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 Remote control frequency

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Bearcastle



Location: Brie

PostSubject: Remote control frequency   Wed Jul 22, 2009 1:56 pm

I have the choice of having 27 Mhz or 40 Mhz.

Is there any good reason to choose one instead of the other?

scratch
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Carl Hibbs
Admin


Location: Haute Normandie - visitors welcome

PostSubject: Re: Remote control frequency   Wed Jul 22, 2009 3:52 pm

Not really much difference in the garden Laurent. I use both.

Somebody had or published a list somewhere of all the allocated freqencies for model use.

I'm sure it was someone on this forum. Question
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mikeyh



Location: Dordogne France

PostSubject: Re: Remote control frequency   Wed Jul 22, 2009 4:04 pm

It's interesting if you 'google' '27Mhz or 40Mhz' I know that they say that 27 gives a lot of problems, but there seems to be as many against as for. so as Carl says it doesnt seem to make a lot opf difference. the thing to avoid is the herzband that model fliers use!

Mikey
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Guest
Guest



PostSubject: Re: Remote control frequency   Thu Jul 23, 2009 1:20 am

27 MHz was used traditionally in R/C system. More than 20 years ago, with the occurence of very highly powered Citizen band radio (CB), this frequency band which was already quite crowded have became very noisy and driven to a lot of big crashes. So it was replaced by miscellaneous frequencies, though, not all the same in the world nor within Europe. In the US, this is 72 MHz (unlegal in France), In Germany, this is 40 MHz (also unlegal in France). The legal frequencies in France for R/C equipment are in 41 MHz band, while some channels are strictly reserved for Aircraft, considered more critical equipment (mind why ?).

Now, the frequency 27 MHz is still used by toys and other low cost equipment, nearly always in AM modulation. It have though disappeared from ordinary R/C equipment.
Whatever the band (41 or 27 MHz), it is advisable for good quality transmission to use FM modulation, more reliable, which is in R/C equipment using a coding, either PCM or PPM, also improving reliability.

For a new equipment, no option, go for the 2.4 GHz band, which is replacing at high pace old R/C band, due to the use of automatic frequency shifting in case of parasites, so no quartz, no reservation, no checking of all neighbour quartz, no scanner in meetings and peace of mind for everyone.
Also, and this is not negligible, in 2.4 GHz the antenna is only 15 cm long. The lowest cost radio is Spektrum DX5e, 100 Euros for Transmitter + receiver without servos. Plus this is built by the original developer of the system.

Ha. And as a part of my future garden train web space, I've prepared a more detailed web page about all those radio stuff. I can send you the page prototype if you want - in french -.

Though for garden train, you may have a look on the RCS page I've already published.
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pjti



Location: Galizano, nr Santander, Nth Spain

PostSubject: Re: Remote control frequency   Thu Jul 23, 2009 2:36 am

France

*
27 MHz RC models (all kinds)
*
35 MHz (35.000 and 35.010 MHz) Airplanes
*
41 MHz RC models
o
41.000 - 41.100 MHz Airplanes
o
41.110 - 41.200 MHz All models
*
72 MHz (72.210 - 72.490 MHz) All Models
*
Note: 2.4 GHz is also allowed (10 mW and 100 mW)

Copied and pasted from somewhere.

It looks like 40mhz is not legal in France from most of what I have seen.
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Carl Hibbs
Admin


Location: Haute Normandie - visitors welcome

PostSubject: Re: Remote control frequency   Thu Jul 23, 2009 8:41 am

Interesting and comprehensive inforformation. Thanks chaps.

But a bit of a shock to me really as I have been using 40.695 (supplied by Regner), 40.715 (Reppingen), 40.775 (Roundhouse) for several years here.Embarassed

The last two are outside of any allocated legal radio band. Shocked

Now... I realise when I was showing at 'Salon Maquettes' a couple of years back there was some stressed out security/safety marshal guy bustling around the layout with a frequency scanner. scratch

On further investigation it would confirm as Patrick and Pierre have stated above that 40mHz is okay in Germany and the UK but not in France.

39,000 à 40,600 MHz Réseaux privés
40,660 à 40,700 MHz Appareils faible portée non spécifiques .

40,700 - 40,995 range doesn't appear on any list.

The full list is here.
French radio frequncies

So in anwser to Laurent's question there is a good reason to buy one and not the other...

I'm off to buy some new crystals today before I bring down any more Mirage jets. ExclamationEmbarassed
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Bearcastle



Location: Brie

PostSubject: Re: Remote control frequency   Thu Jul 23, 2009 10:37 am

Well, lot's of possibilities.

I remenber people having crash with the 27 Mhz (aeromodelism) because of citizen band. On the ground it should be allright.

And for the 40 Mhz it's not specific unless you are in the aeromodelism part (just have to change crystal in that case).

That lay the path for another question.

If you use the 40 - 41 Mhz is it only a question of changing the cristal to use it ?
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Guest
Guest



PostSubject: Crystals in 40 and 41 MHz   Thu Jul 23, 2009 7:23 pm

A 40 MHz radio equipped with 41 MHz crystals does work. That decrease the emission power by 10-15%, which marginally decrease the range. Indeed, I own a 40MHz Graupner radio, bought in France with 41 MHz crystals. By chance, the frequency of the crystals supplied were in France allowed for both terrestrial and aerial models (good idea: this was for an hovercraft !)

Beware while buying crystal pairs: in FM modulation, the receiver crystal is *not at the same* frequency as the transmitter. It is shifted from half the channel width or the like, and that width is not the same for all the manufacturers. Have a look on existing crystal to know the difference, or buy original brand crystals (at ultra-high costs...). This is why the crystals are coded. In my case the codes are 405T and 405R (the transmitter is 41050 MHz, and I don't know for the receiver: don't expect me to check, it is deeply buried in a waterproof box, stored elsewhere than my flat...)
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Guest
Guest



PostSubject: Train command page: Advance publishing   Thu Jul 23, 2009 7:34 pm

I had completely forgotten that I had already translated in english the train command page, so here it is:




Command basic principles


It exists mainly two manners to control garden railway trains:

  • Through track, while modulating voltage or sending a coded signal like DCC which give orders to locomotives and accessories. This kind of equipment not being specific to garden trains is fairly well documented and I shall not discuss it here.
  • By radio

I first invite you to have a look on the wikipedia page where I have authored the control schematics.


This page is only about radio control of battery locomotives and live steam locos.


First, it is needed to remind basics about radio frequencies bands used for train control.



Modulation and coding


Before transmitting information, radio signal shall be modulated through a few ways:

  • Amplitude modulation - AM - The simplest to build, but with low reliability and less range.
  • Frequency modulation - FM - A bit more complex to build, with better noise immunity.
  • Frequency Shift Keying modulation - FSK - adapted to digital signal transmission. This kind of modulation is used to transmit data, notably for alarms and garage doors. It shall also be used for industrial data transfer.

Modulations allow transferring rough signal. While transmitting digital signals, it is needed to define a coding.

In order to improve the reliability of model R/C data transfer, PPM and PCM coding are used.

For alarms and garage doors, it exists hopping key coding to kept orders safe. The most used coding is the KeeLoq.



Frequency bands


A frequency band covers a range of frequencies. Often one band cover a range of 1 MHz. This range is generally divided in slices called 'channels'. The width of these channels varies depending usage.

The power is limited by local regulations, which varies widely.

Wave length which correspond to the length travelled by a wave during one period decrease while frequency increase. Sometimes wave length is given instead of frequency. So, 2 meters band is the same band as 144 MHz (radio amateur frequency).

It is useful to know the wave length to define the antenna length. The most frequently used antennas are 1/4 wave long. So, a 1/4 wave antenna at 433 MHz shall be 16.5 cm long.



Traditional R/C frequency bands


  • The 27 MHz band, generally used in AM modulation is now nearly only used for toys. More than 20 years ago, the development of the CB, often used illegally at very high power, have killed its use in R/C models. Its main advantage is that is is legally accepted worldwide. We can find a train command using that frequency at RCS control system, though with FM modulation and PCM coding, much safer than toy systems.
  • 35 and 40 MHz are unlegal in France (Beware, Uk, Swiss and Belgian rules differs).
  • In France, the 41 MHz band is used for R/C, but some channels are used only for aerial models while others are used for terrestrial models.

See also here for band and channels model allocation.



High frequency bands


  • The 433 MHz band is used worldwide for short range equipment like alarms and also for data transmission. The most frequently used channel is 433.92 MHz. for alarms. Power is limited to 10 mW.
  • Europe have defined 868 MHz band as being preferred for short range equipment. Power is generally arounf 1 mW, but the maximum is 10 mW for alarms and 25 mW for unspecific use equipment (Is that also valid in UK ?). One of the advantages is that a 1/4 wave antenna length is 7,4 cm. Generally speaking, range is better than with 433.92 MHz Equipment.
  • 915 MHz band is prohibited in Europe. Its usage in the USA is the same as 868 and 869 MHz in Europe.
  • 900 and 1800 MHz are only for GSM mobile phones.
  • 2400 MHz (2.4 GHz) band imposed itself in R/C with Spektrum equipment from USA. This band being already fully crowded (this is one of the WiFi band), regulations bodies made some difficulties to accept it in R/C and its future in this domain is still questioned. The power was limited to 100mW in France for R/C commands (what in UK ?). The specificity of Spektrum equipment is not only its frequency band but more the fact that it is jumping from one channel to another if the used channel is too crowded or noisy. It could swap channel multiple times per second. This drive to an unknown reliability in R/C world. Following Spektrum fast success, others R/C manufacturers are proposing similar or licensed equipment. We can find low cost chinese equipment (Turborix) in 2.4 GHz but it seems that its power is unlegal (too high) and it is uncertain that it uses any 'frequency jumping'.
The absence of quartz on 2.4 GHz radios and the fact it is no longer needed to handle frequencies during meetings have helped the rise of such equipment.


Battery locomotives



Dedicated transitter commands


  • USA company Aristocraft, after having been one of the first to propose track analogic train radio control with 'Train Engineer' system (TE), have recently proposed a 2.4 GHz system intended for battery powered trains. It have name it in all modesty 'Revolution'. This is early diffusion though the reputation of its manufacturer promise a good future. European and North-american equipment differs due to homologation regulations.
  • USA Airwire and Locolinc equipment are not legal in Europe.
  • Australian company RCS propose a control system with a reduced size transmitter on frequency band 27MHz with FM modulationa and PCM coding. This equipment is described here. The 27MHz band is legal worldwide.
  • In UK, Timpdon electronics proposes equipment in 433.92 MHz with reasonably sized transmitters and a carefully designed system. He is an artisan who built equipment on demand and refuse to sell outside UK (while the frequency used - the alarms one - is recognised in most countries).
  • English supplier Cliff Barker propose a very simple system based upon alarm keyfob.


Commands with classical R/C transmitter


If the weight and size of a traditional R/C transmitter don't rebuff you, it exists modules which shall be installed downstream the R/C receiver. Those modules are not only speed regulators but could (for some) handle front and back light, a sound board with bell and whistle. They are supplied by:


Live steam locomotives


Live steam locomotives being generally built in metal are more problematic than others for radio control. This have driven to quick adoption of Spektrum equipment, who is now proposing a relatively low cost radio DX5, sold 100 Euros with transmitter and receiver and no servos.

RCS company having abandoned its live steam module SD-10, remains for those who are reluctant to use bulky classic R/C transmitters:



(c) Pierre Rouzeau 2009


Last edited by PRZ on Thu Jul 23, 2009 10:30 pm; edited 2 times in total (Reason for editing : 433 MHz)
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Bearcastle



Location: Brie

PostSubject: Re: Remote control frequency   Thu Jul 23, 2009 8:28 pm

Thanks everyone
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