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Parts for Building a Hotspot Yourself

If you look at the PNWSpot site, and my other blog posts, you will quickly find that I am not going to pretend this is all black magic. Rather, PNWSpots are unashamedly similar to many other Pi-Star based MMDVM hotspots available. Everything from cheap kits on Amazon or eBay, to expensive (maybe even over priced) pre-built hotspots from a number of other sellers.

On the front page of this site, I do list the parts that are used. However, where are they purchased, what exact units/models are they? That’s what this post is here to answer, as well as give some alternatives and suggestions.

The Components

Most, if not all Pi-Star based MMDVM hotspots have the same components:

  1. Raspberry Pi (Usually either a Zero W or a 3B)
  2. MMDVM “Hat”
  3. OLED Screen
  4. Micro SD Card flashed with Pi-Star
  5. Case of some sort
  6. Antenna of some sort

Component Deep Dive and Recommendations

Let’s take the list above, talk about each component and give some recommendations and sources:

The Raspberry Pi

For this, you have two main options. A Raspberry Pi Zero W, or a Pi 3B+. You can use a Pi 4, but it’s really not needed.
If you are not super comfortable with soldering, you may want to get a Pi Zero WH (With Header), which comes with the GPIO headers pre-soldered. The Pi 3B+ also comes with the header soldered.

Pi Zero:
Zero W:
Zero WH:

Pros: Small, Cheap
Cons: Slower (Not really a con, do not need the hotspot to be fast for the basic task it is performing)

Pi 3B+
Pros: Faster
Cons: Bigger, More Expensive

The MMDVM “Hat”

This is where all the magic happens. This is what makes the hotspot a hotspot. The MMDVM board is what transmits and receives (along with a number of other functions). This is where you have a number of choices, both cheap and expensive.
You can absolutely get random boards off eBay or Amazon, however these do not always work perfectly and are all more or less basic clones of an original design. The cheap ones you see on Amazon or eBay are usually referred to as “JumboSpots”. The boards I will recommend below have good track records, and most I have used myself.

Simplex vs Duplex? This is a question that you may have now that we are talking about the MMDVM Hats. To make it simple: If you are a heavy DMR user, a duplex hat will let you use multiple timeslots simultaneously, and also let you “interrupt” a conversation to switch talk groups. If you are not a heavy DMR user, there are pretty much no benefits to spending the extra $ on a duplex board.

Pi Zero Hats:

BI7JTA Simplex MMDVM Hat:

This is the primary hat that I use in PNWSpot hotspots. Winters (BI7JTA) is a Chinese ham who builds and sells these boards. They work flawlessly, have modifications by him to improve the design and operation, and you are supporting a fellow ham with your purchase. The biggest “Con” is waiting for the shipping (usually 1-2 weeks depending on what speed you pay for).

These boards come with a 432MHz SMA antenna with the SMA connector pre-soldered to the board. However, you can also source and install a ceramic antenna directly to the board if desired. You also have the option to have the OLED Display pre-soldered.

N5BOC Simplex and Duplex MMDVM Hats:

David Dennis, N5BOC has two very high quality MMDVM hats. One is a simplex hat that actually has an internal antenna by default (you can add SMA if desired), as well as a duplex hat. The description from David’s site explains some of the improvements he has made to the design:

…this board has its own dedicated 3.3V regulator and does not pull voltage off of the noisy Raspberry Pi 3.3V line like all other simplex board do. This board is now a 4 layer board with LARGE ground planes for 3.3V and GND sandwiched in the middle. This acts as one very large decoupling cap the size of the entire board. Also this isolates signals between TOP side and BOTTOM side. Speaking of that all of the Analog RF signals are on the TOP side only and the high harmonic digital signals are all kept isolated on the BOTTOM side. Making this board much more stable. It should also make it more sensitive on receive.   

The SIMPLEX board comes with a 432MHz ceramic antenna mounted on the board.   But if you prefer you can dismount this antenna and install an SMA connector in order to install a standard antenna with some gain. The DUPLEX version has two SMA Connectors and you can choose to add two SMA antennas to the order if needed as well.

Pi 3B+ Hats:

You can technically use most Pi Zero hats on a Pi 3B+, the problem comes when you look for cases. So to be safe, if you plan to use a Pi Zero MMDVM Hat on a Pi 3B+ and want to use a pre-made case, keep it to the simplex boards.

If you do want duplex, get a board designed for use with the Pi 3B+, like the one below

BI7JTA Duplex MMDVM Hat:

Winters (BI7JTA) is a Chinese ham who builds and sells these boards. They work flawlessly, have modifications by him to improve the design and operation, and you are supporting a fellow ham with your purchase. The biggest “Con” is waiting for the shipping (usually 1-2 weeks depending on what speed you pay for).
These boards come with a 432MHz RIGHT ANGLE SMA antenna with the RIGHT ANGLE SMA connector pre-soldered to the board. If you plan to use one of the standard Duplex MMDVM Pi-3B+ Cases from C4Labs as mentioned below, be sure to tell Winters to send you a board with Vertical/Straight SMA connectors soldered to the board, NOT right-Angle. You also have the option to have the OLED Display pre-soldered.

The OLED Display

0.96″ OLED Display

If you buy an MMDVM hat from Winters, BI7JTA above, you can get an OLED display pre-soldered by him. If you want to install yourself (Like I do), or, want to use a different MMDVM board, you will need to search Amazon or eBay for a 0.96″ OLED display with the pins in this order:
| 3.3V+ | GND | SCL | SDA | Many do not come in this order, so just be sure to check!
One thing to note – having a display is absolutely NOT necessary for operation. There are blinking LED’s to display the status, and of course, your radio’s display which will show callsigns and possibly names.

The SD Card

Sandisk or Kingston Class 10 MicroSD Card

This one is simple. Get a 16GB Class 10 or better MicroSD card from a reputable brand. I use units from Kingston or Sandisk.

The Case

Pi Zero Simplex:
Pi Zero Duplex:
Pi 3B+ Simplex:
Pi 3B+ Duplex:

Basically, if you want a great case, just buy one from C4Labs. These are the cases I use for PNWSpot hotspots.

Other Cases
If you want, you can also 3D print cases, or, get cheap metal and acrylic cases from eBay. I am not including any links for eBay, as they are often changing and I really have no experience ordering from the sellers so I cannot vouch for them. In my opinion, unless you plan to modify a normal raspberry pi case or build your own, you might as well buy a case from C4 labs.

The Antenna

99.9% of the time you will be getting an antenna along with the MMDVM board your purchase. If you don’t, most 70CM Ham band SMA antennas will work, however you may need extensions or other adapters to get them to fit with the cases.

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Thoughts on different HotSpot offerings

As many of you have probably seen, there are a great number of hotspots on the market today. Many of them are simply JumboSpots (Chinese-clone MMDVM Pi-Star based hotspots) with a fancy case. I wont even deny the fact that mine are pretty close to being the same (Although, I do source my boards from BI7JTA who has customized his board design).

I will recommend other hotspots

I also will not hesitate to recommend purchases from some of these other sellers, assuming they are transparent in what they are selling, and are not ripping folks off. For Example, we have DMRspot. These folks sell a nice unit, and offer several options. Simplex Premium and Basic, and a Duplex premium.

DMRspot Hotspot Family

So, why do I often recommend them?

  1. Transparency: Images of the inside of their units. Clear descriptions of how their “Basic Spots” are JumboSpots.
  2. Customization: They are using home-brew 3D cases that look fantastic! Its a unique option and I love it.
  3. Quality options: DMRspot is one of the few who offer something special, and that is N5BOC MMDVM Boards from Texas, both simplex and DUPLEX options!
  4. Reasonable Prices. They are good, thats all that I can really say. Knowing what it costs in time and hardware… they are charging a reasonable amount!

DXMINI: I used to often recommend the quality products from DXMINI, but they unfortunately shut down this year. They had quality, custom products at reasonable prices. They were also “just” an MMDVM hotspot, likely with a cheap JumboSpot board inside. However the custom screens, custom cases, attention to detail and reasonable prices made it a great purchase.

Handsome DXMINI V2

But Watch Out

Last week I saw a new seller I had not seen before, who sells nearly identical hotspots to my own, but with JumboSpot MMDVM boards (I think).
Why do I NOT recommend them?

  1. No information on what is being sold, other than a “mmdvm hotspot”.
  2. Limited pictures, none of which really show what is being used in the hotspot (my trained eye tells me its a jumbospot board).
  3. Claims that it is the “Best Hotspot” (not those words exactly)…
  4. $235. Yes, that’s right, someone is selling a hotspot nearly identical to my $140 hotspots, using lower quality (cheaper) parts, for $235.

In Conclusion

So, you have those that want to sell a quality product, using transparency and reasonable prices, and then you have those who are really ripping people off. You do also have everything in-between. I have seen some sellers publicly bash home-built units, and other sellers as being inferior products. I have seen some make claims of being the greatest thing since sliced bread, when in reality it’s just another MMDVM hotspot.

So, just be careful in your purchases, and PLEASE consider building your own. It’s not that hard, and you can always email me for help if you do!