of its potential whereas one has hardly touched the control of the radio. Either it is a departure to leave the tire eraser on the ground, or it is a turn to the handbrake as soon as you touch the radio (both cases being possible simultaneously since the expo is adjusted by lane).
In blue, of the negative expo (enormously, there too): the servo (or the variation) is only at 20% of its race when one is already practically at the bottom on the radio. Situation exactly opposite to the previous one: it is necessary to turn the steering wheel a lot to hope that the model begins to take a turn. With such an expo on the gas, the model will roll in slow motion and will accelerate thoroughly on the last 3-4mm of the race of the trigger: enough to make a wheeling at the start launched.
I never use expo, either on the direction or the gases. I may be wrong, but I first try to focus on the previous settings and my driving. By piloting, it is also necessary to understand how to learn dosing on the radio controls: we all start with an on/off control. Then we learn slowly to adjust the direction and especially the gas for a more streamlined style, less brutal: in my opinion, the exhibition is only interesting for pilots who have a perfect command of the dosing orders and who wish to change the way their model responds to their driving style. I believe that if you read this guide (or like me, as you write it), it is that your driving level has not yet reached the stage where a setting of
Adjustable-Rate Control: Adjustable rate control. OK, that does not mean anything. A priori, it is a function that is found mainly on Sanwa radios (or Airtronics, some Kyosho and others) to replace or complement the exhibition. Because it is an expo function, but with a small difference that justifies giving it a nice marketing name that no one understands. So, the ARC is an expo, with the difference that the answer will be proportional between the neutral and the fixed value, then again proportional but with a different rate from this value up to 100%. Pink lines in the diagram above represent this. So, the same conclusion as for the expo: to reserve to the pilots who already master the
ABS or ALB
ABS is the same as our real cars. ALB stands for Anti-Lock Braking, which is the same thing, but after ABS goes through Sanwa’s marketing department and some other manufacturers.
In all cases, this is a function that must remain disabled on all-electric models. To my knowledge, no electronic dimmer (brushed or brushless) is compatible with this function that can only act on a servo and brakes (which is the case on models with thermal engine).
These are the main features found on most radios. Of course, it is possible to find many others on some high-end radios, but the essential and the most useful were listed above. Remember that it is not the radio that will improve the performance of your model: it is you and your control of driving.
Use and distribution of the signal
How can sound produce in a microphone be received on your radio? The sound produced in the microphone is a low-frequency sound, so it can not be directly transmitted by an antenna to the place of reception, because it would attenuate too quickly. Also, to send a wave, it takes an antenna size of about half of the wavelength, which would require a gigantic antenna, that is why we use a high-frequency carrier wave that we modulate to be able to transmit the information. To be able to transmit information, the carrier wave is modulated so that the amplitude corresponds to that of the signal to be transmitted. However, the frequency remains unchanged to be able to transmit this information. The radio receiver then makes it possible to demodulate this signal, to draw the information, and produce the corresponding sound. The frequency band of the modulated signal lies between the frequency of the carrier signal minus the frequency of the signal to be transmitted and the frequency of the carrier signal plus the frequency of the signal to be transmitted. This type of information transmission is used in various fields: telecommunications (radio, television), defense (the army), radars, or even by private individuals who can transmit on the FM waves.