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Date: Tue, 29 Mar 2011 08:11:05 +0100
Message-ID: <AANLkTi=ddLKRPxPT08M2k98H0kV6pfOgd1-RgkcLR2a-@mail.gmail.com>
From: Roger Lapthorn <rogerlapthorn@gmail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Re: M0BMU 500kHz /P
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Thanks for the information Jim. The 15.3m fibre glass pole looks useful. I
presume this was one bought from an internet supplier and that it collapses
down for transportation.  I can just make out some guy wires in the photo.

Next time I'll get better organised for a 2-way QSO.

73s
Roger G3XBM

On 29 March 2011 00:47, James Moritz <james.moritz@btopenworld.com> wrote:

> Dear Dennis, Roger, LF Group,
>
> Thanks for the additional reports for M0BMU/P. Here are some details of the
> station - see the attachment for pictures:
>
> The TX antenna was a 15.3m fibreglass mast with 4 x 10m long top loading
> wires sloping down to just over 9m. The ground system was 4 x 1m ground rods
> spaced on a 2m circle round the base of the mast. The antenna was tuned with
> approx 300uH fixed inductance near the base of the mast, and connected to
> the 18 - 70 uH fine tuning variometer in the shack about 15m away by a
> transmission line wire about 1.5m above the ground. The antenna ground was
> also connected to the tuner via a return wire about 300mm off the ground.
> The tuner contained the variometer, ferrite cored matching transformer, and
> a common mode choke to isolate the antenna ground return from the shack
> ground. This arrangement puts the tuning and matching controls in the shack,
> and I found it was easy to adjust, with no problems due to unwanted
> resonances or ground loops. The total antenna resistance was only about
> 11ohms, including 2 or 3 ohms due to the loading coil and variometer, so
> antenna current was approx. 3A with 100W PA output. I estimate the antenna
> effective height was 11m, giving Rrad of 0.53ohm, and ERP of 8.6W.
>
> The receive antenna was a single K9AY terminated loop, oriented to reject
> wideband noise coming from the Brookmans Park BC site to the west, and give
> good reception of Eu stations from the east. I found a terminating resistor
> of about 200ohms gave a good null - this is rather lower than the values
> quoted for the HF bands. The RX antenna was positioned about 50m from the TX
> antenna, to minimise interaction, and give the RX preamplifier an easier
> life!
>
> I used my 200W EER transverter rig, although just for CW on this occasion,
> driven by an IC-718 as the IF. The minimalist shack ("hutch" might be a
> better name for it :-)) was supplied with 130m of mains cable going to an
> outbuilding and into a slightly dodgy mains socket, but much less hassle
> than a generator or batteries. It was also quite handy to be able to follow
> the cable and find the gate in the dark!
>
>
> Cheers, Jim Moritz
> 73 de M0BMU
>



-- 
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
https://sites.google.com/site/sub9khz/
<http://vlf_grabber>G3XBM   GQRP 1678    ISWL G11088

--bcaec51dd7517f7dfe049f99c322
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Thanks for the information Jim. The 15.3m fibre glass pole looks useful.=
 I presume this was one bought from an internet supplier and that it colla=
pses down for transportation.=A0 I can just make out some guy wires in the=
 photo.<br>
<br>Next time I&#39;ll get better organised for a 2-way QSO.<br><br>73s<br=
>Roger G3XBM<br><br><div class=3D"gmail_quote">On 29 March 2011 00:47, Jam=
es Moritz <span dir=3D"ltr">&lt;<a href=3D"mailto:james.moritz@btopenworld=
.com">james.moritz@btopenworld.com</a>&gt;</span> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1=
px #ccc solid;padding-left:1ex;">Dear Dennis, Roger, LF Group,<br>
<br>
Thanks for the additional reports for M0BMU/P. Here are some details of th=
e station - see the attachment for pictures:<br>
<br>
The TX antenna was a 15.3m fibreglass mast with 4 x 10m long top loading=
 wires sloping down to just over 9m. The ground system was 4 x 1m ground=
 rods spaced on a 2m circle round the base of the mast. The antenna was tu=
ned with approx 300uH fixed inductance near the base of the mast, and conn=
ected to the 18 - 70 uH fine tuning variometer in the shack about 15m away=
 by a transmission line wire about 1.5m above the ground. The antenna grou=
nd was also connected to the tuner via a return wire about 300mm off the=
 ground. The tuner contained the variometer, ferrite cored matching transf=
ormer, and a common mode choke to isolate the antenna ground return from=
 the shack ground. This arrangement puts the tuning and matching controls=
 in the shack, and I found it was easy to adjust, with no problems due to=
 unwanted resonances or ground loops. The total antenna resistance was onl=
y about 11ohms, including 2 or 3 ohms due to the loading coil and variomet=
er, so antenna current was approx. 3A with 100W PA output. I estimate the=
 antenna effective height was 11m, giving Rrad of 0.53ohm, and ERP of 8.6W=
.<br>

<br>
The receive antenna was a single K9AY terminated loop, oriented to reject=
 wideband noise coming from the Brookmans Park BC site to the west, and gi=
ve good reception of Eu stations from the east. I found a terminating resi=
stor of about 200ohms gave a good null - this is rather lower than the val=
ues quoted for the HF bands. The RX antenna was positioned about 50m from=
 the TX antenna, to minimise interaction, and give the RX preamplifier an=
 easier life!<br>

<br>
I used my 200W EER transverter rig, although just for CW on this occasion,=
 driven by an IC-718 as the IF. The minimalist shack (&quot;hutch&quot; mi=
ght be a better name for it :-)) was supplied with 130m of mains cable goi=
ng to an outbuilding and into a slightly dodgy mains socket, but much less=
 hassle than a generator or batteries. It was also quite handy to be able=
 to follow the cable and find the gate in the dark!<div>
<div></div><div class=3D"h5"><br>
<br>
Cheers, Jim Moritz<br>
73 de M0BMU </div></div></blockquote></div><br><br clear=3D"all"><br>-- <b=
r><a href=3D"http://g3xbm-qrp.blogspot.com/" target=3D"_blank">http://g3xb=
m-qrp.blogspot.com/</a><br><a href=3D"http://www.g3xbm.co.uk" target=3D"_b=
lank">http://www.g3xbm.co.uk</a><br>
<a href=3D"http://www.youtube.com/user/g3xbm" target=3D"_blank">http://www=
.youtube.com/user/g3xbm</a><br><a href=3D"https://sites.google.com/site/su=
b9khz/" target=3D"_blank">https://sites.google.com/site/sub9khz/</a><br><a=
 href=3D"http://vlf_grabber" target=3D"_blank"></a>G3XBM=A0=A0 GQRP 1678=
=A0=A0=A0 ISWL G11088<br>

--bcaec51dd7517f7dfe049f99c322--