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Portable and Emergency Power Considerations for the FT-991A

Yaesu FT-991

Beginning a discussion of the Yaesu FT-991A's power consumption and requirements for portable and emergency power use let's start out by quoting Yaesu's specifications as listed in the manual for reference.  For the sake of all of my discussions please assume the unit requires a negative ground and the stock microphone is used.  The power supply is an AC to DC switching unit fixed at 13.8VDC and is capable of supplying 30A.

The antenna was connected to a dummy load.  Non-squelched volume level set to 50% on internal speaker.  We chose RTTY as the operating mode to represent maximum modulation.

Yaesu Quoted Power Requirements
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Normal Supply Voltage: 13.8 VDC

Receive Current "No Signal": 1.8A
Receive Current "With Signal": 2.2A
Transmit Current HF/50: 23A
Transmit Current VHF/UHF: 15A

Our Observations
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RX No Signal No Scope: 1.49A

RX No Signal w/Scope: 1.51A

RX w/Signal & Scope Vol @ 50%, 3.70MHz: 1.42A

RX w/Signal & No Scope Vol @ 50% 3.70MHz: 1.39A

RX w/Signal & Scope Vol @ 50% 28.50MHz & 14.265MHz: 1.27A 1.25A No Scope

RX w/Signal & Scope Vol @ 50% 147.34MHz MHz: 1.24A  1.21A No Scope

RX w/Signal & Scope Vol @ 50% 441.15MHz MHz: 1.23A  1.21A No Scope

Enabling various filters didn't make a significant difference

 

 

TX:  Noting that the power supply drops from 13.8v to 13.47v under xmit load

1.980MHz LSB RTTY:

100W = 15.56A , 95W on Dummy Load

50W = 12.18A, 47W on Dummy Load

25W = 10A, 23W on Dummy Load

10W = 8.27A, 9.5W on Dummy Load

5W = 7.41A, 4.9W on Dummy Load

3.70MHz LSB RTTY: 

100W = 16.10A, 105W on Dummy Load

50W = 12.62A , 50W on Dummy Load

25W = 10.25A, 25W on Dummy Load

10W = 8.27A, 10.5W on Dummy Load

5W = 7.3A, 5W on Dummy Load

7.270MHz LSB RTTY: 

100W = 16.84A, 100W on Dummy Load

50W = 13.14A, 49W on Dummy Load

25W = 10.32, 24W on Dummy Load

10W = 8.18A, 10W on Dummy Load

5W = 7.12A, 4.9W on Dummy Load

14.250MHz USB RTTY:

100W = 16.61A, 101W on Dummy Load

50W = 12.94A, 50W on Dummy Load

25W = 10.24A, 26W on Dummy Load

10W = 8.12A, 9.8W on Dummy Load

5W = 7.22A, 5W on Dummy Load

28.350MHz USB RTTY:

100W = 15.57A, 92W on Dummy Load

50W = 12.86A, 45W on Dummy Load

25W = 10.18A, 22W on Dummy Load

10W = 8.13A, 9.96W on Dummy Load

5W = 7.12A, 4.9W on Dummy Load

50.100MHz USB RTTY:

100W = 15.12A, 89W on Dummy Load

50W = 10.52A, 42W on Dummy Load

25W = 8.48A, 22W on Dummy Load

10W = 7.02A, 8.9W on Dummy Load

5W = 6.46A, 4.5W on Dummy Load

146.52MHz USB RTTY:

50W = 10.75A, 55W on Dummy Load

25W = 7.72A, 25W on Dummy Load

10W = 6.03A, 11.1W on Dummy Load

5W = 5.02A, 5.1W on Dummy Load

446MHz USB RTTY:

50W = 11.68A, 50W on Dummy Load

25W = 8.42A, 25W on Dummy Load

10W = 6.26A, 10W on Dummy Load

5W = 5.17A, 6W on Dummy Load