FrSky XHT diy 2.4 ghz RF module

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F2B
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Re: FrSky XHT diy 2.4 ghz RF module

Post by F2B »

guzzimeister wrote: 18 Jan 2021, 02:13
F2B wrote: Again, I'm not as concerned about non-LBT protocols causing any danger in normal flying (if the applicable 'grandfathers rights' would, continuing the use of my DJT/DFT and DHT, I bought before the cut off date, would be rendered illegal on the spot but it isn't)
However, in case of any legal issues (crash, damage, injury) using anything outside a CE could be a very expensive adventure in the end.
But what is it, D8+CE or D8, so no CE? I don't know.... :roll: ;)
I've just bought 2 of the XHT boards, one to do a straightforward Fleet XP/FM conversion and the other to do a full conversion of a Fleet TX to s/c plus all the bells and whistles using Phil Green's board. I can report that they do have D8 capability as they are driving the 3 D8 receivers I got from ebay. They also can transmit D16. Forgive my ignorance but what is the problem with D8?

cheers

Jon
It all depends on where you are.
There is no problem with D8 in itself, but if you are in a region where CE rules apply, you're not allowed using any new Tx modules that don't have a current CE approval.
An XHT, that still has the option of the D8 protocol hasn't. The CE approved XHT won't transmit in D8.
So while technically not a problem, it can be a factor in deciding whether you might face any legal problems.
If that's not of any concern (for example, when not in a densely populated area within the EU like I am), then the risks should be neglectible.
Therefore, if I were to get any XHTs. I'd choose the CE version and use D16 receivers with that.
But to each his own... 8-)
F2B or not to be....
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Mike_K
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Re: FrSky XHT diy 2.4 ghz RF module

Post by Mike_K »

F2B wrote: 18 Jan 2021, 08:16 It all depends on where you are.
There is no problem with D8 in itself, but if you are in a region where CE rules apply, you're not allowed using any new Tx modules that don't have a current CE approval.
An XHT, that still has the option of the D8 protocol hasn't. The CE approved XHT won't transmit in D8.
So while technically not a problem, it can be a factor in deciding whether you might face any legal problems.
If that's not of any concern (for example, when not in a densely populated area within the EU like I am), then the risks should be neglectible.
Therefore, if I were to get any XHTs. I'd choose the CE version and use D16 receivers with that.
But to each his own... 8-)
Are you quite sure that the CE marked XHT do not do D8 protocols? I bought one last year from the official UK distributor T9 Hobbysports and it has CE markings and it definitely works OK with D8 Rx and V8II Rx. I assume that as it had CE marking and bought from an official distributor it was EU specification, not an unofficial import.

Also, I understand that if you have any old stock FrSky DHT modules, they can still be legally sold and used, as long as they were manufactured before the current EU directive came into force.
Pchristy
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Re: FrSky XHT diy 2.4 ghz RF module

Post by Pchristy »

The whole issue is a horrible mess! When the EU rules were originally drafted, every nation was interpreting them differently because they were so badly written. The original drafts contained examples of applications for which 2.4 GHz would be legal, but some countries interpreted this as meaning that ONLY those examples were legal! This caused a huge furore, because model control didn't appear on the list of examples and some countries therefore banned it!

There was a huge inquiry into it, at which the BMFA was well represented. The honcho in charge of the investigation castigated the guys who originally drafted the regulations - to their intense annoyance - and ordered them to re-draft them so that they were comprehensible. He also told them to ensure that any existing uses (including model control) remained legal without any variation.

Of course, the bureaucrats didn't like this, and spent several years re-drafting the rules, and the re-drafted ones became the 2015 regulations that we all know and love - not!

Since the whole purpose of spread-spectrum technology is to avoid interfering with other users, it does make you wonder what the point of LBT is!

Since we are now outside the EU - and 2.4 GHz is short range - it may be worth talking to Ofcom and get the regulations relaxed! I spoke to a guy at Ofcom some years ago about the possibility of spread-spectrum on 459 MHz. His answer quite surprised me! He said that if an official body, like the BMFA, requested such a change, then they would seriously consider it. He went on to say that their attitude was to approve such a change unless there were good technical reasons not to! (Bit of a change from the old Post Office days!) He said that if such a request were received, they would consult other users of the band, and if there were no objections, it would probably get approved. They wanted to do away with unnecessary red tape!

I don't think the BMFA ever progressed such a request. Chris Bromley was the Tech. Sec at the time, and I think he quit before putting it forward.

So, I suspect that if the BMFA were to officially request the "rest of the world" 2.4 GHz gear to be legalised, there is a good chance it would be approved. Perhaps we should stir the BMFA up a bit?

As an aside, when I spoke to the Ofcom man, he was aware of the few 459MHz sets from Europe and elsewhere that used frequency hopping. His comment was that this was fine, as although it was frequency hopping, it was still a narrow band signal - not spread-spectrum - and therefore quite legal! He likened it to "changing crystals on a stock set, but very quickly"!

These conversations with Ofcom must have happened around 10 or 12 years ago - can't remember the exact date.

--
Pete
Martin
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Re: FrSky XHT diy 2.4 ghz RF module

Post by Martin »

Transmitters with Multiprotocol modules (that include the D8 protocol as standard), are CE marked and on sale right now. For example, the currently very popular Radiomaster TX16S. It has a CE mark on its base. Perhaps it shouldn't have a CE mark? Is it legal? It's certainly openly on sale, and many thousands of model flyers all across Europe have already bought one.

Perhaps it's legal to sell them, but not for the purchasers to actually use the protocols that are "illegal" in their area? The Radiomaster does all the other "non-compliant" protocols too: FrSky D16-international (the one without LBT), Spektrum DSM2, and many others.
Pchristy
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Re: FrSky XHT diy 2.4 ghz RF module

Post by Pchristy »

If you talk to the Chinese manufacturers, they'll tell you that CE stands for "China Export", and has nothing to do with the EU!

:evil:

--
Pete
JohnRogers
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Re: FrSky XHT diy 2.4 ghz RF module

Post by JohnRogers »

stuart mackay wrote: 15 Sep 2020, 22:28 Works fine, just remember to bind the receiver in Telemetry mode.
Have got a couple of them flying now
Hello Stuart, I am having problems binding a Frsky XHT to a V8FR-II receiver, I notice your comment to bind them in Telemetry mode. Could you explain this please, does it mean putting the jumpers on chn 1 and 2?

Thank you in advance John
Martin
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Re: FrSky XHT diy 2.4 ghz RF module

Post by Martin »

Yes, on the receiver you use the jumper instead of the bind button. Bind button makes the V8FR-II bind to a V8 transmitter, the link makes it bind to a D8 transmitter. Once it's bound, you remove the link and use channels 1 and 2 in the normal way. You can do a brief prod of the bind button, any time the receiver is already powered up and working, to remember the current servo positions as the fail safe positions. But don't press the bind button while powering up - or it will revert to V8 mode, and you'll have to re-fit the link to bind it to your XHT again.

On the XHT module, you need switch one ON, and switch two OFF, to make it work in D8 mode. The XHT can't work in V8 mode - it's either D8, D16 or LR12, depending on the switch settings.
JohnRogers
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Re: FrSky XHT diy 2.4 ghz RF module

Post by JohnRogers »

Hello Hope you can help, I am having problems binding a Frsky XHT with a V8FR receiver. Stuarts made a comment -
Stu wrote:Works fine, just remember to bind the receiver in Telemetry mode.
Have got a couple of them flying now
Does this mean using the jumpers on chn 1 and 2? the instructions I have for the XHT and V8 receiver have conflicting switch positions on the bind board

Hope you can Help John
JohnRogers
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Re: FrSky XHT diy 2.4 ghz RF module

Post by JohnRogers »

Phil_G wrote:I've never handled an X series module but my understanding is that the XHT can only be used with V8 receivers having a II suffix, eg the V8FRII.
The V8FR receiver (no II suffix) doesnt do D8 protocol.
There is only one link, its between the signal pins of channels 1 and 2. A 'bind plug' wont do it as it would join 1 & 3.
Beware that many Frsky receivers are built upside down wrt convention, check the label on the edge. The process is, connect the signal pins of receiver channels 1 & 2 using a link, and switch on the receiver.
Set the transmit module switches to 'D8' mode, hold the modules bind button and switch the tx on. Once its bound, remove the receiver ch1-ch2 link and power-cycle both tx & rx. I found this video which shows an XJT module but the XHT is identical:

Hello Thank you for your quick response. I will have a go in the morning. I could not see my original post so did another one! now I can see both.

Thanks again John
Martin
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Re: FrSky XHT diy 2.4 ghz RF module

Post by Martin »

Here's my reply from the other thread: viewtopic.php?f=62&t=1054&p=10216#p10216
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