Irving Family Web Pages: Rocketry: Igniter Testing, Protocol 1

Experiment One - Igniters attached to tuned receiving dipoles.

Equipment and Setup
The transmitter used was a Kenwood TM-641 Tri-band transceiver operating in the two meter amateur radio band at 147.46 MHz. A three foot Radio Shack 50-ohm PL-259 patch cable connected the transmitter output to an in-line Daiwa CN-460M PWR/SWR meter. Attached to the antenna plug on the SWR meter was as SO-249-to-BNC adapter then an ANLI CM-2 BNC clip mount with 9 foot 50-ohm coax. The antenna was an AEA Hot Rod 1/2 wave, end-fed, 2-meter telescoping antenna. The telescoping length of the antenna was adjusted slightly to provide a 1:1 standing wave ratio on the SWR meter.
The receiving antenna was home-made consisting of two pieces of stripped, 12 AWG THHN house wire, each 19 inches long, taped onto a wooden bracket into colinear orientation with adjoining ends separated by 1/2 inch. The Daves igniters were attached to the adjoining ends of the colinear wire elements by cutting their leads to 1/2 inch then stripping the ends and spot soldering them to the ends of the antenna elements. The resulting antenna was a 1/2 wave receiving dipole at 147 Mhz. with a load consisting of the igniter element with its short leads.
The transmitting antenna and receiving antenna were then attached to the ends of wooden sticks free of obstructions for at least three feet in all directions. Here are photos of the setup. Click on them for full-size views.

Wide view from the transmitting antenna end.

Wide view from the receiving antenna end.

Close up of the transmitter and SWR meter. Close up of the antennas and igniter.

Testing Protocol
For each of twenty transmitting trials, I set the desired distance between the transmit and receive antennas by moving the yellow step ladder and measuring separation with a tape measure. I tested at 16 feet and at decreasing distances (by half) down to three inches. At each distance I tested first at 5 watts then at 50 watts of transmit power. I worked with one igniter sample using decreasing distances until it ignited, then installed a fresh igniter for more testing.
For each transmit trial, I keyed the transmitter and my stopwatch at the same time and then noted the forward power and SWR on the in-line meter. I held the transmit key down for 20 seconds or until the igniter fired. In cases where the igniter fired, it happened almost instantly, and so the transmit time for those trials was about 1 second. I recorded the values imediately onto a pre-formatted table I had printed out. For you radio hams out there, I was careful to listen for radio traffic and ID my station during each transmission.

Copyright © 1996 Donald J. Irving
Document URL: http://www.irving.org/rocketry/igniters/proto1.html
Permission to reproduce and distribute this document is granted providing the entire document is reproduced, including copyright, without change.

Wide view from the transmitting antenna end.	Wide view from the receiving antenna end.
Close up of the transmitter and SWR meter.	Close up of the antennas and igniter.