No subject

[John T. M. Lyles]

I have seen high power and low power Y circulators on low band VHF 
advertized. Several companies make them for 50 MHz range, that I know 
of. The biggest are made by ANT Bosch Telecom, and they are large, 
but can be lifted on a fork lift. Bring large bags of money for 
these, due to the magnets and garnet stuff.


Re: the resistor to gnd from Neg B+ lead of HV power supply.

We have (3) 30 KV DC power supplies rated at 30 Amperes, that provide 
plate voltage for the modulator and Burle 7835 triode RF stage. In 
addition to a series few ohms of resistance in the B+ (and an active 
crowbar circuit for energy dumping), we have a few sparkplugs from 
the neg PS terminal to the wall of the capacitor enclosure, which is 
in reality a large room. The walls are steel, and are earthed with 
wide copper buss. The sparkplugs have had the L shaped ground 
electrode filed away to leave a point and space over to the outer 
rim. They breakdown at around 5 KV at this altitude. Then we also 
have a big Harris or Seimens MOV to the earth point as well. In this 
manner, when there is a cable arc or cavity arc, during the initial 
few microseconds before the crowbar shorts out the PS, there is a 
flash on the gaps and a big jump on the neg lead but not enough to 
punch through insulation. We don't have a resistor, as we don't want 
a linear resistance there, but really just a clamper. We don't want 
any other current to earth during normal operation, although some 
safety 'gurus' put grounds all over the cavity end of the HV cables.

John
K5PRO






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