Features:
The smallest synthesized receiver in the R/c world Corona RP4SI, 4ch single conversion synthesized receiver.

1. Synthesized receiver gets rid of the inconvenience of using the crystal. Receivers with crystal still use the technology of 1970's which have to switch the frequency by changing the crystal. Users have to bring dozens of crystal to flying field. In addition, every changing of the crystal may damage the electron devices. While it is only need to push the button, you can switch to any channel with synthesized receiver.
2. Every transmitter and receiver has production tolerance inevitably. But the production tolerance of the crystal affects it most. Even the most precise crystal has the tolerance of 1-2KHz, and sometimes it will be 4KHz. This is a big tolerance to a 10KHz narrow receiver. Synthesized receiver will correct the tolerance because it can automatically follow the frequency tolerance. It is what will make R/C receiver has the best performance.
II. Lightest and Smallest Synthesized Receiver
RP4S1 uses a state-of-the art receiver chip, and become world's smallest and lightest synthesized receiver.
Synthesized receiver should be larger than the receiver uses crystal. But Corona's technology makes it possible to manufacture a synthesized receiver with light weight. Including the antenna and the packaging, it weighs less than 5g.
III. Long Range
While using the powerful chip, corona designs more and distributes the plus of all levels carefully.
The range of PR4S1 is longer than RS410, RS610 and RS810 series. With a sensitivity of better than 2μV, the receiver range can reach as far as 1 mile on the ground even better.
IV. Ultra Narrow
Usually R/C equipments are used under a busy RF environment, so the band of the receiver must be very narrow. Only one way can ensure the narrow bandusing the expensive multiple ceramic IF filter. Corona promises that all receivers use 4 pole ceramic IF filter and make sure all the receivers have an ultra narrow band.
V. AGC and High IP3 Performance
RP4S1 was designed with a more reasonable and scientific way. It adds an AGC circuit to make itself have a higher IP3. With this technology, it can reject adjacent interference and high frequency block effectively.
VI Auto-detecting
Same with all Corona receivers, RP4S1 auto-detects the shift type (positive or negative) and is compatible with most brand transmitters.
VII. DSP
Nowadays, DSP decoding technology is used by all top grade receivers. Based on the experience of the manufacturing crystal receiver, the arithmetic is more advanced and it works more reliable.
You can hardly notice the glitch of the FM receiver and have no noise problem.
VIII “1-button” Frequency Tune
The frequency can be changed easily with PPL technology. Corona uses this tune button to compensate the frequency difference caused by production tolerance of the transmitter and the frequency wrap of difference brand transmitter. Only 1-button, RP4S1 makes it possible to compensate the frequency tolerance immediately.

Specifications
Synthesized Receiver (single conversion)
Type: RP4S1
Size: 42.5x18.2x9.36mm
Weight: 6.6g
Sensitivity: better than 2.0μv
Selectivity: ±8 kHz at 65 dBdown
Number of Channel: 1-4
Filtering: Dual turned RF circuitry
Filtering: Dual 4 pole ceramic filter
Filtering: DSP filtering with mild algorithm
Shift Polarity: Positive or Negative(auto-detect)
Case: Shrink wrap
operating voltage: 4.8V～6.0VDC
operating current: 17mA
Modulate: FM/PPM
Range: >1.2km/3900ft
Filtering: DSP
Crystal size:  UM-5
Intermediate Frequency: 455KHZ
IP3: +9dBm