Comparison Roidmi 3S vs Promate FM10+

The FM frequency range supported by the FM transmitter.

For normal use of the device, it is necessary that at least part of this range coincides with the tuner range in the car radio, and that there is no full-fledged FM station broadcasting at the selected frequency. However, most modern FM transmitters cover frequencies of the order of 88 – 108 MHz, this is quite enough to find a suitable frequency.

The presence of a display in the design of the FM transmitter.

Various additional information can be displayed on the display : the set frequency, the signal source used, the name of the song being played, etc. This greatly simplifies device management.

Bluetooth technology is intended for direct wireless communication of electronic devices with each other at distances up to 10 m (in the new standards — up to 100 m). In FM transmitters, it is mainly used to receive audio from another Bluetooth device, such as a smartphone. Technically, other use cases (such as remote control) may be envisaged, but they are less common.

To connect an FM transmitter with various gadgets, a Bluetooth connection is more convenient than a wired connection, and not only because of the lack of wires: this technology is supported by a huge number of modern devices, while wired interface compatibility is much less common. On the other hand, the sound quality transmitted via Bluetooth may be lower than with a wired connection.

Wired audio input, usually in the form of a standard 3.5mm mini-jack. The line-in (Aux) input can usually be output from a normal headphone output on a mobile phone or other similar device. And in some models of FM transmitters for linear connection, even their own wire with a 3.5 mm plug can be provided, which eliminates the need to use third-party cables.

The presence of a remote control in the scope of delivery of the FM transmitter.

The ability to control the device from a distance is convenient, first of all, for passengers in the rear seats — for the driver, the remote control on the steering wheel is more relevant (see below), and the “navigator” in the front seat can easily reach the transmitter itself.

The presence of a remote control, mounted directly on the steering wheel. This remote allows the driver to control the functions of the FM transmitter without taking their hands off the steering wheel; This is the best option in terms of traffic safety.

A slot that allows you to install memory cards in the FM transmitter and play music from them. Most often, card readers are made for SD or microSD form factor cards; however, both varieties have several variations (SDHC, SDXC), so before using such a transmitter, it's ok to clarify which varieties the card reader is compatible with.

File formats supported by the FM transmitter.

Almost all models support the MP3 format, which is the most common modern digital audio format. Some devices are also capable of working with WMA — this is also one of the main formats, but for a number of reasons it is used much less often. And even less common is compatibility with WAV — this format provides higher sound quality, but with FM broadcasting this advantage is lost, and the files themselves take up noticeably more space than MP3 and WMA.

The transmitter has a specialized USB port for charging smartphones, tablets and other external devices.

Note that you can also charge external devices from conventional USB connectors; however, specialized ports provide higher power output, which can significantly reduce charging time. It is also worth mentioning that the specific purpose of such a connector can be different: in some models it works only as a power source, in others it can also be used to connect USB drives. Many FM transmitters have two USB ports — regular and charging; this allows you to simultaneously charge an external gadget and listen to music from a USB flash drive. And in modern devices, the old USB A form factor is supplemented by a modern USB-C port.