Tag Mounting

Placing the tags on your rolling stock.

Tags

You should use the StaRFIshrail tags.  These have been carefully designed to be the best compromise for all gauges of model railway - N, OO/HO and O.  They have a read distance of 30mm. If you want to try other tags, see the bottom of this page for specifications, but STaRFIshrail only guarantee that the system will work with StaRFIshrail tags, and the Murata tags mentioned at the bottom of this page.
The StaRFIshrail tags are approximately 9mm by 6mm, and are on a 0.1mm FR4 board.  As you will see from the various photos on this page, these fit well on anything from N to O gauge.
The picture shows the front and back of a StaRFIshrail tag, with a section of N-gauge track for scale.

Tag Mounting and Testing

This is where the magic happens - the communication between the Tag on your rolling stock, and the aerial.  As everyone's layout is different, and there are different gauges and tags, you need to work out which is the most suitable position for your rolling stock.
The picture shows the relative size of the StaRFIshrail tag, the aerial, and N-gauge track.

Basics

The tag has to be mounted with three considerations in mind.
1] The vertical distance between the tag and the aerial.
2] The distance between the tag and any metal in your rolling stock.
3] The centralisation of the tag over the aerial.
In addition, if you want to put two tags on a loco, say, in order to work out direction of travel, they should be spaced at least 30mm apart for N-gauge, or 60mm apart for OO/HO gauge.

Read ALL the information below, before positioning tags.

You need to read and understand all the information below before positioning tags - and look at the photograhs, to show you what you should do, and what should be avoided.  Once you understand this, positioning tags for best reception is easy.

Tag to Aerial Distance

The tag must be placed within the read distance, otherwise the tag will not be read. For the StaRFIshrail tags, the read distance is 30mm.  However, it is best to have a few mm overhead, so try to limit the read distance to, sya, 27mm.  Locos tend to have the bottom of their chassis fairly close to the track, whilst trucks and carriages tend to have the bottom of their chassis around the level of the top of the wheels.
For example, using the diagram on the left, for a OO gauge railway, the following typically applies:
Baseboard 9mm
Trackbed (cork) 3mm
Sleeper and Rail 5mm
This gives 17mm, and with a typical rail to axle centre of 6mm, shows that the tag can be mounted above the level of the axle. To be safe, you can mount the tag 4mm from the bottom of the chassis, and everything will work fine.
For O gauge, you may need much more spacing, but on trucks and carriages, the tag will probably be no lower than the axle.

Tags and metal

It is essential that the tag is placed away from any metal plates by around 3mm.  Some rolling stock is completely plastic, so is not a problem.  Some rolling stock has a metal plate embedded in the base of the truck or carriage, to give it strength, and some rolling stock is completely metal.  You MUST have at least a 3mm gap between the tag and any metal, in order that the RF field can form an electro-magnetic loop.  The tag should also not be mounted with the axle between the tag and the track, as this may affect the electro-magnetic loop.  The picture shows a tag offset from the bottom of an OO truck with a 2mm foam spacer, in the middle of the body (from side to side), and a little distance away from the axle.  To be safe, if there is room, use a 2mm foam spacer.  For all metal-bodied rolling stock, such as that constructed in brass, use 4mm of foam spacing.

Centralise the Tag

The aerial should be placed centrally under the track, and the tag should be placed centrally (side to side) under the rolling stock. It is not essential that this is exactly in the middle, but try and get the tag approximately in the middle, side to side. When placing tags on carriages with bogies, tag should be placed on the bogies, rather than centrally (end to end) of the chassis. The aerial has a fairly tight reading field side to side, and if placed on a curve, the centre of a carriage with bogies may well fall outside the reading range.
The picture shows a bogie mounted tag - no spacer is needed as the bogie is all plastic, and will thus be spaced the required distance away from any metal that might be in the carriage.
For N-gauge, the tag can be mounted either across the track, or in-line with it.  ForOO/HO mounted the tag in-line, and for O gauge, where the larger aerial is used, mount the tag across the track.

Putting the tag in place

The tag can be attached to your rolling stock in different ways. 
The StaRFIshrail tags can be stuck on with double sided tape on the non-chip side - be careful when trimming you do not cut the pcb, or it can be glued on with almost any glue, PVA and UHU work well.  The spacer material supplied with the tag is also self-adhesive.  You can also use masking tape if you want to temporarily stick the tag on, and this can be used over the chip side. 
The picture shows a tag mounted on a 2mm foam spacer between the wheels on a OO gauge loco.

Testing the Tag

You should test that the tag works prior to making it permanent on your rolling stock.  Once you have one aerial installed on your layout, you can use this for testing.  Make sure the tag works, by holding it close to the rails over the aerial, and seeing that the RFID LED works.  Then attach the tag to the bottom of the rolling stock using a piece of scotch tape, run the rolling stock on the rails over the aerial, and check the RFID LED.  If it does not work, then you may need to spacer the tag away from the chassis, and then try again.  Once you have done one or two tags, you will know what works, and then you can permanently attach the tag (and spacer if required).

Examples of StaRFIshrail Tag Installation

N-gauge

StaRFIshrail tag on a Graham Farish 0-6-0 loco.  No spacer required, mounted in-line.  However, in this instance, because of the metal in the loco, the read distance is limited to 21mm - but this is offset by the fact that the tag is very close to the top of the rail.

N-gauge

StaRFIshrail tag on a N-gauge truck - with a 2mm spacer, mounted in-line.

N-gauge

StaRFIshrail on a Dapol DMU - there is no spacer, but the tag is across the track rather than in-line with it, as in this case the tag fits better.

OO gauge

Two tags mounted on a Hornby 0-6-0 shunter, each with a 2mm spacer.

OO gauge

Tag on spacer, showing approximate centring of the tag with the wheels.

OO gauge

Tag on Bogie - no spacer required.

O gauge

Tag on about 12mm of spacer, to bring it close to the position of the axle.

O gauge

Tag on truck - not easily seen!

Other Tags

It is possible to use other tags than the StaRFIshrail tag.
The only two that have been tested are made by Murata, and are available from Digikey.
The 8mm tag has a read distance of slightly over 30mm, maybe a touch more than the StaRFIshrail tag, and it's part number is LXMSAPHA08-136 .
The 3mm tag, which is only suitable for N-gauge and below, and where the aerial is under the track rather than under the baseboard, has a read distance of 15mm, and it's part number is LXMS33HCNG-134.
Other tags may be available, but they must be of the right specification.  The tags use 13.56MHz, and ISO15693 protocol.  Note that tags compatible with the RC522 reader use ISO14443, and thus are not compatible with the StaRFIshrail system.