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Metal bodies and aerials


Regularity
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  • RMweb Gold

Has anyone on here practical experience of fitting aerials into metal-bodied locos, and getting good running?

 

For tender locos, I presume that fitting it into the "coal space" and hiding it under a non-metallic false load would work, and maybe for a PCB type aerial on an nRF24L01+ 2.4GHz transceiver, it might even be possible to put this in the bunker of a tank engine, but what about where the bunker is inside the cab, or indeed for diesel/electric boxes?

 

I have been considering the conversion of Lydham Heath to some form of BPRC, subject to fitting everything in, but if I can't get a transceiver to accept a signal on the ex-GWR 517 loco (see below), it will be a non-starter.

(Carlisle, the 0-6-0, has a plasticard body, so this won't be a problem.)

BCRS0024-1-300x189.jpg

(Linked photo from BCRS website)

 

Obviously, if building for myself, I could consider such ideas as fitting a styrene roof, with the aerial/transceiver under it, but this is rather nicely built and finished by Laurie Griffin, so I would rather not tamper with it.

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This Bagnall has a whitmetal body, albeit no roof..... the receiver is in the left hand coal bunker surrounded by white metal but with coal on top. This works fine for me......

 

36779795244_a684602144_b.jpg

IMG_2043 by giles favell, on Flickr

 

This steam crane has a receiver buried within the body, which is brass and nickel silver - again no signal problems experienced.....

45021378404_139bd958f9_b.jpg

2018-11-06_09-10-28 by giles favell, on Flickr

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For small size I sawed the PCB antenna from an nRF24L01+ and soldered on a short piece of flexible wire about 35mm long. (I think I used the same length as Deltangs use). It has worked fine for the short ranges that I use. I have not tested its ultimate range. This may give you some flexibility - however @Giles' experience is reassuring.

 

Some years ago I had a Deltang receiver in a metal bodied Graham Farish large prairie. I think I ensured that the antenna wire poked out through the window.

 

...R

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Modern comms protocols, run over 2.4GHz, are incredibly good at withstanding all sorts of terrible propagation/reception conditions, so are far less affected by the presence of metal structure, and Intermittent contact at wheel/rail, which used to be a problem with earlier systems.

 

The ‘bit of wire’ in the corner of the cab here is the aerial, and the loco is entirely metal.

 

Provided that the signal can get in, it seems to matter not if it bounces around a bit. I’m sure there must be a minimum hole size, related to wavelength, but my radio theory is weak and decayed, so I don’t know what it is.

 

Range on even very low powers in aggressive conditions is impressive too. I can drive garden trains from indoors on the other side of the house, despite The fact that the house has foil-backed insulation all over it.

 

 

 

 

 

757CE11C-66FA-45EB-8F31-BD76B499EA95.jpeg

Edited by Nearholmer
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8 hours ago, Regularity said:

Has anyone on here practical experience of fitting aerials into metal-bodied locos, and getting good running?

 

For tender locos, I presume that fitting it into the "coal space" and hiding it under a non-metallic false load would work, and maybe for a PCB type aerial on an nRF24L01+ 2.4GHz transceiver, it might even be possible to put this in the bunker of a tank engine, but what about where the bunker is inside the cab, or indeed for diesel/electric boxes?

 

I have been considering the conversion of Lydham Heath to some form of BPRC, subject to fitting everything in, but if I can't get a transceiver to accept a signal on the ex-GWR 517 loco (see below), it will be a non-starter.

(Carlisle, the 0-6-0, has a plasticard body, so this won't be a problem.)

BCRS0024-1-300x189.jpg

(Linked photo from BCRS website)

 

Obviously, if building for myself, I could consider such ideas as fitting a styrene roof, with the aerial/transceiver under it, but this is rather nicely built and finished by Laurie Griffin, so I would rather not tamper with it.

On our all metal live steam locos (16mm), we tend to mount aerials in the cab roofs. They are exposed to lots of different weather conditions, extreme temprerures, steam, oil etc etc.

 

These days with modern RC equipment, we get very few, if any issues. Last season we had a servo wire move and the insulation melted. That loco is twenty years old though. Heat shrink and rerouting put it right.

 

Back in the day, with 27MHz RC kit, in live steam locos we would get the 'rusty bolt', 'rusty rail' or 'wet rail' effects, ie corrosion causing issues or moisture/damp/wet affecting, in effect, the aerial length and thus attenuation type interference and erratic behaviours (plus site specific issues too - including issues with walled gardens). Also, some early mobile phones seemed to cause issues from time to time.

 

Blue Tooth Control (BTC) can be affected by brass bodied locos etc.

 

These days, as Giles states, there should be little or no issues for you, using RC. Indoor model railways are fairly benign environments.

 

Kind regards,

 

CME

Edited by CME and Bottlewasher
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  • RMweb Gold

Next question, how easy is it to connect the output from a DCC system, directly or from the rails, to a transceiver to convert and send the DCC signal over 2.4Ghz, and to then convert the signal back to DCC for feeding to a standard DCC loco decoder?

 

If that sounds clumsy, all I mean is, can something like Tam Valley Depot's "dead rails system" which uses instrument band radio signals, be done using an nRF24L01+ 2.4GHz transceiver?

750_DRS1.002_750.jpg

 

To anyone wondering why I might want to do this, the answer is light and sound.

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Bear in mind that not all of the systems that use 2.4GHz are using what is called WiFi, which is a particular subset of the family of links that operate (in the UK) at 2.4GHz, but going direct to WiFi because it is popular and well-developed, if you ferret about on the web you can find ways to run dcc over WiFi, including "dead rail" sytems.

 

This looks like a commercialised system with multiple options http://www.wifitrax.com/appNotes/WiFi-DCC.pdf

 

 

The question asked about WiFi at exhibitions is very pertinent though, because a hall full of users who have forgotten to turn their personal hotspot off can create havoc. 

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2 hours ago, Regularity said:

Next question, how easy is it to connect the output from a DCC system, directly or from the rails, to a transceiver to convert and send the DCC signal over 2.4Ghz, and to then convert the signal back to DCC for feeding to a standard DCC loco decoder?

 

I would say it is next to impossible because you cannot guarantee the latency of any wireless system - lost packets are common. Much better to send data - for example a number representing the speed - and have the receiver generate the DCC signal based on that data.

 

Also keep in mind that "normal" DCC modules expect the "signal" to carry power as well as information.

 

Another consideration is that the DCC information in the tracks will be for several locomotives. It would make more sense only to send by wireless the data for the locomotive with the receiver.

 

...R

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  • RMweb Gold

Robin,

CV 11can be set so that the last command remains in force until a new one arrives, so constant traffic is not required, and latency of a second or so is not an issue for me.

I am aware of the need to “blend” the signal back into the power, too. Was just asking if it technically simple.

Unless operating a very simple layout, then having direct handset-loco connections is a complication. I can foresee the need for up to 4 drivers, with maybe a dozen locos to choose from between them. The centralisation of DCC allows me to do this with controllers, each able to select a loco providing it is not in use. I know that the Deltang “selecta” would be viable with two controllers in use, but DT himself told me that each receiver could only bind to two transmitters.

Essentially, I want the technology to do what I want, how I want it to, not change how I do things because that’s what the technology dictates.

(A lot of my professional life has consisted of doing things for people with the inevitable response from them of, “ I didn’t know you could do that with xxx.” That’s just my mindset.)

 

Kevin,

I didn’t  mentioned WiFi. It’s a potential option, but I am wary of it for precisely the reasons you mention!

BTLE might be worth considering, I suppose.

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Robin

 

Yes, I think you can be pretty sure that the systems used convert the DCC signal to a numerical form, carry it over the wireless link, then covert it back to DCC format before passing it to the DCC device.

 

The power for the loco can be derived either from an on-board battery or from a constant voltage on the track (but I can’t see why anyone would want to use the latter if using wireless control direct to the loco, except possibly in very tiny scales, where a loco is too small to accommodate a battery).

 

Regularity

 

i know you didn’t mention WiFi, I only dragged it into the conversation because it is a widely available 2.4GHz system (which is what you mentioned) for which DCC-carrying has already been developed and is commercially available.

 

You could carry DCC on a wide variety of radio frequencies (Tam Valley seem to use c800MHz), but I agree with Robert that you would need to convert the strange old DCC signal to a data format first, and reverse the process on receipt.

 

It all seems very roundabout to me, in that the DCC signal must be created in the first place based on a set of digital data instructions .......... it might be simpler not to create it all, packet-up the data, sling it over wireless to a decoder that reads said data. Nowadays, I keep wondering why we don't see IP-addressable devices on model locos, in the same way that we do in light-bulbs for instance. It feels as if DCC is a specialist application, rooted in carrying the signal on the traction power supply, which will die out in time. I notice that the supplier that I pointed to can implement DCC over IP, and that feels like a first step towards getting rid of "the middle bit".

 

Kevin

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41 minutes ago, Regularity said:

Unless operating a very simple layout, then having direct handset-loco connections is a complication. I can foresee the need for up to 4 drivers, with maybe a dozen locos to choose from between them. The centralisation of DCC allows me to do this with controllers, each able to select a loco providing it is not in use.

 

I'm not sure I understand that. Do you mean that you want 4 handsets and each one can select any one of maybe 12 locos?

 

I made something like that using an Arduino-based system with nRF24L01+ wireless transceivers - they don't "bind" in the way that the Deltang system does so each wireless transmission could be to a different loco and there could be 10 or 20 transmissions per second. With my system the control was from a web browser on my PC or phone (or both) and an user could select any loco that was not already in use by another user. Have a look at this Simple nRF24L01+ Tutorial if you are interested.

 

...R

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That is very interesting ......... did you then create the DCC signal on-board the loco, and feed that into the decoder, or did you "behead" the decoder and feed it data in a simpler way?

 

Is the 

38 minutes ago, Robin2 said:

nRF24L01

using a simple form of radio, or is it a form that is very robust like DSSS or FHSS?

 

I ask, because a simple system is likely to be quite interference-prone.

 

 

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10 hours ago, Nearholmer said:

That is very interesting ......... did you then create the DCC signal on-board the loco, and feed that into the decoder, or did you "behead" the decoder and feed it data in a simpler way?

 

I have not used DCC at all but it would certainly be possible to create a DCC signal with an Arduino-type microprocessor

 

 

Quote

Is the nRF24L01

using a simple form of radio, or is it a form that is very robust like DSSS or FHSS?

 

I ask, because a simple system is likely to be quite interference-prone.

They are very robust and have a lot of error correction built in. AFAIK the same wireless devices are used within some of the off-the-shelf RC equipment.

 

...R

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  • RMweb Gold
12 hours ago, Robin2 said:

I'm not sure I understand that. Do you mean that you want 4 handsets and each one can select any one of maybe 12 locos?

Yes.

In data table terms, a many to many match.

Quote

I made something like that using an Arduino-based system with nRF24L01+ wireless transceivers - they don't "bind" in the way that the Deltang system does so each wireless transmission could be to a different loco and there could be 10 or 20 transmissions per second. With my system the control was from a web browser on my PC or phone (or both) and an user could select any loco that was not already in use by another user. Have a look at this Simple nRF24L01+ Tutorial if you are interested.

That's the sort of thing I had in mind, but driving DCC decoders - that is not such a problem as there are plenty of Arduino solutions for that.

 

Thanks: I will have a look.

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