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Created HamShield Advanced Hacks and Tricks (markdown)

spaceneedle 2015-07-06 17:10:25 -07:00
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The HamShield is a very powerful starting point for creating new ways to communicate. You can also improve on a lot of old ways! While this guide may show you some of the interworkings of the shield and its library, you must realize that any physical modifications to the shield is also choice to void our shield warranty. If modifications are done improperly, you may inadvertently lift a pad, damage a critical IC, or interfere with other radio bands. ***You have been warned.***
#### Disabling Band Restrictions
For those in jurisdictions allowing different frequencies than United States, FCC Auxiliary or other regulatory license holders, RF anechoic chambers, dummy loads and perhaps those in international jurisdictions, it may become handy to disable the band restrictions. Otherwise, the library is specifically written to prevent accidental transmission.
This can be done by issuing the simple method .dangerMode() in your sketch. As the name implies, this mode is dangerous if used improperly. The .safeMode() method can re-enable the restrictions.
#### Direct Radio Access (voids warranty)
It is not known, and perhaps remotely possible, to obtain direct access to the radio for FSK purposes. There are two DC blocking capacitors on the input and output of the radio, external to the IC. According to the A1846S block diagram, there is an ADC and DAC directly on these pins. If no blocking circuitry exists inside the chip, it may be possible to directly shift the carrier with a DC voltage. It is also important to note that the shield has internal circuitry that may introduce a DC offset as well as PWM / ADC filtering that will cause additional DC blockage.
#### Audio Amplifier Modification (voids warranty)
It is possible to adjust the amplification levels for additional receive audio boost, however, increasing the amplification may cause distortion into the ADC and headphones.
#### Boosting Power Output
When boosting power, it is best to plug your HamShield into an appropriate amplifier that is built for continuous duty amateur radio use, specific for the band you will be operating in. It is also important to perform filtering, if it is not already provided on your amplifier. This will prevent harmonics from being amplified, which both reduce your radio power output as well as interfere with other radio spectrum users. It is also very important to test the SWR of your setup, make use of a properly tuned antenna, and keep high RF powered antennas away from people and animals.
#### Connecting to a Computer
When connecting to a computer, it is best to make use of a TRRS crossover cable and reduce the audio levels to line level using the .audioLineLevel() method. This will automatically set the volume low enough to prevent distortion.
#### Connecting a Resistor DAC
Some packet radio solutions today use resistor DAC implementations. You can connect the output of this resistor DAC to pin 11 of your Arduino shield or make use of the existing TRRS audio connection for best results.