Eggtimer Quasar

[Jmhepworth]

I soldered a couple of Quasars over the past few days. When I tested them—both times—I forgot to put the run jumper in. Once I put it in, powered it up, changed my WiFi, and logged onto the URL, everything worked. Then I was astonished at how fast the GPS got a fix. Even in my basement, I got a fix in seconds. I wasn’t even planning on trying to get a fix. I just wanted to know if it was working. Well done Cris. I’m looking forward to put one in a Wildman Mach 3 and finding it.

 

[Handeman]

Then I was astonished at how fast the GPS got a fix. Even in my basement, I got a fix in seconds. I wasn’t even planning on trying to get a fix.

So glad it worked so well for you.
Is the GPS chip on the Quasar different than what's on the TX or Mini Transmitter? I had to take my TX Transmitter outside and wait 10 minutes or more to get a fix show up on the LCD Receiver.

 

[Jmhepworth]

So glad it worked so well for you.
Is the GPS chip on the Quasar different than what's on the TX or Mini Transmitter? I had to take my TX Transmitter outside and wait 10 minutes or more to get a fix show up on the LCD Receiver.

Your experience is closer to what I’ve experienced with the EggFinder Mini. That’s why I was so surprised when I got such a quick fix. My first reaction was that something must be wrong.

 

[Jmhepworth]

Cris will have to weigh in on whether a hardware change is responsible.

 

[Charles_McG]

I have found the newer GPS module - the one that comes pre-mounted - to get a lock much faster than the original.

 

[Handeman]

I have found the newer GPS module - the one that comes pre-mounted - to get a lock much faster than the original.

Any tips on how to ID the old vs. the new modules?

 

[KenECoyote]

Maybe it's the new bunch of Chinese spy satellites?

 

[Charles_McG]

Any tips on how to ID the old vs. the new modules?

The old ones were marked GD G403 on top. The new ones are marked Quectel and have a 2D barcode on them.

 

[cerving]

How fast you get a fix depends on a number of things...

* How many satellites are in view.
* Where they are; scattered is good, nearly co-linear is bad.
* The amount of signal you get from the satellites; low on the horizon may mean low signal. Indoors is not as good as outdoors with a clear view of the sky.
* What constellation they belong to; the current and previous modules only decode the US GPS constellation.

And the hardware variables...

* The type of antenna; the square patch antennas work best when pointed "up".
* The quality of the antenna's ground plane; this is why the Mini takes awhile and does not get the same quality of fix as the larger boards, it has a much smaller ground plane. The TX and the Quasar are pretty decent in this regard. An optimal GPS patch antenna ground plane would be at least 4" square, with nothing else around it.
* The Signal to Noise Ratio (SNR) of your GPS' detector, i.e. it's ability to reject non-GPS signals. Typically that's built into the module and not something you have any control over.

Note that it can be possible to have a good fix during flight and lose it completely when you land, if your GPS antenna points at the ground. That's a fault of patch antennas, which unfortunately almost everybody uses. The best GPS antenna would be an amplified helical antenna that you'd somehow keep pointing up at the sky... I don't know of anybody using one, however. They're very expensive... almost as much as a full Eggfinder setup.

 

[SolarYellow]

* The quality of the antenna's ground plane; this is why the Mini takes awhile and does not get the same quality of fix as the larger boards, it has a much smaller ground plane. The TX and the Quasar are pretty decent in this regard. An optimal GPS patch antenna ground plane would be at least 4" square, with nothing else around it.

Would there be an advantage to putting some metallic substrate on the part of the ebay sled that is behind/below the transmitting antenna (the transmitting antenna casts no shadow on it)? Like if my EF Mini is going to be in a BT-60 ebay, foil tape on the part of the sled that's behind the transmitting antenna? Would it need to be connected to the BATT- wiring?

I'm obviously no sparky, and know even less about radio.

 

[cerving]

I don't know if that would help or not... and yes, it would have to be connected to BATT-. Generally a ground plane (or counterpoise) needs to be close to the antenna's "live" element... using the sled as the ground plane might not be effective. Something to play with...