I know it's taboo, but I've been running a ZDZ 40 with the ignition and radio on the same 2200 mah Lithium battery and voltage regulator. Range checks and flys with no problem. RX is PPM.

Now I've got a new Brison 40 with C&H ignition that I want to swap out with the ZDZ 40 in a Patty Wagstaff Extra ARF. The Brison is 4 oz. lighter than the ZDZ, but I would like to stick with the single battery system.

My question is, has anybody experimented using a small capacitor bridging positive and neg. as is done on electric motors (for Electric planes) in order to suppress electrical noise? The capacitor would go where the voltage is still 6 volts, not on the engine side of the ignition module.

The Falkon ignition on the ZDZ seems very well shielded. The C&H seems less shielded. That's why I'm thinking the capacitor might help.

Thanks for any comments.

It can't hurt. Make sure its not any kind of electrolitic. They don't help with RF. Use the largest ceramic you can get.
Its interesting that you have been able to do this. It sure has not been recommended.
Also I would make sure that the C&H version is one intended for a system not using a resistor plug

I too would be interesed in the results of this test.
WHile I would never do this, it is interesting that more and more people are putting the ignition and receiver systems closer.

There are no systems made for non resistor plugs, they all work the same, resistor or not...The completely shielded systems don't NEED a resistor plug, however...
The Bosch cap is better than the one with the set screws that come with the other ignitions that have to have the top of the spark plug ground off...

I have a Rienmuth ignition system I bought several years ago at Toledo. It is intended for use with a resistor plug and has no shielding at all. I have not tried to use it. If you and C&H don't make a nonshielded unit I guess you are in a better position to know that than I am.

What has to be in the ignition module to eliminate the need for shielding?

Wimpy spark, and the use of a resistor lead.

My wimpy spark will jump 5/8" in dry air and work with either solid or resistor wire and a rubber cap...I have over 1000 ignitions out there made just this way....Not many compared to C&H, but significant to this discussion.. It is strong enough to run a 289cc twin at 200+ mph..Fuel was methanol..Rubber caps, solid wire..The plane won the unlimited silver class at Madera..
Even a wimpy spark in a solid wire will cause interference if not installed correctly...

Not yours, Dans old stuff.
We spent 3 days running RFI checks and checking many new coils. You can see the relationship between spark and RFI.
We don't have a hi-v probe that will work yet. But our basic quick check on a coil is to take a spark plug and cut the side electrode off and then buzz it up to 12,000 rpm. If it keeps sparking then it will run any engine anytime. Some coils were falling down at 7000.
Shielding also take a big bite out of spark quality. We THINK its causing some capicator effect.

Gotcha

THe resistor would change the resistance of the circuit and make the spark voltage needed higher and the duration shorter due to the increased resistance. So the spark would be able to build to a higher voltage before jumping the gap. Is that it? Can't see this relationship to RF noise.

The resistor acts some what like a resistor plug. I'm not really sure of why things work as they do, but doing range check you can see what the result is of adding resistance and/or shielding.
The ancient standby has always been a 1w 10K resistor in the lead. Still works good today.
There are two parts of noise one is the spark itself, a spark has an infinate number of harmonics. The other is these ignitions don't have a smooth steady current draw. They take a big gulp of power just after the plug fires to recharge the HV cap. This puts a noise equal to RPM on the battery leads, switch and the battery its self.
Modern raidos are so good that we can get away with many sins in our installlations

The instructions on my unit specifically state it is not a wimpy spark. BTW what is a a wimpy spark?

I have always wondered why a resistor in the spark lead reduces the RF interferance. I think its because it limits the rise time of the pulse that creates the spark. That would reduce the frequency of the generated RF below the bandwidth of the receiver. Have you looked at the frequency spectrum of the spark with a spectrum analyser? With and without the resistor?
Recharging the HV cap should generate RF well below the frequency bandwidth of the receiver. It would be a good idea to check this with a spectrum analyser as well.

the 3W has a very wimpy spark

it also has a 1k ohm resistor in the plug cap...


dave

European manufactured Electronic ignitions are required to be designed to a very stringent safety and RF interference standard. That's why they have BOTH a shielded cap/lead and a resistor spark plug. The ignitions that come with ZDZ, RCS and ROTO gas engines all have this "CE" Mark (Conformité Européene) certifying that they have passed all the required tests. It is kind of like a combination UL (safety) and FCC type B certification (interference), expect that the European standards are more stringent.

The purpose of the resistor, in the plug or in the lead, is to slow down the rise time of the high voltage pulse. This has the effect of reducing the amplitude of high frequency noise that interfere with the operation of receivers. For a simple (and not entirely correct, but you will get the idea) explanation see: http://educate-yourself.org/be/upper...d22may02.shtml


David Garrison

RC Showcase

ZDZ, RCS and ROTO gas engines