I just built a repeater using some cost effective equipment sourced here and there, this could be used as a guide to help you do the same and get you away from the headaches of figuring out what to buy and where to get it.
My setup is as follows...Internet, if you have no internet, then go no further... Some say you have to have this super fast internet, I find this to be untrue as the datastream I see leaving my PFSense Box, is no more than 25Kbps. I should imagine, if you had both slots with traffic on it, this would double. Latency might be an issue, if you are on a satellite connection, I would think you will have issues due to the lag and timing is pretty crucial with DMR.
Raspberry Pi 2 or 3 www.ebay.com/itm/Raspberry-PI-3-Model-B-Quad-Core-64-Bit-1GB-WIFI-Motherboard-PC-Computer-NEW-/232120229741?hash=item360b719f6d:g:5ugAAOSwEzxYbYi7 make sure you don't buy some Chinese knock off. The Pi2 might work better for you, as you will need to turn off the WiFi on the 3, the Pi3 is a faster unit with more memory, so if speed is not of the essence, you could save a few bucks on a Pi2.
Two radios (Mobile) of which is what is found in most repeater setups. These radios, I bought a pair of Motorola CDM1550LS UHF 403 - 470 Mhz, 25,20 and 12.5Khz. You will find many flavors of this radio, the ones I bought range in power from 1 to 26 watts, there is also a 20 to 45 watt version. If you're using this as a hotspot, then I would recommend the low watt version. These I found on eBay, open box but brand new without Microphones for $100 each shipped.
Bruce will give you two options, see below..
MMVDM REV 1.0.1 Assembled and tested includes JST-8 Pigtail connector
Rev 1.0.1 includes the following built in
I2C output (to connect LCD)
Serial output (to connect LCD)
Additional radio sense and control lines to be used for DR1X conversation
Protection diodes on all the radio signals
$60.00USD plus shipping
Clone Arduino DUE Package
MMDVM REV 1.0.1 + 1 Due loaded with the latest MMDVM code with
USB cable and JST-8 Pigtail
$85USD plus shipping
I bought option 2 myself, saved me having to program the Due board with the firmware, but from what I read it is not too difficult.
I did buy a nice case for my Due board off of Amazon, www.amazon.com/gp/product/B00NNXR0DG/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 at a cost of just under $12, it makes the Due much more resistant to shorts and the pins penetrate the top cover allowing the ZUM modem (MMDVM) to plug right into it.
Other items you will need are, some cable 6 foot of multi conductor, the ZUM board has 8 wires that leave it, you should have enough for them and there is another option on the board for RSSI which will take another 2 wires. The cable I had laying around has 5 shielded pairs in a nice flexible cable, worked out great for me.
You will also need some Motorola accessory port connectors www.ebay.com/itm/161624749561?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT just under $9 a piece, you need two of these.
You will also need a USB programming cable for the radios, watch out for the cheap cables on eBay that use prolific chipsets, if you do buy one, you will need a 3.2.2 version Prolific chipset driver.
If you plan to cover a large area with a repeater, you will need a repeater frequency pair and a tuned Cavity/Duplexer. Low power you could probably get away with a dummy load and small RX antenna setup.
Total costs vary, depending on what you use and how you locate your setup. So far, I have about $360 in this repeater, that is without dulplexer, antenna and coax (still looking for a location to install it).
I would also consider using a couple of small 12volt brushless fans to mount on the TX cooling fin, at low power with a lot of use it still gets very hot.
So what now?
You have all the parts, but how do they all go together? That is the fun part, I scraped around for the information, got some help from a friend of mine and scraped some more. You will need to download an image for your Raspberry Pi, you will also need a decent 16 Gb Micro SD for it and a little knowledge of Linux to get this all working. Some of the information I will paste in as it is just to involved for me to explain, I am no linux guru at best I am below a novice user.
As mentioned, the information you need to make this a success is everywhere. If the truth be known, I did get frustrated by the build and almost gave up, but I am not that sort of guy, while I might cuss at it, scream about irreverent information or ask myself "why am I doing this?", I take a few minutes, walk away and come back to it. 3 days, a few hours a day and my setup works great.
So, the image you will need to put on the 16 Gb MicroSD card, I used an image from DMR-UTAH, they use a Linux Pixel image, nice build and works great. You can download it here. drive.google.com/uc?export=download&id=0BxeyR6_rxGV1Mk12X2owVUpBSVE .... I have since moved away from this image, I now use another image that was made for MMDVM and BlueDV, some small modifications and I now have a working system that has an easy way to update the software and has MD380 Tools built in that you can use to setup your TYT MD380 radios, plus the software, gateway for Yaesu system fusion, P25 and more.. Let me know if you want the image and I will upload the latest version of it for you. All you will need to do is burn the image, change a few things and BAM, you're done.
You will need some software to write this image to the MicroSD, you will need some way to write to the MicroSD card, something like this will work for you www.amazon.com/gp/product/B018S7ZNDU/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1 you will also need an SD to MicroSD converter. The software to burn the image is sourceforge.net/projects/win32diskimager/?source=directory I will not get into the in and outs of burning the image, pretty straight forward to do.
When you have all of the hardware required, hook it all up. Raspberry Pi, connect the USB cable that came with the Due board to one of the USB ports and the other to the programming port of the Due, the one next to the unused power supply port. Mount the ZUM board if not already mounted to the DUE and get ready to wire up the 8 pin connector on the ZUM board to the radios.
Wiring for the 8 pin plug is labeled as follows (according the the info supplied with the MMDVM ZUM board).
Pin (1) CTRL not used in this case
Pin (2) COS/STAT_1 cos carrier from the RX radio
pin (3) RX Audio
pin (4) GND
pin (5) GND
pin (6) TX Audio
pin (7) PTT
pin (8) STAT_2 not used in this case
Time to join the the 16 pin Motorola connectors to the 8 pin ZUM connector.
Here you can see the pins of the 16 pin Motorola connector, the large tab on the connector you have is the top of the radio.
Looking at the back of the radio, the 20 pin connector will be on the right, yes I did say 20 pin, you ignore 2 pins to the left and 2 pins to the right, they are unused in this instance and are only used for special connections, besides, your plug will not overlap into them. I will reference the plug above, as both radios use the same plug, we just use different wiring per plug, so let us concentrate on the TX plug, you need to identify one of them as TX and the other as RX, red tape on the TX plug or like I did, red heat-sleeve on the wires for it.
As you can see, from the image above, this is the TX plug, all three wires are on the bottom row of the pins, the three wires sit in pin positions 3,5,7 on the connector, Pin 3 on the TX radio is as follows..
Pin out on TX Radio to PIN on the MMDVM.
Pin 3 on TX is PTT and connects to Pin 7 on MMDVM
Pin 5 on TX is Flat TX Audio and connects to Pin 6 on MMDVM
Pin 7 on TX is Ground and connects to Pin 5 on MMDVM
Pin out on RX Radio to PIN on the MMDVM.
Pin 7 on RX is GND and connects to Pin 4 on the MMDVM
Pin 8 on RX is COS and connects to Pin 2 on the MMDVM
Pin 11 on RX is Flat RX audio and connects to Pin 3 on the MMDVM
As an option, you can run the RSSI from Pin 15 on the RX Motorola, you will need Pin 15 and a Ground run direct to the top of the MMDVM board, to the left of the RX pot you will find RSSI and GND but the header is missing. I have not at this time tested the functionality of this. (Update on RSSI) I have now got this working, there is going to be a few things needed to be done for this, you will need a RSSI.dat file, of which you can find at the end of this tutorial, you will need to enable RSSI or should I say add this line in your MMDVM.ini file, under the [MODEM] section add RSSIMappingFile=RSSI.dat . You will also need to change in your Arduino Due firmware to allow the RSSI to pass, this is found in the Config.h section of the Arduino software compiler, look for //#define SEND_RSSI_DATA and remove the two forward slashes, compile and upload.
So, that is basically the wiring done, you will need to go into your RX radios codeplug and edit the following, Radio Configuration/Accessory Pins/ you can change to RICK or 120R RX or directly change pin 8 to PL and CSQ detect, active low with Debounce enabled. Or you can scroll to the end of this topic and grab the codeplugs, either use them or look for reference.
Burn the image
Now you can burn the image you have from the link I provided earlier, use the Win32diskimager and insert the card into the Pi once completed. Make sure the Pi is hooked up to the Due board with the cable as mentioned above and it is critical you have the other end of the cable plugged into the programming port of the Due. Hook up a monitor or TV using the HDMI out, connect up a wireless mouse and keyboard and power up the Pi. You should at some point end up on the desktop, give it a few minutes.
When you reach the desktop, navigate to the top left and click on the Raspberry, hover over Amateur Radio, then click on Edit MMDVM.ini. You will need to edit this, or you can use mine and change your ID and Callsign, might be in your best interest to copy my settings into yours, again link at the bottom.
Once you have made the changes, save the file, go back to the Raspberry, hover over Amateur Radio, then click on MMDVMHost Background Service Restart. Now go back to the Raspberry again, hover over Amateur Radio then click on MMDVMHost Background Service Console to see what is going on.
In a nutshell
So in a nutshell, that is basically it, you can hook up your radios, on your allocated freq pair, edit your codeplugs for your HTs and or Mobiles and try out the setup. It may or may not work, mine did not work from the get go and I had to increase the TX audio on my MMDVM board, I think as of now I have turned it in some 14 full turns to get it to work correctly, you will need to tweak and tune, this setup is not plug and play by any means.
So I will leave you with some images of my setup, I shall visit this and make corrections or additions. If you have some information and or corrections, please feel free to leave comments. Be constructive about it, sarcasm or plain rudeness will get you removed. I wrote this out of the frustrations I had, the information is limited and spread around, which took me time to find.
RSSI.dat file, needs to be in /home/pi/MMDVMHost/ drive.google.com/open?id=0B78gqDvK_vv7RkxoLXZDOE9fdE0
My RX and TX Codeplugs for the motorola CDM1550LS
If you receive a region error when trying to import these codeplugs, see this topic to fix that issue digiham.boards.net/thread/19/cps-region-hack-cdm1550ls
MMDVM.ini file drive.google.com/open?id=0B78gqDvK_vv7amVVTXhwZXFrY0E don't forget to edit your info in here or it will not work. Reload as per above after every change.
Another image, this one is for the KB5RAB images, there is two types to choose from www.facebook.com/notes/brandmeister-talkgroup-3148/link-to-latest-kb5rab-raspberry-pi-image/171532783251102
Some videos for you to watch, Richard Hyde (KE4GjG) made some interesting videos on the functioning and install of the setup. Thank you Richard..www.youtube.com/channel/UCvKrYliPRMxzppLObHHZjmw
MMDVMHost, MMDVM-Dashboard and some of the gateways require updates once in a while. I have noticed and you may notice also, when you update MMDVMHost, your MMDVM.ini (config file) does not get updated, if it did you would loose all of your settings. Now, due to the non-update with MMDVM.ini, you will notice some items have changed, been removed and even added to the new one on github. I recommend once in a while you visit github for MMDVMHost github.com/g4klx/MMDVMHost, look at the MMDVM.ini and compare the online version and the one you have, make changes and save. Be careful that your versions match, because adding items into an older MMDVM version will probably break your running version..... ALWAYS BACK UP THE MMDVM.INI BEFORE YOU MAKE CHANGES!!!
Shipping was pretty fast, and the quality of the board is excellent. Instructions are minimal but it is designed to do a function, not to tell you how to get it to function with DMR, that is where the above information comes in. Along with the quality, the build is solid, all in all a very nice product. The only thing missing is the header for the RSSI out, but this really does not cause an issue as you can solder wires to the board, but I do not know what that will do to the warranty of the board. You may want to ask Bruce about that, just to confirm that he has no problem with you doing so, before you attempt it.