I’ll wire the soldering iron to the mat.
No, I didn’t do any soldering at that time.
The new activity I was doing was connecting the boards to a phone via the TTL/USB converter and OTG cable. I don’t see that in itself as risky. But I do think excessive handling is a risk. And I wasn’t concerned about ESD.
Hi John
Good, just a precaution to eliminate one possibility.
DON"T do anything like that until everything is working properly. Get everything right first then if you must connect the phone or anything similar and this fails the device you will at least know what caused your problem. Problems like you describe don’t happen for no reason.
Fingers crossed but I think you are on the right track.
Cheers Bob
Success!
I now have two working units.
I expected the latest purchase from Core would work and it does. But the good news is I connected the new antenna to the GPS unit I got from Core six weeks ago. This unit only gave me fixes on two occasions and then produced no sat data since. With the new antenna it works as well as the newest unit.
I can’t say damaged antennae is the only cause of my units failing. But it’s clear that the antenna can be damaged and I now know the bahaviour of the GPS when attached to a damaged antenna.
Thanks to everyone for your interest and help. Still got some careful exploration to do to ensure this new unit keeps on keeping on.
John.
Hi John
Great news. Great progress. Now sit down and have a hard think about what you have just done and any differences to what you did in the past. Something damaged that antenna.
Looking at what you have posted from this direction the thing that stands out is that phone connection.
Before you do it again check everything thoroughly (that is if you intend connecting it again). The data sheet seems to suggest that anything floating around in excess of 3.3V is a possible cause for damage. Just because it doesn’t rate a mention don’t discount that TX pin. Because of your experiences and what I gleaned in my quick look at the data sheet I personally would avoid letting 5V near any pin on this device.
Anyway. Progress and thanks for keeping us up to date on developments. Keep it up, interested.
Cheers Bob
Thanks, Bob. I’m pleased with our methodical approach.
Here’s my new work setup:
It’s a nice mat. Lovely shade of blue. It’s advertised as anti static and heat resistant for working on phones. But it was cheap. Some are costly. Is there any way I can test its anti static property?
Here I’m powering the unit from the Arduino UNO with 3.3v, not 5v. The GPS TX is connected to the UNO RX pin and the UNO’s program is simply reading the RX and sending read data to the laptop USB port. From there it can be displayed in the Arduino IDE monitor or processed by u-center. The GPS has no pin installed at its RX via.
I think this is the simplest and safest arrangement. When I’m satisfied it is stable, I’ll try using the TTL/USB converter. I’ll check voltages at every physical point. Luckily I have some dud units I can use for that – nothing is useless.
Using it with the phone is most important to me. I am aiming to build a setup that is portable and readily displays GPS data that shows its progress in getting the sat data.
Remember that the Neo data sheet applies to the Neo chips, not to the overall board which is not a Neo product as such.
Hi John
The only way to fly. If you jump in sideways and try to start at the middle you can find yourself in a bit of a mess. Go in pointy end first and you will get somewhere.
Most come with a wrist strap. mine connects with a press stud crimped into the mat.
Not that I know of. Just had a quick look at mine. It does not seem to be actually conductive in the “normal” sense. That is just measuring the resistance with a DMM just says OL. Too high to measure. The measurement with meter tips is pretty inconclusive as it will be “X Ω per square”. That means that if you have 2 bars 100mm long and you clamped them 100mm apart you would X Ω. Then if you had 2 bars 300mm long and you clamped them 300mm apart you would still read X Ω. You might get some comparison using a 500V or 1000V Megger, I don’t know, never tried.
A bit of trivia while on the subject of mats. When dealing with RF free space is considered as 377 Ω per square and yes Free Space mats do exist. Very Very expensive. We had to make one up once using a wooden frame and hundreds of 390Ω resistors connected in such a way no matter where you measured you always measured 390Ω per square. Interesting eh, but it worked.
Yes I realise that. A bit of a nuisance really when the board manufacturer does not provide any circuit or details on what all the other bits on the board do. It seems to be common with the current crop of suppliers though. To be fair, some suppliers do provide details but I wish all would do it.
As I mentioned in another thread I tend not to purchase if enough detail is not provided and the supplier is reluctant to come to the party.
Cheers Bob
You might be interested in this screenshot. This is the output from the new unit being processed by u-center. It show that 10x sats are seen. The blue signals are graded as not useable, the green ones are useable. This is good performance and gives me lat, lon, altitude, speed and course, date and time.
The top display places each seen satellite in its position in the sky. You can see G12 is directly overhead. In time these sats will move over the horizon while new ones come into the skyview. “G” indicates it belongs to the US constellation of satellites; “S” I think belongs to the Rusiian constellation (GLONASS).
These type of GPS boards must be manufactured in the hundreds of thousands. I have never seen a proper data sheet from a maker. In fact I have never seen a maker’s name. The “data sheet” on the ebay stores sites generally don’t inspire confidence. Some makers do assemble boards backed up with authoritive data and support. They are far more costly. I’m glad I haven’t junked half a dozen of those, instead of these low cost ones.
Hi John
You are spot on there
Probably far better quality too. Even hough these el cheap boards may look ok but they probably would not stand up to too much “proper” rigorous testing. For instance how much soldering or how much heat can you apply before the track or pad separates from the parent material etc.
There is another school of thought that says you may not have had to “junk” any of the more expensive ones. The peripheral circuitry may be more robust and provide a bit more insulation for the actual module. Hence the extra $$$.
Could it be the peripheral circuitry is the problem on the “junked” units. Probably not but a thought. It would probably be too messy to find out now.
Cheers Bob
Thanks for the graph. Good for relative comparisons but do any of them give actual signal strengths in say dbm or dbµV.
I have another question that interests me you may be able to answer. Nothing to do with this thread so will message you
Cheers
Yeah, that’s the “cheap tools aren’t cheap” theory. I get that, but I’ve no doubt my lack of electronics skills has been the cause of much damage. My skills and respect for these electronic modules have developed. My new mat gives me the feel of doing things properly.
Oh boy, soldering. That takes practice. A good use for the boards I’ve dudded.
All fun & something to do in lockdown.
The signal strength units are dB-Hz.
John.
Hi John
Good you have an understanding in what has been going on. With that attitude progress can only get better, Probably at an exponential rate.
All I can say here is YES in Capitals. There is a fair bit of informative text around which is a handy read. When you are more established read up on High Reliability Soldering. Very enlightening and sometimes surprising, particularly the bits about Gold. It is not quite as good as one might think.
One of the basics to take note of: Apply solder directly to the joint. DO NOT carry solder to the job on the iron. Happy practise.
Does not make much sense. The Decibel or db is a POWER ratio, being a ratio it needs a reference to mean something. For instance dbm is a ratio with 1mW as a reference. dbµV is a ratio with 1µV as reference. Being a power ratio, when used to express a gain or loss using the formula pertaining to voltage the impedances must be the same to get a valid figure or the gain or loss must firstly be converted to power (W) to get the proper figure in db. When used in a sound pressure statement the term db is often used without any reference descriptor. I think the reference here is 20 micro (µ) Pascals (I may be wrong here) which is considered the lowest level the average human ear can perceive.
Hz is simply frequency, used to be called “cycles per second”. Example kHz, MHz, GHz etc.
I don’t understand any implied relationship to decibels. I think some frequency relationships are sometimes referred to in octaves where 1 octave UP is double the frequency of the last one and 1 octave DOWN is half.
Anyway the graphic display is a pretty good comparison. I was just interested in what the actual signal strength is
Cheers Bob
Thought I should give an update since y’all have helped me and I appreciate that.
I now have three good GPS modules and two good antennae and several bad antennae. With a bad antenna, a good GPS will never produce sat data, just scan thru the sats endlessly without holding on to any. A good GPS with a good antenna shows multiple sat signals almost straight away and achieves a positional fix within a minute or two.
I’ve definitely established that antennae can be damaged and what the GPS behaviour is with a damaged antenna. I’m also satisfied that an obscured skyview does not cause a complete blackout of sat data, but results in a reduced number of sats seen and reduced signal strengths.
I reckon the antennae get damaged thru excessive handling. It could be thru static discharge or thru shorting when connecting/disconnecting to the GPS board with power on. There’s no way of telling the antenna has been electrically damaged other than by the GPS performance.
So – take care of the antenna, folks, and don’t condemn your GPS until you’ve tested it with a known good antenna.
Thanks for everyone’s help (esp. Bob with the lessons on ESD).
John. 
Hi John
Thanks for advising all on a great result. You now seem to have lots of spares.
It is very gratifying to see you have apparently got a lot out of this exercise too. I think you have grasped the notion it is mostly better to approach a problem in a logical and methodical manner than rush around reloading software and operating systems and generally running in circles until something works. Nobody is really sure what the original problem was or what fixed it. Taking notes is also pretty much a must . Better than relying on memory.
My interest in this GPS stuff has been stirred a bit also. All I do at the moment is turn on the ignition (not really ignition as I have a diesel car) and the SatNav bursts into life and tells me where I am. Probably just in case I lose track of my house.
Cheers Bob
Hi Bob.
Lots of spares? Lots of duds too.
The good GPS & antenna has been working consistently well.
I’m pleased I’ve established that the antenna is easily damaged. I think many others have either given up on GPS or just bought a new one and not chased the problem down to a bad antenna.
Unfortunately I stuffed up another GPS board today. In disconnecting the antenna I ripped the receptacle out of the board. They are really weakly affixed to the board.
John.
Hi John,
It might be an idea to look into modules with soldered-on antennas to avoid this problem, while they tend to be more expensive, you might save that money in dead NEO-6Ms. If an external antenna is important, some of the breakout boards we sell come with a sturdier SMA connector:
Either way, you’ve done some great research into these affordable modules, and I’m sure others will follow into your footsteps!
-James
Hi John
How did you manage that? If you thought this is a small connector you should have seen one I came across recently. I changed the 1T hard drive on my Mac Mini for a SSD drive. In doing so I had to disconnect an antenna (Wi-Fi or Bluetooth) mounted inside the bottom cover. The co-Ax connector??? I nearly had to use a magnifying glass to see it on the end of the cable. In comparison yours is HUGE.
Cheers Bob
This is the second time I’ve ripped the receptacle out of the board. First time I used needle nose pliers and immediately realised it was the wrong tool to use. Too much compression force (there shud be none at all). That receptacle has a tiny contact area with the board. Very weak.
I followed my own dictum to only use fingernails but I must have gripped it too tight or in the wrong place. Now I’m using these angled tweezers. The prongs go under the plug and I gently lever them upwards. It applies a small controlled force and no compression force.
I’ve come to look on the antenna as the achilles heel of this design of GPS board. I still like this board and now I know where the weaknesses are I can manage them.
Hi John
If you study those connectors closely you may be able to put them back. It looks as if the pin comes out of the connector and stays with the board.
Cheers Bob
Yes, the connectors are still there. My receptacle was torn in two and is not reusable. Core sells them for $1.40. Their page says soldering them on is not too difficult. I remember the Neo caution about soldering on the RF circuit.
When it came off that gold ring part was trapped inside the plug. Extracting it was like neuro surgery. I managed it so recovered the pigtail & antenna.:
These are called IPEX or uFL connectors. I found data sheets from IPEX who make them. They caution about mating and unmating them with too much force or applied at an angle. They are full of design detail but at the micro level. I see that detail thru my microscope that goes over the phone. Just like the Neo datasheet that strongly warned about ESD, the warnings from the maker are there if you can find them.
IPEX make a special mating/unmating tool which has its own instruction manual! Love it. They include guidance on manual mating & unmating.
Hi John
Just had a look at a previous post pic “New Mat”, post 84 05/09/21 showing your soldering iron. What sort of iron is that? For what it is worth I would not attempt to solder the connector with it. It does not look as if the tip is any where big enough to have enough “grunt” to deal with the mass of the connector body. I could be wrong but it looks pretty small.
I think you would need at a minimum 65 - 70W or even 80W with a tip large enough to not lose too much when applied to the connector bulk. If using a tip/iron too small you will take too long and do irreparable damage to the board not to mention the suspect integrity of the solder job.
If this connector is gold plated the gold will have to be removed from the soldering surface before fitting. his is done by “tinning” the surface and then removing the solder by wiping. Do this 3 times and the gold will be removed and you should be left with a shiny tinned surface to work with. Not doing this will result id failure down the track where the gold will part company with the solder and the joint will fail. Although gold is seemingly great stuff to solder ( it is a noble metal and does not even require flux) it will eventually fail. If you want further confirmation of this look up some info on “high reliability soldering”. It would not hurt to do this anyway for your own education.
Cheers Bob
Edit. Just looked up the connector (the $1.40 one) spec on Core site. The dimensions are quite small but I would still go for a minimum 65W iron and a good size tip. You may have to be careful here as the drawing does not show the insulator material. You will have no trouble with Teflon but plastic might tend to melt so you will have to be quick. You will need to be quick anyway to prevent board damage.
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