RF Remote Control Transmitter Quality Control – Frequency Matters

When we make RF remote control transmitters, customers may not know detail parameters inside such as frequency, output power and other jargons, but they may feel that some remote controls batch has longer remote control distance, while other remote control batch has shorter distance, so what’s the difference inside?

Or we can ask, which component has changed in many parts inside remote control transmitter? first guess might be output power has been reduced, but that is not likely to happen, here is why.

Once RF remote control board is designed, the output power is fixed at certain level too, and is not likely to change unless we deliberately change parameter and lower the output power, which we usually don’t do, because either manufacturer, dealer or customer, they all want the maximum distance as possible.

Second guess might be flat battery, that might be the reason if you have used remote control for a long time, and distance goes down day by day, then you may want to check if change a new battery would work, and in most circumstances, they do.

But what if you tried all above and still can’t figure it out? actually the problem might has something to do with frequency, or not so accurate frequency.

While a transmitter works at 433.92Mhz doesn’t mean every single transmitter is working at 433.92Mhz sharp, there is always a deviation due to industrial manufacturing technique as can be found on many other places, in most remote control transmitters, the center transmitter frequency is controlled by onboard crystal oscillator, and the industrial standard is +/- 75kHz range.

Receiver module are all designed to work best and achieve best sensitivity at the very center frequency, and the more transmitter’s frequency deviates from that center, the lower sensitivity or distance would be, but today’s receiver has considered that +/- 75kHz range, and most transmitters would work fine inside the range, even some has longer distance, other has shorter distance.

PT4301 superheterodyne receiver module sensitivity chart

From above PT4301 superheterodyne receiver module’s sensitivity chart at 433Mhz range, we can easily find out that if transmitter’s center frequency deviates 300kHz, then the sensitivity would be around -22dB less, which will cause huge impact to actual distance, or the impact would be even more if your IF filter bandwith set to narrower value, 300kHz is not a impossible value as many manufactuers doesn’t realize how important the accuracy of SAW stablizer is, and many products on market has around 100kHz deviation from center frequency.

For those who is not familiar how huge -22dB is, we can say that in common RF remote control transmitter, a 10dB difference can be considered as huge difference, and will cost very much to achieve that, and after a careless component choice with frequency deviation, all hard work would be meaningless, so we as manufacturer should pay a lot of attention to quality control of these key components, such as MCU chip, RF transistor and SAW filter stabilzer.

At Solidremote Technologies Limited, we work with our quality suppliers to ensure components’ center frequency is better than +/- 75kHz industry standard, thus make sure every remote manufactured has excellent performance in customer’s hand.