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EU. LBT

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Piers Bowlan09/08/2018 08:29:08
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Yes Steve, that is now my understanding, current Spectrum receivers are backwards compatible with DSM2 (they do both). New Spectrum Transmitters are only allowed to transmit on DSMX in the EU as they are LBT compliant. The same Speky transmitters are sold in the US with both DMSX and DSM2 functioning (presumably just different software).

So what you are saying Frank is that if you buy a new DSMX/DSM2 Spectrum receiver and operate it with a pre 2015 DSM2 Tx, then it is illegal?

Edited By Piers Bowlan on 09/08/2018 08:54:05

Steve J09/08/2018 08:58:13
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Posted by Piers Bowlan on 09/08/2018 08:29:08:

New Spectrum Transmitters are only allowed to transmit on DSMX in the EU as they are LBT compliant.

DSMX is EN 300 328 1.8.1 compliant. I believer that DSMX transmitters do not have to Listen Before Talk as the duty cycle of DSMX is below the threshold above which LBT is required.

Steve

Piers Bowlan09/08/2018 09:21:15
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You have lost me there Steve, I am out of my depth. Help! Where is Pete Christy when you need him?

Peter Christy09/08/2018 09:31:37
993 forum posts
Posted by Biggles' Elder Brother - Moderator on 08/08/2018 22:03:15:

Yes but surely T9 are selling into an international market on the internet, so they can sell non-EU legal stuff to buyers outside the UK - hence why they have it. But not to us - that's my point. We can't buy equipment that breaks the law surely?

I think we can, actually! Certainly, back in the late 70s / early 80s, at the height of the CB boom, it was perfectly legal to buy, sell and own CB gear. It just wasn't legal to *use* it!

As far as I can tell (and I am NOT a lawyer), all the EU rules did was to prohibit the *import*, after January 2015, of non-compliant equipment.

However, if the equipment was "in the supply chain", ie: either in a warehouse, or on a freighter from China, it could still be imported and sold *and used* quite legally. It is also legal to continue using non-compliant equipment purchased before January 2015.

Yes, I know its a mess, and it doesn't make any sense, but that's what happens when politicians make technical decisions! Its also pretty much un-enforceable, almost a definition of bad legislation!

I'm trying to prepare a comprehensive answer to some of the points raised in this thread, but it will take a while, so please be patient. It isn't easy to explain in a comprehensible manner!

--

Pete

 

Edited By Peter Christy on 09/08/2018 09:32:28

Cuban809/08/2018 09:59:25
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I don't lose sleep over all this stuff as I use both DSM2 and DSMX quite happily but...........why is it that the US haven't banned DSM2 etc on their new trannies and the EU have deemed it as unsuitable for use on our new equipment? What is so different about the radio environment in Europe to that of the US?

Piers Bowlan09/08/2018 10:20:22
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Maybe it is a cultural thing? In the US they have a different attitude; if it ain't broke, don't fix it!

Cuban809/08/2018 10:34:24
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Something to do with integrating signals into the cellular spectrum.........if your boredom threshold is sufficient this explains things - I think................**LINK**

CARPERFECT09/08/2018 11:38:54
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I emailed T9 hobby and asked if it was legal for them to sell none lbt tx and rx

There reply was

Hi Paul , The delta 8 is a multi protocol receiver mainly for Futaba and Hitec. Yes it will work with Taranis, but why buy the delta it has no telemetry and is only a little cheaper than the X8R.

So you ask a direct question and get a politicians answer. I was not planning to buy anymore delta 8. but i have 3 to use. At £23.40 each thats saved me £70 and thats what this little story is about. I am from Yorkshire and tight lol

Peter Christy09/08/2018 12:40:07
993 forum posts

OK, here is my take on the current situation with regard to the EU / LBT situation. Please note that I am NOT a lawyer, so any comments I make on the legal position are my own personal views and should not be taken as definitive!

First off, there is a misconception that LBT (Listen-Before-Transmitting) is compulsory for compliance with the EU regs. This is NOT the case. However, equipment that is not LBT compliant is subject to further restrictions that can have an effect on our activities.

The EU documentation actually uses the phrase "Adaptive", where LBT is one option, and probably the most appropriate for our purposes.

The EU documentation also specifies that "Frequency Hopping" shall use a minimum of two hopping frequencies. Since DSM-2 uses two frequencies, and implements a form of LBT, it would appear to meet the required criteria at a first glance. Unfortunately, it only "listens" at switch on. At that time it finds two unoccupied frequencies, and then uses them without any further checks. The EU requirement is that the transmitter will "listen" before each hop, which is why DSM-2 has fallen by the wayside in Europe.

Coming back to systems that don't use LBT, there are further restrictions. If the ERP (Effective Radiated Power - the power of the transmitter multiplied by any gain in the antenna) is less than 10mW, then most of the restrictions no longer apply. Bear this in mind, as we will come back to it when we come to receivers!

However, if we don't use some form of LBT, but still output the full 100mW, there is a further restriction on the "Medium Utilisation" factor. (MU)

The MU is defined as MU=(P/100)xDC where P is the transmitted power in mW (ERP) and DC is the Duty Cycle of the transmission - in crude and over-simplified terms, the length of time the transmitter is actually transmitting in any given period of time.

If the transmitter is transmitting 100mW, then the MU is the same as the Duty Cycle. This is what Steve J was referring to in his post. However, if the transmitted power is less than 100mW, then the Duty Cycle can be made bigger to maintain the required MU.

The maximum MU for non-adaptive equipment is 10%.

In simple terms, for us, this means that if you don't use LBT, then you can only transmit for 10% of the available time.

Taking FrSky as an example, their initial EU offering adopted this approach. It worked, and I flew with it for a while without problems. However, in areas where there was considerable congestion / interference in the 2.4 GHz band, this could lead to packet loss (signal drop-outs), which although disguised by the system, lead to reduced response times and occasional lock-outs. As I say, I never experienced this, but it was certainly a theoretical possibility, and FrSky quickly followed up with a full LBT system that has proven to be pretty bullet-proof.

So far that explains the current situation as far as transmitters go, but the situation for receivers is somewhat more complex!

(to be continued!)

Peter Christy09/08/2018 12:40:27
993 forum posts

First of all, consider non-telemetry receivers (DSM-2, FrSky V-series, etc). These only transmit briefly during the bind period, and at very low power output - well below the 10mW limit. As far as I can see, that means they are not affected by the EU LBT regulations and it should in theory remain legal to buy and use them. (Remember my disclaimer about not being a lawyer, though!)

For telemetry receivers, the situation is more complex again, but bearing in mind the above explanation of MU and Duty Cycles, you can see why some receivers that you might expect to be "illegal", aren't!

First off, the ERP of the downlink will be less than that of the hand-held transmitter. The transmitter has an aerial with 2dB gain, whereas the receiver only has - at most - a small dipole, and more probably a simple, short whip aerial. I have no idea how much power the downlink is transmitting, its not easy to measure and the figure seems to be missing from most spec sheets! It could be the standard 60mW, but it could be a lot less. If its 10mW or less, then most of the rules don't apply. Even if its more than 10mW, its unlikely to be anywhere near the 100mW of the ground based transmitter, so the MU is going to be correspondingly lower. If the MU is less than 10%, then again, the receiver is going to be exempt from many of the regulations.

I believe this is how its possible to be still selling receivers for "obsolete" formats that don't, on the face of it, comply with the latest EU regs. The devil is in the detail!

And in case anyone thinks that 10mW is useless, someone I know uses a handheld (legal) airband radio in his full-size glider, and never has any range issues. When I was experimenting with 459MHz many years ago, a friend built a transmitter using an "off-the-shelf" module that only put out 10mW, and flew it to the limits of visibility!

However, I wouldn't recommend such a low power level for a potentially dangerous, big and heavy model!

Finally "grandfather rights". OK, perhaps its not an ideal term, but I think its one that people can understand.

The initial EU 2.4 GHz regulations were almost identical to the American ones, aka: "international" or "rest-of-the-world". Unfortunately, they were so badly drafted that not even European officials could understand them, and as a result, a number of EU countries refused to allow model control on 2.4 GHz.

This resulted in an almighty row, culminating in a meeting with the Commissioner responsible for such things. He agreed that model control was a legitimate use of the band and ordered the officials to redraft the rules properly. I suspect this didn't go down too well with those responsible for the fiasco!

The rules were duly re-drafted, but at the same time they took the opportunity to "improve" them, building in the "adaptive" requirement (aka: LBT).

The start date was 1st January 2015. However, because the trade had to order months, if not years, ahead, it was decreed that existing stock, and that "in the supply chain" could continue to be sold legally.

I think there was a deadline set for the selling of older equipment, but that got moved back at least once, following pressure from the trade.

There is also the grey area that is retro-fitting modules to older transmitters. What exactly is the "transmitter"? Is it the module, or the box into which it is fitted? And which rules should therefore apply to an old transmitter fitted with a new module? Arguments about that could keep the courts busy for years, if anyone had the money to finance such an action!

My conclusions are that it is almost certainly true that receivers for older systems that are no longer EU compliant, can still be sold and used legally. The same probably applies to modules to be retro-fitted into older equipment, though this is a very grey area. Fitting a new, non-compliant module into a new transmitter probably doesn't leave you much wriggle room in the unlikely event of you being caught! However, if the module was bought either before January 2015, or in the transition period, you should be OK.

As a final point, and without getting into the politics of Brexit, I suspect that Ofcom will be a bit more relaxed about what is and isn't OK in the UK post-Brexit. When I enquired of one of their officers about the prospects for spread-spectrum on 459MHz a few years back, he said that if we asked for it, we could probably have it - subject to consultation with other users of the band. He said he couldn't see any good reason to reject such a request. This surprised and encouraged me. I suspect that they have much better things to do with their time and resources than check on the legality or otherwise of systems that are not actually causing a problem, and would probably welcome anything that simplified matters.

Sorry if this has got a bit long-winded and technical, but I hope that answers some questions!

--
Pete

Piers Bowlan09/08/2018 13:18:55
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Wow! Thanks for that Pete yes

Mike Blandford09/08/2018 13:35:29
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Some information on FrSky "D" series receiver. The "D" protocol works with the Tx sending a packet over the air every 9mS, for 3 periods, then the Rx sends a packet back (telemetry) in the 4th 9mS period. By looking at the receiver voltage (that dips while the Rx is transmitting), I see the Rx only transmits for 6.7mS, so only 6.7 mS every 36mS.

The power is, I understand, less than 60mW. I just looked at the FCC test report and this indicates 58.7mW for the DJT module. I'm unclear if this is with the 2db antenna. The Rx, without a 2db antenna may well be lower than 60mW. The range of the telemetry to the Tx will be the same as the control as the 2db antenna on the Tx will provide the same gain when receiving.

According to my calculations, if the Rx only transmitts at 53mW, then it will be under the 10% occupancy.

Mike

Peter Christy09/08/2018 13:48:54
993 forum posts

Hi Mike,

Thanks for confirming my understanding of the situation regarding telemetry receivers.

I think that FCC figure of 58.7 mW will be the figure "at the terminal", without the antenna. A few years ago, I measured a JR DSX9 transmitter at the terminal, and got a figure of 60 mW, as near as I could measure. Multiply that by 2dB (antenna gain), and you get 100mW! Bingo!

I'm pretty confident that the current crop of receivers for "non-compliant" transmitters are fine, and your figures look to confirm this.

Hopefully this will ease the fears of those buying receivers for older equipment.

--

Pete

Biggles' Elder Brother - Moderator09/08/2018 13:50:15
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Very interesting and informative stuff Peter. But if its all the same I shall stick to kit clearly LBT compliant, and know that I'm legal as opposed to hoping I am below some medium use threshold that I can't measure!

Of course others may find MU a useful 'fig-leaf' to hide behind wink 2 I couldn't possibly comment!

BEB

Edited By Biggles' Elder Brother - Moderator on 09/08/2018 13:52:01

MattyB09/08/2018 17:47:00
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Posted by PatMc on 08/08/2018 21:51:02:

I take a different view from BEB & Peter.

T9 only supply CE certified RC gear which is your guarantee it's legal to use. The Delta, D series & V II series Rx's they sell can be used with a Taranis X9D that has been set up in Opentx Companion to allow access to D8 mode transmission. I've seen nothing to suggest that this is illegal but if you have doubts then for £23.40 you could plug in a DJT module (from T9, which of course means it carries CE certification) to do the same job.

Since the all of the Rx's mentioned are current, I don't see how "grandfather rights" (BTW a British legal concept, pre EU) come into play.

 

Posted by PatMc on 08/08/2018 23:02:02:

...Within the last 6 - 12 months I've bought a DJT module in order to use first generation V8 Rx's with my Taranis, a V8R7-II Rx, a couple of V8R4-II & a D4R-2 Rx for use in lightweight models. All purchases were from T9 or other UK retailer (none from HK) all shipped to my home address & carrying CE marks with VAT quoted on each sale. There can have been no doubt they were all to be used in the UK. The CE marks tell me that the vendor hasn't broken any law selling them to me & that it's perfectly legal for me to use them in the UK.

Unfortunately whilst the older V8 and D series kit might still come with CE printed on the back, the certificates of conformity that go with them (which were gained prior to the 2015 changes in legislation) became invalid when the ETSI regs changed and the protocols they used became non-compliant. FrSky know this, so those invalid certs are no longer available on their own website (examples - DJT module and D4R-II RX). By contrast the X series stuff all has certificates available from the FrSky site (here's the X8 receiver cert and the XJT module for example, both dated 2017). Luckily this was discussed before in a thread I started on RCGroups when the regs were changing; here is a sample expired certificate for the original X9D that shows compliance with ETSI EN 300 328 v1.7.1, but not v1.8.1. All the V8 and D series kit had similar certs, though I do not have copies of them on my PC any more.

In short to be legal to import and sell a new certificate of conformity issued post 2015 would be needed for V8 and D8 gear, but FrSky can't get those* since the protocols don't conform with current regs (* - well they could - CE is effectively self certified after all - but it wouldn't be worth the paper it was written on). As per the example on RCGroups some shipments in early 2015 were even stopped going into Germany for this reason, though the UK authorities seem to have little interest in enforcing these regs. I am a bit surprised FrSky's competitors have not done anything to challenge the continued distribution of V8 and D series stuff in the EU, though.

FrSky do make good kit, but when it comes to rules, well... let's just say they are not detail guys! sarcastic

Important point - Any V8 or D series gear imported or sold pre the 2015 change remains legal to use in the UK.

Edited By MattyB on 09/08/2018 17:55:11

Peter Christy09/08/2018 18:52:43
993 forum posts

Posted by MattyB on 09/08/2018 17:47:00:

In short to be legal to import and sell a new certificate of conformity issued post 2015 would be needed for V8 and D8 gear, but FrSky can't get those* since the protocols don't conform with current regs (* - well they could - CE is effectively self certified after all - but it wouldn't be worth the paper it was written on).

But the protocols DO conform, provided they aren't used at the transmitter end! As I've pointed out, and Mike B has confirmed, they meet the maximum MU requirements for non-adaptive equipment, and that is the only thing that has changed post 2015, for our purposes.

Even the transmitters remain conformant provided they were sold prior to the cut-off date. I can't remember when that was at the moment, as it changed at least once. Its certainly well after January 2015.

Getting a Certificate of Conformity is a very expensive business, and I can well understand FrSky not bothering over what they would regard as obsolete equipment. But its not up to the end user to prove he is innocent, it is up to the accuser to prove him guilty, and to do that HE would have to foot the bill for the conformity test.

In short, a Certificate of Conformity might prove innocence, but the absence of one does not prove guilt.

I have bought quite a lot of D8 receivers to use with my retro transmitters fitted with hack modules, and I would certainly be happy to challenge anyone to prove that they weren't conforming to the EU regs. I believe that they do conform, for the reasons stated above.

--

Pete

MattyB10/08/2018 09:45:58
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Posted by Peter Christy on 09/08/2018 18:52:43:

Posted by MattyB on 09/08/2018 17:47:00:

In short to be legal to import and sell a new certificate of conformity issued post 2015 would be needed for V8 and D8 gear, but FrSky can't get those* since the protocols don't conform with current regs (* - well they could - CE is effectively self certified after all - but it wouldn't be worth the paper it was written on).

But the protocols DO conform, provided they aren't used at the transmitter end! As I've pointed out, and Mike B has confirmed, they meet the maximum MU requirements for non-adaptive equipment, and that is the only thing that has changed post 2015, for our purposes.

Even the transmitters remain conformant provided they were sold prior to the cut-off date. I can't remember when that was at the moment, as it changed at least once. Its certainly well after January 2015.

But how do you explain the fact that the DJT module is now available again despite having gone out of stock several times since Jan 2015? We know for certain that does not comply with the ETSI 300 328 v1.8.1.

Posted by Peter Christy on 09/08/2018 18:52:43:

...Getting a Certificate of Conformity is a very expensive business, and I can well understand FrSky not bothering over what they would regard as obsolete equipment. But its not up to the end user to prove he is innocent, it is up to the accuser to prove him guilty, and to do that HE would have to foot the bill for the conformity test.

In short, a Certificate of Conformity might prove innocence, but the absence of one does not prove guilt.

I never said anything in my post about end users, only the legality of importing and selling this equipment. Whether the RXs are compliant technically with v1.8.1 (and I agree with you they almost certainly are) is a moot point - they still need a CE mark to be legally imported and sold, and that CE mark is only valid if an accompanying certificate of conformity is available, which it isn't. Whether FrSky regard the equipment as "obsolete" is irrelevant; if they want to keep selling it here they need to get the relevant certs.

I agree the risk to end users is minimal to zero - it is not up to us to check all the necessary tests and certification have been done by the manufacturer and importer. Those manufacturing and importing the kit though should be conforming to the regulations, otherwise there is not a whole lot of point in the CE system.

Piers Bowlan10/08/2018 11:10:07
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Important point - Any V8 or D series gear imported or sold pre the 2015 change remains legal to use in the UK.

Edited By MattyB on 09/08/2018 17:55:11

So if you use a V8 or D series Rx, which you bought last week, and if someone wished to prosecute you for a non-compliant Rx then the onus would be on them to prove that it was purchased post 2015? How could they do that?

MattyB10/08/2018 13:49:09
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1806 forum posts
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Posted by Piers Bowlan on 10/08/2018 11:10:07:

Important point - Any V8 or D series gear imported or sold pre the 2015 change remains legal to use in the UK.

So if you use a V8 or D series Rx, which you bought last week, and if someone wished to prosecute you for a non-compliant Rx then the onus would be on them to prove that it was purchased post 2015? How could they do that?

See above post... I don't think they could, especially if you had bought them from a UK supplier who was selling them complete with a CE mark. The risk is to the supplier in the main; the only concern as an end user would be if somehow it was proved your TX module or RX was non-compliant an bought after 2015 it might be used by the insurers to get out of covering you. Again, highly unlikely but not a zero risk.

Posted by MattyB on 10/08/2018 09:45:58:

...I agree the risk to end users is minimal to zero - it is not up to us to check all the necessary tests and certification have been done by the manufacturer and importer. Those manufacturing and importing the kit though should be conforming to the regulations, otherwise there is not a whole lot of point in the CE system.

PatMc10/08/2018 15:37:08
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Posted by MattyB on 10/08/2018 13:49:09:
Posted by Piers Bowlan on 10/08/2018 11:10:07:

Important point - Any V8 or D series gear imported or sold pre the 2015 change remains legal to use in the UK.

So if you use a V8 or D series Rx, which you bought last week, and if someone wished to prosecute you for a non-compliant Rx then the onus would be on them to prove that it was purchased post 2015? How could they do that?

See above post... I don't think they could, especially if you had bought them from a UK supplier who was selling them complete with a CE mark. The risk is to the supplier in the main; the only concern as an end user would be if somehow it was proved your TX module or RX was non-compliant an bought after 2015 it might be used by the insurers to get out of covering you. Again, highly unlikely but not a zero risk.

The same criteria would apply if bought from any retailer in EU & EFTA.

If it was proved your TX module or RX was non-compliant and bought after 2015 but carried CE mark then the supplier would be guilty of misrepresentation & fraudulenly applying the CE mark.
Even in the event of a false CE mark, any insurance company using this to get out of covering you would have to have the Rx tested to demonstrate that it was not compliant.
 

Edited By PatMc on 10/08/2018 15:44:29

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