[AMRadio] Stock or modify? BC rig "value" -- Shorting Sticks


Alan Cohen acohen at texas.net
Thu Jun 1 15:28:25 EDT 2006


>
> On my homebrew KW, I built in an interlock on the door that is  
> opened for access to the plug-in coils, since these run with full  
> modulated HV on them when the transmitter is operating.  I would  
> never try to change coils with the rig in TX position.  The more  
> redundancy the better.  When I change coils, the interlock is  
> turned off, the rig is in standby position, the main HV toggle  
> switch is in the "off" position, and I have made it a habit to  
> observe the plate voltage meter to make sure it is at zero.  A  
> shorting stick would'nt be a bad idea, either.
>
> Don k4kyv

Don

Not only is a shorting stick not a bad idea, not using one is a  
terrible idea.  As someone who has spent many hours working on high  
power transmitters, I would NEVER touch anything inside a transmitter  
without first touching it with a shorting stick.  When I do not have  
a proper shorting stick available, I connect a grounded wire to a  
well insulated screw driver and use that as a makeshift shorting  
stick.  There is are no allowable exceptions to the shorting stick  
rule, as far as I am concerned.

Never rely on meters, pilot lamps or switch positions to tell you if  
HV is present.  Switches can short and pilot lights can burn out.   
I've seen at least one high power uplink amplifier where the  
designers used the bleeder resistor as part of the meter multiplier  
string.  An open bleeder meant zero HV on the meter but possibly a  
full charge on the filter caps.  In that situation a shorting stick  
could be the difference between life and death.  Never, ever, touch  
anything inside of a high power transmitter without using a stick.   
Period!

Alan
WA2DZL



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