Legitimate GPS Modules

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I’ve been talking a lot about fake GPS Modules a lot……now let’s talk about legit GPS Modules.

First of all I’ll run over the actual legit GPS chips that I own and have dabbled with.

I have several GlobalSat BR-355S4 pucks.  These have Sirf Star IV chipsets in them which ONLY receive USA GPS system.  I use these with my Uniden Police Scanners.  Simply cut the plugs off of them and wire them to a plug that fits the Scanner.

I think it is important to note that as I mentioned above it ONLY receives GPS.  While this is probably fine for a police scanner, I don’t think I’d trust my life hiking out in the Mohave Desert with a device that had a Sirf Star IV chipset.  I’m not saying GPS would go down………but what if it did?

And I’m not knocking Qualcomm or their Sirf Star IV chipset.  I’m just saying I want redundancy in a life or death situation.

Then this leads me to my next GPS point.

DATASHEETS
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BirdNet-Pi

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I’ve been on a Raspberry Pi project tear lately.  Somehow or another I stumbled into BirdNet-Pi and the best way I can describe it, is that it is like Shazam for bird songs.   It records the call and frequency and plots it on a spectrograph and identifies the bird.

Very Cool!

About a year ago I married my long time girlfriend and we bought a new home just outside of town.  We are on a 1 1/2 acre heavily wooded plot that also has a creek running along one edge.  So the birds love it here.  And my wife loves birds and keeps the feeders clean and full.  So I really did this for her but this project has got me super excited about all the different species of birds around here and their distinct calls.

It’s easy as heck to build.  You need:

  • Raspberry Pi – latest is best however I built this with an older Pi 3 B+.  It runs fine on there.
  • SD card to install Pi OS.  BirdNet-Pi says to use Pi OS 64 bit Lite.
  • USB microphone.  Initially I used an $8 USB mic  and it works but the better the mic…….the better the results you’ll get. I used a Rode mic that costs about $50.
  • OPTIONAL – if you use the better microphone you will need a USB Sound Card. to plug the mic into.  The better mic and sound card make the project a bit more expensive but I think you’ll be glad that you went that route.  if you just want to dabble then just use the cheap mic.

NOTE ON MICROPHONE:  Because the Rode mic I linked above costs $50 and it is a directional microphone I did some research and found an omni-directional mic that costs $20 less.   It is a Lavalier Clip On mic.   I’ve had it up several hours and my bird call detection is WAY up.

That’s it.  Install Pi Os 64 bit Lite with Raspberry Pi Imager.  Be sure to hit Command +Shift + X (Mac) (probably Control + Shift + X on windows) before you write the SD card. This allows you to  set up wifi and change the hostname  and change the timezone and set up SSH if you want.

Pi Imager

Lets proceed!
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More GPS Module Fuckery

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I have this on-going project to find a GPS Module that works with my Uniden SDS200 police scanner.  Obviously this is so the scanner will auto update its location when a GPS Module is connected.

Uniden sells one for $50, so the goal is to manufacture one for less than that amount of money.  Actually, I’ve succeeded several times, with my last build costing about $20.

So, what’s the problem you ask?

Almost every GPS Module I have purchased is FAKE.  The GPS Modules that I know are not fake are from Manufacturer recommended sources, and all cost more than $50.  More like in the $70 range.

The most commonly counterfeited chips are U-blox and specifically the NEO-6 series chips.  An actual, REAL NEO-6M CHIP, not module at  Mouser in the US for is $60 for one.  A NEO-7 CHIP, not module, can be purchased from Digikey for $31 and I did find that Digikey calls the NEO-6 series “obsolete”.  In fact U-blox says the NEO-6 is an old product as well.

6=OLD, 9=NEW

So how is that you can do a search for GPS Modules and find $8 NEO-6M modules all over the place? If a legit chip is $31 or more how can a complete module be $8 or $12?

Answer: It can’t. It’s fake.
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Beware The Fake GPS Modules

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I just started dabbling with GPS modules.  I got my first one from Amazon for about $12.  I didn’t know almost anything about GPS chips but I did know that U-blox chips are pretty prevalent in the Drone community, so I set out to purchase a module with a U-blox chipset.  The Amazon one I linked above (which now shows as unavailable, and I hope I had something to do with that) indicates that it has a NEO-8M chip on it.

Let’s see.

I plugged the GPS into my computer and started U-blox U-center software.  The GPSTXT data indicated

??:??:??  $GPTXT,01,01,02,u-blox ag - www.u-blox.com*50
??:??:??  $GPTXT,01,01,02,HW  UBX-G70xx   00070000 FF7FFFFFo*69
??:??:??  $GPTXT,01,01,02,ROM CORE 1.00 (59842) Jun 27 2012 17:43:52*59

Rebranded Old Chip

Say What? I got a U-blox chip all right but it is a U-blox 7th generation with firmware from 2012. Here’s what the label indicated on the chip.

It says NEO-M8N.

Soooooo, someone took a 7th gen chip that is 10 years old and rebranded it to a current production version.

Not only that, the 7th gen chip does have a firmware upgrade however you can’t apply it because whoever made the module board didn’t include flash rom so it simply cannot be upgraded.  How cool is that?
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Uniden SDS200 GPS

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Uniden SDS200 GPS

WHEN BUYING A GPS MODULE FOR THE SDS200 KNOW THAT GPS CHIPS ARE WILDLY COUNTERFEITED AND THAT BUYING A CHIP FROM AMAZON, EBAY, OR ALIEXPRESS IS LIKELY TO GET YOU A FAKE OR A REBRANDED CHIP.   

I’ve been on a Uniden Police Scanner GPS DIY tear lately and my last radio scanner to need a GPS accessory is my prized Uniden SDS200.  Sure you can buy a GPS unit for about $50, but our goal is to make one for less than that.

Oddly enough, this was the easiest one to make.   Here’s what you need:

  • GPS Module STM32 (not serial) – $12. NOTE:  The previous GPS I had linked is no longer available.  This one should work but I haven’t actually bought this one.  It is probably counterfeit as well.   Also on these breakout boards there is usually a chip for flash memory for upgrading the firmware.  If no flash memory exists you won’t be able to upgrade.
  • Any 4 wire RJ14 telephone cord.  You can get them at Walmart for about $4.  I’d be willing to bet you have one laying around in a junk drawer or hooked to an old phone you’ll never use again.
  • 3D printed case (optional)

Oddly enough I bought a NEO-6M board from one seller on eBay for $8 and it is authentic which really surprised me.  The NEO-6M is a pretty old chip though so I guess I’m not surprised old authentic stock is still out there.  An $8 NEO-6M is HIGHLY RECOMMENDED for this project……..if you can find one.

Conversely, lots of different GPS units will work but they must not be serial devices.  Additionally, make sure you get a 3.3 Volt, TTL logic unit and not an RS-232 serial device.

Let’s wire it up!
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GPS Cable Wiring For Uniden BCD436HP Police Scanner

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I have two scanners, a Uniden Home Patrol 2, and a Uniden BCD436HP.  They have the following in common:

  • Both made in 2014
  • Both GPS compatible
  • Both use the same Mini B 4 pin connector for the GPS connection

BUT, THE GPS 4 PIN CONNECTORS TO THE SCANNERS CAN BE WIRED DIFFERENTLY.  

 

To make your own GPS cable you need:

  • ProMaster #3696 6′ cable – The first people to do this hack used a Rosewill RCW-109 cable.   Good luck finding one of them these days.  What you need is a USB 2.0 Type A Male to Type Mini-B 4-Pin Male.  Make sure it is a 4 pin.  I found some other branded cables on eBay as well
  • BR-355S4 GPS Puck

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Programming a Uniden Scanner With Sentinel

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I bought a new Uniden BCD436HP scanner and decided to install the programming software Sentinel.  I have a couple of computers and decided to do this clean.   And that’s when I realized that using Sentinel for the 1st time is really kind of a beast.  There are a LOT of settings that you probably should run through prior to writing your configuration to your scanner.

The BCD436HP and all of its big brothers are touted as being EASY to program..  By golly you can just plug your zip code into it and it will just start scanning.   While that is true almost constantly on the scanner forums you will see someone do just that and then post:

“Why can’t I hear the Fire Department?  Why can’t I hear…….xxxxxx?

Well, it’s because certain service types aren’t turned on by default.

NO MATTER WHAT, NO MATTER HOW EASY IT WAS YOU WERE TOLD……….THERE IS SOME LEVEL OF PROGRAMMING WORK NEEDS TO BE DONE.  DOING THAT IN SENTINEL IS FAR EASIER THAN DIGGING THROUGH THE MENUS ON THE SCANNER ITSELF.

Let’s get to it, shall we?

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Uniden BCD436HP Scanner

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Always wanted one of these Uniden BCD436HP scanners but the cost was always prohibitive.  For some reason Amazon is running them at around 30% off currently.

The BCD436HP is circa 2014 which makes it OLD in electronics years, and back then digital trunking scanners weren’t really designed to combat Simulcast distortion.  That is where a digital system has multiple antenna towers that broadcast the exact same signal at the exact same time.   Some scanners getting hit with multiple signals will distort, have choppy voice, or robot voice.

The only two scanners on the entirety of planet earth designed from the ground up to deal with Simulcast are the Uniden SDS100 and the Uniden SDS200.

So it doesn’t make a lot of sense to spend big money on a scanner that might choke when just a bit more money gets you a sure thing.  Where I live there is a P25 Phase 1 LSM system that will bring most scanners to their Simulcast knees.  Within moments of slapping some batteries in a scanner I will know if it can deal with Simulcast or not.  Remember when you could actually go to a local store and test a radio before you bought it?  Sadly those days are no more.

Anyway, I didn’t even want to take a chance on an old scanner that was expensive and might not work.  That is, until the price dropped dramatically.  After turning it on for the first time within seconds I received a call on my local Simulcast system and the BCD436HP dealt with it PERFECTLY.  This scanner is a keeper.

NOTE:  Simulcast is odd as hell.  Just because it works in my location doesn’t mean it will work across town, on the system in the next town over, or at your location, wherever that is. 

Now lets talk about a few things I learned about the BCD436HP…………
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Scanner Selection – Part Three

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I have many scanners.  Too many.  After dabbling with all of them the last couple weeks I have come to the conclusion of which one a scanner enthusiast should purchase.

That’s it.  But with some exceptions which I’ll get to in a minute.   You’d think in this day and age there would be dozens and dozens of choices and price wars in the radio scanner market.  There isn’t.   In fact there really are maybe only 15 or 20 choices AT ALL.

I count 8 Uniden digital scanners and 4 Whistler digital scanners.  You can get Unication digital pagers which will track P25 digital systems and there are a couple other offerings (old) from GRE and Radio Shack.   I’m sticking with my estimate of 15 to 20 choices.

Most digital systems out there have multiple towers that transmit the same data at the same time for maximum coverage over the First Responders area of operations.  That is called Simulcast.  It can also produce distortion ESPECIALLY if a couple towers are a few milliseconds out of whack.

Currently there are only TWO scanners that have circuitry designed to deal with Simulcast.

  • Uniden SDS100
  • Uniden SDS200

Hence my recommendation above.  Here are the exceptions.
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Uniden BCD325P2 Mini Review

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BCD325P2

I recently picked up a Uniden BCD325P2 and am currently putting it through its paces.  The scanner is circa 2015 so it isn’t a new offering and I got mine used which is probably the cheapest way to buy one of these.

I don’t regurgitate specs here.  I can’t give you the specifications better than Uniden can.  What I can do is to use something from the common man standpoint and tell you what I think of it.

There is a lot to like about this scanner and first and foremost my favorite feature may be that it uses AA batteries.  Scanners with rechargeable brick batteries are cool but when they drop dead they must immediately be tethered to a power source.  You can also use AA rechargeable batteries in this scanner so you kind of have the best of both worlds.

Also the scanner is really lightweight compared to my Uniden SDS100 or Whistler TRX-1.  Much more suited to the backpack or belt clip or just carrying it around in your hand.

On the “I Don’t Like” side of the equation, it just doesn’t do well with my local Simulcast system, New Bern Public Safety which is a P25 Phase 1 LSM system.   I’m not done playing with P25 threshold settings or using a lesser antenna to try to cut reception from one of the two towers near me.

Now that I have one good, and one bad……Let’s dig in a little deeper.
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