Wireless transmitter
 

On 07/05/2012 08:45, Jim Lesurf wrote:
In raweb.com, Rob
wrote:

It could be a convenient method (for me) of attaching the proper stereo
to the TV system. I'd thought perhaps the technology had actually
'locked down' into something that worked - apparently not then, just yet.

The problem isn't simply a matter of 'technology' as such. It is the
situation:

The problem is that the band/channel being used is also already widely used
for various purposes in a way that includes no 'plan' of who can transmit
how much power from which places. So cross interference becomes a certainty
as the density of users rises. That then at least will degrade the
reliability for any individual user, and either cause pauses or dropouts,
or lower bandwidth to an unacceptable level.

In general, 'broadcasting' and general radio transmission is controlled in
ways designs to avoid cross interference. If someone wants to transmit,
they have to get permission which depends on an assessment of the impact on
other services. But here you end up with 'crowded party' problems - unless
you live well clear of 'competing' users.

FWIW for indoor 'line of sight' you might be better looking to some kind of
near-visible 'optical' system where the transmitter lights up the room in a
modulated way. At least that helps prevent interference from next door. But
of course that won't go though walls, and may be affected by shadowing. I
can't suggest any commercial system, though. Personally, I'm quite happy in
general to use 'wired' systems at home unless there is a specific need to
do otherwise.


OK - thanks for that. By 'technology' I simply meant a wireless method
of relaying sound. After all, radio and TV seem to manage quite well
over many miles. I just wondered if a domestic equivalent had been invented.

Rob

Wireless transmitter
 

On 07/05/2012 13:12, Dave Plowman (News) wrote:
In aweb.com,
wrote:
It'd be nice to have a wireless audio sender/receiver but by no means
necessary.

Well, try it and see. You may be lucky.


No, I think that until it gets better I'll leave it. Thanks anyway.

Rob

Wireless transmitter
 

"Phil Allison" wrote in message
...

"Arny Krueger"
"Rob"
Any opinions on this:

http://www.maplin.co.uk/wireless-pc-...smitter-104993

Would anything be lost over a cable?

In the world of professional audio, wireless connections are considered
to be substandard unless they implement a true diversity reception
system. This means two independent receiving antennas, two independent
receivers, and a detection and logic system that picks the best received
signal at all times. Some of the best systems base the SQ evaluation on
an ultrasonic subcarrier.

Also, the whole system if based on analog (e.g. FM) is surrounded by
companding which can elevate effective dynamic range from about 60 dB to
more like 100 dB.

** OTOH - modern digital communication is almost wholly of the " spread
spectrum " kind and has few if any of the issues that have long plagued
analogue FM systems used by the vast majority of radio mics.

Interesting that the sp,e pf the best 2.4 GHz spread-spectrum-based
equipment uses multiple antennas.

Finally, there should be some kind of frequency mobility so that
interference sources can be completely avoided.

** Frequency hopping does away with that need.

Not entirely.

A single spread spectrum device uses as much bandwidth as the tuneable
frequency range typical, low powered FM audio transmitter.

Right, but the efficiency of spread spectrum gear does decrease if some of
the frequencies that are hopped to are always useless due to a stable
interferring source.

I've been in situations where upwards of a dozen wifi devices operating on
the same channels had useful signal strength at the reception point, and an
additional dozen devices had measurable and/or marginal signal levels. This
lead to an observed situation where the desired access point delivered what
seemed to be acceptable signal levels but a useful connection could not be
maintained.

There are upwards of a dozen identifiable Wifi access points that can be
observed from within my home, some business-related, some clearly home
networks.

From wikipedia:

"Wi-Fi connections can be disrupted or the internet speed lowered by having
other devices in the same area. Many 2.4 GHz 802.11b and 802.11g
access-points default to the same channel on initial startup, contributing
to congestion on certain channels. Wi-Fi pollution, or an excessive number
of access points in the area, especially on the neighboring channel, can
prevent access and interfere with other devices' use of other access points,
caused by overlapping channels in the 802.11g/b spectrum, as well as with
decreased signal-to-noise ratio (SNR) between access points. This can become
a problem in high-density areas, such as large apartment complexes or office
buildings with many Wi-Fi access points.

What you're showing me seems to be a toy, not a professional tool.

** Agreed, but not for the spurious reasons you mention.

Not spurious, but based on a more intense operational environment than you
may be familiar with.

Wireless transmitter
 

In article , Arny
Krueger
wrote:



Right, but the efficiency of spread spectrum gear does decrease if some
of the frequencies that are hopped to are always useless due to a
stable interferring source.

Much the same effect can occur when two (or more) hopping systems try to
use the same band - unless you have a common strategy they can adopt/agree
to avoid each other as they do so. Indeed, when one hopping system
encounters another it can't simply chalk up "avoid slot N" as it can to
avoid clashes with a static transmission in a slot. So adaptive hopping can
actually work better against a static-slot interference than another
transmission that hops in a way it can't predict.

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

Wireless transmitter
 

In article om, Rob
wrote:
On 07/05/2012 08:45, Jim Lesurf wrote:
In raweb.com, Rob
wrote:

FWIW for indoor 'line of sight' you might be better looking to some
kind of near-visible 'optical' system where the transmitter lights up
the room in a modulated way. At least that helps prevent interference
from next door. But of course that won't go though walls, and may be
affected by shadowing. I can't suggest any commercial system, though.
Personally, I'm quite happy in general to use 'wired' systems at home
unless there is a specific need to do otherwise.


OK - thanks for that. By 'technology' I simply meant a wireless method
of relaying sound. After all, radio and TV seem to manage quite well
over many miles.

Only by adopting the agreements/permissions that help them avoid or
minimise interference in a shared channel.

I just wondered if a domestic equivalent had been
invented.

I'm not aware of one. It would require some form of license or permission
from a national (or international) authority and would limit how many
people in a given area could use the system. Cheap domestic systems tend to
rely on a mix of low power, luck, hopping or spreading, and people putting
up with what they get. Some pauses or drops of data rate may be fine for
general computer file transfers. But audio is intolerant of pauses that
cause breaks in the music, and too low a data rate will degrade the result.
So audio is a surprisingly demanding application (in general comms and
computing terms) because of its intolerance to short pauses or breaks.

The alternatives would be ones like the one I mentioned as they would not
cause interference from outside when in a closed room. FWIW I know people
have experimented with 60GHz and 94GHz systems for this precisely to get a
high bandwidth 'indoor' system that would not be affected by neighbours
also using the same system. 60GHz also has the 'advantage' of high air
attenuation so may not make it next door even if it gets out of an open
window! :-)

At present fast modulated IR LEDs are probably a better bet, but I have no
idea if anyone sells these as consumer kit.

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

Wireless transmitter
 

"Arny Krueger"
"Phil Allison"
"Arny Krueger"
"Rob"
Any opinions on this:

http://www.maplin.co.uk/wireless-pc-...smitter-104993

Would anything be lost over a cable?

In the world of professional audio, wireless connections are considered
to be substandard unless they implement a true diversity reception
system. This means two independent receiving antennas, two independent
receivers, and a detection and logic system that picks the best received
signal at all times. Some of the best systems base the SQ evaluation on
an ultrasonic subcarrier.

Also, the whole system if based on analog (e.g. FM) is surrounded by
companding which can elevate effective dynamic range from about 60 dB to
more like 100 dB.


** OTOH - modern digital communication is almost wholly of the " spread
spectrum " kind and has few if any of the issues that have long plagued
analogue FM systems used by the vast majority of radio mics.

Interesting that the sp,e pf the best 2.4 GHz spread-spectrum-based
equipment uses multiple antennas.

** Wanna try that again ???

Red fish on special today where you live Arny?


Finally, there should be some kind of frequency mobility so that
interference sources can be completely avoided.

** Frequency hopping does away with that need.

Not entirely.


** It eliminates signal drops out due to standing waves - which the ONLY
reason FM radio mics employ diversity receiving antennas.


A single spread spectrum device uses as much bandwidth as the tuneable
frequency range typical, low powered FM audio transmitter.

Right, but the efficiency of spread spectrum gear does decrease if some of
the frequencies that are hopped to are always useless due to a stable
interferring source.

** Another very smelly red fish.

Such interference will obviously affect **BOTH** antennas !!!


What you're showing me seems to be a toy, not a professional tool.

** Agreed, but not for the spurious reasons you mention.

Not spurious,

** Utterly WRONG in fact.

As bloody usual.


.... Phil

Wireless transmitter
 

In article ,
Phil Allison wrote:
** It eliminates signal drops out due to standing waves - which the
ONLY reason FM radio mics employ diversity receiving antennas.

You've obviously never used radio mics. Diversity reception can also be
used to vastly increase the coverage range. By using directional aerials
'pointing' in different directions.

--
*The only difference between a rut and a grave is the depth.

Dave Plowman London SW
To e-mail, change noise into sound.

Wireless transmitter
 

"Dave Plowman = Nutcase ****WIT **** "

Phil Allison

** It eliminates signal drops out due to standing waves - which the
ONLY reason FM radio mics employ diversity receiving antennas.


You've obviously never used radio mics.


** You are obviously a ****ing, anencephalic pommy ****.


Diversity reception can also be
used to vastly increase the coverage range.

** Pure idiocy.


By using directional aerials 'pointing' in different directions.


** Pure ****wit insanity.

Get cancer and die ASAP - you revolting, autism ****ED steaming pile of
excrement.



.... Phil

Wireless transmitter
 

"Jim Lesurf" wrote in message
...
In article , Arny
Krueger
wrote:



Right, but the efficiency of spread spectrum gear does decrease if some
of the frequencies that are hopped to are always useless due to a
stable interferring source.

Much the same effect can occur when two (or more) hopping systems try to
use the same band - unless you have a common strategy they can adopt/agree
to avoid each other as they do so.

As a rule wi-fi devices don't have adaptive strategies.

Indeed, when one hopping system
encounters another it can't simply chalk up "avoid slot N" as it can to
avoid clashes with a static transmission in a slot.

Wi fi frequency hopping strategies appear to be simplistic.

So adaptive hopping can
actually work better against a static-slot interference than another
transmission that hops in a way it can't predict.

Right. In some ways Wi Fi is like 10BT ethernet all over again. Its
simplistic strategies and low data rate lead to slow and unreliable
transmission rates due to contention, even when actual usage is relatively
low. Ethernet over wire was somewhat rejuvinated by two order-of-magnitude
increases in basic transmission rates.

Dave Plowman = NUTCASE TROLL
 

Dave Plowman ****ing NUTCASE TROLL


Well, all the mains sockets and lights in your house will have wires going
to them. So the option is to do the same with everything else. Of course
it depends on the design of your house as to how easy this is to do.


** This stinking, know nothing arsehole is a 100% mentally retarded ****.

And Pommyland knows how to breed them by the million.

Killfile the vile scumbag, chase him off the NG.

Or I will.


.... Phil