Signal swamping?

[hayabusaboy]

Hi Guys,
Just have a question to ask, but first a little about what has led to this.
I have a JR3810 on 36MHz. I use a PPM and a PCM reciever in different models. Both glow powered. I do a range check with the PPM no worries, the PCM will make about 30ft before it starts going into failsafe. When starting the models I sit the Tx to my right, in a convienient position to enable me to start the engine and operate the throttle. That is where the second problem occurs, I get jittering with the PPM Rx and the PCM goes in and out of failsafe intermitantly. This is with the antena down. Put the antena up 1 section and the problem goes away.
I am loath to fly a model like this as I'm really concerned that it will lead to the demise of a model that is not my fault.

What causes this kind of problem?
What are possible remedies?

As far as I am aware th Tx has not been dropped and the Rx's seem to be in good order and not faulty.

Thanks for your opinions guys

[Stu_D]

First off I have to state the following is only my opinion and you must
do what you think is the right thing . That being said since when did any
radio work properly when the aerial was not the right length (over or under).

If you want to KNOW if your equipment is good then send it to an expert
and they will be able to tell you .

Always get another person to do a full check over of your plane prior to
a maiden , never trust your own eyes . A range check failure is almost
always due to set up . Have you ever noticed its the same guys who
have radio problems .

The cause of your problem will be found in your set up technique , what
ever it is .

Stu D

[notorious_benny]

Has your Tx ever been left on for a long period of time ie (more than a couple of hours) with the aerial collapsed??

If so you can overheat your RF module which greatly reduces the power of the output RF.

Also what do you classify as a good range test with the PPM rx??? You should be able to get at minimum 100ft with the aeial fully collapsed. I have found 300ft is pretty normal in my glow powered stuff.

My petrol powered model tends to range to about 200ft when it is running on the ground with the nose pointed straight at the Tx. (worse reception position).

My advice would be to go over your setup in your model with a fine tooth comb. If you cant get an adequate range, then you need to get your equipment checked for bandwidth and power output.

Also you should hold the Tx at arms length from your body and at shoulder height while range testing, as your body can definitely mask RF and your range rsults will always be varied.

Another thing is to range test the model while it is away from pit enclosures, and starting pegs. One of my models was only getting about 100 ft before failsafing, I pulled it away from the starting pegs and I got more than double the range.

[notorious_benny]

I dont know what just happened to my post above!?!?! Sorry guys.

[hayabusaboy]

ok, thanks guys.
the ppm setup has been working without fault for 2 years, the only change made was the engine. (does this make a difference as they were both glow?)
I have no problem with doing a range test on the ppm Rx, it maintains signal, antenna down over 50m away.
The PCM Rx, I'm not so sure about. It used to operate with no problems up until recently (no crashes, etc). So I'm puzzled as everything functions normally at home. The last time at the field there was at least 2 other guys having some issues. PPM jittering and PCM hits more than usual. Can the guy who does bandwidth testing check Tx power?

I will try range checks in the open to see if my problem goes away or is less of a problem.

Benny, are you comming up for the DA Challenge?

[notorious_benny]

Hmmmm, if your ppm still works fine then I dont really know I am sorry.

Try borrowing a mates PCM rx, or try the crystal from your ppm in your pcm and see if that fixes the problem. Is the PCM rx in the same model or a different one??? I still agree with Stu that it is more likely to be a set-up issue than anything else, but you cant always be assured of that when dealing with RF.

Cant make the Da challange I am afraid. I cant get outta work!

[hayabusaboy]

too bad you won't be able to make it, but I guess you need to fund you flying addiction somehow.
I'll try changing crystals and look over the model's setups. I may have missed something, might even get someone else to check it over as well. I guess I'll try any means possible to solve this problem.

Thanks for the advice and I'll post the slolution when I find it.