12 Sep
2002
12 Sep
'02
2:02 p.m.
From: "Jeffrey Sharp"
<lists(a)subatomix.com>
On Friday, September 6, 2002, Davison, Lee wrote:
>
> > That's not true. Serial cable can go for a good many feet before
> > the signal breaks down (someone should pipe in with actual data ;)
>
> 450 feet at 9600 bps through multi strand sheilded cable. This was
between
two buildings
and ran through a drain to get under a road. 19200 bps was
tried but was error prone. dropping the speed to 9600 bps worked.
100 feet at 115200 bps through three unshielded wires, wrapped around a
three-foot-tall Jacob's ladder apparatus enclosed in plexiglass. No bit
errors. We gave up and decided to build a device to simulate bit errors.
12 Sep
12 Sep
4:19 p.m.
--- "Dwight K. Elvey" <dwightk.elvey(a)amd.com> wrote:
That's why they built this device I have - a BERT - Bit Error Rate
Tester(?) You hook two serial devices to it and crank the knobs
to inject errors. It can insert as few as 1 error per 1E06 bits
passed through, IIRC.
It's excellent for testing error recovery schemes, V.whatever as well
as those in the protocol stacks. We used it for testing our Bisync
products for proper packet retranmission behavior on noisy lines.
i.e. - to verify that we implemented the HASP protocol correctly
(since one of our advertised features was that our HASP engine did
all the error detection/retransmission, presenting clean blocks of
data to the PDP-11/VAX, reducing its overhead).
-ethan
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From:
"Jeffrey Sharp" <lists(a)subatomix.com>
100 feet at 115200 bps through three unshielded wires, wrapped around a
three-foot-tall Jacob's ladder apparatus enclosed in plexiglass. No bit
errors. We gave up and decided to build a device to simulate bit errors.
Hi Jeffrey
What makes you think that wrapped on the outside of a Jacob's
ladder has either the right coupling or the right frequency
spectrum to effect a RS-232 signal? Arbitrary test like this are
not real world test and only impress those that don't understand
what it takes to interfer with a particular signaling method. 
16 Sep
16 Sep
4:08 a.m.
On Thursday, September 12, 2002, Dwight K. Elvey wrote:
From: "Jeffrey Sharp"
<lists(a)subatomix.com>
Well said. It probably had more to do with a burning desire to do
*something* with the giant Jacob's ladder. But we were still suprised when
nothing happened, none of us being hardware guys.
Someone else mentioned a device that you could insert into a serial link
that generated bit errors with a configurable frequency. That seems like the
way to go here, and it can be done with nearly any machine with two
compatible serial ports.
--
Jeffrey Sharp
Reply to jss at subatomix dot com.
100 feet at 115200 bps through three unshielded
wires, wrapped around a
three-foot-tall Jacob's ladder apparatus enclosed in plexiglass. No bit
errors. We gave up and decided to build a device to simulate bit errors.
What makes you think that wrapped on the outside of a Jacob's ladder has
either the right coupling or the right frequency spectrum to effect a
RS-232 signal?
7975
days inactive
7979
days old
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