Wednesday, November 16, 2011

Maxtroller and Maxduino

After learning about the Arduino microcontroller and hearing how it had been used to turn an old Motorola Maxtrac radio into a trunking scanner, I wanted to try it out for myself.  It's a project that combines both hardware and software aspects.  I would have an opportunity to practice my soldering skills as well as some programming skills.  It had been years since I took a C programming class in college, so I was looking forward to dusting off some of the things I learned.

Instructions for the project written by GroundLoop can be found here:

Instructions Update
Original Unmodified Code
Code Modified to Use Maxtroller Squelch
Code for Maxtroller Discrimator Audio Parking

I won't repeat these instructions here since they are well-written. There were a few differences between my 5-pin Maxtrac radios and the 16-pin Maxtrac radios used in the instructions, but the differences were resolved by comparing my radio's board and the pictures of the16-pin's board.  The biggest software change I made was to wire the CSQ "squelch" circuit to the Arduino and use it to mute and unmute the Maxtrac.  Without this change I was getting very long squelch tails (up to 2 seconds) that were fairly intolerable.  Now the squelch tail is fairly tight and a lot less noticeable.

For my first attempt at building the Maxdunio, I crudely cut a slot in the back of the radio and ran the wires out to the Arduino.  The second time I placed an RJ-45 jack in the side of the front cover next to the speaker.  This allowed for an easy, clean connection to the Arduino or my homebuilt Maxtroller with an ethernet cable.

The original intent of the Arduino code is to interface the Arduino with Unitrunker software to receive tuning commands, process them, and forward them to the Maxtrac.  I also wanted to be able to manually tune an second Maxtrac with an Arduino and use it to feed discriminator audio to my PC and Unitrunker software.  In order to do this I built a small box using a Radio Shack project box.  It allows me to press a button and toggle through various control channel frequencies and output the audio from the Maxtrac to my computer.  I modified the Arduino code to not look for external tuning commands from Unitrunker, but cycle through a set of predefined frequencies when a button is pushed.

Here is the base of my Maxtroller box with a Radio Shack "Dual General-Purpose IC PC Board."  I used this for both the button circuit and the discriminator audio circuit to add a resistor and capacitor inline with the audio.  

For the connection between the Maxtrac and the Arduino I used an ethernet cable.  It was readily available, contained just the right number of wires, and was a neat solution which allowed for easily connecting and disconnecting the box and radio.  Since this box is a stand-alone box without need to interface with the computer, I mounted the Arduino with the USB connection away from the edge of the box for ease of fitting.  A 9v battery fits underneath the Arduino for power.  Since this photo was taken, I have added an external power jack through the side of the box.

Here is my completed "Maxtroller"with the controller box connected to the Maxtrac via ethernet cable. The discriminator audio passes through an onboard resistor and capacitor and out of the box via a mini audio jack.

This was a fun project to put together.  I had frustrations and success in making both the hardware and software work.  I love having the capabilities of an expensive scanner wrapped in a couple of very inexpensive business radios and a couple of microcontrollers.  The audio of the Maxtracs is superior to my other scanners.  And the ability to prioritize talkgroups in Unitrunker provides a lot of functionality in monitoring.

Radio Shack Parts List:

Project enclosure 5x2.5x2 - #270-1803
Dual general-purpose IC PC board - #276-159
1/4-watt 10K ohm resistors - #271-1335
10 μF tantalum capacitor -#272-1436
Size M panel-mount power jack - #274-1582
1/8" Mono panel-mount audio jack - #274-251
Metal standoffs - #276-195
Push button - #275-1566
9v snap connectors - #270-324

Thursday, September 22, 2011

Uniden BC890XLT Discriminator Tap

Last week I bought a used Uniden BC890XLT scanner and added a discriminator audio tap.  Here's how I did it:
The first thing to do was open the case.  The outer sleeves come apart on the top and the bottom.  There are 2 screws on each side and one screw on the back that I removed.  I took both the top and bottom sleeves off to explore the inside, and discovered I only needed to remove the top to tap the discriminator audio.  Once inside I found the location of the discriminator audio which is pin #10 of IC #3, 3359DA.  Pin #10 is on the top right corner of the chip:

Rather than solder to the chip, I preferred to solder to the lead to the resistor at TP3 which is connected directly to PIN #10 of the IC.  I put a 10K ohm resistor in series with a 10 μF tantalum capacitor. 

 I wanted this modification to be removable so I didn't drill a hole in the case. Rather, I ran a connected wire to the outside of the case through an opening in the side of the case. 

I then ran the wire in the space between the case and the outer sleeve on the side.  I then ran it around the corner to the back of the scanner.  I connected the ground wire to the chassis via the screw that holds the accessory RCA jack.  I put heat shrink tubing on the outside of the wires and connected them to a 1/8" mono phone jack.  

Radio Shack Part Numbers:
1/4-Watt 10K ohm resistors - #271-1335
10μF Tantalum Capacitor - #272-1436
1/8" Mono In-line Phone Jack - #274-0333
Assorted Heat Shrink Tubes - #278-1627

Thursday, July 21, 2011

Saying goodbye to a good friend

It is hard to witness history as the Space Shuttle Program comes to an end. While I was never a direct participant in the program, I owe a lot to the Space Shuttle Program for who I am today.

I was four years old when Space Shuttle Columbia launched on STS-1 in 1981. I remember sitting with my parents in our living room watching on TV as the orbiter landed on the dry lakebed at Edwards Air Force base and thinking how cool it would be to be an astronaut and fly on a vehicle like that.

Days and years passed, and as much as I could, I would follow the Space Shuttle program through triumph and tragedy. I enjoyed classes and units at school on space and the U.S. space program. Hanging on the wall in my bedroom throughout elementary school, middle school, high school, and even part of college was this picture on a poster of the launch of STS-1 that I would look at when daydreaming of becoming an astronaut or a pilot.

In the end I chose a school and career path that led me to become an airline pilot, but the roots of my interest in science, math and aviation came from watching the Space Shuttle in all of it's power, majesty in ascent and grace on entry and landing. I hope that there is another vehicle to inspire my children to work hard to pursue their dreams.

So, farewell Columbia, Challenger, Discovery, Atlantis and Endeavour. I thank you. Fair winds and following seas.

Friday, June 17, 2011

Linear Birds

I was excited today to receive my new FT-857D to use on the linear birds. I realize the 857 will only provide half-duplex operation, but paired with my other handheld, it will be adequate. I'm looking forward to having additional passes available each day. I need to now work on some satellite antennas. Perhaps a couple of eggbeaters and a mounted yagi.

In a few days I should receive my 70cm preamp. I'm hoping it will allow me to hear birds like SO-50 that have only 500mW or less power output. It will be yet another set of satellite passes to work.

In light of the recent dire forecast of no sunspots for decades, I'll at least have one aspect of ham radio to still enjoy.


So after over half a year of working the birds I finally pulled out an handheld receiver and worked AO-51 full duplex this afternoon. It was nice to actually hear my downlink and know that I was getting through. I guess I should've done this a long time ago. I need to figure out how to raise my audio level. I'm wondering if the hand microphone I've been using is very effective. It may be time to look for a replacement.

After finally getting some experience in tracking the satellites, I can focus on other areas of making my setup better. It's also ironic that the recent problems of AO-51 have actually made it easier to work it since the power output has been increased. I've now worked over 40 grid squares and am halfway to VUCC Satellite.

Wednesday, May 11, 2011

Aging Satellites

The past week there has been a lot of talk about AO-51 being offline. This has been my favorite satellite to work because it's been very easy. It's kind of sad to see it have issues, and just at a time when I have really gotten interested in working the birds as often as schedule allows.

I guess it's good to know now about the problems before I make a big investment in equipment to work satellites. I hope it can be successfully restored. If not, I hope that it's future replacement is launched sooner rather than later. I suppose I need to realize that traveling that high and fast in space put satellites in an extreme enviorment which makes for shorter rather than longer life expectancies.

Thursday, April 14, 2011

Yuri's Night

On April 12th I marked the 50th anniversary of the first human in space and the 30th anniversary of STS-1 by making some satellite contacts on AO-51 and an HF contact with R3K - a special event station from ARC Energia in Korolev, Russia (Russian Mission Control Center.) It's nice to dust off my arrow satellite antenna and make some new satellite contacts now that the weather is slowly getting warmer.

Wednesday, March 2, 2011

Got to see the final launch of Space Shuttle Discovery. It was neat to be a part of history. Here's a video I took of the launch.


Sunday, February 13, 2011

HT Stand

I've been wanting to clean up my desk for some time now. I saw Scannermaster sells a stand to put your handhelds on, but the price was more than I was willing to pay.

This week my father in law was kind enough to help me build my own stand and all it cost me was the price of some stain. It's nice to organize the desk and have the HTs where I can see them and read their displays.

Digital Scanner

I took advantage of Radio Shack's recent sale and purchased a new Pro-106 digital scanner. Most of the traffic here in Utah is analog, but Hill Air Force Base uses a digital system. It's always interesting to listen to something new.

I'm looking forward to using it next week in Florida to hear preparations for the launch of Space Shuttle Discovery.