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Smart Radio Trouble-Shooting

Guide

Overheating

The Smart Radios are rated to a operate at a case temperature of up to 85 C. At 85 C there will

be some degradation in the output power (model dependent, but typically up to 2-3 dB) which

will result in reduced operating range. If your application allows it, we recommend good heat

sinking.

Poor Choise of Antennas

Antenna selection is a very broad topic, so we will only provide a few important reminders.

1. Make sure to choose an antenna which is designed for the operating frequency of the

Smart Radio. Wideband and dual-band antennas which are designed to work over many

bands generally don't perform as well as narrowband antennas a single particular band

of interest.

2. ¼-wave antennas normally need to be mounted to a ¼-wave radius ground plane. For

example, at 915-MHz, the ¼ wavelength is 82 mm in air. Therefore, a ¼-wave antenna

would need to be mounted to a metal plane of at least 82-mm radius.

3. ½-wave dipole antennas normally do not need to be mounted to a ground-plane.

4. Chip antennas normally need to be mounted on a PCB which serves as a ground plane.

These are not recommended unless you are familiar with antenna design.

5. High gain antennas are directional. That means that the antenna will only have high gain

when they are pointed in a particular direction. Look up the radiation chart if you are

unsure.

6. Antennas have a polarization (horizontal, vertical, R/L handed circular). Polarizing TX

and RX antennas differently can lead to significant loss.

7. In general, cheap antennas should not be trusted unless you have tested them.

Antenna Cable loss

When choosing an antenna cable, keep the following in mind.

1. Make sure to use 50-ohm coaxial cable (not 75-ohm cable)

2. Coaxial cables have different loss per unit length depending on the type and frequency.

Use a calculator like this one

look up the loss specifications from the coaxial cable's datasheet.

3. Every 3-dB coaxial cable loss results in 3-dB loss in the TX power and 3-dB loss in the RX

signal which results in 2x reduction in the operating range.

UART and USB ports

This section covers common pitfalls encountered when using the USB and UART ports. Please

note that for -H hardware, the auxiliary port is either USB or UART, but not both (See Table 1).

https://www.qsl.net/co8tw/Coax_Calculator.htm

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September 8, 2021