Fw: [Hallicrafters] SX-110A question

[Philip Atchley]

Hi,

It's a "safety drain" thing.

When there is wind, even rain etc large static Voltages can accumulate 
on an antenna. I'm sure many of us have seen an antenna lead that was 
just laying there on the table start "sparking" across to a nearby 
ground or across a coax connector, even in the absence of a "real" 
lightening show.  I know I've heard that little "snap, snap, snap" and 
looked around to see where it was coming from.

This can be a real eye opener when you think how much money we spend on 
our radio gear. If this antenna lead is connected to a receiver that 
Static Voltage will appear on the receiver.  HOPEFULLY, you also have a 
good ground connected to the set and the static can drain away, 
hopefully through the antenna input coil to chassis, then to ground.

HOWEVER, if you DON'T have a ground on the radio, the entire radio will 
be raised to the level of the static charge.  This can be very startling 
when you touch it.  The real danger is that it can also break down the 
insulation of power transformers and bypass capacitors as the static 
charge seeks a ground path through them to the power line. Then you get 
120 VAC on the chassis.  The resistor is there to provide a continuous 
"leakage" path to ground through the power line in the absence of any 
other ground thereby preventing static buildup on the device.

Yes, new consumer appliances with 2 wire power cords DO still have these 
resistors.  I repair stereo gear at a local TV shop and even the 
cheapest stereo has what is usually a 3.3 M-Ohm or so resistor between 
chassis )or ground trace) and the large blade of the power cord (neutral 
lead).

73 de Phil,  KO6BB
991 Different NDB's heard to date.

http://www.geocities.com/ko6bb/
Merced, Central California, 37.3N  120.48W  CM97sh

----- Original Message ----- 
From: "Mark Bell" <bell at blazenet.net>


> Maybe I'm a bit dull, but I still don't get the part with the 
> resistor.
>
> With no excess voltage, you have 110V (give or take) across the 
> resistor.
>
> With an excess voltage, say X volts, you have 110 + X across the 
> resistor.
>
> The only thing I see that changes is the current.
>
> Mark K3MSB