DCS Signal Weakens as I add engines to the track

What version of the TIU do you have?  One wonders if you have a failure of some of the gates in the ACT244 that weakens the DCS signal drive and the extra loading of the additional engines are too much for it.

It is the latest version, just can't remember the specific number.  I verified it was about 2 months ago.

 What's your track powered with? How's the wiring (solid connections)? How many connections per block?

If the power draw gets bigger than the wire and joints can handle, you get power dips in areas. That also seems like the signal is lower. So if you fix that, the signal will be better..... if that's the issue!

You shouldn't need bulbs on a TIU version L. If you do, than I would relook at your wiring method.

I did a lot of testing with DCS signal strength about 16 years ago prior to the TCA National Convention in Ontario, CA.  We were setting up a large (25' x 25') layout on the floor and everything had to work exactly right.  In testing in the back yard, I increased the size of the loop until I got signal problems (including echos-duplication of responses due the the PS2 engines seeing the signal twice on the loop and lack of signal, due to standing waves).  I broke the layout into blocks, as this was being talked about on this forum at the time.  This eliminated the echos and lack of signal problems (I had one drop with a lighted lock-on  going to the center of each block).  The blocks were rather long, but with very few track joints due to using very long sections of track.  I had all 9's and 10's at the time.

Good enough, but not quite.  Part of running command control is the ability to run more than one train, on the same track at the same time.

I started running three engines around the track very slowly, doing Track Signal tests on each one.  When the first of the three entered the block, it got a 10.  When the next engine entered the block, the signal was lower (the first engine was between it and the lighted lock-on).  When the third engine entered the block, its DCS signal was poor (I cannot remember the number, but it was way down).  As the first engine passed far enough into the block that the second engine was between it and the lock-on, the first engine's signal dropped.  The signal on the second engine was back up to a 9 or 10 at this point, as was the signal on the third (nothing between the second or third and the lock on.  Once the second and third engine were both between the first (now nearing the end of the block) and the lock-on, the track signal on the first dropped way down.

This was absolutely consistent and repeatable.  I tested the signal strength on all three of the engines and their signal strength levels all behaved in the same manner.

I then moved the drop from the center of one block of track to the end of that block, and added a new drop to the other end (with another lighted lock-on).  The signal strength remained a 10 for a single engine anywhere in the block, and with three on the block, the signal strength of the first and third engines remained at a 9 or a 10, and the strength dropped slightly for the second engine (between the two so that there was one engine between it and the lock-on at either end). The signal performance on this block was consistent and repeatable.  The signal performance on the other three blocks (still with single drops in the center of each block) remained as it was (signal strength varying greatly base on whether there was another locomotive (or two) between the engine with the signal strength being check and the lock-on

I modified the other three blocks to have two drops (one at each end) and all blocks behaved consistently high as described when only one block had been modified to have two drops.

I know that the common wisdom is to have one drop per block.  This is easier to wire and yields consistent results.  I also think that most people will not be operating three or more engines per block.  

Andy Edelmann saw this running at the TCA convention and asked us to do demos for MTH (which Iwe did for several years).  Running with two drops per block for the large layout has worked extremely well for over a decade.  

You can see most of the lock-ons, on the floor layout here:  https://youtu.be/FLR97_hx9WU