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A possible replacement for my broken dab aerial....



 
 
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  #11  
Old April 15th 19, 11:19 AM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 3,382
Default A possible replacement for my broken dab aerial....

On 15/04/2019 08:31, Brian Gaff wrote:
When we took down an old fm aerial from the place I used to work, where it
had been up for more years than I care to remember, I took it home and
cleaned it up but was amazed to find that the connections in the folded
dipole were not anything more than braid to one side and inner to the
other. Thus I guess the impedance could be correct due to the reflector and
director lowering it from 300, but it just seems wrong but actually worked
very well.
The proof of the pudding etc.

Brian


There's a slight trade between getting the impedance right and getting
max gain/directivity. Adjustments to parasitic element spacing usually
go for a compromise.

Bill
  #12  
Old April 15th 19, 04:09 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Posts: 797
Default A possible replacement for my broken dab aerial....

On Sunday, 14 April 2019 23:05:05 UTC+1, Ian Jackson wrote:
In message , R.
Mark Clayton writes
On Sunday, 14 April 2019 09:30:38 UTC+1, Andy Burns wrote:
Woody wrote:

Blakes now do a three ele combined VHF/DAB antenna for a very reasonable
price at Toolstation.

I don't read that as a combined DAB/FM aerial, but a choice between an
FM halo (P/N 54217) or a 3-element DAB (P/N 84718)

https://cdn.aws.toolstation.com/catalogue/vcat/TSUK10079/533main.png


Just do what Bill recommended in this group years ago - vertical FM
dipole. As it happens it is a convenient multiple of the DAB
frequencies, so works fine for both.


Unfortunately, the ratio is 2-to-1, which means that at (say) 190MHz on
Band 3, a 95MHz Band 2 aerial is just about as bad a match as it is
possible to be. But, of course, the proof of the pudding's in the
eating.

We don't need external aerials for DAB where we are, but the FM aerial
gets ~40 stations up to 80km away. More distant ones probably
suppressed by FM capture.


As above.


Only use it for FM, all our DAB radios work indoors on their own aerials just fine.

It is just a simple dipole and so omni-directional.

It is the FM halo ones that don't work - wrong polarisation for a start.

--
Ian


  #13  
Old April 15th 19, 04:29 PM posted to uk.tech.digital-tv
Woody[_4_]
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Posts: 2,037
Default A possible replacement for my broken dab aerial....

On Mon 15/04/2019 16:09, R. Mark Clayton wrote:
On Sunday, 14 April 2019 23:05:05 UTC+1, Ian Jackson wrote:
In message , R.
Mark Clayton writes
On Sunday, 14 April 2019 09:30:38 UTC+1, Andy Burns wrote:
Woody wrote:

Blakes now do a three ele combined VHF/DAB antenna for a very reasonable
price at Toolstation.

I don't read that as a combined DAB/FM aerial, but a choice between an
FM halo (P/N 54217) or a 3-element DAB (P/N 84718)

https://cdn.aws.toolstation.com/catalogue/vcat/TSUK10079/533main.png

Just do what Bill recommended in this group years ago - vertical FM
dipole. As it happens it is a convenient multiple of the DAB
frequencies, so works fine for both.


Unfortunately, the ratio is 2-to-1, which means that at (say) 190MHz on
Band 3, a 95MHz Band 2 aerial is just about as bad a match as it is
possible to be. But, of course, the proof of the pudding's in the
eating.

We don't need external aerials for DAB where we are, but the FM aerial
gets ~40 stations up to 80km away. More distant ones probably
suppressed by FM capture.


As above.


Only use it for FM, all our DAB radios work indoors on their own aerials just fine.

It is just a simple dipole and so omni-directional.

It is the FM halo ones that don't work - wrong polarisation for a start.

--



Er, what is the wrong polarisation? A halo is perfectly good for FM but
useless for DAB. Halos don't work for other reasons on FM.

--
Woody

harrogate three at ntlworld dot com
  #14  
Old April 15th 19, 04:53 PM posted to uk.tech.digital-tv
Mark Carver
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Posts: 6,443
Default A possible replacement for my broken dab aerial....

On 15/04/2019 16:29, Woody wrote:

Er, what is the wrong polarisation? A halo is perfectly good for FM but
useless for DAB.


A halo is the wrong polarization for one or two hundred UK FM
transmitters. It's only of any (limited) use for transmitters with a
significant horizontal component. Fine for Holme Moss or Wrotham,
useless for scores of lower power BBC and commercial radio transmitters.

--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #15  
Old April 15th 19, 07:05 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 3,382
Default A possible replacement for my broken dab aerial....

On 15/04/2019 16:53, Mark Carver wrote:
On 15/04/2019 16:29, Woody wrote:

Er, what is the wrong polarisation? A halo is perfectly good for FM
but useless for DAB.


A halo is the wrong polarization for one or two hundred UK FM
transmitters. It's only of any (limited) use for transmitters with a
significant horizontal component. Fine for Holme Moss or Wrotham,
useless for scores of lower power BBC and commercial radio transmitters.

The gain of a halo on HP is -4dBd.

Bill
  #16  
Old April 15th 19, 08:09 PM posted to uk.tech.digital-tv
[email protected]
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Posts: 79
Default A possible replacement for my broken dab aerial....

Have already tried a simple vertical dipole.

All this will get is the northants, HBB, Oxford, digital1, SDL and BBC ensembles.

I am trying to pick up the three London ensembles.

With the old 13 element DAB aerial pointed to zouches farm and bow brickhill (both coincidentally on the same bearing), I could receive the three London ensembles, SDL, dig1, bbc, northants, HBB and Oxford ensembles.

Hence my search for a very directional high gain dab aerial!
  #17  
Old April 15th 19, 08:14 PM posted to uk.tech.digital-tv
[email protected]
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Posts: 79
Default A possible replacement for my broken dab aerial....

I found this on the internet....

https://cpc.farnell.com/vision/v7-006/aerial-dab-log-6/dp/AP02552?mckv=sINrnUVvs_dm|pcrid|224680055011|kword ||match||plid||slid||product|AP02552|pgrid|5101127 7550|ptaid|pla-370876574793|&CMP=KNC-GUK-CPC-SHOPPING&gclid=EAIaIQobChMIjsCWzObS4QIVTLftCh0v1w8 hEAQYBCABEgIEJPD_BwE

Anyone used these?

It struck me that if you happen to have both DAB and horizontally polarised DTT, there could be a market for a combination log periodic, with horizontal elements for DTT and vertical elements for DAB and then split at the wall plate....
  #18  
Old April 17th 19, 10:16 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 7,673
Default A possible replacement for my broken dab aerial....

In the end it will rely on things you can only try. If the side lobes are
similar to the old one then the gain you get in the direction you want will
work by making them stronger than any interference, if not it won't. I'm not
able to deduce if in your location you might get any co channel problems, so
it is I think going to be a suck it and see approach. other than that most
stations now do have an internet feed so missing ones might be easier to
get with a simple cheap amazon echo dot.
Brian

--
----- --
This newsgroup posting comes to you directly from...
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Note this Signature is meaningless.!
wrote in message
...
Have already tried a simple vertical dipole.

All this will get is the northants, HBB, Oxford, digital1, SDL and BBC
ensembles.

I am trying to pick up the three London ensembles.

With the old 13 element DAB aerial pointed to zouches farm and bow
brickhill (both coincidentally on the same bearing), I could receive the
three London ensembles, SDL, dig1, bbc, northants, HBB and Oxford
ensembles.

Hence my search for a very directional high gain dab aerial!



 




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