@Jerryrails posted:I don’t think I understand any of this but it seems that you are all suggesting I could now use the MTH WTIU and the Lionel Base 3 on my new layout and get them to work together. I just need this gizmo being discussed? Is it doable for someone like me? Is there a path to a hand holding list of directions? I would like to run both Legacy and DCS
Patience grasshopper, it's being fine tuned. I think it'll be soup soon. 
@Jerryrails posted:I don’t think I understand any of this but it seems that you are all suggesting I could now use the MTH WTIU and the Lionel Base 3 on my new layout and get them to work together. I just need this gizmo being discussed? Is it doable for someone like me? Is there a path to a hand holding list of directions? I would like to run both Legacy and DCS
So we already run Lionel and MTH/DCS in our club and in most cases with some fine tuning (GRJ's booster, some signal level adjustment) it works pretty well. I would imagine for a home layout that's enough to get you going.
The problem is this stuff is both locomotive and weather dependent so in a big club with lots of trains and lots of members there are isolated cases where a particular locomotive doesn't work well in a particular part of the layout (and often only in particular humidity levels). The work we're doing on this new suppressor idea is to try to solve those edge cases. We're sharing the progress as we test it out so the other folks with large layouts can share in what we find and learn
@Adrian! posted:So we already run Lionel and MTH/DCS in our club and in most cases with some fine tuning (GRJ's booster, some signal level adjustment) it works pretty well. I would imagine for a home layout that's enough to get you going.
The problem is this stuff is both locomotive and weather dependent so in a big club with lots of trains and lots of members there are isolated cases where a particular locomotive doesn't work well in a particular part of the layout (and often only in particular humidity levels). The work we're doing on this new suppressor idea is to try to solve those edge cases. We're sharing the progress as we test it out so the other folks with large layouts can share in what we find and learn
Where I think this is going to help me personally is with our modular club. Since the wiring is hardly "DCS inspired", the signal levels are not optimal in any case. If this can aid in some way improving the DCS signal quality, that would be a great help.
Cool, that works. Any thoughts on trying shielded inductors vs unshielded?
@gunrunnerjohn posted:Cool, that works. Any thoughts on trying shielded inductors vs unshielded?
I mean step one is to try this one out on the layout tomorrow and see how it goes. If it's helping the DCS performance then I can do a production run... if it totally sucks (as I expect) then I think my next step is hole thru scale components. I mean shorting out my 50 ohm sig gen is a lot easier than shorting out the ~10 ohms of source impedance I measured between the rails.
With a good ferrite core inductor you can get ~20uH or so with a series resistance like 0.01 ohms or so. Then use tantalum caps so the ESR is very low too. That drives the general look of it from the $1 to $15 regime, and the 0.3" scale to the 2" scale, but whatever, it needs to work, right?
@Adrian! posted:With a good ferrite core inductor you can get ~20uH or so with a series resistance like 0.01 ohms or so. Then use tantalum caps so the ESR is very low too. That drives the general look of it from the $1 to $15 regime, and the 0.3" scale to the 2" scale, but whatever, it needs to work, right?
I'm not as worried about the final price as I am about the effectiveness of the filter. 
We spend thousands on the layout and locomotives, etc., so spending a bit more to make them run right doesn't seem to be much of a sacrifice.
OTOH, regarding perfect being the enemy of good enough, it depends on how much more effective the additional cost makes the filter. If we get 90% of the benefit from a $2 parts cost that we could get from a $15-20 parts cost, then it might make sense to do a volume run of the $2 board. I am thinking that the boards would incorporate two sets of filters in parallel if the parts only cost a couple bucks, that would help with the performance it appears.
@gunrunnerjohn posted:I'm not as worried about the final price as I am about the effectiveness of the filter.
OTOH, regarding perfect being the enemy of good enough, it depends on how much more effective the additional cost makes the filter. If we get 90% of the benefit from a $2 parts cost that we could get from a $15-20 parts cost, then it might make sense to do a volume run of the $2 board. I am thinking that the boards would incorporate two sets of filters in parallel if the parts only cost a couple bucks, that would help with the performance it appears.
It seems to be uniquely the model train people in our club that pour $2900 into a locomotive, then immediately spend a month complaining about smoke fluid costing $19.
@Adrian! posted:It seems to be uniquely the model train people in our club that pour $2900 into a locomotive, then immediately spend a month complaining about smoke fluid costing $19.
Actually, that's pretty universal. I had a discussion with a guy about looking for smoke unit home brew recipes for his fleet of Legacy steam locomotives. He couldn't understand my stance of simply buying a couple big bottles of JT's Megasteam and using them until I needed more! He was sure he could save money by mixing up who know what to pour into his engines. 
I thought that the MLCC caps had a very low ESR, is there something I'm missing about their characteristics for this application?
@gunrunnerjohn posted:I thought that the MLCC caps had a very low ESR, is there something I'm missing about their characteristics for this application?
These ones were el cheapo… China film capacitors off Amazon. You’re right… a good ceramic or mlcc is low ESR but like real Murata ones with an actual QC department involved
@Adrian! posted:
These values are right on peaking 451 KHz.
Standard sizes don't do it. 6.8nF is a little too low freq, 5.0nF is a little too high... so split the difference and it's just right.
So Adrian, are you saying that something like 5.9 to 6.0 nF is about right and gives us the magic 455KHz notch?
@Adrian! posted:These ones were el cheapo… China film capacitors off Amazon. You’re right… a good ceramic or mlcc is low ESR but like real Murata ones with an actual QC department involved
I typically buy my stuff like that from Digikey or Mouser, they normally carry higher quality brands.
@Rod Stewart posted:So Adrian, are you saying that something like 5.9 to 6.0 nF is about right and gives us the magic 455KHz notch?
So the ideal value is lying between two standard values (5.0nF and 6.8nF) , so I split the difference like this:
(22uH)--(5nF)--(22uH)--(6.8nF)--(22uH)--(5nF)--(22uH)--(6.8nF)
The effective cap is then the midpoint between those values and yeah its very close to 450 KHz. As I posted earlier... the concept is "working kind of" we still have some issues with the design in terms of series resistance so I'm going to work out a rev 2 with less lossy components.
I'll of course share that when I have it done
I'd love to find some SMT inductors with a lower DC resistance and/or a higher Q. I think the better capacitors can be had in surface mount without too much issue.
I wondered when I'd get to the point where I would be probing my layout with either of my two RF network analyzers! Great work on this, Adrian!
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