Adding DT402D throttle to old Digitrax radio Chief

[riogrande]

I have a Digitrax Chief system bought in the late 90's - the booster is one of the first to come with the new style connector which is allegedely firmware upgradable FWIW. That system came with the DT100 throttle which i had upgraded to simplex radio version DT100R and added the UR91 panel receiver. It has been in storage over 10 year but I want to get it out and start testing it for future use. Start installing decoders etc.

Since the set I have came with the less than user friendly DT100 throttle, I was thinking of getting the DT402D duplex radio throttle and using the old DT100 as a secondary throttle. Will the DT402D work with the UR91 receiver in radio mode? If not, is their any plans announced by Digitrax to allow the duplex throttle to work in simplex mode with the receiver? Or am I committing to having to add a UR92 by getting the DT402D throttle? It just seems for the small price differnce between the D and R versions, I should get the duplex version to have full wireless programming ability when used with clubs and later when I get a UR92 receiver (of course).

Basically I was wondering of the DT402D could work in simplex mode for the short term with the UR91.

Comments?

[bnsf971]

I'm pretty sure it will work, if plugged in. Wireless, I'm not so sure.

[riogrande]

Plugged in of course! I got lots of response on MR forums in the DCC section. They say the DT402D operates on a completely different frequency than the simplex DT402R throttle and UR91 receiver. Looks like an approx $300 investment to upgrade to the more user friendly throttle over the old DT100R hard to use simplex throttle. I may bite the bullet and get the new duplex throttle to give the option to operate with modular clubs in the area and get the UR92 later this year.

[fmilhaupt]

For the benefit of those who haven't seen the other threads elsewhere, the short explanation of the frequency difference goes like this:

The Digitrax simplex wireless system runs at approximately 915-916 MHz. Their duplex wireless system runs at 2.4 GHz, so a simplex Digitrax throttle won't communicate via radio to a duplex transceiver.

When plugged in, neither simplex nor duplex throttles care what kind of radio receiver is on the system and both behave well as tethered throttles.

For a throttle to be able to operate wirelessly with both systems, it would need to have two radios. Figure that'd add $40-50 to the duplex throttle price, if they could even fit both of them into the case.

By moving duplex up to the 2.4GHz band, one of the advantages Digitrax got was that they can more easily have it certified for use outside of the US, Canada and Australia. Certification of devices using the 915-916 MHz band can be problematic and/or extremely time-consuming outside of these countries, which is an issue that NCE has encountered, too.

I've been using both duplex and simplex Digitrax throttles on the same layout since shortly after duplex was released. With both a UR91 and a UR92 connected, both types of throttles play together nicely.

[Paul Cutler III]

FWIW, no one can blame Digitrax for this one. They were the first DCC company to make a radio throttle; years ahead of NCE or anyone else. At that time, 900MHz was the standard free radio band allowed by the FCC. It's why all cordless phones of that era were 900MHz.

Since that time, the FCC has sold off the 900MHz band to AT&T (IIRC). For Digitrax to make new products in the 900MHz range, they'd have to get a license from AT&T...and that's even if they could. Existing products are apparently grandfathered in, which is why DT402R's and UT4R's are still available (have you, riogrande, considered the DT402R instead of the DT402D?)

Anyways, the FCC made the 2.4GHz band free and available at the time they sold the 900MHz band. All new cordless phones are in the 2.4GHz range because of it, and so is the duplex radio throttles from Digitrax.

The differences between 900MHz and 2.4GHz requires a completely different antenna and receiver. Expecting a 2.4GHz radio to be able to send to a 900MHz antenna is about like expecting your walkie-talkie to be able to transmit to your car radio. Sure, they are both radios, but they aren't even close to working together.

[riogrande]

I have considered the DT402R but at first blush it seemed for only a couple dollars more, having full duplex seemed like a no brainer. That was before I found out it wasn't only a few dollars more, but another $125 to be able to use it in radio mode due to the difference in broadcast frequency.

A poster in MRR forums used JRMI or something to do all is programming and consisting, and felt his several DT402 throttles were a waste. His argument is that don't buy a DT402D to do consisting and programming, just use the software and then utility throttles to run trains. Lots of options for sure.

Yes, since I have learned about the difference in bands, it is clear what is and isn't possible. (I have a masters in science so yeah, I have a "clue" about how things work)