Reason why DC mag field disturbs communications on a train

The tracks have sensors for the trains at every rail crossing at a roadway, and at every station. There are also wireless networks in place that use proprietary protocols, which may be more susceptible. Seems unlikely though, considering the industry, that they would have such a vulnerability.

How strong a field could this possible be?

Have you confirmed that it is your field that is affecting them or is it a hunch? Maybe they have a dead spot, only rectified by moving out of a null.

What frequency band are they using? Most RR in US use VHF 160 MHz. Some trackside sensors for passenger trains use LF 10's of KHz coils to pace their position on the track. Is it such a system? Maybe the coils are being saturated?

Why not use a Mu metal sheild for your back wall in place of active cancellation?

Wouldn't elaborate? While it's possible that _their_ system has suceptibility issues? Interesting, to say the least. I'd talk to their boss, the one way up top, that often gets things moving.

I think they need to be a bit more cooperative here.

Europe has an inductive train safeguarding system operating with passive circuits at 500Hz, 1000Hz and 2000Hz (I am not 100% sure about frequencies though) and theoretically a core could saturate, causing malfunction. I've never heard that we had this in the US though, it would have avoided that terrible head-on train crash in L.A., among other accidents.

You wouldn't think so how ever, we do have a crossing point just a few feet up from there. They wouldn't elaborate as to what type of equipment was getting bothered, it may not even be the mag field being generated but the low level of irradiation (ski light) that maybe effecting their systems.

Not sure how ever, so we're setting up a schedule to turn down the gain on the DC amps and align the scan system using a lower external gauss field just to make sure.

In which case, it's not your problem. Ignore them until they get more cooperative.

Sylvia.

We tried that, that actually caused issues with our beam alignment.

What we did is a common practice for steering, we just did it on a larger scale to correct this problem. Most facilities build their units in locations to make sure this does not happen. This unit was put in place before my time and it was just convenient to put it there.

If it was me I would just tell process control to slow the line down and place one extra wrap on the conveyor, this would keep the dosimetry consistent even if the beam drifted a bit for a time. But you can't tell them that, it's balls to the wall 24/7 until something breaks.

We could have other issues that are causing problems with them,- I don't think it's a dead spot for them. The system uses a 100Khz 350K watt oscillator into a pie xformer that generates up a few Mvolts to the beam tune, from there we have electrons being steered down through the dyno rings, etc, etc,,.,

Firstly, you need to know how to spell.....

That carries about as much responsibility as the idiots at AIG handing out $165M in bonuses on our dime.

It seems a fair response. There doesn't appear to be a safety issue involved, just cost and incovenience for the train operator.

If the latter isn't willing to reveal the nature of the equipment that might be affected, then it compromises the OP's ability to understand what he might have to do to obviate the problem, or even whether its his equipment that's causing the problem. The OP has no reason to go to extra trouble (and expense, no doubt) in the face of an obstructive train operator.

Sylvia.

It's always nice, but why is that his first priority when it comes to solving this problem?

Sylvia.

On a sunny day (Mon, 16 Mar 2009 20:35:43 -0500) it happened Jamie wrote in :

Are you sure it is your stuff that does that? Ask them to move to the critical spot, and then switch your stuff off, and see if the problem persists?

While it seems unlikely that there is a connection, I have come across a situation where dc or low-frequency magnetic fields can affect low frequency rf receivers.

Ferrite pot cores and similar inductors can have their core permeability modulated by magnetic fields which are a very long way below saturation. This effect is definitely not just magnetic induction and it is quite difficult to shield against it. (A mu-metal enclosure worked well, and dust iron instead of ferrite for the inductor core worked well enough at much lower cost. I ended up using shielded dust-iron cored inductors from Coil-Q Corp.)

John

Also, what does "DC magnetic field" mean? It should mean "totally static". If it changes in any way its going to induce current in conductors. That includes passing conductors near the field, in which case also no longer static.

"Jamie" skrev i meddelelsen news:VZCvl.151585$ snipped-for-privacy@newsfe14.iad...

If they cannot be bothered to describe the problem then why should you care at all??

skrev i meddelelsen news: snipped-for-privacy@v38g2000yqb.googlegroups.com...

Excellent point - *now*, of course, one remembers an app. note describing a VCO that was controlled exactly like that.

snipped-for-privacy@v38g2000yqb.googlegroups.com...

it is VERY unlikely that the near static magnetic field that you or anybody else creates could disturb the comm equipment on a train. What is far more likely is one of these:

Find out what frequency they are using and use a spectrum analyzer to verify if you are radiating anything on that freq. or not.

Mark

You obviously do not know much about one's responsibilities under the watchful eyes of the FCC. Even if it is not a RADIO, if it emits magnetic energy that can cause a malfunction in an approved system, you can find yourself culpable.

meddelelsennews: snipped-for-privacy@v38g2000yqb.googlegroups.com...

It could affect the mass sensors on the tracks. Likely no effect on the comm gear. Unless, as you say, his noise is RF rich in the wrong spectrum.

(snip)

I would look at that subsystem first!

Yes, we have turned off the unit's operation to verify that the problem cleared up. I have no idea how long the problem has actually been there, they just commented on it one day while I was out in the back area with the doors open as they were reconnecting some box cars down the track.

I'm getting the consensus that it could be ski shine at the edge of the building which is where the top of the vault is. It's an Aluminum roof and we've had that area repaired several times over the years due to ski shine.

This particular unit is designed for 5Me but we never run it over 2.5Mev

I will be checking with a Rad monitor some time this week to verify the strength. We may need to raise the height of the concrete wall around the top of the T-section of the Beam tube..