Re: [HCDX]: ADSL?

["Fernando de Sousa Ribeiro" <s_ribeiro@xxxxxxxxx>]

Robert Joosten <robertj@xxxxxxxxxx> wrote:

> Hi,
>
> >I would be very much interested in your report if ADSL also
intensifies
> >problems with digital interferences dramatically. Here in
Germany there is
> >already quite a discussion going on if things like ADSL might
be the end of
> >DXing terrestrial radio signals of all kinds.
>

According to the ITU-approved version, ADSL (Asymmetric Digital
Subscriber Line) occupies the spectrum between 25.875 and 138.8
kHz, from the subscriber to the telecomms operator, and between
138 kHz and 1.1 MHz, from the operator to the subscriber. All this
traffic flows through common telephone unshielded twisted copper
pairs, from the telecomms switch or the optical network unit
(ONU), right down to the user's home or business. This is really a
matter of concern to all of us; if it's great for internet and
multimedia, it can be the end of  DXing on LW, MW and SW, at
least.

But ADSL can only be an intermediate step before the deployment of
VDSL (Very high bit rate DSL), with a bandwidth that is 4 times
that of ADSL, making things even worse. The only solution to this
resides in fiberoptics, but prices of optical fibres and
components are not low enough to allow the replacement of the
existing copper cables by fibre cables. Optical networks and fiber
to the home (FTTH) are still very expensive solutions.

> I think the Iridium project (and such) generates a lot of QRM as
well. Not
> only for us, SW-DX'ers, but also for solar observatories.
Electrosmog it's
> called in the Netherlands...
>
> 73, Robert.

The Iridium consortium has signed an agreement with the
international astronomers association, according to which the
Iridium satellites are switched off for a couple of hours each
day, to allow for radioastronomical observations. I think Bill
Gates has signed a similar agreement too. It certainly is
catastrophic for radiotelescopes, looking for extremely weak
signals from deep space, to have satellites radiating directly on
to them.

Fernando de Sousa Ribeiro
Oporto, Portugal
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