Irving Family Web Pages: Rocketry: Igniter Testing, Protocol 2

Experiment Two - Igniters attached to their standard leads.

Equipment and Setup
The transmitter setup for experiment two was the same as with experiment one except that the stick upon which the transmitting antenna was mounted was held in my hand instead of being mounted on a short step ladder. The radio equipment setup is described fully in the protocol article for experiment one.
For the receiving antenna, I used a Daves igniter attached to the wire leads it came packaged with. Out of the box, Daves brand igniters are attached to six foot zip-cord wires which keep the two igniter leads parallel to oneanother as they lead away from the igniter. (Recall that in experiment one I built the dipole elements so that they point away from the igniter in opposite directions.) Keeping the leads parallel to one another drastically reduces the wire's capability to conduct RF energy into the igniter. It is also more like the conditions one would expect at a launch site. The main difference between this configuration and a launch site configuration is that at a launch site the ends of the zip cord leads would in turn be attached to long cables running to the ignition control system. I did not perform any testing with long control cables.
For experiment two I hung the six foot igniter/lead from the end of a wooden pole so that the zip-cord hung free from obstructions and the igniter hung free at the bottom of the zip cord. Here is a photo of the setup. Click on it for a full-size view.

The igniter hanging on its six foot zip-cord lead is to the left. The igniter is at the bottom end of the wire lead. The transmitter antenna is to the right at the end of a stick I am holding in my hand. This allowed me to "wand" the transmitting antenna all around the hanging igniter lead at various distances and orientations while transmitting.

Testing Protocol
I performed two tests with the six-foot lead configuration. One was with the free ends of the zip-cord wire shorted (twisted) together as they come packaged. The second test was with the ends open (separated). For each of these two configurations, I transmitted continuously for over one minute while wanding the transmit antenna all around the hanging zip-cord. I moved the transmit antenna back and forth up to a minimum distance of about one inch away from the hanging zip-cord. I also moved up and down along the zip-cord.
After testing with the six foot configuration, I cut the zip cord to a length of 38 inches which is 1/2 wave length at the frequency I was using. (147.46 MHz.) Once again I tested with continuous tranmission for over one minute, both with the lead ends shorted and open. After this I cut the zip-cord to a length of 19 inches which is 1/4 wave length at the frequency I was using, and I repeated the testing with the lead ends shorted then open.
After completing these tests, I verified that the igniter I was using was good by peeling the zip cord apart and stretching the two leads in opposite directions. I then hung the igniter by one of the separated leads. This configuration was now essentially the same receiving antenna configuration as my dipole configuration in experiment one. I wanded the antenna close the the hanging igniter and it fired at a distance of approximately six inches. This assured me that the igniter I was using for experiment two was in fact a good one.

Copyright © 1996 Donald J. Irving
Document URL: http://www.irving.org/rocketry/igniters/proto2.html
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