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What creating antennas from wire, what is length and size of the wire to be used?
The length of the antenna should be measured from the point where it leaves close proximity to the ground, or from the input/output. If a whip is mounted on a box, and connected with simple wire, then that wire becomes part of the antenna.
In the case of the whip, there must be a connection to a ground, even if the ground plane area is nothing more than circuit traces and a battery. The whip and ground plane combine to form a complete circuit. The electromagnetic field is set up between the whip and the ground plane, with current flowing through the field, which completes the circuit. Ideally, a ground plane should spread out at least a quarter wavelength, or more, around the base of the whip, ground planes can be made smaller, but this will affect the performance. The ground plane area must be considered when designing an antenna.
The length is inversely proportional to the frequency and may be calculated by: wavelength in cm = 30,000 / frequency in MHz. Thus, for a quarter wavelength:
l (cm) = ¼ ( 30,000 / freq (MHz) )
The formula should only be considered as a course measurement however since the length may actually be shorter if the whip is overly thick or wide, has any kind of coating, or is not fed close to the ground. It may also need to be longer if the ground plane is too small.
What is the Lead Finish on the Synthesizer package?
All of our synthesizer products are available in lead-free, RoHS-compliant packages. These parts have a 10um thick Matte Tin surface finish that is annealed for 1 hour @ 150C to mitigate tin whisker formation. In addition, we continue to offer our synthesizers with a Sn85/Pb15 solder finish to support our customer's legacy applications.
What is the minimum wait time between power-up and the first register write to the synthesizer?
Registers may be written to the serial port once the supply voltage reaches the minimum supply voltage as specified in the datasheet.
Ensure that the input voltage to the serial port does not exceed Vdd + 0.3 volts as specified in the datasheet.
Can the synthesizer I/O pins be connected directly to a microcontroller?
Yes, but we recommend using pull-up resistors on the synthesizer serial lines. This will prevent the synthesizer from being programmed to an unknown state during microcontroller power-up.