A Sky, cable and digital tv forum. Digital TV Banter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » Digital TV Banter forum » Digital TV Newsgroups » uk.tech.digital-tv (Digital TV - General)
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

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.

Crystal Palace Issues



 
 
Thread Tools Display Modes
  #61  
Old April 5th 18, 12:31 PM posted to uk.tech.digital-tv
tony sayer
external usenet poster
 
Posts: 5,001
Default Crystal Palace Issues

In article , Paul Cummins
scribeth thus
In article ,
(Robin) wrote:

Do you happen to know if they've cracked the "[Don't] shoot" issue
when used in "press to talk" mode?


Setup time for a "PTT" call was in the order of tens of millisenconds.


Are you referring to PPT over cellular in the UK?.
--
Tony Sayer



Ads
  #62  
Old April 5th 18, 01:27 PM posted to uk.tech.digital-tv
Terry Casey[_2_]
external usenet poster
 
Posts: 768
Default Crystal Palace Issues

In article ,
says...

In article ,
Terry Casey scribeth thus
In article 20d04a6d-2f35-42ab-92a4-ac6ab5628909
,
says...


But surely a Group A aerial is built to resist receiving UHF 55/56 anyway?


It sure is!

Look at the red line in this graph for the response of a
Group A aerial:

http://aerialsandtv.com/_wp_generate...e4f6_01_1a.jpg


Yess - since when has the Yagi array been known for being a wideband
unit?..


???

So what is /was Group W if not wideband?

--

Terry

---
This email has been checked for viruses by AVG.
http://www.avg.com

  #63  
Old April 5th 18, 02:06 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,448
Default Crystal Palace Issues

On 05/04/2018 12:30, tony sayer wrote:
In article ,
Terry Casey scribeth thus
In article 20d04a6d-2f35-42ab-92a4-ac6ab5628909
@googlegroups.com, says...


But surely a Group A aerial is built to resist receiving UHF 55/56 anyway?


It sure is!

Look at the red line in this graph for the response of a
Group A aerial:

http://aerialsandtv.com/_wp_generate...e4f6_01_1a.jpg


This one is more up to date and is rather less idealised, although it is
still only representative of the concept.


https://www.dropbox.com/s/w0al2rc1jz...n%202.JPG?dl=0

Bill
  #64  
Old April 5th 18, 02:21 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,448
Default Crystal Palace Issues

On 05/04/2018 13:27, Terry Casey wrote:
In article ,
says...

In article ,
Terry Casey scribeth thus
In article 20d04a6d-2f35-42ab-92a4-ac6ab5628909
@googlegroups.com,
says...


But surely a Group A aerial is built to resist receiving UHF 55/56 anyway?


It sure is!

Look at the red line in this graph for the response of a
Group A aerial:

http://aerialsandtv.com/_wp_generate...e4f6_01_1a.jpg


Yess - since when has the Yagi array been known for being a wideband
unit?..


???

So what is /was Group W if not wideband?

I think the point is that yagis are inherently not wideband because they
are tuned. The more the design is modified to widen the bandwidth the
lower the gain and the poorer the directional characteristics. By the
time a yagi has been stretched to cover the full (old) UHF TV band the
performance is really very poor, and in fact at the bottom of the band
the aerial is hardly functioning as a yagi at all, in that the directors
are not contributing to the performance.
So the expression 'wideband yagi' is really not much more than a
marketing term.

Bill
  #65  
Old April 5th 18, 03:52 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
external usenet poster
 
Posts: 573
Default Crystal Palace Issues

Bill Wright wrote:

https://www.dropbox.com/s/w0al2rc1jz...n%202.JPG?dl=0


"typical" 48 element LP?

  #66  
Old April 5th 18, 07:05 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,448
Default Crystal Palace Issues

On 05/04/2018 15:52, Andy Burns wrote:
Bill Wright wrote:

https://www.dropbox.com/s/w0al2rc1jz...n%202.JPG?dl=0


"typical" 48 element LP?


Go on then, what's up with that?

Bill
  #67  
Old April 5th 18, 07:11 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
external usenet poster
 
Posts: 573
Default Crystal Palace Issues

Bill Wright wrote:

Andy Burns wrote:

"typical" 48 element LP?


Go on then, what's up with that?


I can't see anyone selling LP with that many elements ...
  #68  
Old April 5th 18, 07:17 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
external usenet poster
 
Posts: 573
Default Crystal Palace Issues

Andy Burns wrote:

"typical" 48 element LP?


I can't see anyone selling LP with that many elements ...


Even Blake are in two minds about the "double elements" on their LP36T

  #69  
Old April 5th 18, 07:22 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
external usenet poster
 
Posts: 2,448
Default Crystal Palace Issues

On 05/04/2018 19:11, Andy Burns wrote:
Bill Wright wrote:

Andy Burns wrote:

"typical" 48 element LP?


Go on then, what's up with that?


I can't see anyone selling LP with that many elements ...



When UHF TV first started in the UK the aerial manufacturers agreed on a
way to count the elements on each model of aerial. It was very simple.
Each director would count as one. The dipole would count as one. The
reflector or reflectors, be they one or a dozen, would together count as
one. This made perfect sense because some reflector assemblies were made
from rods, some were wire mesh, and some were perforated plates.

Things got slightly more complicated when aerials with bays of two or
four directors appeared. At first there was the suggestion that each bay
should count as one director. That would have made a kind of sense
because although ‘one’ underplays the benefit of a four-director bay,
‘four’ greatly overplays it. However, Jay Beam decided that they would
count every four-director bay as four directors, so they christened
their eleven-bay aerial (for example) the MBM46. MBM was ‘Multibeam’ and
there were eleven bays of four directors making forty-four, plus one
dipole and one reflector. For a while that was that, until the fashion
for huge reflectors started. By that time the UK aerial market was
fragmented and we were importing from just about every European country.
Some manufacturers started counting the reflector rods individually, so
we suddenly had what appeared to be bog-standard 18 element aerials that
allegedly had 24 elements, and 16 bay high gain aerials that were
advertised as having seventy-odd elements.

Log periodic aerials were briefly popular in the 1970s. Logs are made
from a whole lot of driven half-wave dipoles and nothing else, so
element counting should be straightforward; and indeed it was in the
1970s, when Antiference’s 21 element log was called the TS 21. Wideband
reception now having become an almost universal necessity logs are back
in fashion. But since marketing men always over-rule engineers the
modern products have names that exaggerate the element count by a factor
of two, because they count each half of each dipole as one! Thus the XYZ
'46 element log periodic' has twenty-three dipoles. Ridiculous!

Bill
  #70  
Old April 5th 18, 07:27 PM posted to uk.tech.digital-tv
Andy Burns[_12_]
external usenet poster
 
Posts: 573
Default Crystal Palace Issues

Bill Wright wrote:

since marketing men always over-rule engineers the
modern products have names that exaggerate the element count by a factor
of two, because they count each half of each dipole as one!


Ah I didn't realise my DML26 only has 13 elements ...
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT. The time now is 02:33 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.SEO by vBSEO 2.4.0
Copyright 2004-2018 Digital TV Banter.
The comments are property of their posters.