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Which one?

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Paul Law19/03/2020 11:50:25
25 forum posts

Folks,

Back in the game after a few years away, just wondering if it's worth upgrading my TX ? I have an old PCM 9x with synth module and a DX7s, RX's mostly spektrum and happy to keep it down that route unless otherwise convinced ?

Thanks,

Paul

Peter Christy19/03/2020 12:08:18
1831 forum posts

Nothing wrong with any of that gear, but probably worth changing the battery packs! I still have - and still use - my PCM9x! The 35 MHz band is almost empty these days, but keep an eye out, as people have got sloppy about frequency control!

You can get 2.4 GHz modules to fit the PCM9x if you want to move completely to 2.4 GHz, but it isn't necessary unless you want to.

--

Pete

Don Fry19/03/2020 12:20:59
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4557 forum posts
54 photos

As Peter says, not broke, don't fix it. If you haven't got one, buy a decent battery charger. It will have discharge functions, and will allow you to test your packs. All packs new and old, if they pass a load test, are good. All packs, new and old, wot fail go back or in the broken battery bag.

Welcome back to this vale of tears.

gangster19/03/2020 12:28:23
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1037 forum posts
29 photos

Lovely set of gear the pcm9x and you can get receivers and crystals for next to nothing. I used mine on 35 up until last year I agonised whether to convert or not and finally decided to go for it for the simple reason I might wish to do so and realised the modules cannot be available for ever. I bought the FRsky

djt module Am still very happy with it with the added bonus that it’s easier to carry out to the field with out worrying about keeping the prop and aerial apart.

Safety police. Yes I know!

I also Suggest you do it while the DJT modules are still available. As already mentioned change the batteries check for black wire and look carefully at the switch. Even though the quality of the pcm9x is way better than any equivalent you can buy today those switch’s are crap quality and like others prone to corrosdion

Paul Law19/03/2020 13:13:16
25 forum posts

Thanks for all the replies folks, took all the batt packs out when i took the hiatus, have a Graupner Ultramat 16 charger so good to go there I think.

There seems to be a myriad of 2.4 GHz modules available are they TX/RX specific ?

gangster19/03/2020 13:41:41
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1037 forum posts
29 photos

Great news the batteries are out. Still replace or give a good test. As far as compatibility you will need a module that is compatible with the transmitter and a receiver that is compatible with that module. I use the frsky djt module and v8fr 2 receivers Others may be able to recommend other makes

gangster19/03/2020 13:49:24
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1037 forum posts
29 photos

Paul. DJT modules seem to vary widely in price. Some are frankly crazy. I believe T9 Hobbysports are one of the official suppliers and also one of the cheapest sources as well. They of course will be able to advise on receivers too

Paul Law19/03/2020 13:59:41
25 forum posts

Thanks Gangster, I will have a look

Peter Christy19/03/2020 16:49:13
1831 forum posts

+1 for T9Hobbysport.

They currently do two modules for JR transmitters, DJT and XJT. The DJT supports the older protocols (V8 and D8) which are no longer technically legal. However, as your transmitter pre-dates the 2015 cut-off date, you have "grandfather" rights and can use these legally. (V8 is non-telemetry.)

The XJT supports the newer D16 protocol, and is the one I would recommend. I suspect it also supports D8, the older telemetry protocol, but the website isn't clear on that. I would be surprised if it doesn't, as I think its the same board as goes in the FrSky transmitters.

However, this is academic unless you have some older FrSky receivers. Just go with the XJT module, and get X-series receivers to go with it.

You could also consider one of the multi-protocol modules, but make sure you get the one with a rotary switch on it, like this: **LINK**

The switch enables you to change protocols, and it also supports DSM-2 and DSM-X, so you could use your PCM-9 with your Spektrum receivers as well as FrSky, Hitec, Futaba - to name but a few!

A bit more complex, and it would help to be a bit of a computer geek - or know someone who is - but almost infinitely flexible!

For simplicity, stick to the XJT.

--

Pete

john stones 119/03/2020 16:56:40
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11597 forum posts
1517 photos

Using a 9x with a Frsky module myself, it's the dogs doodahs. yes

Paul Law24/03/2020 12:00:29
25 forum posts

Cheers for all the replies

MattyB25/03/2020 13:20:30
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2105 forum posts
32 photos
Posted by Peter Christy on 19/03/2020 16:49:13:

+1 for T9Hobbysport.

They currently do two modules for JR transmitters, DJT and XJT. The DJT supports the older protocols (V8 and D8) which are no longer technically legal. However, as your transmitter pre-dates the 2015 cut-off date, you have "grandfather" rights and can use these legally. (V8 is non-telemetry.)

I would love to understand how T9 justify selling the DJT after all this time. Nothing new that uses the V8 or D8 protocols has had a valid certificate of conformity since the regs changed in Jan 2016, and the grace period for selling old stock was only 1 year... sarcastic

Some useful info on RCGroups re: the regulation change from back in 2016 and FrSky's responses for those that need help sleeping at night...

Edited By MattyB on 25/03/2020 13:34:53

Phil Green25/03/2020 13:31:48
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1616 forum posts
343 photos

With the present dearth of RF modules, homebrewers are glad they do!

Peter Christy25/03/2020 16:48:34
1831 forum posts
Posted by MattyB on 25/03/2020 13:20:30:I would love to understand how T9 justify selling the DJT after all this time. Nothing new that uses the V8 or D8 protocols has had a valid certificate of conformity since the regs changed in Jan 2016, and the grace period for selling old stock was only 1 year... sarcastic

But if your transmitter pre-dates the regulation change (as Paul's PCM9x certainly does) then you have "grandfather" rights and can continue using the older protocols!

devil

--

Pete

MattyB26/03/2020 12:50:55
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2105 forum posts
32 photos
Posted by Peter Christy on 25/03/2020 16:48:34:
Posted by MattyB on 25/03/2020 13:20:30:I would love to understand how T9 justify selling the DJT after all this time. Nothing new that uses the V8 or D8 protocols has had a valid certificate of conformity since the regs changed in Jan 2016, and the grace period for selling old stock was only 1 year... sarcastic

But if your transmitter pre-dates the regulation change (as Paul's PCM9x certainly does) then you have "grandfather" rights and can continue using the older protocols!

devil

--

Pete

The transmitter in this instance is the module - the Tx is just providing the inputs that drive it, none of the RF side that was certificated originally in the PCM9x is being used. All the modules did have a certificate of conformity so they could be CE marked, but that is no longer valid (or tellingly on FrSky's site) because they know V8 and D8 do not conform to the ETSI regulations.

If you really want I can dig out the old conformity certificates for the modules which I grabbed whilst they were still available, but trust me - selling and using new modules of this type is no longer legal in the UK (but using any your bought before Jan 2016 is fine). Not that this is going to be an enforcement priority for the Police at this time though...

Edited By MattyB on 26/03/2020 12:57:15

Peter Christy26/03/2020 16:24:17
1831 forum posts

I actually had a long discussion about this with an Ofcom official, way back when 2.4GHz had just been legalised.

At the time, they were saying that modules could only be used in transmitters that they had been specifically tested in. ie: If one had been tested in a PCM-9, that didn't mean it was also permitted for use in a PCM-10!

I asked if this meant they were going to ask PC World to certify the WiFi adapters they were selling for laptops in every type of computer they sold that they could be used in? He said he would get back to me!

He actually did, and the answer was that they accepted that type approval held for any suitable transmitter. ie: if it was tested in a PCM-9, yes, it could be used in a PCM-10.

They stated at the time that the "transmitter" was the whole unit - not just the module - as the module was not capable of transmitting unless connected to the main unit.

That being the case, as long as part of the "transmitter" pre-dates the rule change you should be good to go!

Now I am not a lawyer, I'm just re-iterating what I was told by an Ofcom official. And, no, I don't have it in writing. But equally, it is a logical argument. And quite honestly, they will only investigate if a complaint is made. A pretty unlikely occurrence, I would guess!

wink

--

Pete

MattyB26/03/2020 20:13:18
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2105 forum posts
32 photos

You can debate whether usage of one of these new modules is legal in an older TX (that is a little grey), but not sale by an EU vendor. The DJT module is being sold on it’s own by T9, so it has to have a valid CE certification. If you got to the documentation section of the FrSky site the XJT and all the post 2016 TXs that use an XJT or later module have a current cert whereas the DFT and DJT don’t. Those certs did exist on the FrAky site pre-Jan 2016, but as they know V8 and D8 can no longer be sold in the EU they removed the certs (which regerenced the older ETSI version). Case closed!

Paul Law22/05/2020 09:42:27
25 forum posts

Folks,

Obviously a talking point and interesting discussions in these strange times, perhaps over a beer after the world rights itself beer, thanks for all your replies.

Another question your collective knowledge may be able to help me with, now that I have decided for now to go down the XJT route, which keeps the old 9X alive for a while longer, however in keeping with my DX7s can you advise what Spektrum receivers would still be suitable ?

Cheers,

Paul

Nigel R22/05/2020 09:56:44
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3993 forum posts
727 photos

Any currently available receiver will be fine. The AR410 and AR620 seem to be well liked and reasonably priced.

Andy4822/05/2020 11:07:06
1550 forum posts
1 photos

Personally I'd update the lot rather than buying extra modules to prop up an old system. Transmitters and receivers are as cheap as chips these days, smaller and better in many ways. If you lose one model because of the old system, then a new transmitter and receiver would have paid for itself.

Frankly I was glad to get rid of my Spektrum gear like many in our club. I lost 3 models in exactly the same circumstances due due to radio problems within a fortnight. Never had a problem since changing kit, and the only models that have not made it safely back to earth have been due to pilot error.

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