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Receiver Technical Information


What is the voltage of the output signal?

Voltage out is based on Voltage in. Receivers typically operate on a 4.8V DC input voltage. This can be increased to 6.0V, where more power and speed can be derived from attached servos, but a decrease in lifespan for said items might result as well due to increased stress. An ABSOLUTE minimum operating voltage is very near 4.0V. Rx's typically use a 3.3V regulator which requires an additional 0.7V to power itself, resulting in the 4.0V minimum. In application, however, it is typical for performance to become severely degraded as power falls under 4.3V DC.


Is the output signal digital?

Output signals are ANALOG. Receivers vary by design on how they RECEIVE and ENCODE signals. But all deliver very similar output pulse signals, which is used to drive the servo to the desired location. This output pulse ranges from 1000uS to 2000uS, with 1500uS typically being center.


Is the output signal an on/off signal or does it have an internal regulator?

The output signal for each channel is a pulsed signal. The pulse width (commonly 1000uS to 2000uS) is determined by the corresponding channel of the transmitter. When activated by one of the proportional channels (such as elevator, aileron, throttle, rudder, or knob control) the pulse width will vary. This controls the servo movement. Most servos will be centered when the pulse is at 1500uS. Channels that are controlled by a switch (such as the gear channel) will operate the pulse width from two set values such as 1100uS when in one position and 1900uS when set to the other position to activate servo movement.


What signal does the receiver emit to differentiate forward or backward movement?

Direction of movement is determined by the direction in which the respective pulse is shifted off of center (neutral). Center being 1500uS, if the pulse is shifted above 1500uS, the direction of travel is one direction. If the pulse is shifted below 1500uS, the direction of travel is in the opposite direction.


I have an older R127DF receiver that is not marked Hi or Low band, how can I tell which one I have?

If you will pull out your receiver crystal, look into the slot where it goes, you will see the backside of a PC board. If you see a red dot on the PC board then your receiver is High Band. No red dot? Then it is Low band.

If you have an R148DF/DP or R149DP there is a coil directly inside the crystal slot, if you will look at the coil closest to the antenna, this is where the red dot will be if you are on High band. Otherwise if there is no dot, it is again Low Band.


Please explain Hi and Low band to me? I am not sure what the difference is between them.

Most of our 72MHz receivers are now tuned to the center of either a low band frequency (channel 11 to channel 35) or high band (channel 36 to channel 60).

By tuning to each band, you can easily and safely change your receiver crystal to anywhere within this high or low band range, without having to send it in to be retuned.

If you have a receiver that is not marked as to which channel it is, or if it is not marked with a sticker that says if it is High or Low, you can check inside the crystal slot to see if there is a red mark. If there is a red mark, this indicates that the receiver is High band.


Can you tell me the main differences between the R138DP and the R148DP receivers?

The R148DP while being smaller in size and lighter in weight than the R138DP, is higher priced due to the expense of the smaller components. Neither one has better range than the other, with almost any receiver the average range will be as far as the flier can see.


Can I purchase a flight pack in the PCM mode?

Unfortunately flight packs are only available in the FM mode.


My new R149DP receiver says hi and lo, how do I know which one it is?

That receiver works with both high and low band crystals and replaces the older R149DP receivers on separate high and low bands.


Is there is a way to identify if a Futaba R149DP 9-Ch 72MHz PCM 1024 Dual Conversion Receiver is the old or newer one?

To identify as newer R149DP from the older ones, remove the crystal and look at the PCB board that is standing up. If there are no traces and solder (just an empty board) it is the new one.


I am wondering about the amp draw on my receiver. I am using eight S9351's, three S9352's and one S9252's, each in its separate channel. What effect will these have on my receiver and can it handle the load?

The receiver will not have a problem with the number or type of servos used. A large number of servos, such as the number that you are using, could cause the battery voltage to drop below what the receiver requires. You would want to make sure that your servo and battery wiring could handle the current needed from the servos without giving you much voltage drop. Many times this is why NiCd batteries are preferred, as they can deliver more current with less voltage drop than many other battery types.

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