Kato RDC help?

[peteski]

I didn't call it Dual Mode, Atlas did, and they tried to (or did) trademark it.  Early Atlas decoder DID bypass the DCC altogether to run on straight DC.  The early HO models used a jumper.  For N scale the first factory decoders were called eDMD (Dual Mode Decoder).  I can't find any info on these anymore, maybe someone from Atlas can chime it and talk about how they operated.  I don't believe that they worked the same as decoders do now in regards to DC operation.
Jason

I was not trying to argue the semantics or name of the functionality.  I have to dig out some of my early Digitrax N scale decoder literature to see if those had the analog mode operation capabilities - I think they did. That was long before Atlas was selling N scale DCC-equipped locos.  We are discussing N scale models here, aren't we?

I also do not consider a physical jumper being moved as a real "dual-mode" decoder (since moving a jumper physically removed the decoder from the circuit). No matter what the sales literature calls it. 

As far as the decoder bypassing the DCC while operating on DC (without moving a physical jumper), how can it do that? The process I described earlier is probably the closest you can come to "electronic bypass".  In order to bypass the microprocessor, the microprocessor itself would still have to be running its own code to sense DC and remove itself from the circuit.   

[spookshow]

Now that I think about it, I'm not sure what Al Hoop was talking about. If a decoder's CV29 isn't configured for DC operations, it won't respond to a DC throttle at all (as opposed to running poorly or whatever). Perhaps Al would care to elaborate on his suggestion.

IIRC, decoder-equipped locos used to be a bit balky when operated in DC mode (taking a bit of time to decide what kind of current they were dealing with). Things are much improved now, but that said I have no idea how old the decoder in OP's RDC might be.

Cheers,
-Mark

[alhoop]

Now that I think about it, I'm not sure what Al Hoop was talking about. If a decoder's CV29 isn't configured for DC operations, it won't respond to a DC throttle at all (as opposed to running poorly or whatever). Perhaps Al would care to elaborate on his suggestion.

IIRC, decoder-equipped locos used to be a bit balky when operated in DC mode (taking a bit of time to decide what kind of current they were dealing with). Things are much improved now, but that said I have no idea how old the decoder in OP's RDC might be.

Cheers,
-Mark

Your second paragraph provides part of the answer. I just know that my pwm (not pure dc) throttle would run a Digitrax equipped locomotive with the bit not set , just not very well with a lot of stopping, surging and hunting.
I was told that the throttle was fooling the decoder until it caught on, then the cycle repeated. I don't know anything about DCC.
Al

[spookshow]

Your second paragraph provides part of the answer. I just know that my pwm (not pure dc) throttle would run a Digitrax equipped locomotive with the bit not set , just not very well with a lot of stopping, surging and hunting.
I was told that the throttle was fooling the decoder until it caught on, then the cycle repeated. I don't know anything about DCC.
Al

Ah, well there ya go - problem sussed. Genius awards all around! 

Cheers,
-Mark

[garethashenden]

FWIW my RDC has a decoder and runs fine on DC.

[reinhardtjh]

FWIW my RDC has a decoder and runs fine on DC.

All DC is not created equal.  A DCC decoder in DC mode really prefers a nice, spike-less filtered DC.  Some DC power packs do that and some are "half-wave" and some have pulses injected purposefully.   In the DC world most motors (but not all) tend to work better with some sort of pulse power, at least at slow speeds. It overcomes various sorts of friction in the motor and drive train.  The DCC decoders see that and they can become confused and think they are seeing a DCC info stream and try to decode that at which time all sorts of havoc can break out.  Some decoders are better and aren't fooled and some are only fooled for a moment (as alluded to by Allhoop's remarks).