Problems with Multiplex MC4000 2,4GHz

[giuseppe]

Hello I report here a problem I hed with my MC4000 fitted with an HFM3 M-Link module. The problem was essentially a range issue with a temporary loss of control of my glider when it was flying at 400-500m of height. In both cases, the glider recovered from out-of-control and I was able to land safely, but with a lot of scare for everybody at the airfield!

The problem occurred in two different occasions, with two different gliders, in two different airfields, using two different rx (RX9DR & RX12DR PRO). Receivers are new, installed in the models keeping the antennas at 90° and far from metal or carbon. Rx batteries (2x 2S Lipo) were fully charged and in perfect conditions.
After landing, I performed a check with tx in low power mode and I got 40-45m vs. usual range of around 100m. It is like if the range was reduced for some reason!

Another strange thing happened: switching off and then switching on the transmitter, the channel check was emitting the alarm “channel in use”...but I was in 2,4GHz!
I really don’t think so, but can be this a reason of the reduced range???

Many thanks for any feedback and regards to all!

 

[gruni]

Hello I report here a problem I hed with my MC4000 fitted with an HFM3 M-Link module. The problem was essentially a range issue with a temporary loss of control of my glider when it was flying at 400-500m of height. In both cases, the glider recovered from out-of-control and I was able to land safely, but with a lot of scare for everybody at the airfield!

The problem occurred in two different occasions, with two different gliders, in two different airfields, using two different rx (RX9DR & RX12DR PRO). Receivers are new, installed in the models keeping the antennas at 90° and far from metal or carbon. Rx batteries (2x 2S Lipo) were fully charged and in perfect conditions.
After landing, I performed a check with tx in low power mode and I got 40-45m vs. usual range of around 100m. It is like if the range was reduced for some reason!

Another strange thing happened: switching off and then switching on the transmitter, the channel check was emitting the alarm “channel in use”...but I was in 2,4GHz!
I really don’t think so, but can be this a reason of the reduced range???

Many thanks for any feedback and regards to all!

Hi Giuseppe,

did you check the connection of the M-Link-Module into the 5-pin-socket/slot in the transmitter?
How did you mount the TX-antenna?
How does the antenna-cable look like? Twisted?
Connection between antenna-cable and black antenna ok?

Sounds like connection problem, if the faults accured with both receivers.
Phone MPX-service, they will help you.

Could you report any solutions. Thank you.

Regards Gruni

PS: We found out, that the jeti TMe-module fits into the connection slot VERY tight. So maybe there is a brocken connection in the pcb-board underneath the slot. That could explain the fault message about the hf.

 

[giuseppe]

Hello Gruni, thanks a lot for your feedback.
The HFM3 module was initially installed in place of the standard 40MHz module as reported in the instruction manual (and with this configuration I had the first problem some months ago); now, I have installed it inside the tx with a switch controlling which module works (40MHz or 2,4GHz) and also in this configuration I had the problem. The antenna is installed on a side of the FM antenna connection and is bended at 90 degrees as suggested by MPX. The cable looks ok and I was very carefull in the installation not to damage it.
I'll also do a check to the connection slot. Your input is interesting!
End of next week (unfortunately I'm now far from home for some days) I'll do a new range check and I also want to do the test using the external module to be connected to the DIN plug (a friend of mine has one).
Thanks again and regards,

Giuseppe

 

[Gast_38755]

Measurement

Measurement

If the Problem isnt´t solved, you could try to measure the Power Output of
the HFM3-Module.
This could be only done with special Devices, but for comparing you could try to
disturb cheap Audioamp´s like PC-Speakers, this should give an same Level of
Audionoise with the same Distance from the Antenna to the Amplifier.
( approximately )

With the Modules installed switchable, you could get Problems by Higher Resistance
of the Switch and/or Interferences Radiated into the Wires from the Socket to the
Module ( if non shielded Wires used ). I have installed two Modules too, but with no switch
( MPX-Connectors used ) - and i have used shielded Wires for the PPM Signal ( RG174 ).

But you wrote the Problem also appeared with inserted directly in the MPX-Socket.
So the Outputpower could be to low in Case of damaged Wires/Antenna or Module
itself.
The Range Test could be positve, but if the Antenna/Wires to the Antenna are not ok, it
is also possible to loose Range in non reduced Power.

An other Antenna for 2.4 Ghz tested ?

An Range Test with the external Module is an good Idea ( HFMx ).

Range with full Power should be more than 2000m ( Receiver "visible" for the Transmitter ).

Greetings
Bernd

 

[giuseppe]

Hello Bernd, thanks a lot for your suggestions. On the next weekend when I'll be at home and I'll try to do some measurements...with my pc loudspeakers. I Also want to try with the HFMx module, may be also exchanging the antennas.
I didn't use any shielded wire for the ppm signal and, why not, this could be a possible cause of the issue. It's something to re-consider.
Fyi, I attach some pictures of my modification to transmitter.
Thanks again and regards,

Giuseppe

 

[Gast_38755]

Hi Giuseppe,

others also didn´t used shielded wires and reported not Problems.
But the Energy of the Transmission Antennas are surly high enough
to radiate into the ppm Input - possible MPX has installed Lowpassfilters
in the Inputlines that suppress such Noise.
I have made an Audioamplifier for my 2. TX ( Royal Pro 16 ) and had to do
a lot to get the Signal free from RF-Interferences - by the Way, the Audioamp
ist much more sensitive than higher Amlitude Signals ( the ppm Signal should
be much higher ).

But i would not bet for safe Operation with nonshielded Wires ( if they are
longer than some mm´s ).

But on the other Hand, the Transmission from the HFM3 to the RX ist Digital, so
an distorted PPM Signal should bring up Troubles in short Distance too.

Try to evaluate the RF-Output between the HFMx and your HFM3 - then we will
knew more.

Greetings Bernd

 

[giuseppe]

Hello Bernd, I have some news since last weekend I finally did the discussed tests.
At home I did the test with my PC loudspeakers: with both modules I didn't see any real difference. In both cases, the signal looks ok and audible up to 30-40cm from the loudspeakers.
At the airfield I tried to have the same conditions of when I had the problems: model completely assembled and placed on the ground.
First I have done the test - in low power - with the HFM3 M-Link; after I installed the HFMx.
Well, I noticed a clear difference among the two modules! With the HFM3 I got around 60-70m, while with the HFMx I arrived up to 110m and even more.
What I noticed with HFM3 is that the performance is highly variable depending on the position of the antenna on the tx: with the antenna horizontal (see picture above) I have 60-70m, with the antenna toward the ground the distance arrives close to what I got with the HFMx. Viceversa, HFMx seems to be quite insensible to the antenna positioning.
I also changed the position of the glider (first with the tx behind the model, then with the tx on a side of the model), but in both cases I didn't notice and significative difference.
I finally tried to exchange the antennas among the two modules, but also in this case, I didn't notice difference.
Next weekend I would like to perform the test with the HFM3 as it is now installed and removing all the hardware and installing it as Multiplex suggests.
Anyway, what looks strange to me is the impact of the antenna position. Do you have any input on this??
Many thanks and kind regards,

Giuseppe

 

[Gast_38755]

Possible...

Possible...

the Part behind the Antenna could reflect the Signal, if the Distance from the
Antenna to the reflecting Materials is ideal, the the absolute radiated Power
is higher into forward Direktion, if the Distance ist bad - the Signal is lower.

This is used in many Antennas - but the Gain is in case of the directivity.

You could try an Metal Plate of about 15x10cm behind the Antenna, or an
14-15cm piece of wire behind it.
Vary the Distances of this Reflektor´s .

ONLY for Tests, this modifys the Antenna electrical !

Metal parts too close to the Antenna are also not an good idea, but all
Parts with more then 3cm should not affect the electric Data´s.


The directivity will allways be affected - including by your Body ;-) .

Bernd

Edit: Turn the P4000 Antenna for Tests to the left, far away from the 35M Antenna
connector ! - The original Installation uses the same Position, so the
2.4 Antenna is monted in the Middle, rotated to left or right.
It is possible - the 35M Connector disturbes the 2.4G Antenna ( large Piece of Metal ).

I will also test this - i will also do some Tests with M-Link

 

[Roland Schmitt]

In my mc400 i had done nearly the same. The M-Link TX Modul was placed on the same place as on yours. But i used a cable to connect the The M-Link TX Modul directly to the connector of the Mhz-HF Modul in the modul slot. Further on I wired all five connectors and the cable was not shielded.
It had worked perfectly for a lot of months.
Please check the following, ist the antenna completely as deep as possible screwed on the RF cable socket? When i installed the antenna socket at the TX box this was critical point. As a further test you should screw the antenne directly on the RFs Modul HF-Cable, without using the extension HF-Cable.

 

[Gast_38755]

Antenna´s

Antenna´s

Hello Roland,

in english for giuseppe

where do you have installed your Transmitterantenna ?
Mine is located nearly the same Pos. as giuseppe´s .

On the Photo, the Antenna seems to have enougt space to the
Wisherplate - so the installation should be ok.

A friend of mine has got the expensive Measurement for 2.4G - i hope to
use this for Tests.

If there is an Difference between turned right or left Antenna, it seems to be an
Problem of nearby Metal Parts.

I will also test the Differences between the RX7/9 nonlight and light Versions.

Greetings Bernd

 

[giuseppe]

Dear Bernd & Roland, first of all, thanks for using English language! My understanding of German language is quite poor and my writing in German is a real disaster...

Regarding my issue, I also thought to an interaction between 2,4GHz antenna and the 40MHz antenna connector. Unfortunately, rotating the 2,4GHz antenna to the left side I didn’t notice any real difference.
What is very evident is the positive effect of using the antenna oriented toward ground.
What I also thought is that - in any case - the antenna should stay more far from the transmitter case (and also from my body...that’s quite big!) as it is the case of the HFMx module. To do this, I could use (but I don’t know if exist) a sort of rigid extension of the antenna with a length of 25-30mm placed between the connector and the antenna itself.
This would keep the antenna far from the transmitter case.
I'll also check the antenna screwing in the connector. This is a good point, even if it shouldn't have anything to do with the effect I got orienting the antenna horizontally or vertically.
Unfortunately, due to my work, during the week I’m far from home and I can only plan my tests for the next weekend.
Bernd, any feedback from your tests with a field measurment device would be very interesting!
Many thanks to all for your support!
Ciao,

Giuseppe

 

[Gast_38755]

Rigid Extension

Rigid Extension

This is possible !

On the Market, there are some Kind of special Coaxial Cables.
Called semi regid - i have such Cabel in my Stock.

With special Connectors you will have exellent Connections.
This Cable is not a Cable, it is ChopperTube - not Wire !

SR3 is an Type of such Cable, you could get such Cable at

http://www.ukw-berichte.de/


also the needed Connectors ( reverse SMA )

When absolute precise installation, there is very low loss.
Isolation ist PTFE, no worry about soldering Heat.

But its a bit expensive.

I don´t knew where you could get it nearby your location.

Any Contact to Radio Amateurs ? Some of them ( Freaks using extrem HighFrequencys )
will have it and the Knewledge.

Greetings Bernd

Edit - i am Searching for SMA-Reverse, not found yet :-(

 

[ev2driver]

Measurement

Measurement

If the Problem isnt´t solved, you could try to measure the Power Output of
the HFM3-Module.
This could be only done with special Devices, but for comparing you could try to
disturb cheap Audioamp´s like PC-Speakers, this should give an same Level of
Audionoise with the same Distance from the Antenna to the Amplifier.
( approximately )

With the Modules installed switchable, you could get Problems by Higher Resistance
of the Switch and/or Interferences Radiated into the Wires from the Socket to the
Module ( if non shielded Wires used ). I have installed two Modules too, but with no switch
( MPX-Connectors used ) - and i have used shielded Wires for the PPM Signal ( RG174 ).

But you wrote the Problem also appeared with inserted directly in the MPX-Socket.
So the Outputpower could be to low in Case of damaged Wires/Antenna or Module
itself.
The Range Test could be positve, but if the Antenna/Wires to the Antenna are not ok, it
is also possible to loose Range in non reduced Power.

An other Antenna for 2.4 Ghz tested ?

An Range Test with the external Module is an good Idea ( HFMx ).

Range with full Power should be more than 2000m ( Receiver "visible" for the Transmitter ).

Greetings
Bernd

 

[gruni]

???