Antenna + Al Case + OLED+ MMDVM hotspot Support P25 DMR YSF for raspberry pi

Some of our members have expressed an interest in owning/building a DMR hotspot. If you are interested in getting into DMR, this is really the only way to go. We do have a few local repeaters linked to the DMR world-wide networks, but DMR over a public repeater can be frustrating. If you’ve tested the waters with a repeater and are ready to really dive in, a home/mobile Hotspot may be the answer.

A Hotspot is like your own private DMR repeater. In most cases, you will have coverage throughout your house and probably your yard. There are easy things you can do to extend that coverage much further, maybe the whole neighborhood. I put a 5 element yagi on mine and went 5 miles! These Hotspots will also work on Fusion, D-Star and P-25. But we may need some help in configuring those modes as I have never done this.

SPARC now has it’s own talk group (214) on the TGIF DMR Network and we even have a round-table net every Sunday evening at 8:00

You can get on eBay, Amazon or most of the radio gear suppliers and buy a ready-made plug and play Hotspot for $125-$300. This is the easiest way to get connected, but not the cheapest and you probably won’t learn much about how the DMR network works. Many vendors will even pre-program the device for you.

Over the years, I’ve built and programmed 6 or 7 hotspots for either myself or friends. Some of them have had their challenges in the setup, but we learned things in the process. I’ve been looking around to see what’s available for parts and although the prices have gone up a little (due to availability), building one can still be done for less than $70.

If the interest is there, I would like to have a kit night project to build DMR Hotspots for members that would like to participate. There are only a few components we will need:

MMDVM modem/radio board. The last one I bought, was from this vendor. https://www.foxbusiness.com/markets/us-stocks-march-24-2020?fbclid=IwAR163rALosZBrxONRChE-HE794MXj0B0pT0RRp360HAfycW5E83WUPJoMDM

It is very low price. it took about 3 weeks to arrive and it has worked great for over a year. I took a chance on all 3 of those factors because of the price. However, it came from China and that was a year ago. If we have enough interest, I’ll reach out to some contacts and see if I can get a recommendation for a supplier in the current situation. If these devices need to be shipped from anywhere but the U.S., each member will need to procure their own for the project. There are different configurations out there. I would recommend a non-duplex board at this point. I have heard that the full duplex boards come with their own set of challenges. If this has changed, then we will look at duplex boards. There is a big advantage to a duplex board if it works. Some of these offers come with cases, antennas, connectors and so on. What you see in the link is the cheapest way to get one and they way I buy them. The price increases just to have the header pins soldered on for you. Some of the packages have a display, some don’t. You can always add your own display. I’ve found that the tiny little display that fits on top of the board is all but worthless. It does give you some information, but you need to get pretty close to read it. For the tinkerers, the trend is now to add your own Nextion touch display of 3.5” or larger. 7” is really cool. This can be done anytime in the future and there is lots of help and support out there to help you.

The next thing you need is a Raspberry Pi. I have always used a Raspberry Pi ZeroW. They are inexpensive and provide everything you need for the Hotspot. You can use anything Pi3 or newer, just make sure it has built in WiFi. There is a PiZero without Wifi that is cheap and easy to find, but wont work. Don’t ask me how I know this. This is the component that has become difficult to find. I purchased all of mine from Adafruit (great American company) $10 + $5 shipping, you can only buy 1. It looks like right now they have them. If you are going to do this, BUY NOW! https://www.adafruit.com/product/3400

You will also need an SD Memory Card. I use 16GB mainly because they are the best value. Smaller ones can be more expensive. The spec calls for minimum 8GB. The faster the better, but that’s not a big deal.

The last thing you will NEED to have is a USB power supply that can deliver at least 1 Amp. Most of us have these lying around from old discarded devices. If you need one, let me know. Probably between my junk box and the stuff we have at the clubhouse, we should be able to find one for you.

Finally, you may want a case for the whole thing. Most of mine, I devised my own enclosure and I have to admit, they are pretty ugly. These can be purchased separately or with the modem/radio board.

The software, PiStar, is free. We will download that and install it on the devices when we build them.

So that’s an overview of the club project I would like to put together. My calculations show about $70 max. If there is an opportunity to purchase multiple devices at a savings, I believe the club could make the purchase and then sell to the members that are interested. I would only go for this if the seller is a reputable U.S. vendor.

If you are interested in participating, let me know. I’m going to add a sign up function to this post with Mike’s help, so you may already have that option. If not check back in a day or 2 to sign up.

With the current situation, there is no time table on this project at this time. We may even be able to do this virtually over the Zoom meeting app. If you sign up, I’ll count you in for any bulk purchases we might make. If you have questions, please ask. If I made any errors, please let me know.

73 es Gud DX

Mark Walton

K3MRK