Rocket Track - Open Source GPS Tracker for Smartphones

Derek said:

That looks like a nice setup! Too bad you didn't recover it.

Is there any padding between the battery and the tx pcb? I'd worry that vibrations and/or shocks could cause the leads on the bottom of the pcb to puncture the battery.

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The tracker was rubber banded to the threaded rod in the nose cone and wrapped with a layer of closed cell foam padding. It seemed pretty shock resistant. Without getting it back, I will never know for sure, but my sense is the rocket simply got too far away to track.

If it's going high/fast enough to need a tracker, rubber banding isn't going to hold. Zip ties are much better, I zip tie or screw down everything.

You should keep the antenna away from the threaded rod too, it will interfere with the radio signal.

WoShuGui said:

The tracker was rubber banded to the threaded rod in the nose cone and wrapped with a layer of closed cell foam padding. It seemed pretty shock resistant. Without getting it back, I will never know for sure, but my sense is the rocket simply got too far away to track.

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Makes sense. I like the rubber bands 'cause you can get everything adjusted and then add more until everything is as secure as you need. These are the RC airplane rubber bands, so they are pretty strong especially when you double and triple them up. No reason not to add a cable tie at the end to be extra sure though. This nosecone is pretty tight so the best I could do on the antenna was rotate the board so the GPS and XBeePro were about 1/4" from the 1/4" threaded rod. Even that might not be enough considering the LiPo behind the board could be conductive enough to affect range as well. In hindsight, I wished I had gone with a lighter 6/32 rod and a sled to stack the LiPo below the tracker. Guess I will get to do that on the rebuild. :sad:

cerving said:

If it's going high/fast enough to need a tracker, rubber banding isn't going to hold. Zip ties are much better, I zip tie or screw down everything.

You should keep the antenna away from the threaded rod too, it will interfere with the radio signal.

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interesting idea

It has been brought to my attention that the Fastrax UP501 has been discontinued. They are no longer available at Mouser, however there is a seller on ebay that has them.

https://www.ebay.com/itm/High-perfo...074?pt=LH_DefaultDomain_0&hash=item27cf28c8b2

I haven't personally bought one from this seller so I can't vouch for them, but it looks like they have sold many hundreds without any issues.

I'm pretty pissed at ublox for buying the company and shutting them down, but that won't change the situation. At some point I'll probably have to spin the transmitter to accommodate a new gps module.

Derek said:

They are no longer available at Mouser, however there is a seller on ebay that has them.

https://www.ebay.com/itm/High-perfo...074?pt=LH_DefaultDomain_0&hash=item27cf28c8b2

I haven't personally bought one from this seller so I can't vouch for them, but it looks like they have sold many hundreds without any issues.

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Purchased two UP501s from this seller last month. They ship from Taiwan. Had parts within two weeks and they both worked fine, so I would say they are a good source.

BTW, any word on the release of the Android app? Would really like to try it out, but I am not set up to do the build.

WoShuGui said:

Purchased two UP501s from this seller last month. They ship from Taiwan. Had parts within two weeks and they both worked fine, so I would say they are a good source.

BTW, any word on the release of the Android app? Would really like to try it out, but I am not set up to do the build.

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Thanks for the feedback. I'm glad to hear they work and were shipped quickly.

Derek said:

At some point I'll probably have to spin the transmitter to accommodate a new gps module.

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What's really weird is that ublox doesn't appear to have any other offerings with an integrated antenna. There's really nothing Mouser sells that looks viable (SirfSTAR-based receivers don't have a good track record in rockets) except maybe for the Antenova M10382, and that can't be hand-soldered.

Some of the standalone Mediatek-based units, like https://www.adafruit.com/products/790 would probably work OK.

mikec said:

Some of the standalone Mediatek-based units, like https://www.adafruit.com/products/790 would probably work OK.

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It looks like you can still buy the up501 from ublox for the bargain price of $99. Each. Bastards.

https://shop-america.u-blox.com/abashop?s=274&p=hierarchyoutline&hi=400.00&hl=3

That's the replacement I had in mind. It won't be as easy to solder, but gets good reviews. I've used the sirfstar stuff in other products and was never happy with them. I never considered them for the tracker.

mikec said:

What's really weird is that ublox doesn't appear to have any other offerings with an integrated antenna. There's really nothing Mouser sells that looks viable (SirfSTAR-based receivers don't have a good track record in rockets) except maybe for the Antenova M10382, and that can't be hand-soldered.

Some of the standalone Mediatek-based units, like https://www.adafruit.com/products/790 would probably work OK.

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There's a ublox 6 with patch antenna on sparkfun. https://www.sparkfun.com/products/11571

Not exactly solderable but you could epoxy it in place, and create a connection for the 6 pin JST connector.

I think the Ublox receivers are supposed to be the receiver of choice for dynamic applications like rockets (i.e. better than the Ublox w/mediatek UP501).

How about the Venus638FLPx? Needs another SMA antenna, but that might be an okay trade-off if lock is better.
https://www.sparkfun.com/products/11058

WoShuGui said:

How about the Venus638FLPx? Needs another SMA antenna, but that might be an okay trade-off if lock is better.

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I've flown one. It works, but it's very laggy, lock behavior is poor, I really don't recommend it.

Derek said:

It has been brought to my attention that the Fastrax UP501 has been discontinued. They are no longer available at Mouser, however there is a seller on ebay that has them.

https://www.ebay.com/itm/High-perfo...074?pt=LH_DefaultDomain_0&hash=item27cf28c8b2

I haven't personally bought one from this seller so I can't vouch for them, but it looks like they have sold many hundreds without any issues.

I'm pretty pissed at ublox for buying the company and shutting them down, but that won't change the situation. At some point I'll probably have to spin the transmitter to accommodate a new gps module.

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Crap I bought one, now i'm starting to think I should have bought two of them.

TA

mikec said:

I've flown one. It works, but it's very laggy, lock behavior is poor, I really don't recommend it.

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Doesn't the TeleMetrum use a Venus634FLPx?

WoShuGui said:

Doesn't the TeleMetrum use a Venus634FLPx?

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The original one did, but the newer one (v2.0 currently in design) doesn't AFAIK.

I've flown both the 634 and the 638 Sparkfun boards and while they worked for rocket recovery, they have >30 second lags on altitude update and without using AGPS the cold-start times can be extremely long (multiple minutes.) I'm not going to buy another, FWIW.

mikec said:

The original one did, but the newer one (v2.0 currently in design) doesn't AFAIK.

I've flown both the 634 and the 638 Sparkfun boards and while they worked for rocket recovery, they have >30 second lags on altitude update and without using AGPS the cold-start times can be extremely long (multiple minutes.) I'm not going to buy another, FWIW.

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Good to know. Thanks.

Can any one give me the length of the GPS transmitter with this antenna attached to it? I'm working on my new AV bay and I want to see if it will fit. It looks like it might be to long, in which case I would have to go with the wire option.

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TA

mlinny said:

Here is my take on Derek's tracker using through hole components. Now just need to build the receiver.

View attachment 145003

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is the through hole board something available ?

thobin said:

Can any one give me the length of the GPS transmitter with this antenna attached to it?

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I'm sure Derek can give you an exact number. The hard dipole is about 4.2 inches long.

FWIW, I've quit flying hard dipoles because the performance improvement over wire seems pretty small (in theory it's a tenth or two dB better), the hard antenna can mechanically stress the XBee module, and it can be more difficult to mount the tracker.

thobin said:

Can any one give me the length of the GPS transmitter with this antenna attached to it? I'm working on my new AV bay and I want to see if it will fit. It looks like it might be to long, in which case I would have to go with the wire option.

View attachment 155345


TA

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In post two I mention the board is 2.5" long. I can't measure the assembly now because I'm on vacation.

mikec said:

I'm sure Derek can give you an exact number. The hard dipole is about 4.2 inches long.

FWIW, I've quit flying hard dipoles because the performance improvement over wire seems pretty small (in theory it's a tenth or two dB better), the hard antenna can mechanically stress the XBee module, and it can be more difficult to mount the tracker.

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I have the board I just don't have the antenna yet or the XB still in the lay our and planning phase. I'm just looking for the length of the completed package.

Humm if it doesn't really make all that much difference?



TA

thobin said:

I'm just looking for the length of the completed package.

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If the board's 2.5" and the antenna is 4.2", then the total is 6.7" obviously, so call it a little under 7".

If you don't use the dipole, then the wire antenna module is a little cheaper and you don't have to buy the dipole, at the possible impact of slightly worse performance. It might be worth pointing out that the wire antenna works best if it's coming out of the plane of the board, though a bend doesn't seem to make much difference.

mikec said:

If the board's 2.5" and the antenna is 4.2", then the total is 6.7" obviously, so call it a little under 7".

If you don't use the dipole, then the wire antenna module is a little cheaper and you don't have to buy the dipole, at the possible impact of slightly worse performance. It might be worth pointing out that the wire antenna works best if it's coming out of the plane of the board, though a bend doesn't seem to make much difference.

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Ya I had already worked that out, my concern is it looks like the XB hangs over the transmitter board, then you have the screw attachment you have to consider. I only have 6 5/8" to play with. It does however look like you can bend the antenna one way or the other, I might could get a little more out of it if I jack it to one side.

Well I may just have to go with the wire antenna.


TA

The edge of the xbee is slightly inside the board but the sma connector does extend beyond the edge. Mikes estimate of a little under 7" is probably right on.

Crap, well it looks like a wire antenna for me then.

thanks

TA

thobin said:

Can any one give me the length of the GPS transmitter with this antenna attached to it? I'm working on my new AV bay and I want to see if it will fit. It looks like it might be to long, in which case I would have to go with the wire option.

View attachment 155345


TA

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With that antenna attached, the assmebled transmitter is 7-1/8" long.

Derek

Ok thanks looks like its longr than my AV bay by a half inch, ok wire antenna its thanks.

TA

The wire antenna is as good as the RP-SMA antenna, and it saves 1" in length and nearly an ounce in weight. One less thing to come loose, too. Just keep it (and any other antenna, for that matter) away from any metal hardware, and you'll be fine.

How far away? There are two 8" treaded rods that run the length of the AV bay, the clearance will only be 1 to 2 inches. Is that enough?


TA

thobin said:

How far away? There are two 8" treaded rods that run the length of the AV bay, the clearance will only be 1 to 2 inches. Is that enough?

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Antenna performance in general (not to mention this wire monopole in particular) is hard to quantify. The antenna will work best if it's coming straight out of the plane of the module, but a bend an inch or so above the module (1/10th of a wavelength is 1.3" at 900 MHz) shouldn't matter too much, nor should an inch or two proximity to the rods. You should have a lot of range margin with these modules unless you are flying really extreme flights.

I personally put my trackers in the nose cone, not in the avbay, to avoid potential issues with RF interference with altimeters in both directions, but I don't think this is absolutely required (ground testing would be a good idea.)