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Basic Information
Question 1
What is the difference between the internal 27MHz transmitter circuit in the HT82K74E MCU compared with that of other company’s?
Answer
Traditionally the transmitter circuit is composed of external components such as transistor, resistors, and capacitors. Holtek provides an all-in-one solution so as to largely reduce the external component count thus reducing costs and PCB sizes, and enhancing production yield.
Question 2
What is the difference between the HT82D20R and HT82D22R with an internal 27MHz RF receiver compared with the previously released MCUs?
Answer
Traditionally RF signals are processed in analog using a mid-frequency IC, a frequency discriminator and a filter. Holtek provides a solution including an internal RF receiver so as to reduce PCB sizes and hardware circuits, and thus lower the difficulty of hardware design and enhance production.
Question 3
How do I know if the centre frequency of the 27MHz transmitter is correct so as not to limit range?
Answer
A frequency spectrum analyser can be used to check the transmission frequency of the product under test to check if the frequency is the same as that required.
Question 4
What are the recommended specifications for the 27MHz transmitter and receiver?
Answer
Reference for the transmitter oscillator: 27.042MHz ±20PPM/20PF / ESR≦40Ω
Reference for the receiver oscillator: 12MHz ±20PPM/12PF / ESR≦40Ω
Question 5
How many channel options are there when using the Holtek 27MHz wireless solution?
Answer
There are eight channels options for selection: 26.995MHz, 27.045MHz, 27.095MHz, 27.145MHz, 27.195MHz, 27.245MHz, 27.295MHz and 26.945MHz.
Question 6
How do I know if the frequency spacing is correct?
Answer
The recommended frequency spacing should be greater than ±3.5kHz with the spacing the same for both high and low frequencies.
Question 7
Can the receiver sensitivity be adjusted?
Answer
The receiver sensitivity can be adjusted by antenna matching and using the circuit components connected to the Loop Filter LO pin.
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