> The diode is needed because some power supplies have a tendency to
go into a "crowbar shutdown" mode if the AC input goes away (as
during a power failure) while a DC voltage is maintained at its
output by a battery. Such an event will blow fuses and will almost
certainly shut down the repeater.
Crowbar circuits protect against regulator failure in the power
supply by forcing the output to ground, and blowing a fuse (you
hope!)
Paradoxically, using a series diode between the PS and battery makes
it MORE likely that the crowbar will trip, beacuse you then have to
raise the power supply voltage higher.
A simple fuse here, set a bit above the power supply's maximum
current rating, would work better. Alternately, use the diode, but
remove the crowbar, or adjust the crowbar trip point appropriately.
> Unless the repeater operates almost continuously, the power supply
does not need to match the current draw of the radio during
transmit. I have a 50 watt base station set up this way that has a
26 Ah VRSLA battery floated by an Astron RS-10 power supply, and it
has been 100% reliable through many power outages.
Sure, I use this system a LOT in bench and repeater applications.
In the end though, you still have something charging a battery that
was not designed for that service. A proper battery charge system,
designed to be floated across a battery and a load, is a better
solution. The IOTA is also not all that expensive, and being a
switcher, it is very small and efficient.
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