[R-390] Tube receivers and long wire antennas

[ToddRoberts2001 at aol.com]

In a message dated 5/23/2005 12:21:33 AM Eastern Standard Time, 
huffb at avalon.net writes:
Now to my question for the group-The arc between the center conductor and the 
ragged end of the just cut braid was probably a kilovolt or so during that 
storm, a storm that was a couple of miles away. Now I don't intend to leave the 
antenna hooked up to the radio when it is not in use but I'm still concerned 
about front end damage while I'm using it. What does one do about this?

Brad - One thing you can do is wire a standard RF choke across the center 
conductor of the coax and the shield braid (ground). In order to work properly 
the shield braid must be connected to an earth ground. By standard RF choke I 
mean something with a value of 2.5 - 10 millihenries (not microhenries) - these 
were commonly used in small to medium powered tube transmitters as a safety 
choke across the output side of the pi-network. These chokes are still commonly 
available. The choke gives a DC path to ground to bleed off or short any 
static charges to ground and will keep the center conductor of the coax at DC 
ground potential but has a high impedance to RF so it will have little effect if 
any on the RF signal level going to your receiver antenna input. 73 Todd WD4NGG