EMI problem...
 

I'm trying to track down an EMI problem.
This is with my solar powered RC plane.

Specifics:
I'm using standard 6M RC gear from JR on ch 04, FM on 50.880 Mhz.
I've got two receivers that exhibit exactly the same problem.
A JR FM receiver and a berg FM receiver.

Both work fine until I turn on my switching solar maximum power point
tracker.

The power tracker runs 6 seperate channels at about 25W each channel.
The switcher runs at ~ 150Khz +/- 20Khz

I've filered, shielded and added caps with very little effect.

The receiver is in the tail of the airplane the converter in the
front,. There is currently no electrical connection from the receiver
to the other electronics on the plane. I'm currently powering the
receiver from battries. The only connection is capactive to the
carbon fiber airframe.

I'm using an Icom R3 to hunt for the EMI.

The Icom receivers shows the 50.880 signal clear as a bell.
When I turn the TX off the icom sees no no difference in background
signal with the power converter either on or off.


When I run the Icom receiver tuned to 50.880 near the RC receiver I
see a significant reduction in range, but not as much reduction as
when I run the power converter.

My first theory is that I am generating IF or image noise that is
clobbering the receiver.
To test this I set a signal generator out next to the receiver and ran
it at 450Khz, 455Khz and 10.7 Mhz with no effect on range.
(signal generator is an old digital fluke runing 13dbm into a 2 ft
peice of wire)


Any ideas on what I can do to solve this... it is driving me crazy,
I've been working on it for more than a month.

Paul (Kl7JG)

wrote:

I'm trying to track down an EMI problem.
This is with my solar powered RC plane.

Specifics:
I'm using standard 6M RC gear from JR on ch 04, FM on 50.880 Mhz.
I've got two receivers that exhibit exactly the same problem.
A JR FM receiver and a berg FM receiver.

Both work fine until I turn on my switching solar maximum power point
tracker.

The power tracker runs 6 seperate channels at about 25W each channel.
The switcher runs at ~ 150Khz +/- 20Khz

I've filered, shielded and added caps with very little effect.

The receiver is in the tail of the airplane the converter in the
front,. There is currently no electrical connection from the receiver
to the other electronics on the plane. I'm currently powering the
receiver from battries. The only connection is capactive to the
carbon fiber airframe.

I'm using an Icom R3 to hunt for the EMI.

The Icom receivers shows the 50.880 signal clear as a bell.
When I turn the TX off the icom sees no no difference in background
signal with the power converter either on or off.


When I run the Icom receiver tuned to 50.880 near the RC receiver I
see a significant reduction in range, but not as much reduction as
when I run the power converter.

My first theory is that I am generating IF or image noise that is
clobbering the receiver.
To test this I set a signal generator out next to the receiver and ran
it at 450Khz, 455Khz and 10.7 Mhz with no effect on range.
(signal generator is an old digital fluke runing 13dbm into a 2 ft
peice of wire)


Any ideas on what I can do to solve this... it is driving me crazy,
I've been working on it for more than a month.

Paul (Kl7JG)


Try the image frequencies (probably 29.48MHz, but possibly 72.28MHz).
You may also want to try RX +/- 455kHz as well.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

This may be simple overload of the front end of the RC reciever. I
suspect it has little selectivity before the first stage and the tracker
unit is simply blowing through the filter.

It's been quite awhile since I did any RC work, but if it has a separate
Rx Antenna input to the RC reciever, you might try wrapping the reciever i
tin foil, and adding some high pass filters between the antenna and the
reciever. Make sure to shield the filters too, that much energy could
easily couple into the coils used in building the high pass filter.



Jim Pennell
N6BIU

How would one of the Minicircuit Prepackaged can filters be?
My guess is smaller, lighter and more robust than what I can build.

I've been using some adhesive backed Cu and Al tape to shield things,
tried shielding the Rx, to no avail, but a front end bandpass filter
was going to be my next step.

Paul


On Tue, 06 Jul 2004 05:07:37 GMT, "Jim Pennell"
wrote:

This may be simple overload of the front end of the RC reciever. I
suspect it has little selectivity before the first stage and the tracker
unit is simply blowing through the filter.

It's been quite awhile since I did any RC work, but if it has a separate
Rx Antenna input to the RC reciever, you might try wrapping the reciever i
tin foil, and adding some high pass filters between the antenna and the
reciever. Make sure to shield the filters too, that much energy could
easily couple into the coils used in building the high pass filter.



Jim Pennell
N6BIU