Some GPS trackers will still transmit Rf if they lose a lock from the GPS satellites. Some won't. If they stop transmitting an Rf carrier when they lose a GPS lock, one can't resort to using RDF techniques that could save the recovery. I actually experimented with a 900 Mhz GPS tracker (Eggfinder actually) and found a 900Mhz Yagi did provide a directional fix with garbled packets right at the limit of the Eggfinders ground footprint. Was an easy peasy thing to test as I had a visual direction where the rocket went down and lost the Rf link. (Can do this with a ground test too with a large enough field.) The Yagi did point in the right direction when I got closer before viable positions came in. If the GPS antenna was in the dirt, as long as Rf energy was being transmitted to swing an Rf meter, I could have done an RDF recovery from there on out.
Most say that with 900Mhz RDF isn't possible but in the terminal phases of recovery of a rocket "on the ground" where you know the general whereabouts of the rocket, it is highly DOABLE.
I have to be honest I have not ever had a totally sight unseen rocket with a 900Mhz tracker go up/down. Yeah, lost 'em on the up side but someone would see 'em coming down. If sight was lost during the whole flight, I'd use my best guess and go out using my 900Mhz Yagi as it does indeed improve the ground footprint. No attenuator is required on this band. On 400Mhz or 144Mhz an attenuator is helpful for RDF but if flying a GPS tracker is not needed generally. My 400Mhz and 144Mhz handheld Yagis have attenuators on them as they are essential for pure RDF tracking. The ground footprint is larger on 70cm and 2 meter bands. On 900Mhz not so great a footprint but good enough.
If serious about 900Mhz tracking/recovery, one should invest in a 900Mhz Yagi to have onsite just in case. If sport flying where one "sees" where the rocket is landing be it in corn or tall grass with a GPS tracker a Yagi is likely not needed though as I said it does increase the ground footprint and helps if one knows the general direction but doesn't see where the rocket came down.
Sure, if flying on the playa out west in the wide open spaces, a Yagi might be more needed as the salts on the salt flats suck up Rf energy like a sponge and folks tell me the tracker ground footprints are ridiculously small on the ground. That last known position is the key along with knowing the drift trend to get a rocket back. When one knows the way, they can point the handheld Yagi in the right direction to maximize the prospect of getting a ground signal and the rocket back.
With the "dirt" in the cornfields of the Midwest, we have better ground radio footprints so recovery is easier. Plus we don't fly as much totally sight unseen flights as we want to stay within the constraints of the launch sites we fly as lest we piss off the "neighbors".
Kurt
Most say that with 900Mhz RDF isn't possible but in the terminal phases of recovery of a rocket "on the ground" where you know the general whereabouts of the rocket, it is highly DOABLE.
I have to be honest I have not ever had a totally sight unseen rocket with a 900Mhz tracker go up/down. Yeah, lost 'em on the up side but someone would see 'em coming down. If sight was lost during the whole flight, I'd use my best guess and go out using my 900Mhz Yagi as it does indeed improve the ground footprint. No attenuator is required on this band. On 400Mhz or 144Mhz an attenuator is helpful for RDF but if flying a GPS tracker is not needed generally. My 400Mhz and 144Mhz handheld Yagis have attenuators on them as they are essential for pure RDF tracking. The ground footprint is larger on 70cm and 2 meter bands. On 900Mhz not so great a footprint but good enough.
If serious about 900Mhz tracking/recovery, one should invest in a 900Mhz Yagi to have onsite just in case. If sport flying where one "sees" where the rocket is landing be it in corn or tall grass with a GPS tracker a Yagi is likely not needed though as I said it does increase the ground footprint and helps if one knows the general direction but doesn't see where the rocket came down.
Sure, if flying on the playa out west in the wide open spaces, a Yagi might be more needed as the salts on the salt flats suck up Rf energy like a sponge and folks tell me the tracker ground footprints are ridiculously small on the ground. That last known position is the key along with knowing the drift trend to get a rocket back. When one knows the way, they can point the handheld Yagi in the right direction to maximize the prospect of getting a ground signal and the rocket back.
With the "dirt" in the cornfields of the Midwest, we have better ground radio footprints so recovery is easier. Plus we don't fly as much totally sight unseen flights as we want to stay within the constraints of the launch sites we fly as lest we piss off the "neighbors".
Kurt
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