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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 UK Hi-Fi History



 
 
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  #11  
Old November 13th 16, 09:22 AM posted to uk.tech.digital-tv
Ian Jackson[_5_]
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Posts: 42
Default OT UK Hi-Fi History

In message , Mark Carver
writes
On 12/11/2016 12:49, Ian Jackson wrote:
In message ,
Graham. writes
I just read about the Wrotham AM vs FM Band II tests. What was the
radiated bandwith for AM?
More generally, what was the radiated bandwith for 405 line TV sound?
I assume it was rather more than 9 kHz, but I really don't know.


I believe that New Zealand was rather slow in introducing FM. The reason
was because it was considered that AM could probably provide an adequate
service. As they were so remote from the rest of the world, they could
transmit wideband Hi-Fi AM with little risk of causing interference to
anyone else.


AM in the US has a 10 kHz bandwidth, always has done. It sounds very
good, in fact better than some of our UK FM stations that insist upon
driving themselves into distortion, and compressing down to about 3dB
of dynamic range.

The USA is, in certain respects, similar to NZ.

Historically, one administration has been in charge of frequency
allocations for the whole country, and arranged that there was
more-than-adequate frequency spacing between transmitters in similar
geographical locations.

Also, to reduce their out-of-area signal strength, some transmitters go
to low-power during the night-time.

This means that the normal listener is probably never going to find a
strong interfering signal only 10kHz away - and, potentially, this
enables a higher upper-frequency limit for transmitter modulation, and
broader IF bandwidths of receivers.
--
Ian
  #12  
Old November 13th 16, 02:17 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 1,915
Default OT UK Hi-Fi History

On 13/11/2016 09:54, Alan White wrote:
On Sun, 13 Nov 2016 09:37:39 +0000 (GMT), charles
wrote:

ISTR that the pre-emphasis on FM was different on the two sides of the
Altantic.


It was. 75 microseconds here, 50 microseconds there, or the other way
around.


That was broadcast wasn't it? I don't know about CB.

Bill
  #13  
Old November 13th 16, 03:31 PM posted to uk.tech.digital-tv
Mark Carver[_2_]
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Posts: 322
Default OT UK Hi-Fi History

On 13/11/2016 09:56, Ian Jackson wrote:


Broadcast FM radio is indeed slightly different (75us in the USA, and
50us in most of the rest of the world) -


Also, as I discovered only recently, the reason *all* US FM
transmissions are on 'odd' numbered allocations (88.1, 88.3,
88.5....... etc) is to avoid producing any 'taboo' allocations
due to the 10.7 MHz IF image.


--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #14  
Old November 13th 16, 04:56 PM posted to uk.tech.digital-tv
tony sayer
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Posts: 4,978
Default OT UK Hi-Fi History

In article ,
Graham. scribeth thus
I just read about the Wrotham AM vs FM Band II tests. What was the radiated
bandwith for AM?


More generally, what was the radiated bandwith for 405 line TV sound? I assume
it was rather more than 9 kHz, but I really don't know.


ISTR it was up to 15 kHz just because it was AM didn't limit the
bandwidth but i suspect as ever it was down to whatever GPO line was
feeding it..

--
Tony Sayer



  #15  
Old November 13th 16, 05:16 PM posted to uk.tech.digital-tv
Mark Carver[_2_]
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Posts: 322
Default OT UK Hi-Fi History

On 13/11/2016 17:56, tony sayer wrote:
In article ,
Graham. scribeth thus
I just read about the Wrotham AM vs FM Band II tests. What was the radiated
bandwith for AM?


More generally, what was the radiated bandwith for 405 line TV sound? I assume
it was rather more than 9 kHz, but I really don't know.


ISTR it was up to 15 kHz just because it was AM didn't limit the
bandwidth but i suspect as ever it was down to whatever GPO line was
feeding it..


It probably only as high as 15 kHz, once UHF had started, and SiS
implemented, and that signal used to feed the 405 line Txs !


--
Mark
Please replace invalid and invalid with gmx and net to reply.
  #16  
Old November 13th 16, 07:01 PM posted to uk.tech.digital-tv
Ian Jackson[_5_]
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Posts: 42
Default OT UK Hi-Fi History

In message , Bill Wright
writes
On 13/11/2016 09:54, Alan White wrote:
On Sun, 13 Nov 2016 09:37:39 +0000 (GMT), charles
wrote:

ISTR that the pre-emphasis on FM was different on the two sides of the
Altantic.


It was. 75 microseconds here, 50 microseconds there, or the other way
around.


That was broadcast wasn't it? I don't know about CB.

I doubt if there is any standard for CB.
--
Ian
  #17  
Old November 13th 16, 09:00 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Posts: 509
Default OT UK Hi-Fi History

On Sunday, 13 November 2016 20:01:46 UTC, Ian Jackson wrote:
In message , Bill Wright
writes
On 13/11/2016 09:54, Alan White wrote:
On Sun, 13 Nov 2016 09:37:39 +0000 (GMT), charles
wrote:

ISTR that the pre-emphasis on FM was different on the two sides of the
Altantic.

It was. 75 microseconds here, 50 microseconds there, or the other way
around.


That was broadcast wasn't it? I don't know about CB.

I doubt if there is any standard for CB.
--
Ian


I used to have a license for it and there certainly is.
  #18  
Old November 13th 16, 09:33 PM posted to uk.tech.digital-tv
Ian Jackson[_5_]
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Posts: 42
Default OT UK Hi-Fi History

In message , R.
Mark Clayton writes
On Sunday, 13 November 2016 20:01:46 UTC, Ian Jackson wrote:
In message , Bill Wright
writes
On 13/11/2016 09:54, Alan White wrote:
On Sun, 13 Nov 2016 09:37:39 +0000 (GMT), charles
wrote:

ISTR that the pre-emphasis on FM was different on the two sides of the
Altantic.

It was. 75 microseconds here, 50 microseconds there, or the other way
around.


That was broadcast wasn't it? I don't know about CB.

I doubt if there is any standard for CB.
--
Ian


I used to have a license for it and there certainly is.


I did a quick Google, and thought that ETSI EN 300 433 V2.1.1 (2016-05)
might apply.
http://bit.ly/2g47VO2
I've had a look at section 6.5.3 "Angle modulation (FM modulation with
Preemphasis/Deemphasis)", but I can't say I understand what it really
means. It seems to be more a test set-up rather than a spec.

This document is just as vague:
http://bit.ly/2g4cOqs
--
Ian
 




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