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| To: | [email protected] |
|---|---|
| Subject: | Re: LF: Measuring earth resistance |
| From: | "Dick Rollema" <[email protected]> |
| Date: | Mon, 16 Dec 2002 13:45:58 +0100 |
| In-reply-to: | <[email protected] .telenor.no> |
| Reply-to: | [email protected] |
| Sender: | <[email protected]> |
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To All from PA0SE Jan-Martin, LA8AK. wrote: but suppose the values of the noise generator are for the range 3-30MHz, the coupling capacitors must be increased for VLF The noise bridge was indeed not designed for LF but there is plenty of noise on LF and the bridge can be perfectly nulled on 136kHz. But the X-control has hardly any effect as its range is from 190pF till -155pF (means inductive reactance) and that amounts to -j6.15 kohm till j7.54 kohm as minimum values that can be measured in parallel with Rx. But for measuring earth resistance the X-control is not used because I bring the aerial system into resonance so that only a pure ohmic resistance has to be measured. To make the X-control useful on LF it might be better to connect C1 in series with R3 and C2 in series with Zx; but I have not investigated that. I used the parallel version because at high frequencies it is easier to compensate for the parasitic capacitances of R3 and C2. 73, Dick, PA0SE -----Opprinnelig melding----- |
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