When does a tracker become necessary

DRAGON64 said:

Thanks for the heads up. I had looked at Egg Timer products in the past, and even lined up a professional board builder to do the work, but later decided not to put faith in an electronics kit. I will not toss the idea, as the cost is attractive... I will probably go with the T3 system from MissileWorks for my first foray into tracking.

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Can't go wrong with a T3 either. Just use an Android device and good to go with live tracking. If you use an iPhone, the Featherweight GPS tracker will be available with more features at just a bit more cost: https://www.featherweightaltimeters.com/featherweight-gps-tracker.html Kurt

Saturday morning, I launched my MAC Performance Scorpion on a J240 to 5583'. Ground wind was about 10 MPH. Rocket came down 1.1 miles away. I entered the coordinates from the BRB900 receiver into my Magellan hiking GPS navigator. I was able to drive to within 600' of the rocket, then walk over and pick it up. Saved me hours of wandering around trying to find where it came down.

DRAGON64 said:

Thanks for the heads up. I had looked at Egg Timer products in the past, and even lined up a professional board builder to do the work, but later decided not to put faith in an electronics kit. I will not toss the idea, as the cost is attractive... I will probably go with the T3 system from MissileWorks for my first foray into tracking.

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Just make sure you've got your batteries fully charged. My predator voltage meter read full charge on my 1S lipo, but the performance was NOT full charged. My last position told me exactly where the launch rail was lol.

Kurt, did MWC mention if 9V batteries were acceptable for the T3? I forget.

Bat-mite said:

Saturday morning, I launched my MAC Performance Scorpion on a J240 to 5583'. Ground wind was about 10 MPH. Rocket came down 1.1 miles away. I entered the coordinates from the BRB900 receiver into my Magellan hiking GPS navigator. I was able to drive to within 600' of the rocket, then walk over and pick it up. Saved me hours of wandering around trying to find where it came down.

View attachment 334557

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What's the startup cost for your setup John?

I'm happy with the T3 for now, but learning is always good.

Transmitter is about $200, receiver about $100. Handheld Magellan 315 navigator used is about $25.

No HAM required.

Excellent, thank you!

Well after speaking with my club I am focusing my attention in two (different) directions. HAM route with Atlus Metrum and the Featherweight route (once released).

Nytrunner said:

Just make sure you've got your batteries fully charged. My predator voltage meter read full charge on my 1S lipo, but the performance was NOT full charged. My last position told me exactly where the launch rail was lol.

Kurt, did MWC mention if 9V batteries were acceptable for the T3? I forget.

What's the startup cost for your setup John?

I'm happy with the T3 for now, but learning is always good.

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The T3 manual says 1S 3.7V for the Air tracker and the base "could" run on 1S 3.7V or 2S 7.4V. No 9V mentioned. Afraid you'd have to graduate to Lipos with this one unless you cobble together a voltage regulator. (I wouldn't do that.)
I use have two B6's a v1 and v2: https://hobbyking.com/en_us/imax-b6ac-v2-professional-balance-charger-discharger.html https://hobbyking.com/en_us/imax-b6-50w-5a-charger-discharger-1-6-cells-genuine.html

These things only do one pack at a time, can charge, discharge and balance charge plus there is a Storage setting that will either charge the battery up to the optimal storage voltage/capacity or discharge it to the optimal
storage voltage/capacity. Lipos lose life if stored at a full charge. I plop all mine to the storage setting in the winter or if not using for a while and every month or two stick them back on the charger to keep them at the storage setting and charge them up only
when ready to use. Lipos are not like Nimh or Nicads and took me a time to break bad habits. (Old man syndrome) Established R/C folks will recognize this and some are very paranoid about Lipo care and feeding. Plus
if the charger says the pack is over discharged and trashed, it's trashed. No blasting with current like could be done with Nicads or Nimh cells to salvage some life. Just can't be done with Lipos. Don't try it, it's dangerous.
Take them to the recyclers. I've dorked batteries in testing when I forgot to unplug them and turn off the device I was testing. Too bad, once gone they're gone and have to order a new pack.

Never, ever, ever, ever dead short a lipo, you'll kill it and the device it's plugged into. Plus could start a fire. Kurt

viciouspeanut said:

Well after speaking with my club I am focusing my attention in two (different) directions. HAM route with Atlus Metrum and the Featherweight route (once released).

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Ham route has one advantage in that you're not sharing the 900Mhz frequencies with every Joe that shows up with a no license required tracker. You'll be able to access the 70cm, and 2 meter APRS trackers and by golly the propagation
is indeed better than 900Mhz hands down. Thing is, is 90% of us aren't pushing the limitations of the 33cm (900Mhz) band GPS trackers with our sport flying. The Multitronix device shows 900Mhz can do very long range tracking but it
is capable of 1 watt output.

The Ham route also means one would have to invest in an H/T that can do APRS and in my book that's a Kenwood D72A (the 74A can work too but is too rich for me). Other Yaesu stuff can give you a compass rose and an arrow but the Kenwoods can do live
map tracking. There's the expense with the H/T. Two meter tracking could be had with an AP510 https://www.radioddity.com/sainsonic-ap510-aprs-tracker.html and this little baby: https://www.hamradio.com/detail.cfm?pid=H0-015928
Unfortunately neither could be used for record attempts but if looking for maximum performance on the cheap they are options. (I do both non-licensed and Ham band APRS)

I'd say go the non-Ham route and see how you like it. If the airwaves get crowded so you have to wait to fly at the launches you frequent, get a Tech license and go APRS. It's sort of like the 6 meter ham band for R/C flying in the past.
Not many did R/C on 6 meters in the old days. Kurt

ksaves2 said:

I'd say go the non-Ham route and see how you like it. If the airwaves get crowded so you have to wait to fly at the launches you frequent,

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Is this really a problem? My understanding is that BRB900 and MW T3 are uniquely paired so that there is no interference. I have both, and yet to experience a conflict with other users.

From MW site:

"Your XBee radios come pre-configured for private networking and interference-free operation as we manage all radio network ID's...."

Buckeye said:

Is this really a problem? My understanding is that BRB900 and MW T3 are uniquely paired so that there is no interference. I have both, and yet to experience a conflict with other users.

From MW site:

"Your XBee radios come pre-configured for private networking and interference-free operation as we manage all radio network ID's...."

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Weeellllll, I've seen folks complain about it with EggTimers at large launches. How the spread spectrum rigs work/play with the different modes on the ISM band remains to be seen. The thing that will protect "us" is not that many folks partake of this hobby
so I don't think any one site could get "saturated" with enough XBees to be noticeable.

Even in the old RDF days if someone came up on the same frequency could make it frustrating to find who it is and get the tracker out of the rocket and shut off (or shut off in place if there's a switch) once recovered.
I used to scan the 200Mhz "animal tracker" bands with a Kenwood TH-F6A H/T on the "B" band using USB and CW modes and heard a lot of signals in bygone Midwest Powers. Last couple of years GPS tracking is ramping up big time. Kurt

DRAGON64 said:

Which begs the question; how here watching and providing feedback have lost there vehicle anyway due to GPS or RDF failure to locate (?) By that, I do not mean if it was lost to a rocket eating tree etc. I mean physically could not locate their rocket due to a loss of signal.

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I lost one rocket with rdf. I believe the transmitter broke loose from the mount and was broken. It was a pretty hard acceleration flight.

Conversely, I do not have a gps, but my friend Kevin has had a couple. First, the GPS flight, which was terrible. It took forever to get a lock on satellites and usually lost lock in flight. Later, he got the Big Red Bee 900 MHz GPS. We are probably experiencing 60-70% with this unit.

Kevin, after seeing my success with RDF picked up a used Walston. He flies both gps and rdf, but it is usually the rdf that gets us to the rocket.


Sent from my iPhone using Rocketry Forum

If you want to get your feet wet, it is hard to go wrong with the MissileWorks T3 - a ready to go system for just $150. License free and works with your Android phone.

I started with 900 MHz systems in 2010 and they work great for me. I like the idea of no HAM needed, GPS tech, data logging, small receivers, and the interface with the ubiquitous smartphone. It is only going to get better. Yes, you better practice before sending it up 20k feet, but the learning curve is short and intuitive.

RDF needs a lot more elaborate gear, licensing, and practice. Reliable but stale technology, in my view. Reminds me of Marlin Perkins tracking a moose on Mutual of Omaha's Wild Kingdom in 1972!

Buckeye said:

Reminds me of Marlin Perkins tracking a moose on Mutual of Omaha's Wild Kingdom in 1972!

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"Oh, no! The moose sees Jim! It looks angry. Oh, good heavens -- it's attacking Jim! Let's see if he can fight his way out." [Long scene of Jim fighting the moose from multiple camera angles.] "Well, once again, Jim has proven he's more than a match for our furry friends."

ksaves2 said:

It's sort of like the 6 meter ham band for R/C flying in the past.
Not many did R/C on 6 meters in the old days. Kurt

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Look I might be twenty five something... But I still remember physical crystals that went into R/C cars and planes before 2.4GHz existed and how if you had the same frequency color crystals it would constructive/destructive wave interference and crash.

If you and another flyer have Altus metrum products go talk with the RSO about which frequency you want upfront and the RSO will make certain no other HAM flyers are using that frequency when you fly to avoid interference. Granted it's still the operators responsibility to make sure the channel is clear. You can select from a whole list in .050 MHz increments. I had to do that at Hellfire 22 due to the amount of flyers. There were three others with Altus products. Some more secluded events you won't have anyone with FCC gear.

Bat-mite said:

"Oh, no! The moose sees Jim! It looks angry. Oh, good heavens -- it's attacking Jim! Let's see if he can fight his way out." [Long scene of Jim fighting the moose from multiple camera angles.] "Well, once again, Jim has proven he's more than a match for our furry friends."

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^^^ :lol:

Yeah, Jim did all the hard work.

My $.02 worth:

I've used GPS trackers for years and love 'em! I use the inexpensive trackers that can be found on Ebay and in dozens of flights have had ZERO failures of the system Yes, you have to get an AT&T go-phone account, and I spend about $100/year for service (anything less than loading $100 and the data you've bought expires in about 60 days without a reload and you might lose it, but $100 is good for 1 year and will give you right at 400 call/texts to the tracker at $.25 per call/text). But that's small change compared to losing hundreds in hardware and countless hours building. Also, you have to launch in areas with AT&T cell service - no problem on the east coast), but with the tracker onboard, it gives me HUGE peace of mind.

How does it work? The tracker uses GPS satellites for positioning and cell phone 3G service for transmitting that data to you. When you need to know where the tracker is located (i.e. when in the rocket) call the tracker and it texts its location back to you. I install my trackers in the nosecone and use the same tracker for rockets as small as 2" diameter up to my 4" rockets (tracker size limits me below 2" by its width). Turn on the tracker and let it go through its startup sequence, then call to check operation, and install in the nosecone. Once launched, I can "call" the rocket with my phone and the tracker sends a text back to me with LAT / LON coordinates in a hyperlink on my phone. When I click that link, a pin is dropped on Google Maps showing the location of the tracker, and I can literally get directions right to the rocket. The maps are VERY accurate, and I've even seen dirt roads, creeks, trees, ponds, and the like shown on the maps that will give you landmarks as you walk/drive to your rocket.

To protect the tracker in the nosecone, I use old car seat foam and cut it to shape to fit snugly in the nosecone with a little carved out spot for the tracker. I have one of these foam inserts for each of my rockets, so when I go to fly a different rocket, the tracker just gets swapped to the rocket being flown.

Where did I get my tracker? Ebay. Here's a link to one like I NOW use. I say NOW because I used to use a 2G tracker until January 2017 when AT&T abandoned 2G service, so I had to update to a 3G tracker. Link: https://www.ebay.com/itm/TK207-3G-G...e=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

I can't say enough good things about these little devices. They stay on, they stay powered for about 60-80 hours after a battery charge (done with the same cord you charge your Android phone with), and I've not had one lose power in flight...

S

Andrew_ASC said:

Look I might be twenty five something... But I still remember physical crystals that went into R/C cars and planes before 2.4GHz existed and how if you had the same frequency color crystals it would constructive/destructive wave interference and crash.

If you and another flyer have Altus metrum products go talk with the RSO about which frequency you want upfront and the RSO will make certain no other HAM flyers are using that frequency when you fly to avoid interference. Granted it's still the operators responsibility to make sure the channel is clear. You can select from a whole list in .050 MHz increments. I had to do that at Hellfire 22 due to the amount of flyers. There were three others with Altus products. Some more secluded events you won't have anyone with FCC gear.

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Weeeelllllllllllllllllllll Andrew. In the bad old days. If one wanted to fly R/C on the 6 meter band they had to pass a written test AND be able to pass a Morse code test.
Not many people went that route except dedicated Hams. I go as far back as when there were 5 frequencies on 27Mhz.

So, a Ham flier could show up with a 6 meter setup and if there was no other Ham around on their frequency could generally fly with careless abandon. Same thing once 70Mhz frequencies were available. The 6 meter guy would likely be able to pull the 50Mhz pin off the board and fly without waiting.

So if a Ham rocket person shows up with 70cm or 2 meter trackers, they won't likely have to worry about what's going on in the 900Mhz band will they?
Now one exception here is it's easier to pass a Technician test as there is no Morse code required anymore so there is the likelihood there are more Rocket
folks with Technician or higher licenses (I tested from Tech to General in one sitting.) These people will have to watch their frequency separation then amongst themselves but again their number will likely be lower than the no license required trackers. (Which will become ubiquitous mind you.) I've seen some launches that invite people to post their frequencies and settings in advance so folks with programmable equipment can put settings in, in advance so's not to interfere with each other. Of course not necessary for spread spectrum stuff on the ISM band. But I do wonder if the band gets crowded how well things like EggFinders and Spread Spectrum stuff play together.

Kurt KC9LDH

SammyD said:

My $.02 worth:

I've used GPS trackers for years and love 'em! I use the inexpensive trackers that can be found on Ebay and in dozens of flights have had ZERO failures of the system Yes, you have to get an AT&T go-phone account, and I spend about $100/year for service.... Here's a link to one like I NOW use. I say NOW because I used to use a 2G tracker until January 2017 when AT&T abandoned 2G service, so I had to update to a 3G tracker. Link: https://www.ebay.com/itm/TK207-3G-G...e=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

I can't say enough good things about these little devices. They stay on, they stay powered for about 60-80 hours after a battery charge (done with the same cord you charge your Android phone with), and I've not had one lose power in flight...

S

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Does your TK207 only work with text messages or does it have an app that allows real time tracking on Google Maps? If the latter, you can get a free FreedomPop sim and save the annual $100. But you can't send "real" text messages with FP, so that won't work if you need to send a text to the tracker to get its location. I'm still using cheap 2G trackers (under $20) with a SpeedTalk sim ($5 a month), working flawlessly so far (knock on wood). Also using cheap Android phones (e.g., Nexus 4, under $50) with the free Insane Rockets app and the free FP sim, that's perhaps a better alternative for larger rockets able to carry a phone (150g), because the phone also is an altimeter and gives flight data.

ksaves2 said:

Ham route has one advantage in that you're not sharing the 900Mhz frequencies with every Joe that shows up with a no license required tracker. You'll be able to access the 70cm, and 2 meter APRS trackers and by golly the propagation
is indeed better than 900Mhz hands down. Thing is, is 90% of us aren't pushing the limitations of the 33cm (900Mhz) band GPS trackers with our sport flying. The Multitronix device shows 900Mhz can do very long range tracking but it
is capable of 1 watt output.

The Ham route also means one would have to invest in an H/T that can do APRS and in my book that's a Kenwood D72A (the 74A can work too but is too rich for me). Other Yaesu stuff can give you a compass rose and an arrow but the Kenwoods can do live
map tracking. There's the expense with the H/T. Two meter tracking could be had with an AP510 https://www.radioddity.com/sainsonic-ap510-aprs-tracker.html and this little baby: https://www.hamradio.com/detail.cfm?pid=H0-015928
Unfortunately neither could be used for record attempts but if looking for maximum performance on the cheap they are options. (I do both non-licensed and Ham band APRS)

I'd say go the non-Ham route and see how you like it. If the airwaves get crowded so you have to wait to fly at the launches you frequent, get a Tech license and go APRS. It's sort of like the 6 meter ham band for R/C flying in the past.
Not many did R/C on 6 meters in the old days. Kurt

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I was going post a caution on the PicoAPRS tracker but I heard from the developer and is going to address some issues like needing once every 5 seconds transmission like the Beeline GPS devices and beaconing while lying still on the ground.
https://www.hamradio.com/detail.cfm?pid=H0-015928 This thing is small but would only be able to be used for recovery and not records. Kurt

Years ago I purchased the com-spec R-300A and one of the transmitters. I never used the product and ultimately sold it. At the time it was highly recommended over the GPS options, as the GPS options were quite pricey. Com-spec has remained the same price wise, so I would ask if this system is as good as an entry level GPS system like the T3 from MissileWorks (?)

DRAGON64 said:

Years ago I purchased the com-spec R-300A and one of the transmitters. I never used the product and ultimately sold it. At the time it was highly recommended over the GPS options, as the GPS options were quite pricey. Com-spec has remained the same price wise, so I would ask if this system is as good as an entry level GPS system like the T3 from MissileWorks (?)

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I just got a T3 and am eager to try it and compare it to my TeleMetrum and my cellular GPS trackers. As the T3 has GPS and is just $150 for the complete TX/RX system, it seems to me to be a better option than the Com-Spec, which is $350 for the R-300A, at least $50 for the transmitter, and is RDS only (no GPS). See https://www.com-spec.com/rcplane/index.html .

I wouldn't count out radio systems. I'd like to get one and try it out down the road.

There's numerous stories of times when one system or the other failed, and the 2nd type saved the day (or the rocket)

DRAGON64 said:

Years ago I purchased the com-spec R-300A and one of the transmitters. I never used the product and ultimately sold it. At the time it was highly recommended over the GPS options, as the GPS options were quite pricey. Com-spec has remained the same price wise, so I would ask if this system is as good as an entry level GPS system like the T3 from MissileWorks (?)

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I haven't flown it but as it stands currently wouldn't be acceptable for records and the current GPS chipset is limited to 60,000 feet. No onboard memory for position recording. Also the beacon interval on the stock PicoAPRS is 10 seconds and for APRS tracking of
rockets needs to be at least every 5 seconds. The beaconing is also triggered based on movement and time. Problem there is once a rocket is down, one doesn't want the tracker to shut down.

That said I've corresponded with the developer, Taner Schenker, and he sent me a firmware that allowed decreasing the interval to once every 5 seconds. He is also going to send me a firmware "hardwired" with my callsign and remove the distance
triggering. That would eliminate the problem of the device "clamming up" after landing. Taner's concern was someone doing high rate beaconing over the National APRS frequency of 144.390. I respectfully countered with the comment that he designed the
PicoAPRS to be tuneable off the National APRS frequency so one could do high rate tracking for local situations (like rocket flying). He said he would send me the firmware with my callsign "hardwired" so I couldn't distribute it. Which is fine with me.

Taner also showed me a picture of a prototype balloon tracker he is developing that has a Ublox chipset. I made some suggestions and perhaps my input might benefit a product that can be used for tracking rockets also.

The advantage of the PicoAPRS is the size and the .5 to 1 watt output on the 2 meter band. Again, it and the larger Sainsonic ap510 with the higher power output would have longer range and a larger ground footprint than the lower powered 900Mhz trackers.

It could be an economical way to track an aggressive flight efficiently though the disadvantage with both these devices is the altitude limitation on the PicoAPRS and neither of them could be used for record attempts. Also the formality of getting a Ham license.

I say the more options out there for tracking rockets the better. People would get discourage and quit sooner if they lose rockets and hardware all the time.

Kurt

ksaves2 said:

I say the more options out there for tracking rockets the better. People would get discourage and quit sooner if they lose rockets and hardware all the time.

Kurt

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Absolutely. Especially for those in the hobby that don't have as much disposable income.

billdz said:

I just got a T3 and am eager to try it and compare it to my TeleMetrum and my cellular GPS trackers. As the T3 has GPS and is just $150 for the complete TX/RX system, it seems to me to be a better option than the Com-Spec, which is $350 for the R-300A, at least $50 for the transmitter, and is RDS only (no GPS). See https://www.com-spec.com/rcplane/index.html .

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Yeah and the 50mW AT-2b RDF trackers went away after the FCC got after them. They violated power output limitations placed on animal trackers. I bought a tracker from them and at the time, they could be had on the 1.25M ham band just above the animal
trackers and they programmed my callsign in: https://www.com-spec.com/rocket/manual/at_2b_transmitter_manual.pdf Perfectly legal to this day and I don't know why they just didn't make the 50mW trackers available to Hams only. Would have been good for Fox-Hunting. Me thinks one of two things were at play here. Either they didn't see a big market for a Ham only tracker or some parts or components went out of production.

Anyone using an AT-2b treat it gingerly because I heard they don't repair them anymore. Kurt

DRAGON64 said:

Years ago I purchased the com-spec R-300A and one of the transmitters. I never used the product and ultimately sold it. At the time it was highly recommended over the GPS options, as the GPS options were quite pricey. Com-spec has remained the same price wise, so I would ask if this system is as good as an entry level GPS system like the T3 from MissileWorks (?)

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It's interesting when you ask that. GPS is quite different from a RDF system. The RDF is generally seen as more reliable because all you need is a transmitter to output radio pulses. It doesn't have to do anything else and can do so quite reliably under very severe conditions. With that, you just need a receiver that can detect the radio pulse. Nothing decoded or processed about it, just receive it and indicate the strength of that received signal.

GPS is much easier to interpret, but relies on a much more complicated and technically sophisticated solution. The tracker unit not only has to output a radio signal, but it must receive GPS satellite signals and process them. Then it has to transmit a data packet of information instead of just transmitting a radio pulse. The receiver must do more then just indicate signal strength of a pulse, but receive and process a data packet and then display it in a human readable format.

The new GPS technology can be very reliable, but the use of that technology in hobby built equipment can lend itself to issues and problems that the older RDF didn't have. If you are an adamant proponent of KISS, then you would say the RDF is the way to go. If you are a proponent of modern technology then the GPS is the way you want to go.

When you ask if an RDF system is as good as a GPS unit, you are asking about apples and oranges. Price wise, the newer GPS units are now cheaper than the RDF setups. As for "as good as" that is a matter of opinion.

Handeman said:

The RDF is generally seen as more reliable because all you need is a transmitter to output radio pulses. It doesn't have to do anything else and can do so quite reliably under very severe conditions.... If you are an adamant proponent of KISS, then you would say the RDF is the way to go. If you are a proponent of modern technology then the GPS is the way you want to go.

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For maximum reliability, how about a tracker that does both, like the TeleMetrum? I've been into rocketry for less than a year and am not any kind of expert, but I'm having trouble with the notion that RDF is more reliable. If the rocket lands hard (or in water) and the tracker goes dead, with RDF you are out of luck, you do not have any way to find the rocket. With GPS, you can still find the rocket because you'll have the position a second or two before impact. That happened to me a few months ago -- my Chute Release failed to release the chute and the Telemetrum turned off as soon as the rocket hit the ground. As the attached map shows, I could still see where the rocket landed.

billdz said:

For maximum reliability, how about a tracker that does both, like the TeleMetrum? I've been into rocketry for less than a year and am not any kind of expert, but I'm having trouble with the notion that RDF is more reliable. If the rocket lands hard (or in water) and the tracker goes dead, with RDF you are out of luck, you do not have any way to find the rocket. With GPS, you can still find the rocket because you'll have the position a second or two before impact. That happened to me a few months ago -- my Chute Release failed to release the chute and the Telemetrum turned off as soon as the rocket hit the ground. As the attached map shows, I could still see where the rocket landed.

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Many have been there and done that too with a GPS tracker including myself. I didn't have a long walk but I didn't see where the rocket went in. It was straight out in front of me as indicated on the live map I use to track. Walked out to it and just made my local position on the map intersect with the rocket's fincan sticking out of the ground With RDF, unless one can hold the bearing, they are S.O.L for a longer recovery. If there is the room, one can fly two trackers one GPS one RDF for redundancy.

900Mhz doesn't lend itself for RDF tracking anyways for several reasons so no one should go in with the thought they can RDF a 900Mhz tracker.

Here is another plus for Ham Radio APRS (besides being "record" getting ready with the
Beeline GPS's). With the 70cm and 2 meter band trackers as long as one gets a carrier signal, in a pinch one can RDF to a GPS tracker as long as it's beaconing. If one's APRS GPS tracker can be set to beacon no matter what, the option is there to RDF it as long as it's sending

I have to admit though with the dozen Beeline GPS flights I've had to sight unseen land, even though I have the ability onsite to RDF 70cm and 2 meters, I've never had to do it.
A simple Marvin West Attenuator can do both bands: https://www.west.net/~marvin/k0ov.htm Be careful to "shut off" the push to talk switch (in the programming screen) in the H/T when using an electronic attenuator or you'll kill it. Get a Ham license and pickup
a Beeline RDF tracker on 70cm and get an H/T (handi-talkie) with a true signal strength meter. Yagi antenna, homemade or otherwise with the simple electronic attenuator and
one will be in business. I've tested out the Beeline RDF's with the above setup and it
works as well as the overpriced commercial animal trackers. Invest in a Kenwood D-72A
and you'll be able to do APRS tracking from the 72, from the 72 and an attached Garmin Mapping GPS or from the 72 and a Windoze or Linux tablet. Get a 70cm RDF tracker and the 72 is perfect.

Gotta kill another hour and half before Midnight Mass for Christmas. Hope everyone gets what they want, have a Merry Christmas and a Happy Fly'in New Year.
Oh, I got what I wanted. Had to "pass" a do or die recertification exam which everyone walked out of (including me) thinking they flunked it. I made it with room to spare so I be
really glad. Found out last Thursday and been sweating it since November 9th when I took it.

Kurt

billdz said:

For maximum reliability, how about a tracker that does both, like the TeleMetrum? I've been into rocketry for less than a year and am not any kind of expert, but I'm having trouble with the notion that RDF is more reliable. If the rocket lands hard (or in water) and the tracker goes dead, with RDF you are out of luck, you do not have any way to find the rocket. With GPS, you can still find the rocket because you'll have the position a second or two before impact. That happened to me a few months ago -- my Chute Release failed to release the chute and the Telemetrum turned off as soon as the rocket hit the ground. As the attached map shows, I could still see where the rocket landed.

Click to expand...

You are assuming you will be downloading position packets until right before it lands. Most of the GPS failures I've seen is loss of lock on satellite at launch and it never reacquires or loss of packet data after launch because the receiver never picks up packets, which may be the same thing, but with everything that has to work right for GPS to work, who can tell. In that case you have no data at all (except where it was when it was on the pad) not even a general direction of where the rocket went. That is almost never a failure mode for RDF.

As for landing in water or lawn darting and loosing the RDF because of how or where it lands, if you loose the RDF signal, you have probably lost the rocket anyway because of how or where it landed. Yes GPS may be able to tell you where it went, but you probably still lost the rocket in most of those cases.

In nominal flights, I would say RDF is slightly more reliable than GPS just because it's a much simpler system and thus has far fewer failure modes. When judging the cost/benefit, IMHO it's hard to recommend anything but the newer GPS units.

This will probably be one of those "here we go again" arguments on TRF for a while. Personally I really like my GPS T3 system, but I find the Walston to be very good and very reliable. It's nice to be able to confirm apogee event with the Walston, which isn't something you can do with the GPS unit, but having the graphic display of right where the rocket is on the GPS is so much better then listening for beeps as you manipulate the yagi to get a fix.

Your battery in most GPS units lasts 5-12hrs at most. RF lasts 7-40 days.
When flying higher altitudes over 15,000 ft you may end up being directly under rocket and in a radio null area. losing contact.
You may NEED to come back next day if getting dark or days later. I came back a month later to find a project, battery in my Tela would have been loooong dead.

Sometimes faster speeds [over 1.2 mach] GPS radio cuts out due to ITAR & base only re-acquires after rocket slows down . You may not get lock back till way later on the way down....has happened to me.

For instance on flight to 28,000 GPS says landed 500 ft on right side of road....smack in the middle of milo field. Due to last packet received was probably several hundred feet above ground. When I go out there [3.7 miles] RF tracker [Marshall] was pointing to left of road in bare field...there it was BEHIND a 2 ft hill. Never would have seen it.

I will never fly without both, just as I use 2 altimeters for redundancy.