rorywquin

RE users - I see the Multiplex has the first software patches available on their site and the scanner is now available! I ordered mine yesterday from Hoellein!

Jeddy

I am interested in the scanner, wonder if anyone can answer a question about it?
I understand that is stops you turning on if someone is already on your frequency, however it would be even more useful if it alerted you to someone turning on on your frequency! I don't suppose it does, does it???
(2 expensive models were recently trashed at our club because of this, despite peg boards etc.!! If I could hear if someone turns on on my frequency I at least stand a chance of getting them to turn off before it's too late hopefully).

RCfun-RCU

The scanner does not warn you if somebody turns a transmitter on on your frequency. I guess it would be impossible. How would the scanner be able to difference between your transmitter broadcasting on a frequency and another Tx on the same frequency. Also when in scanner mode the TX does not emit a radio signal.


Best regards
RCfun

rorywquin

I particularly wanted the channel check BECAUSE I have a synth. module !!

It is amazing how many people blame interference for crashes and I don't want anybody looking my way because I have the facility to dial up any channel I choose!!

Personally I think it would be a good idea if a channel check module was mandatory in all radios !!

JohnMac

Sadly, It is beyond currently available technology for the scanner to see another Tx being switched on whilst your own Tx is on the same frequency. But if it could, so what? will it give you an alarm?You will instantly be alarmed by the fact that your model is out of control so it will make no difference even if it were possible.
Were it possible I would not want my Tx to give me an alarm but rather to launch an Alarm anti radiation missile at the offending Tx! That should do nicely.
At some point in the future all manufacturers may fit a channel check facility and then everyone SHOULD be safe.
Even further in the future is frequency agile radio were the Rx tells the Tx of interference and they both change to a new freqency.
BTW I have had a scanner on my MC4000 now for about 5 years. In not one instance where a pilot has shouted interference after a crash have I been able to detect anything on his channel!
Regards,

John.

HarryC

My Feedback: (1)

Brilliant! Perhaps Mpx can include that in the next software upgrade for the Evo?

Harry

Jeddy

Thanks, I see the problem, although can't see that's insurmountable (maybe the Evo could also broadcast a 'watermark' in its transmission that it could detect and ignore it's own signal).
Because we all fly closish together, what I was hoping is that if my Tx started warning me I could just shout out "turn off channel xx" and that would hopefully alert the joker who had just turned on to turn off before he launched his model, and maybe even while his aerial was still down and before he had started interfering with my model. Or maybe the Evo could do the shouting for me?! (But I do prefer the missile idea).
It may however still be worth me buying a checker, otherwise next time it could be me forking out $800 on a new model - for someone else!!!

rorywquin

Interestingly in the manual that came with my scanner MPX explain how two tx transmitting on a frequency apart and located close together can create interference on frequencies one channel away from the two being transmitted. Eg 63 and 65 are transmitting they will create interference on 62 and 67.

So on the scanner I would see 63 and 65 as strong bars (strong signal) with smaller bars (weaker signal) for 62 and 67. They have a technical name for it which, I can look up if anybody is interested!

I hope I got that right, but that is the gist or what they say.

This is part of their explanation in the manual on how to read the results on the scanner and use it properly!

HarryC

My Feedback: (1)

I have been protected once by the channel check. The other user of my frequency landed, gave me the peg and came to chat. I switched on but got the red light. Told him he had not switched off. He assured me he had but I insisted and when he checked, oops, he had forgotten to switch off. So my channel check protected me, not him. Thank you Multiplex.

The 4000’s scanner has two sensitivity settings. In long range setting it will show intermodulations between transmitters but they are really of such low power they are not a problem. We have flown happily with them for decades without us knowing they exist, seeing them on screen just scares you for no good reason! At the short range setting it only shows those Tx that are turned on.

Harry

JohnMac

Jeddy,
Sadly, what you are suggesting won't work. You can "encrypyt" the signal as much as you like, if there is another Tx on the same frequency, ther Rx will be unable to "hear" the encrypted signal.
The answer is quite simple. Everyone should use Multiplex!!
Regards,

John.

JohnMac

Harry, Good idea.
However, The software upgrade will be 4/6d.
The Alarm missile will be £1.9 million.
However, Baldrick has a cunning plan. If we all buy Estes rockets and strap them to the TX, and then we start a rumour that the Tx has this capability and that instant but very personal destruction will follow.........
It could just dissuade a few idiots from switching on unduly don't you think?

HarryC

My Feedback: (1)

John, your plan is so cunning that you could pin a tail to it and call it a fox!

H

Lynx

It's actually not that difficult to check to see if another transmitter is on. All you have to do is turn yours off. I wouldn't see why it wouldn't make sense for them to program in a single frame skip to power down the RF module, and then power it back up, skipping that one frame where it would be quiet enough to detect anyone else using the channel. At 50 frames per second no one is going to miss 1 frame every 5 seconds. It would at least give you the piece of mind to know weather or not the hit you're experiancing is noise or another RC signal.

JohnMac

Lynx,
That did occur to me but I still thnk that the knowledge gained would be rather academic. You would now know exactly why your model crashed!
If you are going this far, why not go the whole hog and build in frequency agility? Or just fix a future date when ALL transmitters need to be fitted with channel check facilities?

rorywquin

And then we could keep it simple and have channel check in all transmitters!!

Jeddy

Give every synth tx a unique code which it sends hidden in the main signal, then if you have a synth receiver you can program in that code, and it ignores any signal that doesn't include that code. That way everyone can fly on the same channel and not interfere!!!?! We can have a sky full of models - I guess the problem then becomes being hit down by another model instead of shot down by another tx.

HarryC

My Feedback: (1)

It doesn’t work that way Jeddy. The radio frequency is either on or off and with more than one Tx generating the on, several ons will overlay one another. The Rx doesn’t see each individual on signal that is overlapping and wonder which is its on signal. it just sees one on signal whether there is one Tx or 50 Tx that are at the on state. Even if you added an identifying code to the start of each on signal the Rx could only tell which is its on if each Tx takes turn about to transmit. When all transmit at the same time all the signals become as one to the Rx.

What we really need is mobile phone technology – just imagine not being able to use your mobile until you got the peg for that frequency! But mobiles are run from one central computer through one aerial – would your club, indeed could your club install a central controlling computer and one aerial at your site, to which you each plug in your Tx via a buddy lead and let that central computer and aerial do the radio work?

Pseudo random frequency hopping at very high hopping rate might work but if we use PPM we can’t hop faster than one servo’s data, i.e every 2 milliseconds and the possibility exists of one or more servos in sequence being on in-use channels and so getting totally corrupted data. Even with frequency hopping there are only so many frequencies out of the total available that could be used at any one time otherwise the conflicts would be too frequent so some automatic system of preventing switch on, like Multiplex channel check would still be needed.

In reality, the solution to all our problems exists, probably several times over but either cost or lack of commercial pressure on the manufacturers is preventing it being implemented.

Jeddy

Funnily enough, on the two main sites we fly from we're swamped by aerials - one huge telecoms tower on one site, and a couple of Royal Navy comms aerials on the other site.

However even if the technology existed I don't suppose we'd get permission - we're having problems enough trying to get a anemometer etc. connected to a PC for web access on one of the sites!

I understand that a while ago it was suggested that all our members should have tx's which had channel checks on them to prevent conflicts - needless to say this was very quickly dismissed.

Back to the peg board...

JohnMac

Jeddy,
What a shame your club didn't go through with it! If all the clubs in the UK made Channel Check Tx's the rule, guess what? Channel Check would be available from every manufacturer faster than you could draw breath.

Lynx

If the entire spectrum available to RC users was commonly used and maintained we could probably increase the refresh rates of an 'intelligent' transmitter by a factor of 5 or more. The real world doesn't work like that though <G> First RC channels are interleaved in between commercial ones so it's impossible to do that easily. The main reason is there just aren't enough users to justify it. Cell phone tech has gone through the roof, but look at how many millions of people use them. With that kind of user base you can justify the cost of developing technology to do that. For RC use it would cost more to develop than they could get out of it. Not to mention it would required all major receiver/xmitter companies to collaborate together and petition the FCC to reassign spectrum space and come up with standards etc... It just won't happen in this lifetime.

Jeddy

John, I think if the club had gone through with it, it would have folded, as half of the members wouldn't want or be able to invest in a tx that could channel check, and I wouldn't have started flying a couple of years ago if I was faced with my first tx costing £x00's. Mind, if it had been mandated a number of years ago, it would have been a cheap add on when I started flying! I guess we need to find a large initial base to bring the costs of mass production down to a level acceptable to everyone else.