Hi Graham and Ian,
Following below is a reply to a member of the Yahoo DCC group with reference to wiring the DCC bus as a ring main from Richard Johnson of DCC Concepts. It may answer some of your questions.
Devils advocate as ever :-). If you have no problem now you probably won't get one...
However you are simply wrong about the track being a ring - it is not... nor is a rail the same as wire... if it was, droppers would be unnecessary.
Most importantly, you haven't made any sort of "ring" of your track unless you have no points and no isolation gaps at all. (even an insulfrog point creates a break in a rails continuity) The recommendation to not ring the main and to terminate the bus is a good one, and it is NOT an urban myth at all...
The ring has no effect on shorter layouts / smaller layouts but as the layout grows larger there ARE problems developed by creating a ring. These have been discussed ad nauseum on many lists and it is clear that once the layout grows beyong the average size it is unwise to ring the main.
The conventional wisdom is to use a bus that radiates in a tee or similar fashion from the boooster, with the booster in the centre. the time and cost to do it this way is no different to making a ring, and experience says that while some layouts may have no problem with a ring, some DO... so why argue the point anyway.
Especially as it is also clear that a terminated bus has a clearer waveform than a non-terminated one - a very good reason NOT to loop the bus as you cannot terminate a ring. If you looked at the size of the spikes created by every slight short on the layout you'd never question this, and installing the suppression created by the termination clearly works to reduce these as well as cleaning up the waveform, meaning longer decoder life and less chance of things such as missed or misinterpreted commands.
My counter agrument, put simply:
I have never seen a runaway or a control problem with a layout wired with adequate droppers and a terminated power bus. I have seen AND FIXED several larger layouts with constant problems where wiring was inadequate, used ring mains and did not terminate the bus.
These layouts also had a mysterious problem of decoders failing in use after several months and point motors changing themselves due to confused data or interference on the bus. These same layouts ceased to exhibit the problems after the bus was corrected (all had ring removed, all terminated, one had the bus re-routed to stop crosstalk between power bus and other wires... and of course termination was installed.
NOT creating a ring is simply best practice and there is absolutley no benefit in creating one, so why cause confusion by seeding doubt on what has been learned over a decade or more of DCC operation. I therefore highly reommend that a ring main is not used, and terminators are installed as a matter of course (we are talking a few pence only for the resistor and capacitor, so why NOT do it).
Its not necessary for us to agree, diverse opinion is part of life...
This is simply what I have learned from a long period of research and seen/done with my own eyes and hands. Putting this approach into practive worked without exception and the improvements carried out had results that were clear and unambiguous.
If you do not wish to follow the same path then that's your choice and I wish you well - this is a hobby, not a religion!
I simply recommend to all DCC'ers **that it is the safest, best and most reliable method, **that doing it costs no more,**That is no more difficult and CAN result in a problem free and pleasant DCC experience.
So why NOT do it?