Re: DCC & N_Gauge

On Jun 3, 10:51 pm, Wolf K <weki...@xxxxxxxxxxxx> wrote:
Nigel Cliffe wrote:
Graham Harrison wrote:
I'm not totally convinced that all DCC is equal.   I can't prove it
but I have had experiences which lead me to believe that some DCC
controllers work better with certain chips than others.   This should
NOT be an issue but.....

Two major "within specs" issues exist:
a) Speed steps supported. One or two older (or dead cheap) controllers (eg.
Bachmann EZ) only work on 28 speed steps, yet decoders support 128.  This
can make some locos look "notchy" when running, and can be a pig to dial out
with speed curves, acceleration settings, etc.. (been there, tried to see
what was possible).

b) Track voltage.  There is considerable variation in track voltage between
systems, and some systems have user-control of the track voltage. Generally,
more volts = faster running.  Also, normal advice for N is to aim for a
system with a lower than average track voltage.

There is one other issue, and that's the shape and cleanliness of the
signals. They are supposed to be square wave, but of course in practice
this doesn't happen. Some controllers produce wave forms that are sloppy

Also what does the controller do during power up/down. Advice for ZTC
command station users (from ZTC) is to fit an isolating switch and
disconnect during power-up/down, or when restoring popwer after a
shutdown due to overload. The ZTC system does not control the outputs
correctly and can put out enough crap to confuse some decoders,
causing Lenz decoders to runaway, for example.

enough to make some decoders hiccup. In addition, "echo" occurs, because
of the way bus wires are connected to each other and the rails. There
should be a terminator at the end of each bus. Echoes can interfere with
the signal, too. (Source: article in NMRA's Scale Rails within the last
year - don't have the issue any more.)

Strictly speaking they're filters, not terminators and are not always
neccessary, depending on the quality and length of wiring.

For a terminator to be effective, the bus wiring would need to be a
known, controlled impedance and the terminator matched to that
impedance. The NMRA, of all people, ought to know better! It's simply
not sensible to treat a DCC bus as a transmission line, since the
loads keep moving and every single layout would be different and
require individual solutions!

MBQ
.

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