Dad Man Walking
Dontree Member
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- Aug 26, 2012
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There has been a bit of tooth-gnashing on some other threads about the degradation of the Eggfinder RF signal when the transmitting antenna is positioned near a metal object such the central threaded rod in some nosecone setups. So we decided to test a couple of different setups to see what the fuss was all about.
We set up the Tx board with a rubber antenna about six inches long (something like 2-4db gain, if I recall), and a similar antenna on the Rx module. Our test range was along the RR tracks running through town, where we had line-of-site across the ground. We shoved the NC with the Rx module inside into a bush about 4-5' off of the gound, and started walking. These are obviously not optimal conditions for the 900Mhz radios, but we were not interested in maximum range in real launch conditions, just the difference between the signal with the antenna next to the threaded rod vs. being on the opposite side of the bulkhead.
With the antenna installed inside the NC, parallel to the threaded rod (around 1" away) we got signal for up to 1/2 mile over the ground. Over the second half of that distance we started to get signal loss at the receiver but we would reacquire fix after a few seconds. At the 1/2 mile point we could no longer acquire a signal. We then repositioned the Tx board/antenna so it was on the opposite side of the bulkhead, opposing the threaded rod. In this configuration, we got out to 0.6 miles before the signal dropped out entirely. So according to my my hillbilly engineering, I'm a-figurin' that there's potentially a 20% degradation in signal strength when the antenna is sharing space in the nose cone with a steel threaded rod.
The ground tests do not represent the performance of the system in clear air. This weekend we flew the same set-up - same Tx and Rx antennas, with the Tx antenna mounted opposing the threaded rod, outside of the nose cone. Flight was to 14,000 feet, Mach 1.5+. Two Rx units tracking, both lost fix only once, at the same time and only for about a couple of seconds during the "up" phase, not sure if that was during boost or coast. Both Rx units locked through the rest of the flight.
Impressive little piece of kit! Thanks for making this possible for us, Cris.
We set up the Tx board with a rubber antenna about six inches long (something like 2-4db gain, if I recall), and a similar antenna on the Rx module. Our test range was along the RR tracks running through town, where we had line-of-site across the ground. We shoved the NC with the Rx module inside into a bush about 4-5' off of the gound, and started walking. These are obviously not optimal conditions for the 900Mhz radios, but we were not interested in maximum range in real launch conditions, just the difference between the signal with the antenna next to the threaded rod vs. being on the opposite side of the bulkhead.
With the antenna installed inside the NC, parallel to the threaded rod (around 1" away) we got signal for up to 1/2 mile over the ground. Over the second half of that distance we started to get signal loss at the receiver but we would reacquire fix after a few seconds. At the 1/2 mile point we could no longer acquire a signal. We then repositioned the Tx board/antenna so it was on the opposite side of the bulkhead, opposing the threaded rod. In this configuration, we got out to 0.6 miles before the signal dropped out entirely. So according to my my hillbilly engineering, I'm a-figurin' that there's potentially a 20% degradation in signal strength when the antenna is sharing space in the nose cone with a steel threaded rod.
The ground tests do not represent the performance of the system in clear air. This weekend we flew the same set-up - same Tx and Rx antennas, with the Tx antenna mounted opposing the threaded rod, outside of the nose cone. Flight was to 14,000 feet, Mach 1.5+. Two Rx units tracking, both lost fix only once, at the same time and only for about a couple of seconds during the "up" phase, not sure if that was during boost or coast. Both Rx units locked through the rest of the flight.
Impressive little piece of kit! Thanks for making this possible for us, Cris.
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