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Date: Fri, 02 Mar 2007 20:44:34 +0100
To: rsgb_lf_group@blacksheep.org
From: Marco IK1ODO <IK1ODO@spin-it.com>
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Subject: Re: LF: RFI from 136kHz transmissions
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At 18.24 02/03/2007, you wrote:

>In the discussion that I am currently having with Ofcom over the RFI 
>assessment for 501-504kHz applications, the question has been raised 
>as to whether interference has been noted with nearby neighbours, 
>etc, from the transmissions at 136kHz. The licence allows operation 
>on 136kHz without any RFI assessment. It would be helpful to have 
>honest feedback on this if anyone has examples to offer. In such 
>cases I would like to know details of the aerial, distance to the 
>neighbour concerned, power into the aerial and approx ERP, and 
>likely cause (if it's other than straight V/m) and cure.
>
>It would also be worthwhile knowing those who have done significant 
>operating using up to the 1W erp from aerials that are in close 
>proximity to the neighbours, e.g. 5 to 10m or so, and not had any 
>RFI problems.
>
>Not sure the best way of doing this, but rather than clog up the 
>reflector with replies it might be best for people to e-mail me directly.
>
>I will of course collate the data anonymously; it could make life a 
>bit easier if I could convince Ofcom that from a practical 
>perspective -10dBW at 500kHz isn't going to cause much problem as 
>far as RFI is concerned. Of course that may be pre-judging the facts!
>
>73 John, G3WKL
>  RSGB HF Manager
>
>g3wkl@btinternet.com

John,

I'm QRT on 136kHz since a few years, but I had TVI problems on my own 
antenna due to switching parasites from the PA. Cured adding some 
ferrites and LPF at the output. No direct problems from RF fields. 
PWR> 900W, Marconi 13m high 23m long, neighboroughs at 10m or so, my 
TV antenna at 4m from the end of the Marconi. About 18kV on the wire 
(6A RMS, 3.2kOhm Z), so RF field at ground was in the order of 
1500V/m - fluorescent lamps were useful RF field indicators ;-), and 
the field near the vertical wire and the tuning coil was some 20kV/m, 
of course.

73 - Marco IK1ODO

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At 18.24 02/03/2007, you wrote:<br><br>
<blockquote type=cite class=cite cite=""><font size=2>In the discussion
that I am currently having with Ofcom over the RFI assessment for
501-504kHz applications, the question has been raised as to whether
interference has been noted with nearby neighbours, etc, from the
transmissions at 136kHz. The licence allows operation on 136kHz without
any RFI assessment. It would be helpful to have honest feedback on this
if anyone has examples to offer. In such cases I would like to know
details of the aerial, distance to the neighbour concerned, power into
the aerial and approx ERP, and likely cause (if it's other than straight
V/m) and cure.<br>
</font><br>
<font size=2>It would also be worthwhile knowing those who have done
significant operating using up to the 1W erp from aerials that are in
close proximity to the neighbours, e.g. 5 to 10m or so, and not had any
RFI problems. <br>
</font><br>
<font size=2>Not sure the best way of doing this, but rather than clog up
the reflector with replies it might be best for people to e-mail me
directly. <br>
</font><br>
<font size=2>I will of course collate the data anonymously; it could make
life a bit easier if I could convince Ofcom that from a practical
perspective -10dBW at 500kHz isn't going to cause much problem as far as
RFI is concerned. Of course that may be pre-judging the facts!<br>
</font><br>
<font size=2>73 John, G3WKL</font><font size=2 color="#0000FF"> <br>
&nbsp;</font><font size=2>RSGB HF Manager<br>
</font><br>
<font size=2>g3wkl@btinternet.com</blockquote><br>
John,<br><br>
I'm QRT on 136kHz since a few years, but I had TVI problems on my own
antenna due to switching parasites from the PA. Cured adding some
ferrites and LPF at the output. No direct problems from RF fields.
PWR&gt; 900W, Marconi 13m high 23m long, neighboroughs at 10m or so, my
TV antenna at 4m from the end of the Marconi. About 18kV on the wire (6A
RMS, 3.2kOhm Z), so RF field at ground was in the order of 1500V/m -
fluorescent lamps were useful RF field indicators ;-), and the field near
the vertical wire and the tuning coil was some 20kV/m, of
course.<br><br>
73 - Marco IK1ODO<br>
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