Quote from updates:
Across Shenzhen, Earl’s RF team has some of the most challenging tasks at hand. Our originally grandiose idea for Earl’s radio has met its biggest opposition, the FCC. The rules and regulations set in place by the FCC currently limit what Earl’s radio is certified to be used on. In order to market Earl to the general public, Earl will be certified under FCC Part 95A and Part 90. FCC Part 95A covers 15 GMRS channels in the 462 MHz range. While most GMRS radios also include certification for use on FRS frequencies as well, Earl’s antenna is designed to be removable (we’ll explain this in a moment). Per FCC Part 95B, the antenna of an FRS radio must be an integral part of the transmitter, i.e., non-removable. As for MURS radios, they have another set of rules. FCC Part 95J states that MURS radios shall not be certified if equipped with a capability not listed under MURS frequencies. Hmm... But here comes the good news. Earl meets FCC Part 90 requirements. The RF system we’re using is essentially two radios in one. Earl transceiver works on both the 2m (136-174 MHz) and 70cm (400-480 MHz) bands. The longer wavelength of VHF (2m) allows for better propagation over small hills and through forests. The shorter wavelength of UHF (70cm) allows for better propagation through buildings and urban areas. We wanted the best of both worlds and a fortunately the FCC does allow a radio to be both Part 95A and Part 90 certified.Here’s the downside. To transmit on GMRS frequencies, the FCC requires users (of any GMRS radio) to pay $85 for a license. This license covers you and your family for five years, no test necessary. For additional frequencies in the 2m and 70cm bands an Amateur Radio license is required. First time users are required to pay $14 and complete a 35-question multiple choice written exam. The license grants full operating privileges on all amateur bands above 30 MHz. (Note, these regulations only apply to the use of Earl within the USA) Earls RF output power has been trimmed from 5 watts down to 2 watts. Supporting 2w, 1w and 0.5w power modes. There were a number of factors leading us to this decision. The number one concern was battery life. Two-way radio systems use a lot of juice. While radio manufacturers may claim that their radio will last 12 or more hours, remember that the battery duty cycle assumes 5% for transmission, 5% for reception and 90% in standby. A 5w radio would require a significantly larger (and heavier) battery, running at 7.2v, instead of the 3.8v battery Earl’s system is designed to use. All that extra power increases the risk that Earl may become inoperable until the solar charging system has time to replenish the battery. But there’s always compromise. Earl’s included antenna is removable. Capable of transmitting on both 2m and 70cm bands, users that wish to increase the Earl’s range will be able to attach higher gain antennas via an SMA connector. Bubble pack GMRS and FRS radios are limited by the FCC to using non-removable antennas, limiting their effective transmission range. That 5w radio with fixed antenna has aERP (effective radiated power) of around 1.5 watts. While many of these radios advertise up-to XX miles, two-way radios are line of site. Due to the curvature of the earth, two users standing on flat ground, have an effective transmission range of around 6 miles. By increasing the antenna gain and adding elevation to your transmission point, we can increase the range of Earl much much further.
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