StaRFIshrail

Installing Aerials

How and where to place aerials

Installing Aerials

Installing aerials in easy, providing you follow a few basic rules, and will result in detection of rolling stock easily.
When installing a system for the first time, please follow the Out-of-Box testing advice first (press button below to go to Testing page).
Once you have installed one or two aerials, then it becomes much easier - remember extra aerials are available if required, or if you find you have placed them in the wrong place.  Attaching with masking tape to start with is probably a good idea, as this can be removed - the sticky back on the aerial is more or less permanent.

Placing Aerials

Aerials need to be placed reasonably accurately with respect to the track, to give the best performance.  The aerials are rectangular, 25mm long and 15mm wide, with a little tag at one end where the wires connect.  On one side there is a pull-off strip, which exposes a sticky surface.  This sticky strip is permanent - once stuck you will almost certainly not be able to remove the aerial without damaging it. The aerial is very thin, but actually quite robust.  The aerial must be kept flat, but the tag on which the wires are attached can be bent through 90 degrees, if you are mounting the aerial under the track, rather than under the baseboard.
The RF field of the aerial is quite small, it only extends around 5mm outside all around, so aerials can be fitted very close to one another without interfering.  This does, however, mean that the aerial need to be placed correctly with respect to the track.  The aerials should be placed "in-line" with the track, with the long edge parallel to the rails.
You can mount the aerials without using the sticky back - just tape the aerial to the bottom of the baseboard using masking tape - this will enable you to reposition the aerial if you need to.
The aerials come fitted with a 0.1" housing, which can be plugged directly into the reader board.  However, you can extract the crimped cables from the housing, if you are installing the aerials above the baseboard, which will make it easier to thread the wires through the baseboard, and then put the housing back on.

Gauge considerations

There are two sizes of aerials - small at 25mm by 15mm, and large at 45mm by 35mm.The small aerials have a read distance of 30mm, the large aerials have a read distance of 42mm.
For Z gauge, use the small aerials - with the StaRFIshrail tags you will get 30mm read distance, but the smaller Murata tags (3mm square) you will get 15mm.
For N-gauge, use the small aerials and the StaRFIshrail tags, for a read distance of 30mm.
For HO/OO gauge use the small aerials if your baseboard and track bed are less than 18mm.  If, however, you have the North American preferred 1/2" Homasote over 1/2" ply, then you should use the large aerials.  Use the StaRFIshrail tags with either aerial type.
For O gauge, use the large aerials - though you can use the small aerials if your baseboard and track bed are less than 12mm. Use the StaRFIshrail tags.

In general, you should try and place the aerials beneath the baseboard, providing your baseboard is not too thick - most model railways are on a 9mm (3/8") baseboard, but if you have a thicker baseboard, then you will need to work out the distance between the aerial and the tag, to make sure that there is less than 30mm between the two.  


Aerial Length


The reader board comes in 4 flavours - Short, Medium, Long and Extra.

For the 25mm by 15mm aerials, the length of the aerial wire is:
Short 13cm
Medium  23cm
Long  43cm


For the 45mm by 35mm aerials, the length of the aerial wire is:Long  9cm
Extra  33cm


The reason for the different lengths is the matching of the aerial to the reader board.  You must understand the above, and order the correct aerial length and type when ordering the reader boards, which come with the matched aerials.  If you are ordering extra aerials, make sure they are matched to the reader board.  Do NOT make a different reader board and aerial length/type combination, this will result is a much reduced read distance.





Aerial positioning

You MUST mount the aerial centrally to the track - this will give the best pickup, especially at high speed.  The best way to do this is to drill two small holes (maybe 1mm) centrally between sleepers at around 30mm apart, and then use these as the positioning point when installing the aerial under the baseboard.  A mm or two either way won't make much difference

Under the baseboard

This is the easiest way to install aerials, especially on an existing layout.  However, you need to make sure that the read distance is kept less than 30mm - ideally, a few millimetres less than this will give some overhead.
You should centre the aerial in the middle between the tracks, and use the aerial in-line, that is the 25mm length in the direction of travel.  The easiest way to do this is to drill two small holes (1mm) in the centre of the track, about 30mm apart, and then align the aerial between these holes from the underneath.
With a 9mm(3/8") baseboard, a 3mm track bed, and a normal HO/OO track, the distance to the running rail top will be around 18mm.  With wheels of 12mm diameter, this means that the tag should be placed a couple of millimetres above the line of the axle.


Above the Baseboard

If you have a thick baseboard, you can install the aerial immediately under the sleepers, or under a trackbed such as cork.  If you are doing this on a new layout, then there is little problem .  You can either drill a 8mm hole and feed the aerial wire with housing through it, or a 6mm by 3mm slot hole - done by removing the aerial crimps from the housing, feeding the wires through the baseboard, and then re-assembling the housing.  The aerial can then be stuck to the baseboard, the track laid on top, and then landscaped. 
For existing layouts, you will need to make the hole, remove the landscaping, fit the aerial, lay the track back and then re-landscape.
If you are running N-gauge or below, and want to use the smallest 3mm tags, then you will need to put the aerials under the track. You may put the aerials across the track for N-gauge, but for HO/OO and O gauge, the aerials must be in-line with the track.
For O-gauge, use the 45mm by 30mm aerials - this is an ordering option.
The picture shows a 25mm by 15mm aerial mounted below the sleepers on HO/OO gauge - you could also mount it below the trackbed.

Gaps between Aerials

The aerials cannot be too close together, and you must maintain the minimum distances shown in the picture.  However, the distances are actually quite small - even for N-gauge, where parallel track spacing is around 33mm, you can put two aerials side-by-side under parallel tracks.  For OO/HO gauge, you can even put an aerial centrally spaced under back-to-back points, and there will be no false reads.

Running Aerial Wires

Aerial wires should be taped to the bottom of the baseboard.  They should not be coiled or bundled, and where there is extra length, they should be snaked.  They should be kept 10mm away from other aerials wires.  If you have crossing aerial wires, consider how you could re-route the wires to stop the crossing - it may mean putting the aerials in a different order on a dual or quad reader, or even moving the reader board.
Note that some aerials may have a red stripe on one wire - this is because the aerial wires have been unzipped from a multi-way flat cable - there is absolutely no difference between aerials have a red stripe and those that do not.

DOs and DO NOTs in Pictures

DO SNAKE CABLES

Where aerial cables are longer than required, snake the cables.

DO KEEP CABLES APART

Keep aerial cables 10mm apart.

DO TAPE OVER CONNECTIONS

Tape over the point at which the aerial wires meet the aerial - this will give strain relief, and will make the wiring more robust.

DO NOT COIL CABLES

DO NOT coil aerial cables when they are too long, this will result in degraded performance - always snake longer cables. Keep aerial cables 10mm apart.

DO NOT BUNDLE CABLES

DO NOT bundle aerial cables, always keep them 10mm minimum apart.

DO NOT ALLOW CABLES TO HANG

Cables should be attached to the bottom of the baseboard, not allowed to hang. Although this won't affect performance, damage could easily occur to the aerial.

DO TAPE CABLES TO BASEBOARD

Keep the cabling neat by taping the aerial cables to the underside of the baseboard.

DO CROSS CABLES AT RIGHT ANGLES

Where aerial cables need to cross other cables, try and do it a 90 degrees - this will stop interference.

DO USE CORRECT LENGTH CABLES

The reader board and the cable length MUST be matched - if not, read distance is severely compromised.

DO NOT RUN CABLES OVER AERIALS

Aerial cable should not run over other aerials - route the cable around.

DO NOT CROSS AERIAL CABLES

If aerial cables cross, try changing the order of plugging the cables to a multiple reader, or changing the positions of the readers.

DO NOT LEAVE AERIALS UNCONNECTED

Reader boards MUST have all their aerials connected - otherwise the reader chip could overheat.


StaRFIshrail is a trading name, and trademark, of 292 Design UK Ltd
CBUS is used with permission of the Copyright holders.
CAN is a trademark of Robert Bosch GmbH.