Loss of Freeview Channels with 4G Mobile

On Mon, 19 Nov 2012 14:07:07 +0000 (GMT), Jim Lesurf
wrote:

In article , Bill Wright
wrote:
Jim Lesurf wrote:

As it is, it seems crazy to me for OfCom to dream that using ch60
makes sense when 4G is in operation. Makes the whole issue far harder
to deal with.
Why have they done that? It's very strange.

Beats me. I can only assume that the suits who agreed the details are
innocent of any real understanding of practical RF. So they assume a
1MHz-ish gap will be fine. To an accountant thinking of selling spectrum on
a MHz/quid basis a gap looks like a 'wasted asset' I guess.


AIUI there was *a lot* of pressure from the Treasury to maximise the
'digital dividend' and it would have been hard for Ofcom to resist
fitting in the maximum possible channels.

In message , Woody
writing at 20:49:34 in his/her local time
opines:-
"Steve Terry" wrote in message
...
Woody wrote:
I just can't seem to get 'Y2K' out of my mind.
I wonder why?

I'm wondering why you're comparing Oranges with Apples?

There's not a single analogy with Y2K and randomly transmitting
on 700 to 800MHz affecting UHF TV

The analogy was that everyone was worried silly about Y2K and the
end of the World as we know it - and what happened. Essentially
nowt.

'Essentially nowt' happened only because every live COBOL programmer in
the land, and some who had to be specially disinterred for the purpose,
spent about a year and thousands of pounds putting the CC back into the
YYMMDD dates that had been used in programs in the 60s and 70s, to save
thousands of pounds on memory and storage.

(It was popularly supposed, at the time those programs were written,
that by the year 2000 the computers themselves would be writing the
programs, and more effectively and efficiently too).

However, I see no teams beavering away on avoiding this new Armageddon,
while many teams are beavering away on bringing it about :-(

I have already said that my opinion puts me firmly in the
'unlikely' camp.

I'm waiting for the musical - '4G and Bust'

--
Roy Brown 'Have nothing in your houses that you do not know to be
Kelmscott Ltd useful, or believe to be beautiful' William Morris

On Mon, 19 Nov 2012 20:49:34 -0000, Woody
wrote:

There's not a single analogy with Y2K and randomly transmitting
on 700 to 800MHz affecting UHF TV

The analogy was that everyone was worried silly about Y2K and the
end of the World as we know it - and what happened. Essentially
nowt.

Nothing much happened on the day because lots of people had done lots
of work beforehand to find and fix the problems BEFORE they happened.
Are you and others really that stupid to think that nothing happened
at all?

In article , Woody
scribeth thus
[snip]
Well they should able to cope with that sort of channel spacing
PMR
equipment does. What shouldn't happen is another TX go out of
params
that much and be left like that!...


[snip]

When you fit a 19" rack mount Tx which has a cooling fan
protruding on the front panel, then secure the rack by closing a
door which has no ventilation at that height the thing cooks -
and what happens when a Tx (in this case 100W) cooks.........?

Thats an excellent example of **** poor installation;!.

Ought to be bought to the attention of Ofcom's field staff.

|When its doing what it didna oughta again....





--
Tony Sayer

"Woody" wrote:

A bit tight that, but after a fashion it can be done.

I have a paging customer with a private paging system in the
153MHz general paging band. They suffer horrendous RFI from
another national paging organisation 50KHz away when their Tx's
overheat and go a tad dirty.

We got some crystal filters made in the States - last order was
$240 apiece for a dozen - but they are 40dB down on one side
50KHz away and 60dB or more down on the other side 200KHz away.
Only downside is 6dB insertion loss. They are about 3" long and
1" sq with a BNC on each end.

So yes it can be done - at a price.


1. Being "a tad dirty" implies the other organisation's transmitter
(which you said is 50kHz away) is spreading onto your customer's own
frequency. How does _any_ filter fitted to your receivers help under
these circumstances? It's at the transmitter where a filter would be
effective (or better still, a transmitter that didn't go a tad dirty
when hot!)

2. You have pagers with BNC antenna sockets?

--
Chris

In message , at 20:11:59 on Sun, 18 Nov
2012, Steve Terry remarked:
You seem to have completely forgot that you, your neighbours,
and people walking by will all be using phones on 4g. Many within
50 feet or less of your TV.

Isn't the problem people walking within a few feet of the front end of
the TV aerials? Watch out for chimney sweeps with phones!
--
Roland Perry

In message , at 20:49:34 on Mon, 19
Nov 2012, Woody remarked:
The analogy was that everyone was worried silly about Y2K and the
end of the World as we know it - and what happened. Essentially
nowt.

That's because a lot of people did a lot of work (and replaced a great
deal of equipment before they would otherwise have done).
--
Roland Perry

In article , Roland Perry
wrote:
In message , at 20:11:59 on Sun, 18 Nov
2012, Steve Terry remarked:
You seem to have completely forgot that you, your neighbours, and
people walking by will all be using phones on 4g. Many within 50 feet
or less of your TV.

Isn't the problem people walking within a few feet of the front end of
the TV aerials? Watch out for chimney sweeps with phones!

I *knew* there was a reason we abandoned sending young lads up chimneys.
They would only use their mobiles up there to watch HDTV!

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

On Tue, 20 Nov 2012 06:42:36 +0000, Chris Kirby
wrote:

"Woody" wrote:

A bit tight that, but after a fashion it can be done.

I have a paging customer with a private paging system in the
153MHz general paging band. They suffer horrendous RFI from
another national paging organisation 50KHz away when their Tx's
overheat and go a tad dirty.

We got some crystal filters made in the States - last order was
$240 apiece for a dozen - but they are 40dB down on one side
50KHz away and 60dB or more down on the other side 200KHz away.
Only downside is 6dB insertion loss. They are about 3" long and
1" sq with a BNC on each end.

So yes it can be done - at a price.


1. Being "a tad dirty" implies the other organisation's transmitter
(which you said is 50kHz away) is spreading onto your customer's own
frequency. How does _any_ filter fitted to your receivers help under
these circumstances? It's at the transmitter where a filter would be
effective (or better still, a transmitter that didn't go a tad dirty
when hot!)

2. You have pagers with BNC antenna sockets?

Read the thread.

Roland Perry wrote:
In message , at 20:11:59 on Sun, 18 Nov
2012, Steve Terry remarked:
You seem to have completely forgot that you, your neighbours,
and people walking by will all be using phones on 4g. Many within
50 feet or less of your TV.

Isn't the problem people walking within a few feet of the front end of
the TV aerials? Watch out for chimney sweeps with phones!

Not if you have a sharp bandpass filter at the TV, the problem will
be how much screening the TV itself will have to inband signals.

When I wipe out my freeview STB with my 430MHz handheld in
the house, it's not RF getting into the aerial outside.

Steve Terry
--
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