GPS Tracking Range to 30,000 feet using Eggtimer TX and receiver, is it possible?

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John Feller

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Hello all,

I want to have GPS Tracking by using Eggtimer TX. Can I achieve this by connecting yagi antenna to Eggtimer receiver instead of SMA Antenna?
 

Jimmy Neutron

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Wow! Just curious which rocket and motor setup are you using to get to 30,00 ft?
 

Wayco

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If you can keep the Yagi pointed to the rocket during the flight, you might be able to track it that way, but I wouldn't recommend it.
I flew a CF Mongoose 75 on an CTI M840 to 28,905 ft. back in November 2015 with an Eggfinder and normal "Rubber ducky" antennas. Tracked the entire flight and recovered it four miles away. Only real problem with that flight was the recovery gear was draped across cat's claw bush and hard to remove.
 

John Feller

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If you can keep the Yagi pointed to the rocket during the flight, you might be able to track it that way, but I wouldn't recommend it.
I flew a CF Mongoose 75 on an CTI M840 to 28,905 ft. back in November 2015 with an Eggfinder and normal "Rubber ducky" antennas. Tracked the entire flight and recovered it four miles away. Only real problem with that flight was the recovery gear was draped across cat's claw bush and hard to remove.
I have also flown with eggtimer in last year, with the system you used, I only tracked to the 9800 feet, unfortunately. Then the connection were lost.
 

cerving

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You don't need a Yagi to go to 30K, the rubber duckie on the LCD receiver will do it. I've personally tracked rockets over 6 miles away... then it landed behind a hill, picked up the packets as I was driving around the back, and got it back. Yagi's are highly directional, which makes them great for RDF since you know the signal came from "that way", but they're not ideal for GPS tracking, especially if you lose sight of it and don't know which way it went. RDF relies on getting a signal on the ground after landing, GPS relies on getting a signal in the air as it's descending. Fortunately, the latter is easier since it's in clear air.

I would recommend using the TX or the TRS over the Mini for high altitude flights... the antenna works better because of the larger ground plane.
 

Wayco

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I have 22 rockets with their own Eggfinders mounted in the N/C that regularly fly in excess of 10,000 ft. It would take a considerable effort to data mine all those flights, but most of them got good data throughout their many flights. Occasionally I will have a rocket loose lock under high thrust, and I have had glitches with systems that didn't record the flight, but I have never lost a rocket with an Eggfinder GPS in it. All of my Eggfinders are the standard TX with a stubby antenna, and the RX with the longer antenna.

If you are having a problem with losing signal at 10k ft., you should check your installation and what is around your antennas. Metallic paint and all thread are common problems that attenuate signal strength.
 

ksaves2

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The beamwidth on 900Mhz I’m told is too narrow to keep a Yagi pointed at a rapidly moving rocket. Also there will be lost positions no matter what due to the Mach lockout and reception can be garbled due to spinning of the rocket and the doppler effect at high subsonic speed can interfere with the GPS signal reception from the satellites.
One thing you can do is get a good omni directional antenna on both the transmitter and receiver.
Linx Technologies is a good place to look: https://linxtechnologies.com/wp/.
I have found a mag base cell phone mobile antenna good for 900Mhz on ebay I put on the roof of my SUV and it seems to work ok. I haven’t been able to directly compare it with a simple SMA Linx antenna on the LCD receiver though.
Don’t give up on the Yagi thing. Once your rocket is down and more or less stationary, you generally will be able to point the Yagi in the general direction of where the downed rocket is. I‘ve tested the Yagi against a Linx omni directional antenna and the Yagi out performs it. I did a recovery using the Yagi and when I first saw positions coming in, stopped walking and unscrewed the connector and screwed on the omni. The signal disappeared. Put the Yagi back and it started getting positions again. The ground Rf footprint is larger with the Yagi.
The other thing is if one is flying on the Playa, the salts suck up Rf like a sponge so the ground footprint is very small and it’s essential to get that last known position close to where the rocket landed. Out in the open, it’s easier to get a visual on the downed rocket so one has a bit of leeway here as opposed to the Midwest that has more vegetation.
If you switch to the 2 meter or 70cm Amateur radio band then yes, the beamwidth of a Yagi antenna is wide enough to effectively be able to point in the direction of a flying rocket and improve packet reception and decoding.
Consider doing shakedown flights with lower powered motors to see how your setup responds. If it works to your satisfaction, then attempt the 30k’ flight. Especially if you’ve never GPS tracked before. Gremlins can creep in no matter how careful you are. Best of luck. Kurt Savegnago
 
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John Feller

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I have 22 rockets with their own Eggfinders mounted in the N/C that regularly fly in excess of 10,000 ft. It would take a considerable effort to data mine all those flights, but most of them got good data throughout their many flights. Occasionally I will have a rocket loose lock under high thrust, and I have had glitches with systems that didn't record the flight, but I have never lost a rocket with an Eggfinder GPS in it. All of my Eggfinders are the standard TX with a stubby antenna, and the RX with the longer antenna.

If you are having a problem with losing signal at 10k ft., you should check your installation and what is around your antennas. Metallic paint and all thread are common problems that attenuate signal strength.
We put the GPS in EBAY and there were nothing more than two steel threaded bars and eyebolt near the ebay as metal. We were using the EU/UK version which has 869 MHz system. As I remember the US version has 433MHz system which is stronger than 869MHz. Would it be the case for connection lost?
 

Wayco

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When I first started flying Eggfinders, I put one next to a piece of all thread, which is what I think you are describing as "two steel threaded bars". The results were a dramatic decrease in range.
Anything that decreases the signal strength could be the cause for a lost connection.
 

John Kemker

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We put the GPS in EBAY and there were nothing more than two steel threaded bars and eyebolt near the ebay as metal. We were using the EU/UK version which has 869 MHz system. As I remember the US version has 433MHz system which is stronger than 869MHz. Would it be the case for connection lost?
Only the Ham version uses 433MHz. The regular Eggfinders use 900MHz.
 

DaveW6DPS

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A yagi can be a problem to keep aimed at the rocket. There are a number of omni-directional antenna designs that might work well, but you may have trouble finding them for that band. I don't know the regulations for Europe or the UK, but in the USA we can use any type of receiving antenna, but the transmitter antenna usually may not be changed (except on amateur radio gear).

A bigger issue is if you are launching 30,000' up, how far will your rocket drift downrange? IF you have a good handle on the winds aloft you can add a receiving station downrange in about the area you expect the rocket to land. I have seen some flight where 900MHz gear available in the USA has worked fine at distances out to about 10 miles, but I have also seen some where a specific piece of equipment didn't perform well at all.

Another thing to consider is the noise level on the band you are using, at the location you are flying. Your digital signal needs a fairly good signal to noise ratio, and a high noise level can be challenging.

Asking about the range possible, or likely, with radio equipment sounds like a simple question, but accurately predicting the range in the real world has a number of variables and can drive you nuts.
 

cerving

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There are a lot of things that can affect getting a good GPS fix download. First, you need a good GPS fix, that's a function of where the satellites happen to be and (perhaps more importantly) the kind of GPS antenna you have. 99% of the ones that are used in rocketry are patch antennas, those are the square ones that you see. They are really a fairly wide-beamwidth directional antenna... approximately 180 degrees, with a smaller "node" pointing in the reverse direction. If your rocket is spinning, that can affect the quality of the fix. The best GPS antennas are the helix antennas, those are more omnidirectional but are significantly more expensive; the amplified ones cost more than rest of the GPS circuitry combined. The other thing you need is a clear radio path from the transmitter to the ground, that's where the allthread and other antenna issues come into play. It's fairly common to lose the GPS feed and still have an RF feed... "some" systems will let you know that this is occurring so you know that the issue is the GPS fix and not the RF. Plus, if there is "other" telemetry than the GPS you'll still get that data.
 

timbucktoo

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99% of the ones that are used in rocketry are patch antennas, those are the square ones that you see
Cris, I am having a hard time picturing this square patch antenna you mention. Any pics?
 

ksaves2

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Shoot, I forgot about the patch antenna for 900Mhz. I bought one on sale about the time the 900Mhz EggFinder came out for about $20.00. It works well. I put mine on a fiberglass pole that in and of itself was
an outdoor antenna for the early 49Mhz wireless phones. I used it in 1980 to get neighborhood coverage of my wireless telephone. That was before cell phones were widely and cheaply available. Got a connector cable an SMA connector and plug it in to the LCD. I use it only during the launch phase as a range extender. It’s too heavy to carry to the recovery site. A handheld 900Mhz Yagi is easier to use once the rocket is down.
Kurt Savegnago
AF315507-35C5-4D51-A1C5-D81CBC14D626.jpeg
EC6A7CAA-1890-4B46-87D6-E9C3224DB127.jpeg
 

ksaves2

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Here’s a link for some patch antennas if one wants to look at them: https://www.l-com.com/wireless-antenna-900-mhz-8-dbi-flat-patch-antennas

I’ve had a couple of small rockets that landed nearby but the chutes streamered and were not seen. No visual on descent whatsoever. Landed about 450 and 500 yards away on a harvested cornfield and positions were beeping in nicely using the pole/patch antenna above from the launchsite after the rockets were down. That can be a very good feeling if one is getting valid positions after the rocket is down without loss of signal.

I switched to the screw-on omni like shown in post 14 and walked out with a tablet using a live map. Stupidhead here still wandered around at what he thought was the recovery site until said idiot increased the zoom on his mapping program!! I was still 15 feet away and the black rocket against black dirt is hard to see.

Suffice it to say, if one has the room in the rocket, put a beeper on the harness because the ears make a very good terminal tracking device!!

With smaller GPS trackers, it doesn’t take much to put a smaller rocket up for a completely sight unseen flight.
A GPS tracker will expedite the recovery so one may go on to flying their next rocket. Kurt Savegnago
 

dvdsnyd

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I have 22 rockets with their own Eggfinders mounted in the N/C that regularly fly in excess of 10,000 ft. It would take a considerable effort to data mine all those flights, but most of them got good data throughout their many flights. Occasionally I will have a rocket loose lock under high thrust, and I have had glitches with systems that didn't record the flight, but I have never lost a rocket with an Eggfinder GPS in it. All of my Eggfinders are the standard TX with a stubby antenna, and the RX with the longer antenna.

If you are having a problem with losing signal at 10k ft., you should check your installation and what is around your antennas. Metallic paint and all thread are common problems that attenuate signal strength.
@Wayco
What stubby antenna are you using on your standard Eggfinder Tx?
Thanks,
Dave
 

ksaves2

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@Wayco
What stubby antenna are you using on your standard Eggfinder Tx?
Thanks,
Dave
Look at the antennas in post #14. Here is a link to Linx antennas: https://linxtechnologies.com/wp/p/a...s/connector-terminal-mount-ism-lora-antennas/. Look at the datasheets and one would want to tune their EF as close to the frequency with the lowest SWR to get the most bang/signal for the buck. Would have to put a connector of choice on the EF unit. SMA or SMA-RP. Make sure one gets the antenna to match the connector. Kurt
 

Wayco

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Thanks Kurt.
I’m up in Red River, New Mexico avoiding the 100 plus degrees of heat down in Goodyear.
There are lots of old threads on this forum to help you with antenna selection, search is your friend.
I think I get mine from Mouser. When I get back to the valley, I will post up the part number and a link.
 

ksaves2

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Thanks Kurt.
I’m up in Red River, New Mexico avoiding the 100 plus degrees of heat down in Goodyear.
There are lots of old threads on this forum to help you with antenna selection, search is your friend.
I think I get mine from Mouser. When I get back to the valley, I will post up the part number and a link.
Hi Wayco,
I’ve read your post for years. I haven’t flown in awhile but I’m retiring July 1st at 63.5 years of age. After a deep house cleaning, cleaning up and organizing my two small shops (one in garage and one in basement), I’ll be back and flying with QCRS. The Peoria Illinois group, PARS succumbed with the death of the prefect and is no more. That‘s too bad because when the weather was agreeable, the flying site in Metamora, Illinois was fantastic with a 15k waiver. Started out at 25k but land owner was concerned some rockets might land in town so we happily cut it down a bit. Had a lot of fun out there. Saw a full scale Phoenix missile fly there on a research O motor. Would have been a nominal flight if one of two parachutes didn’t streamer. Bunged up the tail end but it was repaired by the owner and eventually had that hairy loop and crash at one of the Midwest Powers in the past. Owner didn’t check the CG on a sawhorse and with the O/P motor in the rocket was butt heavy. Oh what a little nose weight would have done. Kurt
 

dvdsnyd

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Thanks Kurt.
I’m up in Red River, New Mexico avoiding the 100 plus degrees of heat down in Goodyear.
There are lots of old threads on this forum to help you with antenna selection, search is your friend.
I think I get mine from Mouser. When I get back to the valley, I will post up the part number and a link.
Hi @Wayco
Hope you had a nice trip!
Would you be able to post the part number/link for the antennas you are using?
I really appreciate it!
Thanks,
Dave
 

Wayco

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Still up in the cool country catching trout. Check my post in the “What I did today instead of rocketry” thread.
We will be coming back to Goodyear tomorrow, give me a bit and I will post a link for them.
 

dvdsnyd

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Still up in the cool country catching trout. Check my post in the “What I did today instead of rocketry” thread.
We will be coming back to Goodyear tomorrow, give me a bit and I will post a link for them.
Enjoy! Looks like you are having a lot of fun and catching a lot of fish!
 

ksaves2

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Yup, I helped mix the 6 inch O motor. I was upset the flier didn’t get a bunch of us from the rocket club to try to balance out the loaded rocket on a sawhorse to check the CG before bringing the rocket out to fly. The rocket was an L3 project that flew successfully on an M at MWP 3 to 1410’. Later, once the group learned to mix, it flew fine at a local launch on an N motor. Flew fine except the flier decided to use two chutes instead of three on the sustainer and one of the two chutes streamered, the rocket hit hard and was damaged. It sat for a few years and the flier re-engined it with a 6 inch motor hole. He also invested in a big 3 phase lathe to make the motor casing. I think the chuck was something like 16 inches.
It was a big mother. Neighbor was a retired machinist from Caterpillar who helped teach the art of using the lathe. The motor was a work of art with knurled closures that were threaded and pinned.
Ohhhhhh, what a little nose weight could have done!!
Motor was fired three more times though the rocket flights were all failures mainly during the recovery phase.
Last firing at MWP the casing had taken on too much heat cycling and the rocket went up the rail, the aft portion of the motor circumferentially ruptured and burning grains dropped out as the rocket tipped over on the ground off the rail. The burning grains that fell on the ground consumed the rocket and burned a tire off the launch trailer.
At least it was a ”safe” event. The flier gave up on the large motors after the 6 incher failed.
Retrospectively, the nozzle was a solid chunk of graphite and there still is a bit of heat transfer to the metal casing
especially with a motor as large as this. That caused the metal to lose its temper/strength. A better solution would have been a machined phenolic graphite nozzle holder but then it’s my opinion that these large diameter motor casings won’t have the life expectancy of the smaller commercial stuff and using a phenolic nozzle holder would only marginally increase the casing life. Kurt (7 more days to retirement!:))
 
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