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New Member
I recently purchased a HO scale C420 with sound and DCC. When I run it on my
Digitrax DCC layout the button F6 witch is supposed to be the doppler shift does
not operate the doppler, instead it just gives me a read out of my locomotives
speed. That is when it is running. When it is in neutral F6 is supposed to be
start-up. Instead it gives me the read out of what address my locomotive. Even
when the locomotive is in shut down the F6 button does not start the locomotive back up. What needs to be done to fix this problem. Also as a side note, I have reset it many time, mostly due to the fact that I accidentally put the locomotive into shut down.


Fleeing from Al
What does the documentation from Atlas say about what keypress works with doppler shift? Does the decoder even have doppler shift? The instructions that come with the Digitrax give you the usual button presses that work with most decoders but only if that decoder has that feature. That's why reading the documentation that comes with your engine is so important, especially with sound, since combination sound and motor decoders will often have slightly different button combinations than a standard motor decoder.


Fleeing from Al
Yes, but what does the Digitrax documentation say? Just because the Atlas documentation says F6, it doesn't mean your controller will handle F6 in the same way. It may have a different key combination than the Atlas decoder is calling for. Again, both decoder and control station documentation tell you how the majority of things work but not all. You may be able to reprogram the F6 function to work with the doppler effect on the Atlas decoder but that may involve changing some CV's on the decoder.


In Training Down Under.
sounds like a QSI decoder like I have in my BLI's F6 does the doppler effect on my Lenz system

I thought that was a NMRA standard, f6 on one system should do everything the same on a decoder (unless reprogrammed) on any other system?


BNSF dude

BNSF foamer
It gives status readout on F6? What? My friends RS-27's do doppler on F6 and readout on I think F10 or F11.

BNSF dude

BNSF foamer
Ok, I think someting may be wrong with your Q1a or Q2 sound chip. Call Quantum Sound or email them about the issue. Sorry I can't provide a link at the time as I haven't a clue to what their website is.


Here is a page, from Digitrax, that I've used quite a bit - the last paragraph :[

Digitrax has a pretty good support section on their site.

One of the things that confused me for a while is the F6 needs a few seconds to "reset" after being pushed for doppler. Also the engine must be moving (medium or higher speed) for the doppler to work. I hold the F2 for a count of 4 and at the 2 count press F6. Some locomotives sound better than others.

Let us know what you found when solved.
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From the QSI manual:

F6 Doppler Shift Operation Method
1) Start the Horn/Whistle by pressing and releasing the F2 key.
2) Press F6 as the locomotive is moving towards you. The Horn/Whistle and other locomotive sounds increase in
volume and shift in pitch as the locomotive passes by and then reduce in volume.
3) Press F2 button again to shut off the Horn/Whistle or continue blowing long and short blasts by pressing and repressing
F2. If you shut off the Horn/Whistle for more than five to seven seconds, the sounds will gradually return
to normal.
If the bell was on during DopplerShift, it will automatically turn off prior to the sounds returning to normal.
If Doppler Shift is initiated without the Horn/Whistle blowing, the sounds return to normal soon after the Doppler Shift
is finished.
Doppler Shift is speed dependent. The greater the speed, the greater the amount of pitch change as the locomotive
passes by. There is no Doppler Shift at speeds less than 15 scale miles per hour (smph); instead you will hear a short
air let-off when F6 is pressed.
Try using the F6 key to affect chuffing sounds (sans Whistle or Bell) to create interesting environmental effects.
Note: Some base stations produce an intermittent and independent horn signal interruption that causes an
unexpected Doppler Shift. If this happens frequently, you may want to disable the horn triggered Doppler Shift
by setting CV 51.2 bit 0 to 0.
Note: With some Command Stations, using the horn button to activate the Horn/Whistle, and then while this button
is held down, pressing F6 causes the Horn/Whistle to shut off instead of causing a Doppler Shift effect.

You may also do a default on the decoder and see if this clears it up. There shouldn't be a problem with using Digitrax. .;):)

EDIT: Oops! you said that you have already did a default. CV8 set to 8 ??
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