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uk.tech.digital-tv (Digital TV - General) (uk.tech.digital-tv) Discussion of all matters technical in origin related to the reception of digital television transmissions, be they via satellite, terrestrial or cable. Advertising is forbidden, with no exceptions.

OT - FM aerial



 
 
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  #11  
Old December 12th 06, 07:29 PM posted to uk.tech.digital-tv
Mark Carver
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Posts: 7,633
Default OT - FM aerial

Max Demian wrote:
"Nigel Cliffe" wrote in message
...
Tim.. wrote:
Thanks for the info so far so good...

The next question is.... which direction do I point it in?! (assuming
rod type)


A simple rod dipole is just stood vertically (vertical polarisation).
There isn't any "direction" about it.


Isn't VHF/FM broadcast with horizontal polarisation any more?


The BBC upgraded almost all of their transmissions to 'Mixed Polarisation'
during the 1980s and early 90s. They now have horizontal and vertical
components, so horizontally polarised receiving aerials were not affected.

Commercial radio used mixed or in some cases circular from the outset in 1973.

However recently built (mid 90s onwards) BBC and commercial radio FM
transmitters often employ vertical polarisation, I think because the Tx
antennas are easier (read cheaper) to mount on the masts ?


--
Mark
Please replace invalid and invalid with gmx and net to reply.
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  #12  
Old December 12th 06, 07:56 PM posted to uk.tech.digital-tv
tony sayer
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Posts: 5,001
Default OT - FM aerial

In article , Mark Carver
writes
Max Demian wrote:
"Nigel Cliffe" wrote in message
...
Tim.. wrote:
Thanks for the info so far so good...

The next question is.... which direction do I point it in?! (assuming
rod type)


A simple rod dipole is just stood vertically (vertical polarisation).
There isn't any "direction" about it.


Isn't VHF/FM broadcast with horizontal polarisation any more?


The BBC upgraded almost all of their transmissions to 'Mixed Polarisation'
during the 1980s and early 90s. They now have horizontal and vertical
components, so horizontally polarised receiving aerials were not affected.

Commercial radio used mixed or in some cases circular from the outset in 1973.

However recently built (mid 90s onwards) BBC and commercial radio FM
transmitters often employ vertical polarisation, I think because the Tx
antennas are easier (read cheaper) to mount on the masts ?


Cheaper, some site operators charge a fortune for individual aerials



--
Tony Sayer

  #13  
Old December 12th 06, 07:59 PM posted to uk.tech.digital-tv
tony sayer
external usenet poster
 
Posts: 5,001
Default OT - FM aerial

In article , Tim.. the.farm.ha
writes

"Chris" wrote in message
.. .
OOn Tue, 12 Dec 2006 16:24:54 -0000, "Paul D.Smith"
wrote:

The basic advice was "don't use the circular ones, they're rubbish". I
eventually put up a simple verticle dipole (antiference I think) but then


I agree with this but a lot depends on where you live. It probably
makes sense to put up an aerial that is OK for FM and DAB if that
proves possible. See this URL for some general advice on DAB:
http://www.wohnort.org/DAB/aerials.html

This is a link to an specialist aerial wholesaler that I have used who
also sells retail including mail order: http://www.scantec.org.uk/



Thanks for the info so far so good...

The next question is.... which direction do I point it in?! (assuming rod
type)

Same as TV (sutton coldfield- but about 50miles away - there are closer
analogue TX's but none which are outputting digital TV..

Tim..



You point your FM aerial a three element or more Yagi array either an
Antiference or Triax to the appropriate FM transmitter for your area.

Then you point your TV aerial at the right DTV transmitter. Not all FM
and DTV stations are co-sited.

Dab.. Is it even worth bothering about other than for reception on
portables with 2" speakers?..
--
Tony Sayer

  #14  
Old December 12th 06, 08:32 PM posted to uk.tech.digital-tv
Tim..
external usenet poster
 
Posts: 16
Default OT - FM aerial


"tony sayer" wrote in message
...
In article , Tim.. the.farm.ha
writes

"Chris" wrote in message
. ..
OOn Tue, 12 Dec 2006 16:24:54 -0000, "Paul D.Smith"
wrote:

The basic advice was "don't use the circular ones, they're rubbish". I
eventually put up a simple verticle dipole (antiference I think) but
then

I agree with this but a lot depends on where you live. It probably
makes sense to put up an aerial that is OK for FM and DAB if that
proves possible. See this URL for some general advice on DAB:
http://www.wohnort.org/DAB/aerials.html

This is a link to an specialist aerial wholesaler that I have used who
also sells retail including mail order: http://www.scantec.org.uk/



Thanks for the info so far so good...

The next question is.... which direction do I point it in?! (assuming rod
type)

Same as TV (sutton coldfield- but about 50miles away - there are closer
analogue TX's but none which are outputting digital TV..

Tim..



You point your FM aerial a three element or more Yagi array either an
Antiference or Triax to the appropriate FM transmitter for your area.

Then you point your TV aerial at the right DTV transmitter. Not all FM
and DTV stations are co-sited.

Dab.. Is it even worth bothering about other than for reception on
portables with 2" speakers?..



Ok, That little lot has explained afair bit.

I think I shall test out a 3 or 5 bar Yagi from the afforementioned firm
pointed at sutton (we have line of sight, despite the distance) on its own
fly lead for the moment. Then possibly go to the extreme of combining it
with the DTV signal down the same cable.

Cheers all.

Tim..


  #15  
Old December 12th 06, 09:12 PM posted to uk.tech.digital-tv
Nigel Cliffe
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Posts: 68
Default OT - FM aerial

Max Demian wrote:
"Nigel Cliffe" wrote in message
...
Tim.. wrote:
Thanks for the info so far so good...

The next question is.... which direction do I point it in?!
(assuming rod type)


A simple rod dipole is just stood vertically (vertical polarisation).
There isn't any "direction" about it.


Isn't VHF/FM broadcast with horizontal polarisation any more?


Most BBC transmitters have been both horizontal and vertical for more than a
decade. Not sure about the commercial ones.

I read it was to help car reception (vertical aerials), but might be
transmitter costs as others indicated.


- Nigel


--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/


  #16  
Old December 12th 06, 09:18 PM posted to uk.tech.digital-tv
Nigel Cliffe
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Posts: 68
Default OT - FM aerial

john wrote:
"Nigel Cliffe" wrote in message
...
Tim.. wrote:


The next question is.... which direction do I point it in?!
(assuming rod type)


A simple rod dipole is just stood vertically (vertical polarisation).
There isn't any "direction" about it.


You can make it more directional by spacing it at a correct distance
from a mast - so the mast acts as a reflector along the full length
of the dipole. That will give a heart shaped pattern known as
cardioid.



Good point. And even without that trick, the mounting has some impact on
reception.


Don't buy a cheap aerial from the likes of B&Q as the cable is
attached around the top of a self tapping screw which goes through
the plastic and element!
It's a poor design as water gets inside and corrodes the connections.
Then it will run down your coax. Give it six months and your
reception will be poor.



Or put cheapy B&Q aerial in the loft, where water shouldn't be a problem,
and it will work fine for years :-)
I have one doing just that.


I agree about their problems outside.


- Nigel


--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/


  #17  
Old December 13th 06, 12:38 AM posted to uk.tech.digital-tv
Paul Ratcliffe
external usenet poster
 
Posts: 2,486
Default OT - FM aerial

On Tue, 12 Dec 2006 19:41:01 +0000 (GMT), charles
wrote:

Use a decent dipole, cover the end of the coax inside the connection
point in self amalgamating tape were you split the inner core from the
braid, then waterproof with grease after making the connections. Centre
to the element pointing up and braid pointing down.


That doesn't sound like a decent dipole - no balun :-(


Agreed, but who makes decent Band II aerials? I want one...
  #18  
Old December 13th 06, 12:41 AM posted to uk.tech.digital-tv
Bill Wright
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Posts: 8,408
Default OT - FM aerial


"Tim.." wrote in message
...
I think I shall test out a 3 or 5 bar Yagi from the afforementioned firm
pointed at sutton (we have line of sight, despite the distance)


You're barmy using a big FM aerial somewhere where you have LOS to a
powerful transmitter.

Bill


  #19  
Old December 13th 06, 12:42 AM posted to uk.tech.digital-tv
Bill Wright
external usenet poster
 
Posts: 8,408
Default OT - FM aerial


"Nigel Cliffe" wrote in message
...
Max Demian wrote:
Most BBC transmitters have been both horizontal and vertical for more than
a decade. Not sure about the commercial ones.



Peterboro' was vertical for years, then it was horizontal (and a bit bent).

Bill


  #20  
Old December 13th 06, 09:12 AM posted to uk.tech.digital-tv
tony sayer
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Posts: 5,001
Default OT - FM aerial


Ok, That little lot has explained afair bit.

I think I shall test out a 3 or 5 bar Yagi from the afforementioned firm
pointed at sutton (we have line of sight, despite the distance) on its own
fly lead for the moment. Then possibly go to the extreme of combining it
with the DTV signal down the same cable.


Run separate cables if you can.. combine if you absolutely cannot!..

Can you say where you are or postcode even?..
Cheers all.

Tim..



--
Tony Sayer

 




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