Re: [RTrak] RTrak-HAB doesn't lock
- On Wed, Mar 27, 2013 at 3:18 PM, Patrick Wood <winston@...> wrote:At this point I'm looking at things like does the expanded PVC mounting material (the black stuff in the picture) contains enough carbin to cause RF propagaiton problems (shileding, multiapth, etc)? Do the GPS units have some systemic problem (bad firmware, can't handle sitting on a shelf for 6 months, etc)?That may be your issue... Up to those antennas should be horizontal to the skyThe antenna IS facing the sky. I've already been through a flight with these units with unreliable operation because they were facing the horizon.This ain't my first rodeo; these trackers will go on balloons that'll push the total number of flights I've helped with up to about 75 or 80 (I've lost count).I don't have antennas or a 3.3V RS232 interface to check things like that; I'll probably send them to Jason and let him see what he can see.-Jason
> Got some RTrak-HAB models that worked and have been on the shelf forResurecting a year-old thread with a followup. I haven't had time to
> several months. I built new packaging (to allow for the very position
> sensitive GPS antenna) and the things won't get lock. I've had them
> outside with the GPS antenna facing at most 10 degrees or so off
> vertical, and only one of the 4 has locked, and that one took about 30
> or 45 minutes.
mess with them, but this time when I got the unit out of storage the
same thing happened, only worse.
I wired in external GPS receivers (Garmin GPS18) and all the GPS
problems went away.
Problem is with the GPS, and it's systemic (4 units with same
problem). Still no idea if it's the GPS, the supplied amplified patch
antenna, or what. I just know the device is usable with an external
GPS on it.
I guess I'll desolder something so the onboard GPS isn't consuming
power, and go with this config until they are damaged or lost.
Check the antennas!
I have 5 or 6 units plus there’s another dozen I’ve been involved with that others own and the only problem has been the antenna feed lines and a broken cable shield where the shield is soldered to the antenna is almost always the problem. I hate RG-174 cable like what’s used on the antennas as the dielectric insulation melts easily damaging the cable when it’s soldered and always use RG-178 teflon cable instead. The shield breaks just as easily but I don’t have to worry about destroying the cable when soldering it at least. To cure the shield breakage problem I slip a short piece of copper tubing about 1/4” long over the cable where it’s soldered to the antenna and that’s soldered along with the shield to the antenna’s metal cover. The tubing extends where the cable is able to flex away from where the braid is soldered and has solved the problem completely. It’s a bit of work of course as to replace the cable the metal cover has to be removed to unsolder & solder the cable center conductor. Most antennas where damaged from use, but several actually arrived not working. The shields were fine on those, but I suspect a tiny fragment of the shield was shorting out the signal in the SMA connector somehow. Doesn’t say much for the quality of workmanship but there’s been no more antenna problems since replacing the feed lines. The other solution is to simply buy better constructed antennas of course.
> On Mar 30, 2014, at 5:34 PM, "Barry Sloan" <bs@...> wrote:Now you tell me. :)
> Check the antennas!
It did occur to me, but I dont have a way to test. I do have some RG174 with SMAs already on it for this project (2m antenna leads) that I can use to replace what's on there.
> hate RG-174 cable like what’s used on the antennas as the dielectric insulation melts easily damaging the cable when it’s soldered and always use RG-178 teflon cable instead.I actually have some Teflon 178 ( bought it by mistake) but don't have any connectors or an appropriate crimp tool.
I also have a candidate - the tape supplied on those antennas is top notch, and one of the cans opened a bit when I removed it.
> The other solution is to simply buy better constructed antennas of course.Got any suggestions? I have no desire to ditch the rtrak or to spend another $80 on a garmin gps18 to make it work.
I’ve compared about a dozen different antennas and the one supplied with the RTrak is as good as any in regard to how well it receives and only problem has been a couple with a problem at the SMA connector end of the cable and the braid failing at the other end after a bit of use. The braid problem would be about the same with any of similar construction and to avoid the problem I would get a puck style one, like https://www.sparkfun.com/products/464, as the enclosure provides the needed strain relief. The problem with that however is not only the extra weight of the enclosure, but the long feed line and its weight and why I have removed the case and shortened the feed line on all such antennas I purchased initially while looking for the best one to buy. Since you don’t have a crimper for SMA connectors I would simply get another RTrack antenna (https://www.sparkfun.com/products/177). Like I said, it performs as good as any and is what I have been buying when needing another antenna and just limit the amount of flexing that’s allowed where the coax is soldered to the antenna either by how it’s mounted, like attaching the feed line a short distance away from the antenna to whatever the antenna is attached to using a tie wrap, silicone adhesive or whatever.
As for opening one of the cans a bit when removing the 3M tape – Ouch and, yes, 3M does make excellent tapes. A much safer way is to use solder wick to remove as much solder as possible and then to free the can from the circuit board simply lift on the can gently at each spot that had been soldered while reheating the can a bit.
And with RG-178 (and other teflon type cable resistant to soldering temperatures) you don’t necessarily need a crimper to attach a connector. I have several dies for my crimper that work in most cases, but bought some SMA connectors on eBay for a good price that require an odd sized crimp die so rather than using the supplied crimp ring to hold the braided shield in place where it slips over the connector body I simply wrapped fine gauge wire (wire wrap wire from which I had stripped the insulation) around the braid to hold it in place as tightly as possible and then soldered it to the connector body. After slipping some heat shrink over the area it’s hard to tell the difference from using a crimp ring.
Another SMA – teflon cable option is to buy a ready made cable to use, like
In this case, cut one connector off for a 6” cable or in half for two 3” cables. There are countless cables like this of various lengths available on eBay, DX and the like and many times for less than the cost of the connector and cable. Teflon cable isn’t easy to find for a decent price here in Canada so I often buy and use such cables even though I have a fair stock of connectors and a crimper to use.