Hi Modelers
Back in March of this year I decided to upgrade two of my DT402 throttles to Duplex operation by sending them back to Digitrax for the upgrade and I bought two UR92 recievers to add to the UR91s (Digitrax assures me that they will work in harmony) that I had been using for over ten years. I also bought a couple of UT4Ds to supplement the other UT4Rs I had.
Digitrax made the conversion and I had my throttles returned back to me in about a month.
Right away I was pleased with not having to "plug-in" to select a new address but there were a few occasions when the white LED (the "flashlight" feature) would blink meaning the throttle has lost communication with the UR92 and Loconet.
Now, I have a pretty average basement under a ranch house so my layout room is about 65' by 40' with a laundry area in the center. Therefore, I figure two UR92 will cover this area (one UR92 on either side of the laundry area) since Digitrax says the UR92s are good for a 300 foot range under ideal conditions. My old simplex UR91s worked flawlessly and I never had any lost communication issues.
Well, I tried various locations for the UR92s and trying to use different Duplex Group Names and channel numbers but to no avail. If I try to use the throttle more than about thirty feet away (not 300!) I get a blinking white light and no response from the throttle!
If you read the late Bob Hartle's response to this 2012 thread here:
http://cs.trains.com/mrr/f/744/t/204283.aspx
...you can get a feel for what I'm talking about. Unfortunately, there are no real solutions in the linked thread and anything I have looked up under UR92 poor reception doesn't have any clear solutions.
Part of my layout runs into my work room where I have a six track staging yard and today I was making up some trains in there and I had absolutely NO throttle response. It is only a 2 x 4 frame wall with drywall between the throttle and the UR92 which is only about fifteen feet away at this point! I decided that I'm getting fed up with this situation after "upgrading and improving" my Digitrax system.
I wondered if anyone else has had the same experience. I always have my tin-foil cap on when I'm operating the layout so none of the stray 2.4 GhZ signals are scrambling MY memory!
Short of buying ANOTHER UR92 any help would be appreciated...
Thanks, Ed
Ed, I have an NCE system, not Digitrax, so I have no business replying to this thread. But I would point out that NCE has a product called a "repeater" for such purposes. The repeater increases the saturation of the radio signal in hard to reach areas. Perhaps Digitrax has something similar.
Rich
Alton Junction
The Pacific Southern club is a large basement layout (90x45) that had been using NCE's wireless throttles until they had intermittent problems. They had both a primary antenna and 2 secondary repeaters.
The NCE system operates at 916.5 MHz in the industrial, scientific and medical (ISM) band. It looks like Digitrax operates in the ISM band at 2.4 gHz. The ISM bands are unlicensed and usage is restricted to lower power that hopefully minimizes interference, but use must be tolerant of other transmissions. (bluetooth also operates above 2.4 gHz and uses frequency hopping to avoid prolonged outages due to interference).
I borrowed a spectrum analyzer from work and we were able to capture an intermittent interferring RF transmission at the NCE wireless frequency that would occur several minutes apart for several (10s) of seconds.
Disabling the automatic gain control (AGC) in the NCE wireless radios seemed to help because it maintained a constant gain, avoiding the need to readjust after the interferring went away allowing immediate reception of NCE signal.
greg - Philadelphia & Reading / Reading
If your throttles battery gets below a certian level, the throttle will not respond. Two of the guys at our club did tests and figured this out. I also believe it is a line of sight operation. I personally prefer to keep it plugged in so have no first hand experience that way. Our club has a second room for staging where you have to plug in since it has no ur92s in it.
CGW121If your throttles battery gets below a certian level, the throttle will not respond. Two of the guys at our club did tests and figured this out. I also believe it is a line of sight operation.
Low batteries could contribute to this, but would think Digitrax would be able to say more. Have you checked with them yet?
When they discuss reception in terms of "line of sight" it's usually because the cited max range is based on the assumption of line of sight in the free air, no walls, furniture, people, etc in the way. Start putting stuff in the way and that reception distance drops sharply. Still, would think you'd have better reception than you're getting if the actual max distance is about 1/10th of the cited max range.
The mention of 2.4 gHz band leads me to suspect some other device is emitting and being picked up as interference by the Digitrax system. Do you have a wireless router in the house? Or a wireless video camera as pat of a home security DVR system? Both could be on 2.4 and causing interference. How close are the neighbors if you don't have 2.4gHz devices running? You could upgrade other systems if turning them off obviates the problem with the Digitrax link.
Mike Lehman
Urbana, IL
I became disillusioned with radio control DCC throttles when using mine: I saw my three brass engines heading to the end of a yard track, and my throttle was unresponsive. And. The end of the yard track was the end of the table. There was a nail there, too. BAAMMMM! Which was far far better than what I was envisioning. That really got my attention, and radio hasn't been used since.
That said, I'll throw out a thing from left field:
I heard somewhere about using ground planes for our DCC radio antennas:
https://en.wikipedia.org/wiki/Ground_plane
Dimensionally, metal pie plates work just fine.
Just a thought.
Ed
There are some utilities which can help set the UR92's to use a 2.4GHz channel that is otherwise not used, or at least the least use. This will help greatly.
Digitrax simplex runs in the same 900Mhz band that NCE does. Duplex uses 2.4GHz. 2.4GHz has shorter range no matter what, plus for 2-way transmission the power levels are required to be reduced. There are no repeaters for Digitrax, you just add more transciever units - they work like cells and can hand off from one to another as you move about the space. Human bodies are good radio blockers - the UR92's should be up high, and anecdotably upside down - the circuit board is the ground plane and the two little wires that stick up are the antenna, if the ground plane is between you and the antenna, you will get a much reduced signal. If you have a wireless router - if it's upstairs, you probably have weak signal downstairs, but if you put it downstairs, things probably work just fine upstairs. The UR92 (and UR91) are no different - mount them high and upside down for best signal coverage.
Turn off sleep mode on your DT402D's. If the throttle goes to sleep, it may not reconnect immediately when you press a button or move the throttle. You get more power savings by turning off the sleep mode and not constantly fiddling with the knobs than you do by having sleep enabled but constantly adjusting something to keep it awake.
Always use good batteries. A typical rechargeable "9V" is really 8.4 volts and is already almost too low for reliable operation, even when freshly charged. There are alternative ones that charge up to 9.6V (1 more cell). They have less maH capacity but the higher voltage is more critical with Digitrax throttles, especially if you properly manage the power as above - also turnt he backlight off or to the lowest setting. Unless operating in the dark, the backlight is not needed and is one of the biggest current consumers in the circuit.
The knob twiddling is the biggest problem - I see it at club shows all the time. Some guys will take a fresh good battery and start runnign a train, and a half hour later be frantically swapping it out for a fresh one to regain control. I'll take one in the morning, run a few hours, take it out, and after lunch run another session with the same battery, no problem. We have both simplex and duplex in operation, although at regular train shows like Timonium, the UR91's are just shut off because any NCE layout operating nearby just kills all Digitrax simplex - NCE is way too chattery, constantly broadcasting (because of the polled nature of the throttle bus), and since they use the same frequency, it prevents Digitrax simplex from operating, Since the duplex is on a different frequency, it works fine. And despite the wifi in the building for all the POS terminals so the vendors can take credit cards, it works fine. There are some channgles in the Digitrax duplkex 2.4GHz spectrum that are typically not used by wifi routers, so switching to those makes a big difference. Also don;t operate microwave ovens around 2.4GHx wireless anything - I used to have a 2.4GHz cordless phone that got disconnected every time someone turned on the microwave - the side of the microwave was pointed right at the phone base. We have a small microwave we set on a center table for people to heat up lunch at the club shows - first time it was set up right in front of our radio pole, and everyone lost control the first time someone went to heat up some food.
Bob did get his duplex working reliably, but I never did get a chance to see his layout. Last time I saw him just before he passed, he invited me to stop over next time I was out there (I live on the other side of PA, but my GF's family is from out Bob's way and we go out every Christmas). Sadly, I got the news of his passing not long after.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I will add that drywall is also a pretty darn good 2.4GHz signal attenuator. My router is in the room here with my desktop and server and cable modem, and if I hook up my laptop, I get max signal strength at any point in the room. If I walk into the hall, even with the laptop theroetically closer to the router than if I am in the same room but far corner, the signal is weaker. If you think 2.4GHz is bad - 5.8GHz is even worse. Diagonally outside the room and about 20 feet away as the crow flies is my TV with a Roku which uses 5.8GHz 802.11n. Signal strength is down by half just that short distance (through drywall) away. I have a feeling to get top performance when I set up the railroad computer int he basement, I'm going to have to just run an ethernet cable up and hard wire it. Or add a repeater, or a seperate, non-internet connected router so I can use WiThrottle.
Fifteen feet does not sound like the norm for the duplex. I operated at a large modular meet with my DT402D and was easily 25-30 ft from some of the receivers and never had any problems. Something must be interfering or attenuating.
Rio Grande. The Action Road - Focus 1977-1983
riogrande5761Fifteen feet does not sound like the norm for the duplex.
You're correct, there. In the situation where I'm only fifteen feet away the, particular arrangement of the aisle I have the bulk (!) of my body and the fact that there is a plaster mountain in the "line-of-sight" to the UR92. This mountain is made of "old school" methods using wire screen for the shell. As I'm learning from the above replies, these are all bad conditions for a 2.4 GHz signal to penetrate.
I always start a running session with freshly charged Powerex batteries and I watch the DT400 readout for a voltage status. Even after a few hours of use, they rarely show less than 8 volts. Randy, thanks for the hint to turn off the sleep mode—you're right about taking a long time to wake up the throttle.
Thanks for all the info so far gentlemen...
It looks like my best option is to add another UR92.
Thanks again, Ed
does anyone know how the Digitrax system operates in the 2400 MHz band (the ur92 spec sheet simply says 2400 Mhz band)?
Is it similar to the approach used at 916.5, which i'm guessing is on/off keying or does it use some spread spectrum technique (e.g. freq hopping, DSSS, ...)?
I see wifi has defined overlapping 20 MHz channels and bluetooth uses 1 MHz channels. I don't believe there are defined channels of fixed bandwidth recognized and honored by all technologies.
the image belows shows that there is a lot more usage that just wifi, bluetooth and cordless phones.
AFAIK, Digitrax uses a scheme with channels similar to wifi. They use a canned RF module, it is not something they designed. Photos and information cn be found in the FCC certification, the FCC ID is LV3RF24. In addition, there are 15 IDs that can be selected, so that even if there are two Digitrax layouts on the same channel, they would each have a unique ID and so couldn't control each other's trains. The DT402D and UT4D throttles may need to be plugged in one time to grab the Loconet ID for the layout, after that they operate completely tetherless. The throttle will automatically detect the Loconet ID, so you can use the same throttle on multiple layouts with different IDs, it will change to the one being used each time you switch to another layout.
As for range issues - a wire screen mountain will also make a very good RF block, doubly so if any of the nails or staples holding the screen contact something that is grounded. Our club modular layout stretches out about 150 feet now, and the radio pole is on the isnide, about 20 feet from one end. There is one UR91 and one UR92. We often let kids run the trains, and the throttles work even at the far end on the outside of the layout, so well over 100 feet. But there's nothign in between, although there may occasionally be bodies in the way as a kid holding the throttle will be just above the tabletop.
looks like the UR92 uses a transceiver module from Nordic Semiconductor that is capable of tuning from 2400 to 2525 MHz on 125 1 MHz channels and operate at 3 different data rates, 250 kbps, 1 and 2mbps using G FSK, a step up from on/off keying.
it's not obvious if the system will change channels during operation if it detects interference on the current channel. I think this would be more difficult to implement than a frequency hopping approach, possibly listen before talk, that wouldn't be trivial, especially if there are multiple digitrax systems (multiple layouts) in operation.
i'm always surprised by the technology used in model railroading.
One thing that I noticed with the UR92 is that it appears to have the same "doughnut hole" reception problem as NCE's radio receiver. If you're standing within four to six feet of it, it often won't pick up your transmissions. Back away a step or two, and everything's fine.
In that case, a second UR92, placed so its reception area would overlap, solved our problem, in exactly the same way that a strategically-placed repeater did for a troublesome switching area on my buddy's NCE layout.
We had some initial interference with our Digitrax Duplex installation that was caused by using the default wi-fi channel (quite a few nearby neighbors were using the same channel), but changing it cleared that up quickly. I used a free wi-fi analyzer progam for my Android phone to chase that down, and also to improve the performance of the homeowner's own wi-fi network in the process.
Using 9.6V batteries (we use Maha Powerex) for both our simplex and duplex throttles has helped us achieve very good results.
-Fritz Milhaupt, Publications Editor, Pere Marquette Historical Society, Inc.http://www.pmhistsoc.org
gmpullman Thanks for all the info so far gentlemen... It looks like my best option is to add another UR92.
Take a look at these instructions.
http://www.digitrax.com/tsd/KB37/ur92-adding-more-ur92s/
I don;t think the Digitrax duplex will channel hop automatically. Pretty sure you have to set what channel to use.
I would say your layout room is not average at 65 x 40, much larger. My UR92 and duplex throttles work fine when at least 50+ feet away and through 2 walls. We've tested it.
Richard
rrinker There are some utilities which can help set the UR92's to use a 2.4GHz channel that is otherwise not used, or at least the least use. This will help greatly.
Randy,
I presume you are refering to this DigiGroupSetup utility?
http://www.digitrax.com/tsd/KB3/ur92-digigroupsetup-read-me/
Do I need a PR3 to use this or will the RRCirkits LocoBuffer II work? I have selected a few random channels on the UR92s but unless I know where the conflict is that seems like a shot in the dark. Maybe I'll play with this utility when I have a chance.
Richard, You're correct that the layout is a "folded dogbone" and the laundry room and stairway divide the two ends of the bone.
Tonight I am going to mount the UR92s up high on the posts that support the wood beam and rafters. Should have done this sooner!
Randy, If I recall correctly there are no wire "rabbit ears" like on the UR91 but I can install the UR92s upside down anyway since I'll never reach them to plug in a throttle.
Rich, Thanks for the link to the Digitrax KnowledgeBase! I had not seen that page and it will be very helpful. I'm still not clear on the "Duplex Group Channel" versus the "Duplex Group Name"? Sometimes the Digitrax terminology is confusing. Such as option switches, thrown or closed? Cant they say on or off? maybe Open or Closed?
I have a third UR92 on the way. It will mount close to the workroom with the staging yard but still be in the vicinity of the main layout so a triangulation may work better.
I seem to recall getting a new cordless 2.4 GhZ phone years ago to replace an older 900 MHz one. Reception distance dropped from 500 feet to about fifty feet! I could carry the 900mhz phone to my mailbox and still hear and talk fine, the newer one would drop out if I went into another room.
Thanks for all the help, everyone!
fmilhauptOne thing that I noticed with the UR92 is that it appears to have the same "doughnut hole" reception problem as NCE's radio receiver. If you're standing within four to six feet of it, it often won't pick up your transmissions. Back away a step or two, and everything's fine.
This is very true in my situation as well!
Can you believe that when I am between the two UR92s and each one is only about eight feet away from me I will not have communication? Presently they are mounted in the fascia which is 5mm luan plywood, but I still have a poor signal when I'm in a corridor that connects the two ends of the layout so there isn't much wiggle room there but if I hold the throttle over my head, it helps... just gives me a sore neck and blurry vision
I'll see if that changes after I try a new location as mentioned above.
Yes, I use the Powerex 9.6 batteries and I'm happy with them.
Unfortunately DigiGroup Setup does not work with a Locobuffer. Needs a PR3 or MS100. However, newer versions of JMRI have Duplex Gropu Setup under the Loconet menu, and that will work with a Locobuffer. Does the same thing, there is a channel scan tab and another tab to set the channel and the Loconet group ID.
If you had such problems with a 2.4GHz cordless phone, I suspect you are near a large source of interference ont he 2.4GHz band. Do you live near a military base with radar (the tracking system, not Gary Burghoff)? Or a manufacturing plant that might use microwaves for some industrial process?
Randy and everyone else who helped with suggestions...
Over the last two nights I moved my UR92s up toward the basement ceiling on the wood beam that supports the rafters.
Very noticable improvement in my signal strength! I still get a little drop-out when I'm in that corridor which joins the two halves of the layout and when the third UR92 arrives I'll experiment with its location, too.
I have a 24" x 24" grid suspended ceiling over most of the layout. I didn't intentionally ground it but I'm sure it gets a ground through the seven fluorescent troffer fixtures that lay in it even though they have a pretty heavy coat of paint on them. I have no idea if this can affect the signal (ground plane, again) and I DID mount the UR92s downside-up.
When I get a chance I'll look at the JMRI app and see what it can do for me.
I'm not close to any military installations or airfields but I know there can be some pretty heavy microwave traffic and I've heard some hams talk about odd bursts of interference that they can't seem to track down. That phone I had was probably just an early low-power model. The Panasonic I have now operates at 1.9GHz and it has been very reliable.
I used to work with a guy that could have been Gary Burghoff's twin brother, same voice, too! I frequently have MASH DVDs playing while I'm working on models!
Thanks again for everyones help. Ed