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Kevin McMurtrie
Guest

Thu Oct 09, 2014 10:15 pm   



In article <slrnm38gd7.6mj.kpgpbhdw_at_localhost.localdomain>,
kpgpbhdw_at_kpgpbhdw.com wrote:

Quote:
I am thinking of building some sort of device that can recieve DTV
signals, amplify them, and transmit them downward. This is to deal
with bad DTV reception at my house, where line of sight is poor.
The device would be mounted on the roof, and powered by a solar cell and
rechargeable battery system. The advantage over a conventional outdoor
TV antenna would be not requiring any cabling or lightning protection,
as the device would be electrically self-contained (and held up by a
wooden frame).

Has anyone done this? Can anyone point me towards resources for doing
this?

Thanks.


A normal mast-mounted amplifier with a low gain should work. They
usually run off 9 to 15 VDC @ 20mA. Lithium Iron Phosphate and Lead
Acid are the easiest types to charge. You can buy a solar recharger.

The hard part will be making sure that you're not illegally broadcasting
interference outside your property. The retransmission will be prone to
feedback, over-modulation, and multi-path.

I'd simply use a longer cable to where the signal is better.

--
I will not see posts from astraweb, theremailer, dizum, or google
because they host Usenet flooders.

Don Bruder
Guest

Thu Oct 09, 2014 10:21 pm   



In article <JIrZv.578562$ck2.152790_at_fx17.am4>,
Tom Gardner <spamjunk_at_blueyonder.co.uk> wrote:

Quote:
On 08/10/14 23:50, RobertMacy wrote:
On Wed, 08 Oct 2014 14:27:23 -0700, Tom Gardner <spamjunk_at_blueyonder.co.uk
wrote:

...snip....
In which case it is no longer passive and will require a
licence (almost certainly).

Do the job properly: either ask OFCOM or run a cable.

I've never gotten a broadband amplifier to operate well with its output
being fed back into the input willy nilly. Unless I originally wnated that
oscillator.

:)


also, a fibre glass pole has some chance of not attracting lightning. just
some chance, because when it comes to high voltage EVERYTHING conducts.

Lightning conductors actually /deflect/ the chance
of a lightning strike, since their sharp point tends
to /reduce/ the ionisation in the vicinity.


You've got that exactly backwards - pointy stuff increases both local
ionization, and the likelihood of an arc either hitting or jumping from
the pointy object.

This fact is why the folks who play with Tesla coils use either a ball
or a torus as the high-voltage output terminal on their coils - unless
they're trying for a specific type of directed discharge, of course.

The idea that a lightning rod should be pointy revolves around the
concept that the increased local ionization surrounding the sharp point
should cause the the lightning rod to be struck, and the current
directed down the attached conductor to ground, resulting in reduced or
no damage to whatever is being protected.

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Tom Gardner
Guest

Thu Oct 09, 2014 10:40 pm   



On 09/10/14 17:21, Don Bruder wrote:
Quote:
In article <JIrZv.578562$ck2.152790_at_fx17.am4>,
Tom Gardner <spamjunk_at_blueyonder.co.uk> wrote:

On 08/10/14 23:50, RobertMacy wrote:
On Wed, 08 Oct 2014 14:27:23 -0700, Tom Gardner <spamjunk_at_blueyonder.co.uk
wrote:

...snip....
In which case it is no longer passive and will require a
licence (almost certainly).

Do the job properly: either ask OFCOM or run a cable.

I've never gotten a broadband amplifier to operate well with its output
being fed back into the input willy nilly. Unless I originally wnated that
oscillator.

:)


also, a fibre glass pole has some chance of not attracting lightning. just
some chance, because when it comes to high voltage EVERYTHING conducts.

Lightning conductors actually /deflect/ the chance
of a lightning strike, since their sharp point tends
to /reduce/ the ionisation in the vicinity.

You've got that exactly backwards - pointy stuff increases both local
ionization, and the likelihood of an arc either hitting or jumping from
the pointy object.

This fact is why the folks who play with Tesla coils use either a ball
or a torus as the high-voltage output terminal on their coils - unless
they're trying for a specific type of directed discharge, of course.

The idea that a lightning rod should be pointy revolves around the
concept that the increased local ionization surrounding the sharp point
should cause the the lightning rod to be struck, and the current
directed down the attached conductor to ground, resulting in reduced or
no damage to whatever is being protected.


This is very very embarrassing. You are right.

Now I'm wondering where I got that misinformation from. Probably
school, although an inverted neuron might also be to blame.

Digging out my 1973 Physics textbook, it states; "The very high
density of charge [on lightning conductor tip] causes the charge
to flow upwards from the tip and so the opposite charge on the
clouds is slowly neutralised".

If wackypedia is anything to go by, perhaps that stems from
Benjamin Franklin's presumptions, and ignores Tesla's improvements.
Well, Tesla being ignored isn't exactly news Sad

Brian Gregory
Guest

Fri Nov 07, 2014 6:29 am   



On 07/10/2014 23:30, Tom Gardner wrote:
Freeview is designed to be received with a roof mounted outdoor aerial.
Of course it's not going to work well with an indoor aerial.
Get a proper aerial fitted.

--

Brian Gregory (in the UK).
To email me please remove all the letter vee from my email address.

Tom Gardner
Guest

Fri Nov 07, 2014 7:42 am   



On 06/11/14 23:29, Brian Gregory wrote:
Quote:
On 07/10/2014 23:30, Tom Gardner wrote:
Freeview is designed to be received with a roof mounted outdoor aerial.
Of course it's not going to work well with an indoor aerial.
Get a proper aerial fitted.


For the avoidance of doubt: I did /not/write that!

In fact your premise is false: Freeview has certain signal requirements, which
do not include antenna placement.

I know of an indoor antenna that has worked perfectly since 1990, i.e. for 24
years. Transmission distance: 24km, and in the diffraction zone of a hill
between the tx and rx.

Given that there will, at some stage, be several 4G base stations 1.5km away on
the direct line of sight (on top of a students' union buildign), it is probable
that even a /rooftop/ antenna will not work under those conditions. (That's
based on OFCOM's reports into tv rx overload characteristics, presumed base
station strength and path loss).

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