[Amps] HV Resistor Source

[John Lyles]

Carborundum resistors were also common in tube FM broadcast transmitters 
down to 1 kW level for the same application. Dale or Ohmite (or Ward 
Leonard!) 25 watt wirewound resistors don't hold off voltage well across 
4 kVDC, when there is a low impedance breakdown to ground at the RF 
circuit/tube. If one is lucky, they blow open like a fuse, as mentioned 
by others. If not, they allow the load arc to take out a bit more metal 
than Eitel and McCullough can tolerate. It's an insurance policy, not 
needless over-expense, by my estimation.

Big amp here running today at 325 kW avg. Don't use globars for series 
limiters at that level, use active crowbar devices with very small 
resistance to keep the crowbar alive when clamped.
73
John
K5PRO


On 4/17/13 4:19 PM, Carl wrote:
> Ameritron/MFJ sells a Globar they use for a glitch in their "senior"
> amps. Overpriced and uneeded IMO at those power levels. A plasma isnt
> going to even get started before the fuse blows anyway...this aint a
> 250KW application!
>
> Carl
> KM1H
>
>
> -