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Small DIY GPS powered by BCD-436HP -- make it yourself!

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After buying two Uniden BC-GPSK Serial GPS Receivers (I have a number of HP1's, a number of BCD-436HPs, one HP2 and one 536HP) I decided it would be nice to have a small, battery-powered GPS unit with a display and capable of feeding GPS data to more than one scanner at a time. I started looking around for useful information about the GPS port connector pinouts, etc. and found this VERY useful thread: http://forums.radioreference.com/uniden-tech-support/307752-gps-cable-mod-uniden-scanners.html.

I pulled out an Arduino Uno, a TFT LCD module, an Adafruit Ultimate GPS module and a protoboard and created a small GPS unit with a display and 4 USB sockets so that I could connect up to 4 radios at a time (with Rosewill RCW-109 cables). Works perfectly and was fun to build.

After reading comments in several threads asking, "Since location-based scanning is a thing, why don't scanner manufacturers include built-in GPS?"

I decided to ask and answer a different question..."Why wait for scanner manufacturers to integrate on-board GPS into their scanners?"

The BCD-x36HPs, HP-1, HP-2 and others have a dedicated GPS port that wants RS-232 NMEA GPS data. GPS modules are readily available that spit out NMEA GPS data, but at TTL levels rather than RS-232 levels. So, if you combine a GPS module, a TTL <--> RS-232 converter and a compatible cable, you get GPS for your scanner. If you power the GPS unit from the batteries in your scanner, you get portability. See attached photo for parts I used and final result.

Note: Neither the mini-USB control port nor the 4-pin GPS port on the BCD-436HP seem to provide power...so "power the GPS unit from the batteries in your scanner" means connecting Vin on the GPS module and TTL-side of the voltage converter to the positive terminal of the top-most battery in the BCD-436HP. No +V connection is needed on the RS232 side of the converter, and you'll get a ground connection from the GPS cable (which also means the GPS module is only powered up when plugged into the GPS port, so there's your "off" switch.

So, why keep waiting? Make it yourself today!

And no...I will not build you one, sell you one, sell a parts kit, begin a kickstarter, etc. -- what part of "Make it yourself" wasn't clear? ;-)

MUCH credit and appreciation to this thread: http://forums.radioreference.com/uniden-tech-support/307752-gps-cable-mod-uniden-scanners.html
 

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#2
DIY Arduino-based GPS for multiple scanners, with display

In my previous post I referenced the GPS x36/HPx GPS unit I built last summer. I've attached a photo here in case my description wasn't clear. This GPS unit can feed GPS data to up to 4 scanners simultaneously.

GPS coordinates on the display have been altered, so if you go to that LAT/LON I have no idea what you'll find but I know it won' t be me! :)

Same parts as described in previous post, plus an Arduino Uno and LCD TFT shield. The data from the Adafruit Ultimate GPS module is being passed directly to the Serial RX on the Arduino Uno, and then to the TTL <--> RS232 level converter.

Build one, it's fun!

-rbn
 

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Edit, nevermind. I forgot the radio needs RS-232 not TTL.
Funny...I read your post post a few minutes ago just before walking out of the house for the day, then came back to quickly reply & suggest ensuring you're sending the radio EIA-standard RS-232 levels rather than TTL levels and that the baud rate of your GPS unit matches the baud rate your scanner is expecting.

Glad to hear it was an easy fix, even though I was no help at all in the matter! ;-)

-rbn
 

mancow

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#5
Funny...I read your post post a few minutes ago just before walking out of the house for the day, then came back to quickly reply & suggest ensuring you're sending the radio EIA-standard RS-232 levels rather than TTL levels and that the baud rate of your GPS unit matches the baud rate your scanner is expecting.

Glad to hear it was an easy fix, even though I was no help at all in the matter! ;-)

-rbn
Thanks for trying though. I'm working in embedding a tiny GPS inside the HomePatrol.
 

daveharpe

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#7
Neat project, but it does make you wonder why Uniden hasn't added this to the radio natively. My Kenwood TH-D72A dual-band HAM transceiver is six years old and has an onboard GPS...and it's a smaller radio.
 

blantonl

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#8
I'm going to take this project one step further and embed an HC-05 Bluetooth module with a TTL/RS-232 converter in the radio (either an HP-2 or a BCD436) and have it paired to a likewise HC-05 mounted in the trunk and permanently.powered. That way I can grab and go with my 436 or HP-2 and it will automatically pair up and provide GPS support in the car without having to connect any other cables other than antenna and power to the scanner.
 

mancow

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This is what I embedded in the HomePatrol.
https://www.sparkfun.com/products/13670


I used a micro TTL-RS232 converter off ebay like this.




I could have gone direct to the HomePatrol's TTL side of the UART but opted to just hook to the RS232 side through the converter for safety sake. Plus, if I want the HomePatrol can now become a GPS source out of the GPS port instead of a sink.

I had to remove the antenna from the board and remote it with an very small thin piece of coax I had from another device. The Antenna was glued in place along the top edge of one of the boards and looks out through the top of the plastic between the top buttons. The GPS board was tac soldered farther down and sources power from a 5 v point on the board.

It works great, even locks on while inside the house, and no more messy wires. I haven't noticed any sort of interference at all.

There is enough room to do the same with the 436. That's my next plan when I get around to it. The 536's metal body makes it more difficult if using an all in one GPS unit but I might just mount a regular sized cheaper module in it due to the extra room and put an SMA out the back for a simple antenna.
 
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fourthhorseman

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wbswetnam

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I remember asking in the RR forum several years ago "Why can't Uniden mount a GPS unit into the HP-2?" and I was assured by numerous 'experts' that it "just isn't possible".
 

wx5uif

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#15

fourthhorseman

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#16
Easy as pie,componants are secured by 3M 2 side tape..clear for windows.
used JST 4 pin plugs, very small. so it can be quick disconnected from the main boards,

the power is supplied internally, and the RX/TX pads are located up by
the mini USB connector.

the ladybird has no RTC batt, but it does not matter.the 436 eats up the 9600
or 4800 bd rate.

everything fits great, plenty of room for the componants..
and cost me about 30$ out of pocket..

So my Q is this,...Im an Idiot...I figured this out in about 2 days.
so Why Uniden could not do this...I dont know..If I can do it for about
30,,uniden can for less than 10( for parts)...
 

fourthhorseman

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Luckily I took internal pics of a radio i did for another person..
this one has a micro slider switch for on/off ability..
My 436 gets about 6 hrs on 3AAs...2400Mah charged @ 200ma
via my LaCrosse charger.

Pic of the TX/RX pads,

and

Power rail..its 3.7 which is ok for the LadyBird, but I still used the regulator/stepper
to play it safe...
 

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fourthhorseman

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I remember asking in the RR forum several years ago "Why can't Uniden mount a GPS unit into the HP-2?" and I was assured by numerous 'experts' that it "just isn't possible".
Funny,
about 6 months before DSD/linux came out I asked,
Is it possible to pipe the digital trunked signal into a
laptop to decode...
Response was ..No..No..No..Never...too complex..
vocoder proprietary this and that....

Today we have SDRTrunk, DSD+ and LRRP...Love that LRRP...

Its like hearing movie critics rate a movie...
its just their opinion, Not fact...

And honestly,,if UNIDEN could not do this,,and No college education ME
can get it done..JFC....Im open to a job offer Paul!.LoLz...
 

phask

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One of the reason's that I believe Uniden stated was the possibility of interference at some freqs, birdies, something , also price, even if it only cost YOU 5 bucks, that might translate to 20 bucks or more price increase.

I think they have an internal GPS in that new CD/scanner thing. I'd also guess we will see it in the next generation of scanners now.

I wonder how that would work with a low in car mount though? I have my GPS antenna on the dash. Wonder if that chip/antenna has good enough reception? I do know earlier ones would loose it in weak signal areas and that newer chips do much better. (Been geocaching/mapping/etc/ since SA was turned off).
 
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