New UP antenna

[up2615]

Also the firecracker isn’t what people think it is. It’s pretty much just a housing for a very flimsy element inside - not as awesome or super as people think they are/were - and why the Sinclair gained popularity.

if you crack one open you’ll see it’s just some wire. One of the reasons why Motorola incorporated a SWR sensor into their radios (will display “bad antenna” on the display in a high SWR/short condition).

Thought I would chime in on the firecracker.

I am posting this information about my interest regarding this very popular North American VHF railroad antenna as there seems to be some incorrect information on this and other sites regarding it. To clear the air...

The ASP-16's predecessor was, as far back as I can ascertain, a Farnsworth Radio Laboratories model M500-2. The antennas patent was submitted April 28th, 1947 by Robert G. Schriefer of the Farnsworth Research Corporation of Indiana, and granted November 28th, 1950, number 2,531,476 as an "Ultra-high frequency antenna". Here is one in my collection with before/after restoration. It is unique in the fact that there are two dissimiliar metals that make up the antenna. The inner support and outer can is steel, however the foot is brass.



Today's version of the ASP-16 antenna is an omnidirectional, 50 Ohm, all brass, rugged, single band, non-tunable type with a nominal frequency bandwidth of 4 MHz between 158-162 MHz when properly attached to a surface that will provide an acceptable ground plane. Overall length excluding SO-239 is 11 3/8" with a weight of 4lbs 4 oz and a listed power capability of 100 Watts.



The antenna is comprised of a SO-239 UHF connector on the center bottom of a circular mounting foot that has four holes to mount to a locomotive or railcar. The foot is 2 13/16" in diameter which is welded (brazed) to a 1" diameter brass pipe that extends from the mounting foot approximately 11" to a brass disk. This brass disk (looks as if it) is welded to a 3" diameter, 1/8" thick cylinder that is 8" long that surrounds the supporting 1" pipe and makes up the most visible part of the antenna.

The center conductor of the coax enters the antenna via an SO-239 in the mounting foot and is brought up through the 1" pipe via a silver wire to a wide nut encapsulated in plastic. The energy is then sent through the 1" pipe via holes to the outside 3" cylinder via silver all thread that is electrically coupled to it via star lock washers held in place by ny-lock nuts. From here the electrical path takes the energy up to the top disk of the antenna where the center supporting pipe will take it all the way to ground via the supporting foot and the ground of the SO-239.



The antenna really isn't as flimsy as some would say. In my personal experience with this antenna I have found it to have just as good of radiation qualities of a quarterwave whip. Other than having a higher profile over the Sinclair Excaliber antennas which make it a bit more susecptable to damage the engineering and construction that goes into this antenna is one of the reasons it is quite robust - making it a little more expensive.

You can see the same photos at: Firecracker Photos

 

[up2615]

Hello Arlo,
This picture came from another group but is also on Union Pacific. Any chance this is what the antenna you saw looked like? I don't have an answer for what it is exactly but if it does look similar, maybe someone else will be able to identify it.

The antenna you are referring to is made by PCTel and is model # PCT-LCMGPS-PTNF-UP. The antenna when available from PCTel never contained the suffix of UP. Pretty sure the 'UP' suffix was added for UP's mass order of the model and may have contained other special spec'd options. The antenna covers LTE Cellular, MIMO of 2x690-2700MHz @ 2dBi + GPS. So anything you can think of between 690 and 2700MHz could be used - possibly WiFi too.

 

[PJH]

The “firecracker” hasn’t been used on any new order of locomotives (essentially) since the 1980’s, give or take. The SD50 was the last model where you saw any decent installation of them - and was mixed. SF and BN had mixed orders with them, Southern had some as well.

The antenna housing itself was not flimsy, but the element was and was subject to internal corrosion, and degradation of performance.

The SD60M is where you started to see the low profile antennas take hold as well as better technology developed.

 

[AK9R]

Folks, the antenna that the OP asked about is clearly larger than a locomotive "firecracker" antenna and it's not being used on a locomotive.

Let's try to stay on topic.

 

[wa8pyr]

So what your saying is: It is an awesome super expensive plastic case for a coil of cheap wire. Sounds like a lot of products in use.

Actually metal, specifically painted brass. Not sure what kind of antenna PJH is referring to but the actual firecracker antenna I've used/installed (the ASP-16) is a broadband 1/4 wave antenna; it uses a large piece of tubing instead of a piece of stiff wire to both make it physically shorter (11" vs 18") as well as wider bandwidth (covers 158-162 MHz). The outer part you see is an integral part of the antenna, not just a housing for a piece of wire. The whole antenna is pretty heavy and very substantial. Has an SO-239 connector at the bottom and fastens down with a whole mess of screws. Handles 100 watts.

A picture in an earlier post showed one taken apart; basically what's going on is that the center tubing and wire are an extension of the feed cable coming from the radio, making it a top-fed 1/4 wave.

Some railroads use the Sinclair Excalibur, which looks like an inverted ice skate but apart from that is a wide-bandwidth 1/4 wave antenna with very low profile (about 3").



As far as what the OP is asking about, I'm almost positive I've seen that thing in a catalog in my office (I remember making rude jokes about it's appearance); I'll have to dig around and look.

 

[PJH]

This is a better view of the antenna that the OP is speaking of.

 

[INDY72]

From this view, it looks like an longer version of the same thing discussed. From it being mounted on what appears to be a CP (Control Point) box, that antenna would be 18 to 24 inches in length topping an 30 to 32 inch mast? Total height including structure would be about 8 to 10 foot? Even at 100 Watts, that would not be too big a RF footprint. Around 5 miles give or take a mile?

 

[PJH]

Again, they are just Wi-Fi data antenna use for locomotive access and status and a few other applications.

in signaled territory they are colocated at the signal shack (typical two mile spacing). In TWC areas, they are placed at strategic locations.

the modern locomotive antenna farm consists of the following antennas:

1 Voice Radio
2 220 PTC
2 UHF DPU
1 UHF EOT
3 GPS
Cell/Wi-Fi options

Wi-Fi is typically used for internal data to the railroad and cell is used for Trip Optimizer, LEADER, remote diagnostics, event recorders or whatever.

 

[iceman977th]

Just saw this photo come up on RP.net with the same antenna as PJH listed, except on the B&LE. I assume it's for cellular for codeline, nothing else B&LE would be using it for.

Mike

https://railpictures.net/photo/751653/