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The dAISy has only one receiver, which hops between the two AIS channels. This design may be adequate for areas without extremely high density of AIS traffic. The dAISy literature says the receiver takes 10-mSec to change channels. In AIS transmission, the data is sent in time slots that are 26.2-mSec long. The receiver channel switching time is thus about half as long as one transmission time slot. This implies that a single receiver switching channels would be unable to receive all AIS transmission, as every time it just switches from one channel to the other it must lose at least one of the time slots in the transmission pattern. And, of course, when the dAISy is listening on one channel is will be missing all transmissions on the other channel. Ships that are moving send out data at a rate of once every two seconds to once every ten seconds, depending on their speed. In a period of listening of one minute, a moving ship would then make between six to 30 transmission. The chances that a single receiver AIS system would receive at least one of those transmission are good. Ships that are not moving transmit more infrequently, and may only transmit once every three minutes. If a single-channel receiver misses their transmission, it will be three minutes before it has another opportunity to receive it.
The receiver sensitivity is rated at -100-dBm, which is not as good as some more expensive receivers, but user reports tend to describe its reception as quite impressive. For comparison, the em-trak R100 AIS receiver sensitivity is rated at better than -107dBm at 20% Packet Error Rate.
The dAISy power consumption is a very modest 0.020-Ampere (or less) at 5-Volts, or 0.1-Watt. This should not be a drain on any power source. It is primarily intended to get its power from its USB connection. No provisions are made for powering from 12-Volts. Adapting the dAISy to work from the 12- to 14-Volts of a boat's battery would need extra circuitry.
The dAISy sends its data output to the USB bus at 38,400-bps. This suggests that the dAISy is likely to be best suited for use with a computer, and not with a marine chart plotter, which typically expect data to come via NMEA-0183 or NMEA-2000 interfaces. There is an optional 3.3-Volt TTL data output, but it will need more circuitry to be able to interface to NMEA-0183 ports.
For comparison, the em-trak R100 can be powered from either USB or 12-Volts and has both USB and NMEA-0183 serial data outputs. The em-trak also costs almost four times as much as the dAISy, as it retails for around $225.
No matter the drawbacks, at the $60 price level there is no alternative: the dAISy has this market captured nicely. To date over 200 have been shipped by the manufacturer. Customer reviews are generally favorable. With its small size, you could attach it to be back of the screen of a laptop computer and have a very mobile AIS ship-spotting rig.
For more information see
https://www.tindie.com/products/astuder/daisy-ais-receiver/