Frequently asked questions
Appropriate frequency for your application:
For NLOS (Non Line of Sight) and long range applications such as ground robots, lower frequencies typically yield better results. Given the same power output and antenna gain, throughput and sensitivity, 400 MHz will travel significantly further than 2400 MHz. For any given distance, the attenuation suffered by radios waves (Free space loss) increases with frequency. The higher the frequency, the more loss you encounter.
At any given distance, free space loss at 2.4 GHz is 8.5 dB higher than at 900 MHz, and about 15 dB higher than on 450 MHz. There are other factors as well, including Fresnel-zone and noise/interference from other devices and environment. What does this mean to me? If equal coverage is desired from 2.4 GHz and 450 MHz in identical conditions, the loss must be made up by a larger antenna.
Pros and cons of higher vs. lower frequencies:
As stated earlier, lower frequencies will reach farther given the same RX sensitivity and environmental variables. Higher frequencies, however, tend to be typically cleaner and less crowded, while given the shorter wavelength of higher frequencies, antennas are smaller for the same gain. A simple unity gain antenna for 2400 MHz is much shorter than for 450 MHz, which means a high gain 8 dB omni or directional antenna will be significantly smaller in the higher frequency range.
What is channel width?
Channel width refers to the occupied bandwidth of a radio transmission. A device operating on 2412 MHz and using a 5 MHz channel means the center of the channel is on 2412 MHz and spreads 2.5 MHz in either direction. In this case, 2409.5 to 2414.5. How does this affect you? Given the same bit/Hz performance, a channel occupying 10 MHz instead of 5 will have double the throughput, which translates to more data. Keep in mind, however, most receivers sensitivity decreases as channel width increases, which might affect total performance. A receiver will be better able to understand signals coming from a transmitter with smaller channel width.
What channel width do your devices support?
For DVB-T video transmitters we use 1/2/3/4/5/6/7/8 MHz channels, while our OFDM Ethernet devices are capable of operating with 2.5/5/7/8/10 MHz channel widths.
What is the Fresnel zone and how does it affect wireless devices?
Being able to see from your radio's antenna to the receiving radio's antenna might not necessarily mean LOS (Line of Sight). Radiation pattern from antenna to antenna is not just a straight line, but rather elliptical. The farther the two antennas, the greater the diameter of the wave.
In order to achieve perfect radio LOS, all obstacles from the Fresnel zone must be removed.
There are calculations available to determine the Fresnel zone.
Why is there latency in Digital video transmitters compared to analog?
In a typical digital video transmitter, the images must be compressed before being sent through the radio, then decompressed on the receiver side. There are many variables that affect total encode-transmit-decode times. Typically latency will vary based on video compression settings and ultimately the speed of the video encoder/decoder. Hardware encoding/decoding tends to be significantly faster than software encoding/decoding.
Ultra HD, DVB-T compliant COFDM HD/SD transmitter available from VHF to 2.4GHz
Artemys & Explorer Tactical Robots, the only small tactical robots with 1080p COFDM video systems on the market