Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]

Re: LF: Measuring earth resistance

To: [email protected]
Subject: Re: LF: Measuring earth resistance
From: "Dick Rollema" <[email protected]>
Date: Mon, 16 Dec 2002 14:14:58 +0100
In-reply-to: <[email protected]>
References: <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
To All from PA0SE

I wrote:
................
> Measuring earth resistance at 50Hz has no meaning  for the loss at 136kHz
> because the earth resistance (impedance is more correct) is frequency
> dependent.
 
Upon this Uwe, DJ6WX, remarked:

but you use a noise source ie. not 136kHz only. does that not matter ?

The noise source indeed produces noise over a wide band of frequencies. But as a detector a receiver is used and therefore only a small frequency band around 136kHz is used to balance the bridge. The width of that band depends on the pass band of the receiver. Because the bridge can  theoretically  be balanced  for one frequency component of the noise only it is necessary to use as small a bandwidth as possible. With a wide pass band of the receiver a minimum in the noise can still be found but it is not very pronounced. So the narrower the pass band of the receiver, the deeper the noise minimum becomes.

73, Dick, PA0SE
<Prev in Thread] Current Thread [Next in Thread>