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In-Reply-To: <4D53AE84.6932.312944@jurgenb2.3sdesign.de>
References: <4D53AE84.6932.312944@jurgenb2.3sdesign.de>
Date: Thu, 10 Feb 2011 10:56:04 +0000
Message-ID: <AANLkTinbzpGRKxq3eHdMuYxaTs=Rvd_eYq_iyDisKUz6@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: how to get ground rod ressitance low
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I installed about 20 earth rods around the periphery, with a couple in the
centre region,  of a small garden abt 6m x 12m with heavy clay soil.  Each
rod consisted of as much 15mm copper water pipe as I could bash in before=
 it
buckled, typically 0.6 to 0.8m each.  There were also about 4 or 5 proper
full length rods.  All these were wired together with thick bare single
strand wire which was also buried just under the surface.

The DC resistance measured to mains earth / neutral (PME system in use) wa=
s
in the region of 3 ohms, and stayed reasonably constant whatever the weath=
er
/ ground sogginess.    The whole lot was bonded to mains earth with three
runs of 10mm^2 cable (and yes,  I know IEE wiring regs say only one bond=
 of
16mm^2 should be used, but that's a practical thing of being able to check=
,
not an actual safety rule  I wanted better RF resistance, so three).

At RF, resistance of the Tee antenna system - which is mostly due to groun=
d
losses is :
73kHz   180 - 220 R
137kHz  90 - 130 R
503kHz  25 - 28 R
1.9MHz  10 - 13 R
Higher than this antenna transmission line effects become significant.

All originally determined from V / I measurements and recently confirmed
with DG8SAQ NetAn.

Andy
G4JNT




On 10 February 2011 08:23, Jurgen Bartels <jurgenb2@3sdesign.de> wrote:

> I just discovered that my ground rod isn't ideal by having the assumed=
 0
> ohm to
> earth. Measuring with 10VDC the current from neutral/waterpipe to the ro=
d
> gives
> about 140 ohms.
> I use a 8mm rod 1m long in wet soil. I put in another one and tried seve=
ral
> places nearby and got it a bit lower, but far away from ideal.
> So I assume the surface size is too small, one the other hand I want a
> small
> rod that can be pulled out with ease in spring when the season is over.
>
> What resistance do you get usually and what size do you use?
>
> Stefan, you wrote yesterday that you got 65 ohms with your rod on sunday=
.
> That's still pretty high
>
>
>
> Jurgen Bartels  Suellwarden, N. Germany
> hor. Antennas: 11-ele 45-87MHz 13-ele Band-III, 48-ele UHF, FM: 15.11
> TV: Winradio G305 / Fly2000 + video noise filter & variable IF BW
> FM: Downconverter + Perseus + Speclab as WFM demod.
> MW: staggered 300m Beverage 320=B0,  30 x 4m EWE 320=B0, Winradio & Pers=
eus
> http://dx.3sdesign.de/tv_offset_list.htm
> http://dx.3sdesign.de/station_list.htm
>
> http://fewo.3sdesign.de  - Vacation home: DX right at the Northsea coast
>
>
>
>
>

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<div>I=A0installed about 20 earth rods around the periphery, with a couple=
 in the centre region, =A0of a small garden abt 6m x 12m with heavy clay=
 soil.=A0 Each rod consisted of as much 15mm copper water pipe=A0as I coul=
d bash in before it buckled, typically 0.6 to 0.8m each.=A0 There=A0were=
 also about 4 or 5=A0proper full length rods.=A0 All these were wired toge=
ther with thick bare single strand wire which was also buried just under=
 the surface.=A0=A0 </div>

<div>=A0</div>
<div>The DC resistance measured to mains earth / neutral (PME system in us=
e) was in the region of 3 ohms, and stayed reasonably constant whatever th=
e weather / ground sogginess.=A0=A0=A0 The whole lot was bonded to mains=
 earth with three runs of 10mm^2 cable (and yes,=A0=A0I know IEE wiring=A0=
regs say only one bond of 16mm^2 should be used, but that&#39;s a practica=
l thing of being able to check, not an actual safety rule=A0 I wanted bett=
er RF resistance, so three).</div>

<div>=A0</div>
<div>At RF, resistance of the Tee antenna system - which is mostly due to=
 ground losses=A0is :</div>
<div>73kHz=A0=A0 180 - 220 R</div>
<div>137kHz=A0 90 - 130 R</div>
<div>503kHz=A0 25=A0- 28=A0R</div>
<div>1.9MHz=A0 10 - 13=A0R</div>
<div>Higher than this antenna transmission line effects become significant=
.</div>
<div>=A0</div>
<div>All originally determined from V / I measurements and recently confir=
med with DG8SAQ NetAn.</div>
<div>=A0</div>
<div>Andy</div>
<div>G4JNT</div>
<div>=A0</div>
<div><br><br>=A0</div>
<div class=3D"gmail_quote">On 10 February 2011 08:23, Jurgen Bartels <span=
 dir=3D"ltr">&lt;<a href=3D"mailto:jurgenb2@3sdesign.de">jurgenb2@3sdesign=
.de</a>&gt;</span> wrote:<br>
<blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8e=
x; PADDING-LEFT: 1ex" class=3D"gmail_quote">I just discovered that my grou=
nd rod isn&#39;t ideal by having the assumed 0 ohm to<br>earth. Measuring=
 with 10VDC the current from neutral/waterpipe to the rod gives<br>
about 140 ohms.<br>I use a 8mm rod 1m long in wet soil. I put in another=
 one and tried several<br>places nearby and got it a bit lower, but far aw=
ay from ideal.<br>So I assume the surface size is too small, one the other=
 hand I want a small<br>
rod that can be pulled out with ease in spring when the season is over.<br=
><br>What resistance do you get usually and what size do you use?<br><br>S=
tefan, you wrote yesterday that you got 65 ohms with your rod on sunday.<b=
r>
That&#39;s still pretty high<br><br><br><br>Jurgen Bartels =A0Suellwarden,=
 N. Germany<br>hor. Antennas: 11-ele 45-87MHz 13-ele Band-III, 48-ele UHF,=
 FM: 15.11<br>TV: Winradio G305 / Fly2000 + video noise filter &amp; varia=
ble IF BW<br>
FM: Downconverter + Perseus + Speclab as WFM demod.<br>MW: staggered 300m=
 Beverage 320=B0, =A030 x 4m EWE 320=B0, Winradio &amp; Perseus<br><a href=
=3D"http://dx.3sdesign.de/tv_offset_list.htm" target=3D"_blank">http://dx.=
3sdesign.de/tv_offset_list.htm</a><br>
<a href=3D"http://dx.3sdesign.de/station_list.htm" target=3D"_blank">http:=
//dx.3sdesign.de/station_list.htm</a><br><br><a href=3D"http://fewo.3sdesi=
gn.de/" target=3D"_blank">http://fewo.3sdesign.de</a> =A0- Vacation home:=
 DX right at the Northsea coast<br>
<br><br><br><br></blockquote></div><br>

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