>
> I can't imagine why an amateur would want to use a
> switching supply for a filament. What reason is there to do
> that?
I use a switching supply to run the filament of a GS35b in a 70cm amp
for several reasons:
1. The filament volts should be backed off a little to allow for
additional heating due to back-bombardment. The switcher has a pot for
voltage adjustment - easy!
2. The switcher is regulated - good for field days when the genny is
wandering a little and you've set the volts "just so", as per (1).
3. The switcher is current limited, reducing the current surge at switch
-on. Check the surge current that a nice, low-impedance toroidal
transformer is capable of delivering to a cold filament and you might be
rather shocked.
Regards,
Dave
VK3HZ
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