More GPS Module Fuckery

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

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 -*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


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) – $12NOTE:  THIS TURNED OUT TO BE A REBRANDED U-BLOX 7 CHIPSET SOLD AS A NEO-8M.  It works and is good enough for a police scanner……..but it was not as described.  Also on these breakout boards there is usually a chip for flash memory for upgrading the firmware.  No flash memory exists and the firmware cannot be upgraded.  
  • 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.

Lots of different GPS units will work but they must not be serial devices.  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

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



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

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.


Let’s get to it, shall we?

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Uniden BCD436HP Scanner

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

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


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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Getting a Police Scanner Part Deux

I recently wrote a blog on selecting a Police Scanner and I wanted to do a deeper dive on how to select one and how to begin the set up process.

The process begins at

The first thing we are going to do is inspect our area and determine what systems we want to follow.

Then we’ll take a peek at the antennas used to transmit and determine whether or not we have something called Simulcast.

Simulcast is when multiple radio towers transmit the same thing at the same time.  This is obviously done to provide a larger coverage area to ensure our First Responders don’t hit any dead radio zones in their area of operations.  But, Simulcast can cause horrific distortion and some radio scanners simply cannot do Simulcast systems very well at all.
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The Wonderful World Of Windows

Now that I have a proper Windows laptop again I had forgotten how much stuff out there is Windows only.  Here’s a quick list of stuff that I can really only do or do best with Windows.  This list is unique to me and the toys I dabble with:

  • Police Scanners – I’m a scanner geek and the two most popular brands of scanners are Uniden and Whistler (arguably).  Neither one provides any programming software or firmware update tools in anything but Windows.  Advanced 3rd Party Software such as Proscan or others is also Windows only.
  • RTL-SDR – While you can most certainly do RTL-SDR stuff on Linux and Mac the most fun software such as DSD+ or the most intuitive control software, SDR#, is Windows only.
  • CNC Machines – I have a NextWave Shark HD500 CNC machine.  All firmware tools, and  control software are Windows only.  The very best CNC software is from a company called Vectric and is called either VCarve or Aspire.  All variants of VCarve and Aspire are Windows only.
  • Vinyl Sign Machines – I have a Roland GX-24 vinyl sign cutter. While there are various Mac or Linux software offerings the very best pro sign making software solutions are Windows only.  (Flexi, CoCut, etc.).
  • Laser Engraving and Cutting –  The very best software for Lasers is Lightburn which in fact is cross platform and offers Mac and Linux versions.  The Mac versions have USB issues and the Linux versions are just buggy in my opinion.   While I can generally work Lightburn to my laser via the Mac version OVER ETHERNET, when I need to move one of my more portable lasers around the best reliable method is to use the Windows version.

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