Modem question

Hello,

what a maximum range is possible for 4800bps full duplex wire (a pair of 
0.9 mmm wires) modem ?

Regards

Roman Rumian

Roman Rumian wrote:
> Hello,
> 
> what a maximum range is possible for 4800bps full duplex wire (a pair of 
> 0.9 mmm wires) modem ?

What is the footage of the bobbin ?

VLV

On 09/07/2010 05:55 AM, Roman Rumian wrote:
> Hello,
>
> what a maximum range is possible for 4800bps full duplex wire (a pair of
> 0.9 mmm wires) modem ?

What standard?  How noisy is the environment?

For a custom made modem, with a comm format tailored to be whatever it 
takes, just name your distance and start counting your money.

Specific modem standards (i.e. ITU-T V.29) will have specific 
characteristics, but even those will have performance that varies wildly 
with the quality of the installation of the wire.  If you use one of the 
telephone specifications and you put it on telephone-grade wire with a 
telephone-grade installation, you should be able to make it work over 
many miles.

Your best bet is to either look around the web, ask on a group where 
folks actually use modems instead of trading information on how best to 
design them, or attempt to buy a modem with a guarantee of how long a 
wire it'll work on.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On 09/07/2010 05:55 AM, Roman Rumian wrote:
> Hello,
>
> what a maximum range is possible for 4800bps full duplex wire (a pair of
> 0.9 mmm wires) modem ?

What standard?  How noisy is the environment?

For a custom made modem, with a comm format tailored to be whatever it 
takes, just name your distance and start counting your money.

Specific modem standards (i.e. ITU-T V.29) will have specific 
characteristics, but even those will have performance that varies wildly 
with the quality of the installation of the wire.  If you use one of the 
telephone specifications and you put it on telephone-grade wire with a 
telephone-grade installation, you should be able to make it work over 
many miles.

Your best bet is to either look around the web, ask on a group where 
folks actually use modems instead of trading information on how best to 
design them, or attempt to buy a modem with a guarantee of how long a 
wire it'll work on.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On 09/07/2010 05:55 AM, Roman Rumian wrote:
> Hello,
>
> what a maximum range is possible for 4800bps full duplex wire (a pair of
> 0.9 mmm wires) modem ?

What standard?  How noisy is the environment?

For a custom made modem, with a comm format tailored to be whatever it 
takes, just name your distance and start counting your money.

Specific modem standards (i.e. ITU-T V.29) will have specific 
characteristics, but even those will have performance that varies wildly 
with the quality of the installation of the wire.  If you use one of the 
telephone specifications and you put it on telephone-grade wire with a 
telephone-grade installation, you should be able to make it work over 
many miles.

Your best bet is to either look around the web, ask on a group where 
folks actually use modems instead of trading information on how best to 
design them, or attempt to buy a modem with a guarantee of how long a 
wire it'll work on.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Hi Tim,

W dniu 2010-09-07 22:01, Tim Wescott pisze:
(...)
>> what a maximum range is possible for 4800bps full duplex wire (a pair of
>> 0.9 mmm wires) modem ?
>
> What standard?

No standard, or anyone fitting the need.

> How noisy is the environment?

It's hard to say. We have 20+ kilometers of wire pair, and the customer 
wants to have duplex transmission at minimum 4800bps.
Thirst idea is to measure frequency characteristic of this pair.
Probably it is also possible to drive that pair with high amplitude 
signals (24 volts or more) to have better SNR.

> For a custom made modem, with a comm format tailored to be whatever it
> takes, just name your distance and start counting your money.
>
> Specific modem standards (i.e. ITU-T V.29) will have specific
> characteristics, but even those will have performance that varies wildly
> with the quality of the installation of the wire. If you use one of the
> telephone specifications and you put it on telephone-grade wire with a
> telephone-grade installation, you should be able to make it work over
> many miles.

How many ?
Have found two pairs modem for 19200bps at distance 20+ miles (36km), 
but we have only one pair.
I am searching for ready to use device/algorithm/solution, as I prefer 
other type of DSP development activity (professional audio). ;-)

> Your best bet is to either look around the web, ask on a group where
> folks actually use modems instead of trading information on how best to
> design them, or attempt to buy a modem with a guarantee of how long a
> wire it'll work on.

Agree.

Many thanks for your answer Tim. :-)

Best regards

Roman Rumian

Vladimir,

I do not understand your question.

Regards

Roman Rumian


W dniu 2010-09-07 21:40, Vladimir Vassilevsky pisze:
>
>
> Roman Rumian wrote:
>> Hello,
>>
>> what a maximum range is possible for 4800bps full duplex wire (a pair
>> of 0.9 mmm wires) modem ?
>
> What is the footage of the bobbin ?
>
> VLV
>

Hi Tim,

W dniu 2010-09-07 22:01, Tim Wescott pisze:
(...)
>> what a maximum range is possible for 4800bps full duplex wire (a pair of
>> 0.9 mmm wires) modem ?
>
> What standard?

No standard, or anyone fitting the need.

> How noisy is the environment?

It's hard to say. We have 20+ kilometers of wire pair, and the customer 
wants to have duplex transmission at minimum 4800bps.
First idea is to measure frequency characteristic of this pair.
Probably it is also possible to drive that pair with high amplitude 
signals (24 volts or more) to have better SNR.

> For a custom made modem, with a comm format tailored to be whatever it
> takes, just name your distance and start counting your money.
>
> Specific modem standards (i.e. ITU-T V.29) will have specific
> characteristics, but even those will have performance that varies wildly
> with the quality of the installation of the wire. If you use one of the
> telephone specifications and you put it on telephone-grade wire with a
> telephone-grade installation, you should be able to make it work over
> many miles.

How many ?
Have found two pairs modem for 19200bps at distance 20+ miles (36km), 
but we have only one pair.
I am searching for ready to use device/algorithm/solution, as I prefer 
other type of DSP development activity (professional audio). ;-)

> Your best bet is to either look around the web, ask on a group where
> folks actually use modems instead of trading information on how best to
> design them, or attempt to buy a modem with a guarantee of how long a
> wire it'll work on.

Agree.

Many thanks for your answer Tim. :-)

Best regards

Roman Rumian

On Tue, 07 Sep 2010 22:36:51 +0200, Roman Rumian
<rumian.wytnij.@agh.edu.pl> wrote:

>Hi Tim,
>
>W dniu 2010-09-07 22:01, Tim Wescott pisze:
>(...)
>>> what a maximum range is possible for 4800bps full duplex wire (a pair of
>>> 0.9 mmm wires) modem ?
>>
>> What standard?
>
>No standard, or anyone fitting the need.

A very basic approach:

Figure out how much power the wires will transfer without melting,
then back the power off to achieve however much safety factor you want
for the system.

That'll provide a benchmark for the max transmit power.

Then sort out how much interference, cross talk, and noise the wires
will be susceptible to along the way.  That'll depend on what sorts of
shielding the wire has, twists, etc.   That'll give you an idea of the
interference power levels.

Then sort out the Noise Figure of your receiver design.

Once you have those, you can get a rough estimate of the maximum range
possible.

>
>> How noisy is the environment?
>
>It's hard to say. We have 20+ kilometers of wire pair, and the customer 
>wants to have duplex transmission at minimum 4800bps.
>Thirst idea is to measure frequency characteristic of this pair.
>Probably it is also possible to drive that pair with high amplitude 
>signals (24 volts or more) to have better SNR.

Yes.

>> For a custom made modem, with a comm format tailored to be whatever it
>> takes, just name your distance and start counting your money.
>>
>> Specific modem standards (i.e. ITU-T V.29) will have specific
>> characteristics, but even those will have performance that varies wildly
>> with the quality of the installation of the wire. If you use one of the
>> telephone specifications and you put it on telephone-grade wire with a
>> telephone-grade installation, you should be able to make it work over
>> many miles.
>
>How many ?
>Have found two pairs modem for 19200bps at distance 20+ miles (36km), 
>but we have only one pair.
>I am searching for ready to use device/algorithm/solution, as I prefer 
>other type of DSP development activity (professional audio). ;-)

If you want to use existing equipment then you're at the mercy of the
performance of whatever equipment you want to use.   You'll need the
specs of candidate equipment, including max Tx power, etc.

To get full duplex, though, you need to find something that does TDD
or FDD within the capabilities of the wire.


>> Your best bet is to either look around the web, ask on a group where
>> folks actually use modems instead of trading information on how best to
>> design them, or attempt to buy a modem with a guarantee of how long a
>> wire it'll work on.
>
>Agree.
>
>Many thanks for your answer Tim. :-)
>
>Best regards
>
>Roman Rumian

Much will depend on the wire and where you're putting it, so don't
expect any guarantees from manufacturers.   If the line is susceptible
to interference it'll degrade performance substantially.


Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com

What you need is called a modem for physical lines. Those modems can 
push ~100kbit/s through the dedicated physical pair at the distances of 
several hundreds km. They are quite expensive, too.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com


Roman Rumian wrote:

> Vladimir,
> 
> I do not understand your question.
> 
> Regards
> 
> Roman Rumian
> 
> 
> W dniu 2010-09-07 21:40, Vladimir Vassilevsky pisze:
> 
>>
>>
>> Roman Rumian wrote:
>>
>>> Hello,
>>>
>>> what a maximum range is possible for 4800bps full duplex wire (a pair
>>> of 0.9 mmm wires) modem ?
>>
>>
>> What is the footage of the bobbin ?
>>
>> VLV
>>
>