FT 897 Small Internal DC Supply

The idea here is to pack a small AC to DC supply into one side of the FT897 Battery Compartment inspired by the Gamma Research HPS-1A∞. The Gamma Research itself won't quite fit into the 897, but the equivalent can be built within the space constraints. The other side of the FT897 Battery compartment would still be available for a battery, so you can have AC and battery ops internally. This is much smaller than the Yaesu internal supply, which adds 1/2" to the radio height when installed. This design adds no height, fitting entirely inside the existing battery space.

The Gamma Research is rated at 5A continuous or 22A at 1/4 duty cycle. It consists of a 13.5V dc 5A switcher power supply feeding a 5F capacitor across the output. The capacitor takes up the current peaks in SSB and CW modes. In continuous modes like PSK31, AM, FM, RTTY the power must be lowered to about 30 watts out, in SSB mode the full 100 watts peak output can be reached.

Note that I have not done this yet, there is a little engineering to be done.

Size of the Yaesu FT897 Battery Compartment

• (need to find my notes or remeasure, but the important detail is 1+1/8" height available, the other dimensions are both about 7" as I recall)

Supplies

• 60W+ 12 or 15V switcher, readjust to 13.5V
• 3x5 inch footprint, must be less than 1+1/8" tall to fit
• Condor switcher 3x5x1" 12V or 15V 65W Supplies Digikey Catalog Page∞

Capacitors

• 25F 2.7V NessCap, 5 each in series, with balancing resistors produces a 5F capacitance
• NessCap Digikey Catalog Page∞

Equalizing Resistors

• Voltage Equalizing resistors are required across each of the series capacitors to maintain voltage balance and protect the capacitors from the overvoltage that could otherwise result
• reported from one source as 51 ohms 2 watt in the Gamma Research supply. Don't know if this is correct. Some research needed here to determine the proper value.

Related Items

• LithiumIronBatteries

AlanB WB6ZQZ

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CategoryHamRadio