The DRA-818 UHF and VHF transceivers

The DRA-818 is a transceiver in a roughly postage stamp IC. The ICs they use internally are similar to those used in other import radios. They do not have the ancillary circuits such as audio amplifiers or battery charge handling. There are two distinct flavors of these modules, a 134-174mhz version and a 400-470mhz version. Supply voltage is rated at 3.3 to 4.5V however I’ve used these on a 5V supply with no problem or salvaged 18650 laptop batteries.

There are a high power of .5/1W RF output and 8 selectable audio levels. Controlling is done with standard 9600 8/N/1 serial protocol. Keep in mind a voltage level converter is required to go from RS-232 to levels acceptable to the IC. I’ve used a MAX232 variant with no issues. Although there are 18 pins, there are only 12 used. These are:

-Squelch detection (inverted logic output)

-Squelch detection (inverted logic output)

-speaker output

-PTT (TX low)

-Sleep mode (active low)

-RF power selection (low .5W, floated 1W)

-power (3.3-4.5V)

-2 ground pins

-Antenna (50 ohm nominal output)

-RXD (serial input TTL levels)

-TXD (serial input TTL levels)

-mic input

-mic input

 


In my experience with this IC it’s very particular with newlines when formatting input data. I spent a decent bit of time researching, a few blog posts by others and trying a few methods to get it working. I ended up settling on Python for dealing with this. Code will be in the next post.

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