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Old 02-18-2020, 04:20 PM   #151 (permalink)
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Originally Posted by Greg Elmassian View Post
It's pretty simple conceptually, but often overlooked since most users are not engineers.


Basically in DCC you are trying to deliver the cleanest signal to the locomotives.


This means with the least distortion as compared to what comes out of the booster.


Have you heard of the use of snubbers at the ends of a "dead end" track?


Do you know about signal reflections?


If you do, then I probably don't need to say much more other than it happens at these frequencies.


Perhaps you understand the concept of ground loops?


Let me know if you are familiar with any of the above, as I can answer you in very few words.


Yes, to "current wisdom" is to connect a feeder to every rail, basically saying my joiners are crap... but you can cause other issues that affect the integrity of the signal, and then that still does not address dead end tracks.


Greg

Greg,

As a radio/radar technician with over 40 years experience in both ground and aircraft installations I am very familiar with signal reflections and ground loops.

Have never heard of using snubbers at the end of dead end tracks but it would make sense to control transients and spikes especially when points are switched.
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Old 02-19-2020, 02:05 PM   #152 (permalink)
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Great, so I can speak at a higher level!


So first DCC being a square wave, we have ringing, etc. distorting the signal.


The reflections at the ends of tracks will be necessarily out of phase reflections and further distort the signal, in extreme situations can radically reduce the signal as you know about an 180 degree out of phase signal.


In HO layouts, where the largest market is, it is very common to use a "snubber" at the end of any track segment, normally a resistor and a cap in series, to kill any reflections.


So, the problem of too many feeders is the potential for adding more signal that is not exactly in phase, due to the difference in distance since there is more than one path to any location, and by putting feeders close together, you actually enhance that danger....



most DCC issues is distortion of the waveform, not power issues.


soldering jumpers of course helps indoors, and outdoors the ultimate is bonding track sections together, better than clamps.


Anyway, there's the gist of it, more feeders can control voltage drop and get around bad joiners, but can have a detrimental effect on the signal quality.


Some day, let me tell you why stainless steel track is better for signal integrity than brass track...


Best regards,


Greg
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Old 02-19-2020, 08:48 PM   #153 (permalink)
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Thanks Greg,
No need to explain stainless track I only run track power for my HO layout the Large Scale one is battery.
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Old 02-19-2020, 11:21 PM   #154 (permalink)
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By the way, besides gleaning information from people I consider experts, I have actually put a scope on the rails in various places, and I'm lucky enough to have a portable DCC packet analyzer, that combined with my engineering background allow me to be confident in the analysis.



Of course this flies in the face of some of the "common wisdom" ha ha.


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