DCS interferes with scanner?

The track signal of Legacy/TMCC is only 455KHz, probably well below your scanners range.  The DCS signal is a much higher frequency that your scanner is receiving easily, probably through the antenna.

Dales right,

You could put a filter on your scanner coax but it might be more expensive than you want to fool with

David

OK, is it having problemds:

1.  In one range of freqs?

2.  Anything the scanner can pick up?

What freqs does the DCS system use?

What scanner are you using?

The Remote transmits at 916.5 MHz and the TIU at 905.8MHz. 

The track signal for DCS is 3.27mhz, that's probably more likely the source of interference.

I guess the "devil is in the details" so here is some more pacific information:

1. DCS can be powered up- no problem.
2. The remote being on or off- no problem.
3. No MTH engine on the track, then add track power- no problem.
4. MTH engine on the track with DCS on- no problem.
5. MTH engine on the track, DCS on, add track power- PROBLEM.

The remote on or off makes no difference.  The engine doesn't need to be keyed in, or started up, just any (tried several) MTH engine setting on the track causes the "hiss" as soon as track power is applied.

I have two scanners, same effect either one, both are Radio Shack, one is a Pro-2052 base, the other a Pro-164 handheld.

I only monitor the AAR frequencies, which span 159.xxx thru 161.xxx.  I also scan the car defect monitors, which generally run between 450 and 500.xxx.

Being this only happens with DCS (not Legacy Cab 2) it is probably what Dale pointed out and obviously engine communication.

Thanks for your time and responses!  Curious if anyone else is able to use a scanner in their train room with DCS and MTH engine(s).

Stack

Well, track power is when the DCS signal would be available all around the layout, so it makes sense that's when you'd get the interference if it's the 3.27mhz.

How and where is your coax routed?  Have you moved the scanner to different areas of the room? Does this hiss happen on all bands ie police, city services, airplane bands?

Might try grounding the scanner chassis to a water pipe to see if hiss increase/decreases/no effect.  I suspect there is and intermod or birdie as we hams call it that is creating a spurious frequency that falls in the 160MHz passband.

In #4, when you say "DCS on", does this mean the TIU is powered but no power is going to the track?

If so, doesn't the interference only occur when an MTH engine is receiving power?  Note that in DCS, the TIU only talks to the engine when executing a specific command.  It does not continuously transmit like some command systems.

One experiment is to manually lift the MTH engine off the track when hearing the hiss.

If the hiss goes away, is it convenient to take the power feeding the TIU input and run it directly to your track (don't backfeed the TIU output in so-called passive mode)?  The engine starts up in conventional neutral.  So with the TIU completely unpowered and no DCS anywhere (except in the engine), any interference?

Hi Stan,

Yes, by DCS I mean TIU can be on and not cause the interference.  The interference occurs when a MTH engine is on the track, and, track power is initiated.  The engine does not have to be addressed, just sitting on the track.  If I lift the engine off the track the "hiss" stops, even if the track power remains on.  No difference if the engine is addressed or not.  Very good suggestions.  I'm not ruling out my TIU might be shot.  It has seen a lot of use in eight years, and one of the channels hasn't worked for a couple of years.  I don't want to have to make alterations just to run the scanner, I like the affect of hearing local transactions between dispatch and engines for CSX and NS while running.  When I'm running all Lionel, I'll run the scanner.

RRMAN, It's not a birdie and I only (exclusively) monitor the AAR frequencies.  The interference is definitely generated by a (any) MTH engine.  As I said, I'm not ruling out my TIU is going south.  If anyone has a scanner i.e. handheld and wants to do a quick try at this, I'd be curious what the outcomes are!

Thanks Guys,

Stack

I used my good Yeasu all-band handheld with long 2 meter antenna, and discovered a whine noise from 160.200MHz then every 200KHz increment to end of RR band that came and went with TIU on and off with or without engines on track.  Near track created the highest signal of course.  No noise on two meter (144MHz), 1 1/4 meter (222MHz) or 70 cm (420MHz) or other non-ham bands.  Interesting that it seems to only be in 160MHz.  Signal was powerful enough to break squelch no matter where I was in room or nearby areas.

Of course this is highly unscientific method and probably a spread spectrum analyzer could spot other interference frequencies of interest, especially those that could beat againt the radios internal IF amplifiers.  Or a different radio might hear other interferences.

Thanks rrman for taking the time to check this out for me.  My house is only single story so I increased my mast height another 10', which forced me to move my scanner another 10', and it ended up in the train room.  I was wondering if my TIU was the blame, guess it's not!

Stack