Kieran Sullivan <[email protected]> writes: > The telemetrum seems to take a very long time to acquire enough > satellites to get a position lock, perhaps 15 minutes or so.
That's on the long side of what we usually see, but this depends on many, many variables. > The telemega installed in the same rocket instead takes only a minute or > two at most. I think they use different GPS receivers, so it's not > just RFI that makes the telemetrum take an age to get GPS lock. Same GPS receiver, but different antennas. The issue is that the PCB for TeleMega is wide enough that we can use a very high quality, high gain GPS patch antenna. But at only 1 inch wide, TeleMetrum's size is just below a knee in the tuning curve (patch antennas have to be tweaked for a given ground plane size) for that antenna, so we can't use it and had to find another antenna that's "ok" but clearly just not as good. Our volumes are low enough that getting custom patches cut just for our needs hasn't happened yet, but I sincerely hope to find a better GPS patch for TeleMetrum eventually. > Once locked, the performance of the telemetrum is very good. Thanks, agreed, the issue is time to first fix being slower on TeleMetrum than TeleMega. FWIW, based on testing here, I would expect TeleGPS to be similar to TeleMetrum but we get better reports on it. I wonder if that's because it's often just turned on earlier in the prep process, ergo longer before launch so it doesn't *seem* to take as long, or if anyone has actually done side by side testing in the field? Bdale
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