Sorry to disagree with you MYNH&H. For what Steve is planning to do, he should have no appreciable drop in voltage. It's only after you get out for any length on the LocoNet that you will experience any drop in voltage (usually after about 1,000 feet of telephone cable). Your main source of voltage drop on the LocoNet is with the throttles that are connected to the LocoNet.
If you cruise the files of the Digitrax@YahooGroups discussion forum from abut 2 years ago, you will find e-mails about voltage drop. I was the originator of those questions. Our club, Ottawa Valley HOTRAK, was having problems with the LocoNet. A scope told us that we had large drops in voltage as we plugged in more throttles. Why were we getting this drop in voltage? We thought that the battery in the throttle would power the throttle. All anyone could say about our problem of voltage drop on the LocoNet was to outchange our telco jacks for UP3/5 panels. Nobody could give me an answer as to why we should do this. So, with the help of some people such as Rex Beistle down in Colorado, we undertook some experiments.
From the various throttle types, here's the power that's sucked up
Throttle Type Volts milliamps
UT1 15.5 0.25
DT100 15.5 0.25
DT300 10 13.95
DT400 10 13.95
This is without any load to the throttle (ie sending and receiving signals). As we added more throttles to the LocoNet (again with no load), the voltage kept dropping. We added a couple of LT1 testers - you should have seen the voltage drop!
Contrary to popular opinion, the 9 volt battery in the throttle does not provide power to the throttle. It only serves to keep the display lit and the inards going from the time you unplug the throttle to the time you plug it back in. If you have an IR or radio throttle, it powers the IR or radio. If you don't have a battery in the throttle, no harm is done. In fact, you can save some weight and discard the battery - unless you like to look at your throttle display when you are unplugged. A battery in a throttle has nothing to do with powering the throttle. If you don't believe me, read your DT100, DT300, DT400, UT1, UT2, UT4 manuals and find a sentence which very clearly says that the battery powers the throttle for receiving and sending LocoNet signals. You won't find such a sentence.
While technically, Pins 1 & 6 are not the same, they do serve the same function. In fact, when you are doing any testing with a ohm meter, you can tie the wires for Pins 1 & 6 together. They provide power to the throttles or any other devices that are connected to the LocoNet. There is one exception. Pins 1 & 6 should provide the signals to any boosters attached to the DCC system. If you provide the signals to a booster from Pins 3 & 4, the booster will fight with the command station for control of the network.
For anyone who has a home layout, they don't have to worry about voltage drop on the LocoNet if they only plug in a few throttles (usually anything less than a dozen or so throttles). If they do have voltage drop so that the DCC system no longer functions properly, they should look at the load they have placed on the LocoNet, the power supply to the command station, or their wiring. The load would also include any LEDs they have connected to the LocoNet.
Now, to the question of why the UP5 panel is recommended. Try to find why they recommend UP5 panels over telco jacks. When you find the answer you will find the weakness in the Digitrax system.
As more throttles (devices) are added to the LocoNet, the more the voltage in Pins 1 & 6 drops. As you approach the threshold voltage of 7 volts on Pins 1 & 6, the throttle starts to send and receive weak signals. This can result in garbled instructions being sent to the command station and out onto the tracks resulting in runaway trains particularly if you have the CVs set in your locomotive decoders for analog enabled.
So, you need to pull up the voltage. One way to do this is to unplug some throttles. Another way to do this is to use the UP5 panel. Another way is to feed Pins 1 & 6 out on the LocoNet with voltage from a 12.5 volt regulated power supply. If you have to use UP5 panels or regulated power supplies on your home layout, then you should trade in your DCC system.
Now, why do they recommend using the UP5 panels? Simply because the Digitrax DCC system doesn't put out enough power on Pins 1 & 6 to power the throttles. So, how does the UP5 panel solve the problem? We have to look at the sequence by which the throttle receives its power. The throttle receives its power in the following order
When plugged into a UP3/5 Panel
From the UP3/5 panel if the UP3/5 panel is connected to a wallwart
From the UP3/5 panel if the UP3/5 panel is connected to the track power
From Pins 1 & 6 if the UP3/5 panel is not connected to a wallwart or to track power
When plugged into an RJ12 telco jack
From Pins 1 & 6 unless Pins 1 & 6 in the telco jack
If your UP3/5 panel isn't connected to a wallwart or track power, it is only an expensive telco jack.
However, if you are using DCC on a home layout, you will probably never have to worry about all of this.
Hope this has added to your knowledge of Digitrax DCC.
Have fun. (I am!)
Bob M.