Do some defect detectors transmit at a lot more power than others?

[JoshuaHufford]

On my local UP line running across Missouri, the defect detector at milepost 109.2 always comes in much stronger than any other, even if I'm closer to others. The other night was a record though, I measured the distance and I picked it up 38 miles away (used google maps measure tool), and I often pick it up even if I'm 20-25 miles away from it, this never happens with the other detectors in my are.

I'm just curious why this might be. I was using a Uniden hand held scanner with a roof mount antenna on my car at the time.

Thanks!

 

[iMONITOR]

Possibly be due to antenna location/mounting. Other metal acting as a director/reflector, creating somewhat of a directional yagi antenna effect?

 

[burner50]

Yes, some of them do, and some do not transmit over the air on voice frequencies at all.

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[spdfile1]

I'm big on monitoring Defect Detectors and it could be a couple factors. Different power settings, atmospheric conditions, what the other guy was mentioning about the signal reflecting off of metal objects and your location. I once sat at the edge of CSX DeWitt Yard in East Syracuse,NY and picked up the Syracuse Detector about 5 miles to the west of me but also the next detector which was the Memphis Detector about 20 miles west of me & also the Kirkville Detector about 10 miles east of me. Boy what a day that was!!!! All using a 1/4 wave whip tuned to 160 MHz!!!!!

 

[JoshuaHufford]

I doubt it is reflecting signals or the atmosphere because I routinely pick it up 20 miles away, and frequently pick it up 30 miles away all in different locations. However 38 miles was a new one, maybe it was the atmosphere that night.

 

[INDY72]

There has ben a LOT of tropo lately.. Big tropo. Mainly on the East side of the MS River, but some big ones in the ArkLaTex too.

 

[JoshuaHufford]

There has ben a LOT of tropo lately.. Big tropo. Mainly on the East side of the MS River, but some big ones in the ArkLaTex too.

Yes there has been. My ATCS server located in central Missouri has been picking up MCPs on the NS line in central Illinois at times!

 

[RRR]

As a signal maintainer, I have experience with DED and HBD units, they do not transmit very high power, and usually have a simple 1/4 wave VHF antenna mounted on top of the case. The best units were the "Southern technologies" ones that were used especially on NS in the 80's and up until the mid 2000's, very reliable units (on the electronics/radio side) You have to remember, all the DED/HBD unit is trying to reach is the receiver in the cab of that locomotive that went by about a mile or so ago. They are not intended to reach great distances, although due to terrain and good receivers on the listeners end, etc.,some do more than others. I have not saw one with an amplifier or any type to enable it to transmit more power. I have saw a couple with the 1/4 wave antenna up on a pole before, but thats pretty rare.

 

[JoshuaHufford]

Thanks for your insights, I always like to hear from people that work for the railroad.

I have seen this detector in person, it has an antenna probably 30 ft. in the air, but it is also right next to the Missouri river so it is pretty low elevation.

 

[spdfile1]

Speaking of detectors I've been putting together "Railfan Guides" for the CSX System and on some of the "Albany Division" subdivisions I've included sound recordings of the detectors back when they still said Conrail!!!! Click on the this link https://wiki.radioreference.com/index.php/CSX-Albany_Division and select from the list the following subdivisions to listen: Buffalo Terminal Sub, Mohawk Sub, Rochester Sub, Syracuse Terminal Sub, St. Lawrence Sub & West Shore Sub. These are recordings I made back in the early to mid 2000's

 

[KC2zZe]

As a signal maintainer, I have experience with DED and HBD units, they do not transmit very high power, and usually have a simple 1/4 wave VHF antenna mounted on top of the case.

DED?
HBD?

 

[radioman2001]

All the commercial branded detectors I have worked on have a power output of 1-5 watts. There were a few we replaced which were CDM-1250 mobiles turned down to 20 watts, but both had just a 17 in whip on the box for an antenna. Range can depend on location, such as on a hill or rise, and 5 watts can travel quite a distance if on top of a hill compared to your RX location.

 

[N9PBD]

DED?
HBD?

DED = Dragging Equipment Detector
HBD = Hot Bearing Detector "Hotbox Detector"

 

[baayers]

It’s funny that I see this thread because I experienced the same thing Saturday night. The atmosphere was playing super nice and I successfully heard a defect detector from north of Ocala. I live in Pinellas County now so that made the defect detector a little over 100 miles away.

The other thing that can make a difference for every day reception is your height. I remember when I lived in California one time I was heading up to big bear and as my height above sea level continue to increase so did the amount of rail traffic I heard. On top of the numerous amounts of defect detectors I was hearing I also successfully heard both sides of the conversation between a Pacific surf liner train and union pacific dispatch where they were setting up a meet just north of Ventura.

 

[N9PBD]

If you're interested in what VHF propagation is doing right this minute, check out VHF Propagation Map The site monitors amateur radio Automatic Packet Reporting System (APRS) beacons, and plots the ranges.

You never know what you're going to hear when tropo starts opening up.

 

[JoshuaHufford]

If you're interested in what VHF propagation is doing right this minute, check out VHF Propagation Map The site monitors amateur radio Automatic Packet Reporting System (APRS) beacons, and plots the ranges.

You never know what you're going to hear when tropo starts opening up.

Wow this is really interesting, thanks.

So the darker the color the better I'm assuming?

Is there anything similar for the 900 Mhz range?

 

[N9PBD]

Wow this is really interesting, thanks.

So the darker the color the better I'm assuming?

Is there anything similar for the 900 Mhz range?

The more red the longer the range, and this is the only one I've seen like this. It leverages a pretty extensive worldwide network of amateur radio APRS stations on 144.390 MHz, that are linked via the Internet (http://aprs.fi) hence the VHF nature of the site.

 

[RadioDitch]

All the commercial branded detectors I have worked on have a power output of 1-5 watts. There were a few we replaced which were CDM-1250 mobiles turned down to 20 watts, but both had just a 17 in whip on the box for an antenna. Range can depend on location, such as on a hill or rise, and 5 watts can travel quite a distance if on top of a hill compared to your RX location.

I've had the same experience. Generally I've seen between 2-5w with a 1/4 wave NMO whip mounted on the box. The big exception I recall is up in Quebec on the QNS&L. Several of their detectors on the south end are cranked up to 50w with pole mounted Sinclair SD210 single dipoles due to the nature of the railroad being perched on a granite shelf for quite a ways, and train lengths that regularly exceed 8,000ft. UP also has (or had) a couple up on Donner that were using 20w-25w.

 

[wbloss]

Yes there has been. My ATCS server located in central Missouri has been picking up MCPs on the NS line in central Illinois at times!

can you talk a bit more about the ACTS Server - is that the 900MHz stuff or something else?
Thanks

W



PS - have been hearing some RR NXDN in far SW MO

 

[burner50]

I've had the same experience. Generally I've seen between 2-5w with a 1/4 wave NMO whip mounted on the box. The big exception I recall is up in Quebec on the QNS&L. Several of their detectors on the south end are cranked up to 50w with pole mounted Sinclair SD210 single dipoles due to the nature of the railroad being perched on a granite shelf for quite a ways, and train lengths that regularly exceed 8,000ft. UP also has (or had) a couple up on Donner that were using 20w-25w.

In dark territory, it is extremely advantageous to have detectors transmit further distances so that if something is occupying the main track without authority, crews around then will have ample warning...

Dispatchers hate it because they hear all of them from their towers and the chance of a train overrunning their authority is low.

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