Remote-Control Project

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Anonymous Poster #1	Remote-Control Project 11/03/2025 2:44 PM
	Hey everyone, I’m building a DIY remote-control transmitter for a small model vehicle and trying to use the TDK5111F (315 MHz ASK/FSK transmitter) which supports a 2.1 – 4 V supply. Everything is soldered up and the module seems to transmit, but the signal range is shorter than expected, even though the matching loop antenna is per the datasheet. When the model vehicle turns or the transmitter is slightly covered, the signal cuts out earlier than I thought it would. My supply is a 3.3 V regulator shared with the transmitter and the microcontroller; I’m wondering if the supply or layout is compromising performance. I’d love advice on good antenna loop size or layout tweaks for better range and enough decoupling or separate supply for the transmitter so it stays strong under load. Thanks a ton!
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Deefburger Guru Join Date: Mar 2011 Location: Sebastopol, California Posts: 1205 Good Answers: 54	#1 Re: Remote-Control Project 11/03/2025 11:10 PM
	Your antenna's shape and or configuration may be the spoiler. Use an omnidirectional circular wave antenna or a tuned and possibly loaded whip on the vehicle and a yagi or a dish at the Transmitter/Receiver pointed at the vehicle at all times and then check your signal response. Enable RSSI if you have that enabled in the vehicle MCU and T/R firmware. You might have to roll your own antennas for 315mhz. Dish would be a bit bulky. A yagi would work ok and be fairly easy to construct. Cut a good whip from stranded copper and load it at the bottom (bottom load coil) and cover it (capacitive top load) with heat shrink. Locate a friendly neighborhood ham operator to help. How many watts are you transmitting as control, and how many do you have coming back from the vehicle? __________________ Most people are mostly good most of the time.
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Rixter Guru Join Date: Apr 2010 Location: About 4000 miles from the center of the earth (+/-100 mi) Posts: 9911 Good Answers: 1141	#2 Re: Remote-Control Project 11/04/2025 6:31 PM
	The problem could be the relative orientation of the transmit and receive loop antennas. Try orienting the loop antennas (both transmit and receive) so the plane of the loops are horizontal.
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