AVR-Chat

RS232C is such that if the voltage swings +/- 6V it is in compliance.

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----- Original Message -----

But may receivers will work at a swing of 0 to 5 volts.

stevech@san.rr.com wrote:
> *RS232C is such that if the voltage swings +/- 6V it is in compliance.*

Peter Gargano
--
Tech Edge Pty. Ltd.    http://techedge.com.au     http://WBo2.com
ph : (02) 6251 5519    Int'l : +612 6251 5519     Fax : +612 6251 0558
Street addr : 37 Jalanga Cres.,  Aranda,  ACT 2614, Australia
Postal addr : PO Box 288, Jamison Centre, ACT 2614

Peter Gargano wrote:
> stevech@san.rr.com wrote:
> 
>>*RS232C is such that if the voltage swings +/- 6V it is in compliance.*
 >
 > But may receivers will work at a swing of 0 to 5 volts.
 >

Maybe, but what about max speed reliability? Negative drive removes transistor
base charge faster.

That was funny Russ, this may be more true of a mosfet's gate charge, 
not a bipolar which works quite a bit differently (minority carrier 
charge, electron holes, etc). Anyway, what speed are we talking about? 
100Mhz? 10Mhz? 1Mhz? The speeds that RS-232 operate at can be handled 
easily by the slowest of the slow transistors.

Have you seen the reverse diode across the base emitter? This would 
clamp the voltage to -0.3V internally anyway.

Engineers are people that get their hands dirty, right? Ok then, how 
about hooking-up a scope to the receiver and driving it at say 115.2K 
via a quick and dirty 100K series pot so that you can vary the input 
voltage. This will confirm the reliable turn-on threshold and by placing 
a series diode you can cutout the negative transition (although this is 
not as good as 0-5V drive) to confirm that part too. If a diode is used 
then it really needs a 1K pull-down resistor after it.

Since I suggested this and since I design all kinds of coms gear anyway, 
I will run some real tests and post the results to settle this matter in 
a less academic but in a more "engineer" like manner.

*Peter*


Russell Shaw wrote:

> Peter Gargano wrote:
>> stevech@san.rr.com wrote:
>>
>>> *RS232C is such that if the voltage swings +/- 6V it is in compliance.*
>  >
>  > But may receivers will work at a swing of 0 to 5 volts.
>  >
>
> Maybe, but what about max speed reliability? Negative drive removes transistor
> base charge faster.

On Dec 15, 2005, at 4:07 PM, stevech@san.rr.com wrote:

> RS232C is such that if the voltage swings +/- 6V it is in compliance.

No, 3 volts positive/negative is the minimum specification. Six volts  
provides one with a comfortable margin.

In practice many receivers accept anything under 0.25 and anything  
over 3.0 so 0.25 to 3.0 is the "no man's land" while the spec says -3  
to +3 is the undefined region.

I have never seen a so-called RS-232 implementation that required  
more than 3 volts if the ground was connected correctly between the  
two systems.

--
David Kelly N4HHE, dkelly@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.

Peter Jakacki wrote:
> Russell Shaw wrote:
> 
>>Peter Gargano wrote:
>>
>>>stevech@san.rr.com wrote:
>>>
>>>>*RS232C is such that if the voltage swings +/- 6V it is in compliance.*
>>
>> > But may receivers will work at a swing of 0 to 5 volts.
>>
>>Maybe, but what about max speed reliability? Negative drive removes transistor
>>base charge faster.
 >
 > That was funny Russ, this may be more true of a mosfet's gate charge,
 > not a bipolar which works quite a bit differently (minority carrier
 > charge, electron holes, etc).

If you know how BJTs work, you'll know about stored base charge in saturated
switching.

 > Anyway, what speed are we talking about?
 > 100Mhz? 10Mhz? 1Mhz? The speeds that RS-232 operate at can be handled
 > easily by the slowest of the slow transistors.

Well, old technology without a baker clamp or gold-doped switching
transistors (or a homebrew job) may use an NPN common-emitter input
transistor like a BC548 (Beta=300, ft=300MHz etc).

If this was driven with ~5V via a 10k resistor (with a base-emitter diode),
the stored charge would be atleast 68pC, excluding depletion
capacitances and excess storage in the base-collector epitaxial layer.
The input thresh-hold would be ~0.7V.

Now with 0V applied, the base charge can only be removed by 0.7V
across 10k. The switch-off delay-time is then ~1us. 115200 baud is 8.7us/bit.

Not all logic pulls down to ground or to supply, so the RS232 drive
could be 0.8V->3.3V (TTL: http://www.interfacebus.com/voltage_threshold.html)
which makes it impossible at any speed. If the pull-down voltage was more
typically 0.5V, that would be a delay time of 3.4us. The noise margin is
ratshit too.

 > Have you seen the reverse diode across the base emitter? This would
 > clamp the voltage to -0.3V internally anyway.

Only after the stored base charge is rapidly removed.

 > Engineers are people that get their hands dirty, right? Ok then, how
 > about hooking-up a scope to the receiver and driving it at say 115.2K
 > via a quick and dirty 100K series pot so that you can vary the input
 > voltage. This will confirm the reliable turn-on threshold and by placing
 > a series diode you can cutout the negative transition (although this is
 > not as good as 0-5V drive) to confirm that part too. If a diode is used
 > then it really needs a 1K pull-down resistor after it.

It would be advisable to use a 1k shunt if you were attempting unipolar drive
anyway.

 > Since I suggested this and since I design all kinds of coms gear anyway,
 > I will run some real tests and post the results to settle this matter in
 > a less academic but in a more "engineer" like manner.

I never "tinker" things into existance, which is *not* engineering.
I write electronics simulation software and did a masters research
degree that included radio-frequency transistor measurement, modelling, and
circuit simulation on both BJTs and mosfets. After that, i designed and
built radio-link fading simulators. I'm an analog/radio-frequency designer,
and only got into software and computer hardware by necessity.

-- 
Russell Shaw, B.Eng, M.Eng(Research)

Ok, this is good, it's getting meaty and I like some of your figures. 
This only takes into account a discrete BC548 and not the typical input 
transistor of the receiver which also happens to be buffered by two 
other transistors in typical inverter follower fashion.

Anyway, I enjoyed you reply and I will get back to the group with some 
observations. I question a lot of the standards in the same way I 
questions rules that require they be followed although the reasons for 
them have long since faded. Observe the principle first and the rules 
take care of themselves. Principles are hard to enforce which is why 
people make rules. Principles don't change but rules do, although they 
can be real slow to catch-up at times.

Tinkering things into existence is not the name of the game but 
tinkering them out is. This way you know where the fall-off area is and 
allow a comfortable margin. Ideally this could be designed and simulated 
but you know for the same reason that you can design and manufacture a 
BC548 that there are also BC547s and 549s, although they are the same 
transistor. Due to manufacturing tolerances these parts would fail the 
desired spec yet are "tinkered" as alternate types.

Sometimes it's not about margins but about knowing what is redundant and 
clearing away the clutter. There are a lot of things about 232 including 
the standard itself that are redundant and I get very tired of people 
quoting the decades old rules that applied back then without taking 
current usage into account. Sub 120K low-speed short-range coms to a PC 
needs high plus and minus volts??? ...come on, nobody but nobody designs 
like this except to keep the voices happy.


*Peter*


Russell Shaw wrote:

> Peter Jakacki wrote:
>> Russell Shaw wrote:
>>
>>> Peter Gargano wrote:
>>>
>>>> stevech@san.rr.com wrote:
>>>>
>>>>> *RS232C is such that if the voltage swings +/- 6V it is in compliance.*
>>>> But may receivers will work at a swing of 0 to 5 volts.
>>> Maybe, but what about max speed reliability? Negative drive removes transistor
>>> base charge faster.
>  >
>  > That was funny Russ, this may be more true of a mosfet's gate charge,
>  > not a bipolar which works quite a bit differently (minority carrier
>  > charge, electron holes, etc).
>
> If you know how BJTs work, you'll know about stored base charge in saturated
> switching.
>
>  > Anyway, what speed are we talking about?
>  > 100Mhz? 10Mhz? 1Mhz? The speeds that RS-232 operate at can be handled
>  > easily by the slowest of the slow transistors.
>
> Well, old technology without a baker clamp or gold-doped switching
> transistors (or a homebrew job) may use an NPN common-emitter input
> transistor like a BC548 (Beta=300, ft=300MHz etc).
>
> If this was driven with ~5V via a 10k resistor (with a base-emitter diode),
> the stored charge would be atleast 68pC, excluding depletion
> capacitances and excess storage in the base-collector epitaxial layer.
> The input thresh-hold would be ~0.7V.
>
> Now with 0V applied, the base charge can only be removed by 0.7V
> across 10k. The switch-off delay-time is then ~1us. 115200 baud is 8.7us/bit.
>
> Not all logic pulls down to ground or to supply, so the RS232 drive
> could be 0.8V->3.3V (TTL: http://www.interfacebus.com/voltage_threshold.html)
> which makes it impossible at any speed. If the pull-down voltage was more
> typically 0.5V, that would be a delay time of 3.4us. The noise margin is
> ratshit too.
>
>  > Have you seen the reverse diode across the base emitter? This would
>  > clamp the voltage to -0.3V internally anyway.
>
> Only after the stored base charge is rapidly removed.
>
>  > Engineers are people that get their hands dirty, right? Ok then, how
>  > about hooking-up a scope to the receiver and driving it at say 115.2K
>  > via a quick and dirty 100K series pot so that you can vary the input
>  > voltage. This will confirm the reliable turn-on threshold and by placing
>  > a series diode you can cutout the negative transition (although this is
>  > not as good as 0-5V drive) to confirm that part too. If a diode is used
>  > then it really needs a 1K pull-down resistor after it.
>
> It would be advisable to use a 1k shunt if you were attempting unipolar drive
> anyway.
>
>  > Since I suggested this and since I design all kinds of coms gear anyway,
>  > I will run some real tests and post the results to settle this matter in
>  > a less academic but in a more "engineer" like manner.
>
> I never "tinker" things into existance, which is *not* engineering.
> I write electronics simulation software and did a masters research
> degree that included radio-frequency transistor measurement, modelling, and
> circuit simulation on both BJTs and mosfets. After that, i designed and
> built radio-link fading simulators. I'm an analog/radio-frequency designer,
> and only got into software and computer hardware by necessity.
>

Peter Jakacki wrote:
> Ok, this is good, it's getting meaty and I like some of your figures. 
> This only takes into account a discrete BC548 and not the typical input 
> transistor of the receiver which also happens to be buffered by two 
> other transistors in typical inverter follower fashion.
> 
> Anyway, I enjoyed you reply and I will get back to the group with some 
> observations. I question a lot of the standards in the same way I 
> questions rules that require they be followed although the reasons for 
> them have long since faded. Observe the principle first and the rules 
> take care of themselves. Principles are hard to enforce which is why 
> people make rules. Principles don't change but rules do, although they 
> can be real slow to catch-up at times.
> 
> Tinkering things into existence is not the name of the game but 
> tinkering them out is. This way you know where the fall-off area is and 
> allow a comfortable margin. Ideally this could be designed and simulated 
> but you know for the same reason that you can design and manufacture a 
> BC548 that there are also BC547s and 549s, although they are the same 
> transistor. Due to manufacturing tolerances these parts would fail the 
> desired spec yet are "tinkered" as alternate types.
> 
> Sometimes it's not about margins but about knowing what is redundant and 
> clearing away the clutter. There are a lot of things about 232 including 
> the standard itself that are redundant and I get very tired of people 
> quoting the decades old rules that applied back then without taking 
> current usage into account. Sub 120K low-speed short-range coms to a PC 
> needs high plus and minus volts??? ...come on, nobody but nobody designs 
> like this except to keep the voices happy.

Unless the RS232 line is driven with an open collector/drain output stage
which guarantees close to 0V, i'd not trust even the fastest most modern
RS232 receiver to be reliable. The other problem is that the fastest most
modern RS232 receiver is extra sensitive to line noise when you have a
low switching margin.

Unless you can guarantee that the input transistor has an adequate shunt
base-emitter resistor instead of a diode, unipolar drive will mean the
speed performance of the RS232 receiver will always be in an all warrantees
void area of the data sheet, which should never be allowed.

Ahhh...isn't good that we finally no longer have AVR problems,
Studio problems, JTAG, Programmers etc.. It does get a little
boring doesn't it :-)

Well if you have nothing to do and since it is Friday (Sydney time)
you may want to try out my new Message Station software which has
been re written using VB2005 instead of Delphi (sorry Delphians :-(
but Borland's price for D2006 was prohibitive).

It will need the new .NET 2 framework for it to install which you can
download from M$ (link provided, 24Mb download, or the setup program will
try and do it for you) and the application is downloadable from the
download page of my updated website (only 230Kb). The application will
communicate with our standard RS485 protocol in 9 bit MPCM mode or
simple ASCII terminated with a carriage return.

I would be interested on feedback as far as downloading and install issues,
if any, as this is my first venture in providing software over the website.

By the way if anyone want to use Visual Basic 2005 (VB2005 express ) it is
now a free download from M$ untill Dec. 2006 and if you register before then
it is free for life. I paid AU$467.00 for the Visual Studio Standard which
allows me to develop applications in Visual Basic, Java, Visual C++ 
and Visual C#.

I would have loved to stay with Delphi but financial issues prevailed.

I will remove the older version from the files section of this site.



Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Email: john@ampertronics.com.au
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
********************************************************

Russell Shaw wrote:

> Peter Jakacki wrote:
> > Ok, this is good, it's getting meaty and I like some of your figures.
> > This only takes into account a discrete BC548 and not the typical input
> > transistor of the receiver which also happens to be buffered by two
> > other transistors in typical inverter follower fashion.

[excess text removed for brevity]

> > Sometimes it's not about margins but about knowing what is redundant 
> and
> > clearing away the clutter. There are a lot of things about 232 
> including
> > the standard itself that are redundant and I get very tired of people
> > quoting the decades old rules that applied back then without taking
> > current usage into account. Sub 120K low-speed short-range coms to a PC
> > needs high plus and minus volts??? ...come on, nobody but nobody 
> designs
> > like this except to keep the voices happy.
> Unless the RS232 line is driven with an open collector/drain output stage
> which guarantees close to 0V, i'd not trust even the fastest most modern
> RS232 receiver to be reliable. The other problem is that the fastest most
> modern RS232 receiver is extra sensitive to line noise when you have a
> low switching margin.


   And, looking at the time when EIA RS-232 was originated, and 
realizing the state of electronic conponents bavk then, it is the noise 
margins that explain the high voltage requirements of the standard.  +/- 
15 VDC wasn't all that radical, considering that noise immunity sucked, 
and noise impulses were often (as measured in practice, not 
theoretically) measured in the 5-10 Volt range.  Given modern components 
and circuit layout techniques, of course noise margins are smaller. 

  One wonders what the engineers who develoiped the RS-232 
recommendation (it is a 'recommendation, *NOT* a "standard, after 
all...RS standing for "Recommended Standard") would have though of the 
LVD transmissioon schemes so common today.  +/- .7 volts!!!   Your 
signal would disappear into the noise!   *grin*

Tom

Thomas Keller wrote:
> Russell Shaw wrote:
> 
>>Peter Jakacki wrote:
>>
>>>Ok, this is good, it's getting meaty and I like some of your figures.
>>>This only takes into account a discrete BC548 and not the typical input
>>>transistor of the receiver which also happens to be buffered by two
>>>other transistors in typical inverter follower fashion.
> 
> [excess text removed for brevity]
> 
>>>Sometimes it's not about margins but about knowing what is redundant 
>>and clearing away the clutter. There are a lot of things about 232 
>>including the standard itself that are redundant and I get very tired of people
>>>quoting the decades old rules that applied back then without taking
>>>current usage into account. Sub 120K low-speed short-range coms to a PC
>>>needs high plus and minus volts??? ...come on, nobody but nobody 
>>designs like this except to keep the voices happy.
>>
>>Unless the RS232 line is driven with an open collector/drain output stage
>>which guarantees close to 0V, i'd not trust even the fastest most modern
>>RS232 receiver to be reliable. The other problem is that the fastest most
>>modern RS232 receiver is extra sensitive to line noise when you have a
>>low switching margin.
> 
>    And, looking at the time when EIA RS-232 was originated, and 
> realizing the state of electronic conponents back then, it is the noise 
> margins that explain the high voltage requirements of the standard.  +/- 
> 15 VDC wasn't all that radical, considering that noise immunity sucked, 
> and noise impulses were often (as measured in practice, not 
> theoretically) measured in the 5-10 Volt range.  Given modern components 
> and circuit layout techniques, of course noise margins are smaller.

It is no different now than then. Back then, RS232 was run around and
between buildings for terminals and mainframes. If you still want to
run those distances, you'll want +/-15V.

>   One wonders what the engineers who developed the RS-232 
> recommendation (it is a 'recommendation, *NOT* a "standard, after 
> all...RS standing for "Recommended Standard") would have thought of the 
> LVDS transmissioon schemes so common today.  +/- .7 volts!!!   Your 
> signal would disappear into the noise!   *grin*

LVDS only works over a few metres length without repeaters and
equalizers. RS232 can do a few km.

There is much less ground noise in the ~400MHz LVDS frequency range and the
short cable lengths it was designed for, and it is differential mode as well.
LVDS is double-terminated 50ohm transmission line, so there is significant
signalling current that is hard for stray electric fields to affect much.
Plus the sync preamble allows the serdes PLL to lock, and a slowish PLL loop
also averages noise jitter. RS232 is a much higher impedance system ~5kohms.

http://www.edn.com/article/CA6288038.html
http://focus.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=SLLA120

Russell Shaw wrote:
> Thomas Keller wrote:
> 
>>Russell Shaw wrote:
>>
...
> LVDS only works over a few metres length without repeaters and
> equalizers. RS232 can do a few km.
> 
> There is much less ground noise in the ~400MHz LVDS frequency range and the
> short cable lengths it was designed for, and it is differential mode as well.
> LVDS is double-terminated 50ohm transmission line,

Correction: 100ohm differential line.

http://www.fairchildsemi.com/an/AN/AN-5017.pdf

Russell Shaw wrote:
>
> It is no different now than then. Back then, RS232 was run around and
> between buildings for terminals and mainframes. If you still want to
> run those distances, you'll want +/-15V.

No, it is different and that is just the point. Nobody runs RS-232 
between buildings, do you? If we don't go as far as using fibre then we 
would use a balanced line drive like RS-422, but never ever RS-232. Yes, 
I still want to run those distance, but no, I am not stuck in the 60's 
because I use RS-422/485 or some other means.

*Peter*

If you don't design to meet the standard, how can you assure your thing will
interoperate, widely? Geesh. Get off the soap box.

-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Peter Jakacki
Sent: Thursday, December 15, 2005 6:29 PM
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] Re: PC COM Ports

Ok, this is good, it's getting meaty and I like some of your figures. 
This only takes into account a discrete BC548 and not the typical input 
transistor of the receiver which also happens to be buffered by two 
other transistors in typical inverter follower fashion.

Anyway, I enjoyed you reply and I will get back to the group with some 
observations. I question a lot of the standards in the same way I 
questions rules that require they be followed although the reasons for 
them have long since faded. Observe the principle first and the rules 
take care of themselves. Principles are hard to enforce which is why 
people make rules. Principles don't change but rules do, although they 
can be real slow to catch-up at times.

Tinkering things into existence is not the name of the game but 
tinkering them out is. This way you know where the fall-off area is and 
allow a comfortable margin. Ideally this could be designed and simulated 
but you know for the same reason that you can design and manufacture a 
BC548 that there are also BC547s and 549s, although they are the same 
transistor. Due to manufacturing tolerances these parts would fail the 
desired spec yet are "tinkered" as alternate types.

Sometimes it's not about margins but about knowing what is redundant and 
clearing away the clutter. There are a lot of things about 232 including 
the standard itself that are redundant and I get very tired of people 
quoting the decades old rules that applied back then without taking 
current usage into account. Sub 120K low-speed short-range coms to a PC 
needs high plus and minus volts??? ...come on, nobody but nobody designs 
like this except to keep the voices happy.


*Peter*


Russell Shaw wrote:
> Peter Jakacki wrote:
>> Russell Shaw wrote:
>>
>>> Peter Gargano wrote:
>>>
>>>> stevech@san.rr.com wrote:
>>>>
>>>>> *RS232C is such that if the voltage swings +/- 6V it is in
compliance.*
>>>> But may receivers will work at a swing of 0 to 5 volts.
>>> Maybe, but what about max speed reliability? Negative drive removes
transistor
>>> base charge faster.
>  >
>  > That was funny Russ, this may be more true of a mosfet's gate charge,
>  > not a bipolar which works quite a bit differently (minority carrier
>  > charge, electron holes, etc).
>
> If you know how BJTs work, you'll know about stored base charge in
saturated
> switching.
>
>  > Anyway, what speed are we talking about?
>  > 100Mhz? 10Mhz? 1Mhz? The speeds that RS-232 operate at can be handled
>  > easily by the slowest of the slow transistors.
>
> Well, old technology without a baker clamp or gold-doped switching
> transistors (or a homebrew job) may use an NPN common-emitter input
> transistor like a BC548 (Beta=300, ft=300MHz etc).
>
> If this was driven with ~5V via a 10k resistor (with a base-emitter
diode),
> the stored charge would be atleast 68pC, excluding depletion
> capacitances and excess storage in the base-collector epitaxial layer.
> The input thresh-hold would be ~0.7V.
>
> Now with 0V applied, the base charge can only be removed by 0.7V
> across 10k. The switch-off delay-time is then ~1us. 115200 baud is
8.7us/bit.
>
> Not all logic pulls down to ground or to supply, so the RS232 drive
> could be 0.8V->3.3V (TTL:
http://www.interfacebus.com/voltage_threshold.html)
> which makes it impossible at any speed. If the pull-down voltage was more
> typically 0.5V, that would be a delay time of 3.4us. The noise margin is
> ratshit too.
>
>  > Have you seen the reverse diode across the base emitter? This would
>  > clamp the voltage to -0.3V internally anyway.
>
> Only after the stored base charge is rapidly removed.
>
>  > Engineers are people that get their hands dirty, right? Ok then, how
>  > about hooking-up a scope to the receiver and driving it at say 115.2K
>  > via a quick and dirty 100K series pot so that you can vary the input
>  > voltage. This will confirm the reliable turn-on threshold and by
placing
>  > a series diode you can cutout the negative transition (although this is
>  > not as good as 0-5V drive) to confirm that part too. If a diode is used
>  > then it really needs a 1K pull-down resistor after it.
>
> It would be advisable to use a 1k shunt if you were attempting unipolar
drive
> anyway.
>
>  > Since I suggested this and since I design all kinds of coms gear
anyway,
>  > I will run some real tests and post the results to settle this matter
in
>  > a less academic but in a more "engineer" like manner.
>
> I never "tinker" things into existance, which is *not* engineering.
> I write electronics simulation software and did a masters research
> degree that included radio-frequency transistor measurement, modelling,
and
> circuit simulation on both BJTs and mosfets. After that, i designed and
> built radio-link fading simulators. I'm an analog/radio-frequency
designer,
> and only got into software and computer hardware by necessity.
>   




 
Yahoo! Groups Links

Peter Jakacki wrote:
> Russell Shaw wrote:
> 
>>It is no different now than then. Back then, RS232 was run around and
>>between buildings for terminals and mainframes. If you still want to
>>run those distances, you'll want +/-15V.
> 
> No, it is different and that is just the point. Nobody runs RS-232 
> between buildings, do you? If we don't go as far as using fibre then we 
> would use a balanced line drive like RS-422, but never ever RS-232. Yes, 
> I still want to run those distance, but no, I am not stuck in the 60's 
> because I use RS-422/485 or some other means.

I run rs232 from my workroom to the garage (30m).

At my previous job, rs232 was run from the lab to various measuring equipment
outside (10-20m).

I know of several radio hams that run rs232 from their radio room to things
outside and up radio towers (10-30m).

RS232 was designed for unterminated lines which keeps things simple,
especially for multi-drop star networks. RS485 requires a single backbone
with terminator.

RS232 can be fed thru radio coax and separated out with a filter, unlike
rs485 which requires a balanced line.

http://www.rs485.com/rs485spec.html

RS485 requires three wires but rs232 only needs two.

Well I don't mind having conversations with Luddites but I really don't 
expect them to be any different either. I do design to meet the 
standard, I have to, but it doesn't mean I agree with it. How do 
standards get set and how do they get updated unless people actually 
question the standards?

These forums are our soap boxes, if we have something relevant to say 
then we should say it, shouldn't we? It would be oh so boring if we all 
meekly shut-up and just quietly ate our gruel.

*Peter*



stevech wrote:
> If you don't design to meet the standard, how can you assure your thing will
> interoperate, widely? Geesh. Get off the soap box.

On Dec 16, 2005, at 7:51 PM, Peter Jakacki wrote:

> Well I don't mind having conversations with Luddites but I really  
> don't
> expect them to be any different either. I do design to meet the
> standard, I have to, but it doesn't mean I agree with it. How do
> standards get set and how do they get updated unless people actually
> question the standards?

The wonderful thing about standards is there are so many to choose  
from there is at least one that says whatever you did/want is the  
standard.

--
David Kelly N4HHE, dkelly@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.

At 12:27 PM 17/12/2005, you wrote:
>RS485 requires three wires but rs232 only needs two.

??? How do you figure that? Let's see RS232 minimum Tx,Rx and
return ground. RS485 data+, data-  and return ground. If you
use a transformer coupled RS485 you don't need ground (2 wires)

Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Email: john@ampertronics.com.au
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
********************************************************

John Samperi wrote:
> At 12:27 PM 17/12/2005, you wrote:
> 
>>RS485 requires three wires but rs232 only needs two.
> 
> ??? How do you figure that? Let's see RS232 minimum Tx,Rx and
> return ground.

Uni-directional or half-duplex (with tristate TX) only needs two wires.
Full duplex requires three.

 > RS485 data+, data-  and return ground. If you
> use a transformer coupled RS485 you don't need ground (2 wires)

Russell Shaw wrote:
> I run rs232 from my workroom to the garage (30m).
I'm sorry to hear that, I'd do the same if I had nothing else. I would 
use RS-422 (not 485) "IF" I needed higher baud rates. The cables are 
usually 4-core + shield so I would not be at any loss. Termination is 
really only needed for high-speed operation as the reflections have 
negligible effect at RS-232 speeds anyway. I've run kilometres of 
cabling in skyscrapers with simple multi-node 19.2K RS-485 networking 
over untwisted fire-proof cabling without the "need" for termination 
even though the cables were not in any ordered configuration. Impossible 
with RS-232.
>
> At my previous job, rs232 was run from the lab to various measuring equipment
> outside (10-20m).
>
> I know of several radio hams that run rs232 from their radio room to things
> outside and up radio towers (10-30m).
>
> RS232 was designed for unterminated lines which keeps things simple,
> especially for multi-drop star networks. RS485 requires a single backbone
> with terminator.
RS-232 is not multidrop and at the low speeds it operates at would not 
need termination.
>
> RS232 can be fed thru radio coax and separated out with a filter, unlike
> rs485 which requires a balanced line.
Cool, I like that, but is it really real RS-232 anymore? (I think not)

>
> http://www.rs485.com/rs485spec.html
>
> RS485 requires three wires but rs232 only needs two.

Place a 1.5V battery across the balanced line to generate a signal, then 
reverse it to invert the signal. Did it require a separate ground? No! 
It is out of ignorance that a ground is connected, it is simply provided 
either for additional shielding or for kludging a particularly bad 
ground loop problem. By powering the remote equipment from the line it 
obviates the need for isolation.

Anyway, I like the fact that you are not strictly abiding by the 
standard and doing what engineers do best .... tinkering ;)


*Peter*

Peter Jakacki wrote:
> Russell Shaw wrote:
> 
>>I run rs232 from my workroom to the garage (30m).
> 
> I'm sorry to hear that, I'd do the same if I had nothing else. I would 
> use RS-422 (not 485) "IF" I needed higher baud rates. The cables are 
> usually 4-core + shield so I would not be at any loss. Termination is 
> really only needed for high-speed operation as the reflections have 
> negligible effect at RS-232 speeds anyway. I've run kilometres of 
> cabling in skyscrapers with simple multi-node 19.2K RS-485 networking 
> over untwisted fire-proof cabling without the "need" for termination 
> even though the cables were not in any ordered configuration. Impossible 
> with RS-232.

Non-termination of such long lengths and of uncontrolled impedance
characteristics is asking for trouble. I'd only do that if i verified
the received waveform with a cro.

>>At my previous job, rs232 was run from the lab to various measuring equipment
>>outside (10-20m).
>>
>>I know of several radio hams that run rs232 from their radio room to things
>>outside and up radio towers (10-30m).
>>
>>RS232 was designed for unterminated lines which keeps things simple,
>>especially for multi-drop star networks. RS485 requires a single backbone
>>with terminator.
> 
> RS-232 is not multidrop and at the low speeds it operates at would not 
> need termination.

There are tristate rs232 chips for doing multidrop.

>>RS232 can be fed thru radio coax and separated out with a filter, unlike
>>rs485 which requires a balanced line.
> 
> Cool, I like that, but is it really real RS-232 anymore? (I think not)

Using RF chokes and isolating caps, the coax looks like normal wire.

>>http://www.rs485.com/rs485spec.html
>>
>>RS485 requires three wires but rs232 only needs two.
> 
> Place a 1.5V battery across the balanced line to generate a signal, then 
> reverse it to invert the signal. Did it require a separate ground? No! 
> It is out of ignorance that a ground is connected, it is simply provided 
> either for additional shielding or for kludging a particularly bad 
> ground loop problem. By powering the remote equipment from the line it 
> obviates the need for isolation.

This is the root cause of unreliable comms.

                  long wire-pair
Box_A <======================================> Box_B
   |                                              |
   | Each box 3kohms common-mode Z to ground      |
   |                                              |
  --- case-ground       Several square           ---
  --- capacitance       metres loop area         ---
   |                                              |
   |   conductive ground/soil/floor/wiring        |
--+----------------<-Ignd->----------------------+--
                      Ignd: ground-current

Your receivers are highly vulnerable to having their common-mode
voltage range exceeded by voltage drop caused by ground-current,
and loop voltage induced by fluctuating magnetic field within
the loop area. Higher-frequency noise will have more effect
because the case capacitance impedes less and the loop voltage
is proportional to magnetic field rate of change. It is highly
susceptable to long-distance lightning interference.

Ground wire *must* be used for reliability.

> Anyway, I like the fact that you are not strictly abiding by the 
> standard and doing what engineers do best .... tinkering ;)

I always work with known and bounded parameters. Never "tinker".

Russell Shaw wrote:

> Peter Jakacki wrote:
> > Russell Shaw wrote:
> >>It is no different now than then. Back then, RS232 was run around and
> >>between buildings for terminals and mainframes. If you still want to
> >>run those distances, you'll want +/-15V
> > No, it is different and that is just the point. Nobody runs RS-232
> > between buildings, do you? If we don't go as far as using fibre then we
> > would use a balanced line drive like RS-422, but never ever RS-232. 
> Yes,
> > I still want to run those distance, but no, I am not stuck in the 60's
> > because I use RS-422/485 or some other means.
> I run rs232 from my workroom to the garage (30m).

  Perhaps so.  That doesn't make your practice reasonable.

> At my previous job, rs232 was run from the lab to various measuring 
> equipment
> outside (10-20m).

  Poor engineering management?

> I know of several radio hams that run rs232 from their radio room to 
> things
> outside and up radio towers (10-30m).


  With all due respect to radio amateurs, who, as a group, have 
contributed greatly to the advancment of communications technology, they 
*ARE*, by self-definition, amateurs, after all.

> RS232 was designed for unterminated lines which keeps things simple,
> especially for multi-drop star networks. RS485 requires a single backbone
> with terminator.
> RS232 can be fed thru radio coax and separated out with a filter, unlike
> rs485 which requires a balanced line.
> http://www.rs485.com/rs485spec.html
> RS485 requires three wires but rs232 only needs two.


  Not the last time I looked.  Unless you are making a unidirectional 
connection, you need at LEAST 3 wires for a proper RS232-C link.  
Ground, TX and RX.

tom

Thomas Keller wrote:
> Russell Shaw wrote:
> 
>>Peter Jakacki wrote:
>>
>>>Russell Shaw wrote:
>>>
>>>>It is no different now than then. Back then, RS232 was run around and
>>>>between buildings for terminals and mainframes. If you still want to
>>>>run those distances, you'll want +/-15V
>>>
>>>No, it is different and that is just the point. Nobody runs RS-232
>>>between buildings, do you? If we don't go as far as using fibre then we
>>>would use a balanced line drive like RS-422, but never ever RS-232. 
>>
>>Yes,
>>
>>>I still want to run those distance, but no, I am not stuck in the 60's
>>>because I use RS-422/485 or some other means.
>>
>>I run rs232 from my workroom to the garage (30m).
> 
>   Perhaps so.  That doesn't make your practice reasonable.

Why?

>>At my previous job, rs232 was run from the lab to various measuring 
>>equipment outside (10-20m).
> 
>   Poor engineering management?

Why?

>>I know of several radio hams that run rs232 from their radio room to 
>>things outside and up radio towers (10-30m).
> 
>   With all due respect to radio amateurs, who, as a group, have 
> contributed greatly to the advancment of communications technology, they 
> *ARE*, by self-definition, amateurs, after all.

Yes but they do a better job of grounding and interference suppression
than most so called "engineers" that are barely more than tinkerers.

>>RS232 was designed for unterminated lines which keeps things simple,
>>especially for multi-drop star networks. RS485 requires a single backbone
>>with terminator.
>>RS232 can be fed thru radio coax and separated out with a filter, unlike
>>rs485 which requires a balanced line.
>>http://www.rs485.com/rs485spec.html
>>RS485 requires three wires but rs232 only needs two.
> 
>   Not the last time I looked.  Unless you are making a unidirectional 
> connection, you need at LEAST 3 wires for a proper RS232-C link.  
> Ground, TX and RX.

That's what i said before, unless the line is half-duplex.

>> ... Unless you are making a unidirectional
>>connection, you need at LEAST 3 wires for a proper RS232-C link.  
>>Ground, TX and RX.
> That's what i said before, unless the line is half-duplex.

Do you mean unless the line is simplex?


Tom

Russell Shaw wrote:
> Non-termination of such long lengths and of uncontrolled impedance
> characteristics is asking for trouble. I'd only do that if i verified
> the received waveform with a cro.
cro??? Of course I verified it with a scope and though I didn't "need" 
termination I still used it.
>
>>> At my previous job, rs232 was run from the lab to various measuring equipment
>>> outside (10-20m).
>>>
>>> I know of several radio hams that run rs232 from their radio room to things
>>> outside and up radio towers (10-30m).
>>>
>>> RS232 was designed for unterminated lines which keeps things simple,
>>> especially for multi-drop star networks. RS485 requires a single backbone
>>> with terminator.
>> RS-232 is not multidrop and at the low speeds it operates at would not 
>> need termination.
>
> There are tristate rs232 chips for doing multidrop.
Please, I am fairly sure the RS-232 standard does not say multi-drop. I 
have implemented multi-drop RS-232 in the distant past but I have better 
things now. Read what Maxim themselves say (they must know I guess).

"Typical RS-232 transmissions seldom exceed 100 feet for two reasons. 
Firstly, the difference between transmitted levels (±5V) and receive 
levels (±3V) allows only 2V of common-mode rejection. Secondly, the 
distributed capacitance of a longer cable can degrade slew rates by 
exceeding the maximum specified load (2500pF). Because the RS-232 was 
designed as a point-to-point rather than multidrop interface" 
(http://www.maxim-ic.com/appnotes.cfm/appnote_number/723)
>
>>> RS232 can be fed thru radio coax and separated out with a filter, unlike
>>> rs485 which requires a balanced line.
>> Cool, I like that, but is it really real RS-232 anymore? (I think not)
>
> Using RF chokes and isolating caps, the coax looks like normal wire.
I have done similar things myself using inductors and caps to isolate 
signals but I like the way amateurs improvise according to knowledge 
without trying to rigidly adhere to standards for the sake of standards 
(no longer RS-232).

>
> This is the root cause of unreliable comms.
>
>                   long wire-pair
> Box_A <======================================> Box_B
>    |                                              |
>    | Each box 3kohms common-mode Z to ground      |
>    |                                              |
>   --- case-ground       Several square           ---
>   --- capacitance       metres loop area         ---
>    |                                              |
>    |   conductive ground/soil/floor/wiring        |
> --+----------------<-Ignd->----------------------+--
>                       Ignd: ground-current
>
> Your receivers are highly vulnerable to having their common-mode
> voltage range exceeded by voltage drop caused by ground-current,
> and loop voltage induced by fluctuating magnetic field within
> the loop area. Higher-frequency noise will have more effect
> because the case capacitance impedes less and the loop voltage
> is proportional to magnetic field rate of change. It is highly
> susceptable to long-distance lightning interference.
>
> Ground wire *must* be used for reliability.
No, you are assuming that current will flow, I do design professional 
equipment for a living, not just for my garage. If my equipment is not 
line-powered then I like to opto-isolate the 485. How can current flow 
in these two situations??
>
>> Anyway, I like the fact that you are not strictly abiding by the 
>> standard and doing what engineers do best .... tinkering ;)
>
> I always work with known and bounded parameters. Never "tinker".
Call it what you will, this is like the chicken and egg thing. How do 
you know and bound parameters unless you "tinker" in the first place????


*Peter*

Tom Becker wrote:
>  >> ... Unless you are making a unidirectional
> 
>>>connection, you need at LEAST 3 wires for a proper RS232-C link.  
>>>Ground, TX and RX.
>>
>>That's what i said before, unless the line is half-duplex.
> 
> Do you mean unless the line is simplex?

Yes, for simplex which is one-way only, and half-duplex.

Half duplex is when the ends alternate between being a transmitter
or receiver, using the same wire. You need tri-stateable transmitters
for that, and a software protocol. It's usually less hassle just to
use 3 wires and full duplex for 1:1 connections. For a multidrop
half-duplex network, the tristateable method can be used, but you
need to make your own higher current tristateable rs232 transmitters.
I've done that, but it's not very economical for component count and
RS485 would be better. I've also tried the dominant pull-down method
like i2c and canbus, but then that's hardly rs232 anymore.

Russell Shaw wrote:
> Tom Becker wrote:
> 
>> >> ... Unless you are making a unidirectional
>>
>>>>connection, you need at LEAST 3 wires for a proper RS232-C link.  
>>>>Ground, TX and RX.
>>>
>>>That's what i said before, unless the line is half-duplex.
>>
>>Do you mean unless the line is simplex?
> 
> 
> Yes, for simplex which is one-way only, and half-duplex.
> 
> Half duplex is when the ends alternate between being a transmitter
> or receiver, using the same wire. You need tri-stateable transmitters
> for that, and a software protocol. It's usually less hassle just to
> use 3 wires and full duplex for 1:1 connections. For a multidrop
> half-duplex network, the tristateable method can be used, but you
> need to make your own higher current tristateable rs232 transmitters.
> I've done that, but it's not very economical for component count and
> RS485 would be better. I've also tried the dominant pull-down method
> like i2c and canbus, but then that's hardly rs232 anymore.

If you use a max3322, it is tristateable and has 1Meg input impedance,
so you can do multidrop rs232 with standard drive-level transmitters.

http://www.ferret.com.au/articles/67/0c012a67.asp

>>Ground wire *must* be used for reliability.
> 
> No, you are assuming that current will flow, I do design professional 
> equipment for a living, not just for my garage. If my equipment is not 
> line-powered then I like to opto-isolate the 485. How can current flow 
> in these two situations??
> 
>>>Anyway, I like the fact that you are not strictly abiding by the 
>>>standard and doing what engineers do best .... tinkering ;)
>>
>>I always work with known and bounded parameters. Never "tinker".
> 
> Call it what you will, this is like the chicken and egg thing. How do 
> you know and bound parameters unless you "tinker" in the first place????
> 
> 
> *Peter*
> 

I tend to play it safe in the middle, less grief. Eat my gruel, issue my 
invoices, eat.

I Use 232 for short hops & use  full 232 chips from AD or Maxim to spare 
customers the issues with half baked implementations that work with some 
desktops but not all laptops etc.

For 422/485 we always use a ground, as per manufacturers recommendations. 
However if ground lift is a problem then full iso is the way to go.  Nothing 
quite so satisfying as watching your ground lead convert to carbon and copper 
vapour when your data lead is by accident the earth reference for a 30KW 
induction heater and a similar sized pump in a nearby building.  Gives you an 
appreciation of why it is easier to play it safe & not skimp.

As for tinkering, I'm with Pete.  Might start the first 'look' in the sim or 
excel but the reality check is to build one and knock it about on the bench and 
follow it with the CRO. Besides, most of the time the bit you need to use 
doesn't have an accurate model anyway, most sims have a very long way to go yet 
;-) Again, a bit of each.

Using a solely theoretical approach assumes that you have a reasonable command 
of the facts at the time, I don't pretend to be that clever. The tinker approach 
makes no such assumption, it is a journey of exploration which often leads to a 
far greater understanding of both the operation and it's boundaries. Theory must 
also be included or else you are just swanning about on the bosses time.

Peter & I probably agree because we are self employed & make the time to 
explore. If I lose this curiosity, pull what is left of my shiraz soaked brain 
out & put me in sales.

-- 

Cheers  ( Long time no hear Pete ;-)

Don

Peter Jakacki wrote:
> Russell Shaw wrote:
> 
>>Non-termination of such long lengths and of uncontrolled impedance
>>characteristics is asking for trouble. I'd only do that if i verified
>>the received waveform with a cro.
> 
> cro??? Of course I verified it with a scope and though I didn't "need" 
> termination I still used it.

Well if you verified it, that's all that's needed.

>>>>At my previous job, rs232 was run from the lab to various measuring equipment
>>>>outside (10-20m).
>>>>
>>>>I know of several radio hams that run rs232 from their radio room to things
>>>>outside and up radio towers (10-30m).
>>>>
>>>>RS232 was designed for unterminated lines which keeps things simple,
>>>>especially for multi-drop star networks. RS485 requires a single backbone
>>>>with terminator.
>>>
>>>RS-232 is not multidrop and at the low speeds it operates at would not 
>>>need termination.
>>
>>There are tristate rs232 chips for doing multidrop.
> 
> Please, I am fairly sure the RS-232 standard does not say multi-drop. I 
> have implemented multi-drop RS-232 in the distant past but I have better 
> things now. Read what Maxim themselves say (they must know I guess).

The maxim data sheet for max220-max249 say multidrop rs232.
http://www.datasheetcatalog.com/datasheets_pdf/M/A/X/2/MAX232.shtml

> "Typical RS-232 transmissions seldom exceed 100 feet for two reasons. 
> Firstly, the difference between transmitted levels (±5V) and receive 
> levels (±3V) allows only 2V of common-mode rejection. Secondly, the 
> distributed capacitance of a longer cable can degrade slew rates by 
> exceeding the maximum specified load (2500pF). Because the RS-232 was 
> designed as a point-to-point rather than multidrop interface" 
> (http://www.maxim-ic.com/appnotes.cfm/appnote_number/723)

A *long* cable might have 5-10nF of capacitance. A max3322 can
do 5V/us into 5nF, so it does a 10V swing in 2us. Assuming no
overshoot and ringing problems, a 12us cycle should be doable,
which is around 76.8kbaud (i'd usually use less than that).

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3612

>>>>RS232 can be fed thru radio coax and separated out with a filter, unlike
>>>>rs485 which requires a balanced line.
>>>
>>>Cool, I like that, but is it really real RS-232 anymore? (I think not)
>>
>>Using RF chokes and isolating caps, the coax looks like normal wire.
> 
> I have done similar things myself using inductors and caps to isolate 
> signals but I like the way amateurs improvise according to knowledge 
> without trying to rigidly adhere to standards for the sake of standards 
> (no longer RS-232).
> 
> 
>>This is the root cause of unreliable comms.
>>
>>                  long wire-pair
>> Box_A <======================================> Box_B
>>   |                                              |
>>   | Each box 3kohms common-mode Z to ground      |
>>   |                                              |
>>  --- case-ground       Several square           ---
>>  --- capacitance       metres loop area         ---
>>   |                                              |
>>   |  conductive ground/soil/floor/wiring         |
>> --+----------------<-Ignd->----------------------+--
>>                      Ignd: ground-current
>>
>>Your receivers are highly vulnerable to having their common-mode
>>voltage range exceeded by voltage drop caused by ground-current,
>>and loop voltage induced by fluctuating magnetic field within
>>the loop area. Higher-frequency noise will have more effect
>>because the case capacitance impedes less and the loop voltage
>>is proportional to magnetic field rate of change. It is highly
>>susceptable to long-distance lightning interference.
>>
>>Ground wire *must* be used for reliability.
> 
> No, you are assuming that current will flow, I do design professional 
> equipment for a living, not just for my garage. If my equipment is not 
> line-powered then I like to opto-isolate the 485. How can current flow 
> in these two situations??

I assumed you were saying the ground wire was not required even in
non opto-isolated setups. You can still have galvanic isolation, but
excessive capacitive coupling to a common ground can still be a problem,
such as capacitance between windings in mains transformers, and MOVs
that connect PCB ground to mains ground etc. With real optos, the
capacitance is small enough.

>>>Anyway, I like the fact that you are not strictly abiding by the 
>>>standard and doing what engineers do best .... tinkering ;)
>>
>>I always work with known and bounded parameters. Never "tinker".
> 
> Call it what you will, this is like the chicken and egg thing. How do 
> you know and bound parameters unless you "tinker" in the first place????

You always imagine how everything is to work, then design/simulate and build it.
I consider cut-n-try poking at hardware "tinkering", but i do calculations or
simulations to avoid that. All the tinkering should only be during debugging,
finding problems about invalid assumptions and mistakes etc. Simulation is
really tinkering in software, but it has to be done for things not easily
calculable, such as monte-carlo tolerance runs.

On Sun, 18 Dec 2005, Russell Shaw wrote:

> 
> >>I know of several radio hams that run rs232 from their radio room to
> >>things outside and up radio towers (10-30m).
> >
> >   With all due respect to radio amateurs, who, as a group, have
> > contributed greatly to the advancment of communications technology,
> they
> > *ARE*, by self-definition, amateurs, after all.
> 
> Yes but they do a better job of grounding and interference suppression
> than most so called "engineers" that are barely more than tinkerers.
> 

If you take a look at the derivation of the word "amateur", you will see 
"From Latin amator, lover, from amatus, pp. of amare, to love". In other 
words, we participate in the hobby because we love it.

Some of the topnotch EE's in the world are also radio amateurs.  I know 
some engineering companies look on EE's who are also hams as a curse and 
some see them as a blessing.  I myself can't see what is wrong with 
someone who loves the subject of his work so much that he spends most of 
his own spare time at it too.

Zack (W9SZ)

--- In AVR-Chat@yahoogroups.com, Russell Shaw <rjshaw@n...> wrote:
> Yes, for simplex which is one-way only, and half-duplex.

My take is that what you are implementing, with your two wires and
reversing ends, a pair of proprietary modems.  RS232 stops at the DB25
connector to your modem and resumes at the DB25 on the other modem. 
What you do in between is your business - to get the data to the other
end any way you like at whatever speed you can on any number of wires,
or not (pull on a string if you like) - but it is not RS232 again
until you convert whatever you created back to RS232.


Tom

Tom Becker wrote:

> --- In AVR-Chat@yahoogroups.com, Russell Shaw <rjshaw@n...> wrote:
> > Yes, for simplex which is one-way only, and half-duplex.
> My take is that what you are implementing, with your two wires and
> reversing ends, a pair of proprietary modems.  RS232 stops at the DB25
> connector to your modem and resumes at the DB25 on the other modem.
> What you do in between is your business - to get the data to the other
> end any way you like at whatever speed you can on any number of wires,
> or not (pull on a string if you like) - but it is not RS232 again
> until you convert whatever you created back to RS232.

  Yup.  Although I'll quibble with you on one tiny detail.  not 
necessarily a DB25...whatever termination you choose to use.  RS0-232 
can be connected wth DB25, DB9, DB50, DIN6,  a "stereo phone plug," or 
coonductors twisted toigether and covered with masking tape.  Whatevber 
carries the electrical signals into and out of the RS-232 interface 
circuitry.

tom

Amateur radio operator people transmit signals for fun and public service
rather than for profit motives, the latter being what a "professional" radio
operator does. That's the intent of the term amateur radio operator.

Steve (licensed ham since 1963)

-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Zack Widup
Sent: Saturday, December 17, 2005 9:51 PM
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] Re: PC COM Ports

On Sun, 18 Dec 2005, Russell Shaw wrote:

> 
> >>I know of several radio hams that run rs232 from their radio room to
> >>things outside and up radio towers (10-30m).
> >
> >   With all due respect to radio amateurs, who, as a group, have
> > contributed greatly to the advancment of communications technology,
> they
> > *ARE*, by self-definition, amateurs, after all.
> 
> Yes but they do a better job of grounding and interference suppression
> than most so called "engineers" that are barely more than tinkerers.
> 

If you take a look at the derivation of the word "amateur", you will see 
"From Latin amator, lover, from amatus, pp. of amare, to love". In other 
words, we participate in the hobby because we love it.

Some of the topnotch EE's in the world are also radio amateurs.  I know 
some engineering companies look on EE's who are also hams as a curse and 
some see them as a blessing.  I myself can't see what is wrong with 
someone who loves the subject of his work so much that he spends most of 
his own spare time at it too.

Zack (W9SZ)




 
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