The reason that's usually given for this choke is as you say, in order to
protect the
operator in the event that the blocking capacitor breaks down. But I have also
had the
same thought that you have: the chokes used are rated at 300 ma and a big power
supply
with a hefty filter capacitor could give it a serious jolt that might not blow
the fuse.
The other possibility is that it's to prevent DC buildup on the pi-network
components
which might precipitate an RF arc. Where would the DC come from? Maybe static
electricity
from the antenna. Maybe the charge on the blocking capacitor could induce a
charge on the
antenna if it's not grounded?
Food for thought. I agree the chokes are puny for safety devices!
On 3/27/2012 2:10 PM, Kathy Bookmiller wrote:
> I was doing some checking out everything on my amp. (NCL2000) and noticed
> that the
> 2.5mh choke that is after the loading capacitor in the amp. was
> open-connection/wire is
> gone. Looking at others amps., I see they all have them-it would be rfc3 in a
> SB200,
> 1.1mh., for example. Since they are in all amps, at least tube ones, what is
> it for? My
> guess it is to short out the HV if the coupling cap. shorted coming from the
> plates,
> but if I'm right, it doesn't seem heavy enough for a good power supply not to
> just burn
> it up and keep on putting the HV on the antenna/output. I think I can save
> the one in
> my amp. if I can get the paint off the wire by scrapping or chemicals and
> reconnect it,
> but by doing this, I'll eliminate one of the 4 sections on the choke, but
> doubt that
> change in value would be a big problem? Enlighten this poor QRPer, Kathy W2NK
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--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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