Fw: [Hallicrafters] SX-110A question

[Mark Bell]

Thanks Phil --

Now I gets it !!   

Mark K3MSB

----- Original Message ----- 
From: "Philip Atchley" <beaconeer at sbcglobal.net>
To: "Mark Bell" <bell at blazenet.net>; <hallicrafters at mailman.qth.net>
Sent: Monday, January 24, 2005 7:31 PM
Subject: Re: Fw: [Hallicrafters] SX-110A question


> 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
> 
>