[Elecraft] [KX3] Boost Buck 13.8 V Regulator

[picmaster at mail.bg]

Hi Phil,

I've seen similar approaches for regulating the heater voltage a vintage Russian military tube receiver. There's a series resistor in the circuit that's connected when the batteries are fresh-charged, and this resistor is bypassed with a switch when the battery voltage falls inside the normal operating range of the tube heater (there's an embedded volt-meter in the tube received for visual check, just like there's such menu in the KX3).

This method is less power efficient than when using a modern SMPS, but it's very "low-tech" and reliable (simpler systems have less and usually more obvious failure modes).

73,
Nikolay // LZ1NRD


----- Цитат от Phil & Debbie Salas (dpsalas at tx.rr.com), на 13.05.2013 в 14:45 -----

> I put two 1N5400 diodes in series with each other (these are 3-amp diodes).  The diodes are physically side-by-side, with the leads connected in series to keep the assembly small.  This all fits nicely between two PowerPole connectors and has a piece of heat-shrink over it.  When connected between my 4S2P LiPo battery (16.8VDC fully charged), I get 14.8VDC on receive, and 14.2V with 2.2 amps on transmit at 10 watts.  When the receive voltage drops to 13V (as monitored on the KX3), I unplug the diode assembly.
> 
> Maybe it is not elegant.  But it is cheap, works great, and doesn’t generate any hash.
> 
> Phil – AD5X

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