This is Part 1 of a 4 Part Article.
Part 1 covers assembling the hardware

A fully equipped Mini-Mega for about $300 and a DMR HT Radio for about $100 and you are ready, set, GO…

by Barry, K0BSB

A very portable mobile rig capable of working the world, and very transportable, Even through TSA. If they object show them the LiON Batteries which you can’t pack. It’s worked for me.

Introduction

I like taking my ham radio with me wherever I travel, by plane, train, or driving. I love letting the civilians marvel at the ease of making contacts halfway around the world, or even several hundred miles away with a nice clear signal. Have them chat with someone settling down for an after dinner drink in England, or chatting with someone fishing off the pier in Australia. I just hand them the speaker mike and let them go, after all I am still the control operator with my HT firmly in my grip. Note: If you operate outside the US be sure to register with the country whose boarders you are operating in, including the nation of registry of the cruise ship you are operating from, and get the captain’s permission as well. It’s a great recruiting tool for Amateur Radio.

This is the Mini-DHAP opened so you can see its innards:

Here is the Mini-DHAP in travel operating mode for both DMR and D-Star. Not shown is my Cell Phone which I use as the Hotspot and as a console for the Mini-DHAP running web based Pi-Star.

This is a Shark OpenSpot setup in Operating Travel Mode, a Brief case rather than a Grab ‘n Go.

So why this stuff rather than using the Shark RF Open Spot. The cost is about the same. Well I find it more flexible, if you have some parts laying around, like an older Raspberry Pi you can put it back to work. Also the Mini DHAP is a much smaller package by the time you add power, Wifi, and other stuff. Also, you may need to bring a laptop to change configuration in the field, I can use my phone for the MiniMega DHAP.

Packing a lot of gear, like I was going on a DXpedition is not my idea of fun though. Besides the comments I get from the XYL about why I need that all that Junk, especially when I remind her that luggage is generally restricted to about 50 pounds.

Packing my Toys for travel, I am down to:

a DMR/DSTAR Hotspot that is 4”x4”x2” weighing 14 Ounces with batteries.
My TYT MD-2017 (DMR) and/or ID-51A (D-STAR) HT(s) with speaker mike(s).
My phone as a terminal and/or My Jetpack Hotspot, incase I want to save my phone batteries

If I want to operate for more than a day add:

a 1.5”x5.5”x4” battery charger.
12VDC adapter with 5.5 x 2.1 mm Coaxial DC Connector for the HT & Battery Charger
HT Charging stand
2 small square Apple style wall wart AC Adaptors, or a small 6 outlet USB power with a USB3 socket to charge my laptop that uses either a 117VAC USA power cord, or a 220V EURO Power cord.
2 flat 6,000 mAh power banks^[1] for our two phones and jetpack, my noise cancelling bluetooth headphones (especially if I am flying) for listening to tunes or movies.

The whole thing fits in a trim cross body messenger bag with my Laptop, or a side pocket in my DSLR camera bag. No Muss, No Fuss! My only outside dependency is either a WiFi Connection, or a Good LTE hotspot connection to the internet is available.

Initial Parts Shopping

You can get many of parts from GigaParts including the Raspberry Pi, the DV Mega, Memory card, and Hardened Power Case. It’s more expensive that way, but you will get all the pieces together shipped to you. However the cost will be about $370, slightly more than the price of the basic SharkRF OpenSpot, but you still have to add the cost of WiFi, an internet source, power etc.

However if you purchase the pieces from various vendors you can save some dollars and a bit of hassle (read that as: get out the soldering iron!). I have included a lot of links to Amazon, It’s where I got a lot of my stuff, however that is not the only source, and the least expensive price. Prices and availability were at the time I wrote the article, YMMV.

You will need a Raspberry Pi (RasPi) a credit card sized Single Board Computer, you can use any version as long as its at least the model B if you already have one laying around. If you are purchasing one, Think about the Raspberry Pi 3 Model B+, as it has WiFi and Bluetooth on the card. but you will need to disable the Bluetooth or repoint it in the setup. It’s well documented on the here. Note: I use Amazon Prime a lot. You may want to consolidate the Amazon Orders to save on shipping. I get my Raspberry Pi’s at MicroCenter in St Louis Park^[2], they have convenient hours, and they are local. They sell the Raspberry Pi for $29.99.
MicroCenter also sell their own branded class 10 memory cards cheap $7 or $8 for either 8 or 16 Gigabyte (GB) µSD cards respectively. Ask for them at the register, when you checkout. I recommend you buy at least two cards (one for backup, more on this later). You only need 4GB for the software we are using so 8 or 16 GB is plenty. However, 32 or 64 will let you use the Pi for other functions when not using it as a hotspot, and they are also pretty cheap. Also you may want to buy an 8 or 16 GB USB Thumb Drive at the same time to save a backup copy and not take up that space on your hard drive as well.
Order the DVMega Card^[3] direct from Gus in the Netherlands (or Eric Osterberg, N0NKI– Locally his prices may vary) the Single Band UHF only for €99 / US $117) or the €135 / US $159 Dual Band UHF/VHF^[4]. Be sure when ordering to check the add wire option, or you will have to do some not fun soldering. The wire allows you to flash the firmware on the DVMega Board directly from the Raspberry Pi. It’s only one wire but the board is crowded, and you need to be careful. I did mine, but I had to get some reader glasses about 1.0 Diopter larger than I need to read.
The Case, a DHAP Mini Mega, can be ordered from Hardened Power Systems (HPS)^[5] for $99. The Coaxial 5mm External power plug disconnects the batteries from the rig when plugged in, so you can run with external power without lighting the Lithium Ion 18650 batteries on fire.
You will need a few more items for the complete setup:
- An sma antenna^[6]. I use a Maldol MH-209 SMA antenna but it is expensive about $30. However, Amazon sells a Retevis RT20 dual band stubby which is compatible with the BOAFENG BF-UV3R, Yaesu VX-1R, TYT TH-UV8R, or the WOUXUN KG-UV6D for about $12. If you have an extra stubby antenna that will fit the above radios you can save some bucks. Optionally a 90 degree SMA connector, however, finding one is an exercise left to the student. I ordered some from Amazon, but watch the sex of the connectors and pins. I ended up ordering another whole set because the connecting pins were the wrong sex.
- Battery Charger^[7]. LiON Batteries have to be charged carefully and properly or they can catch fire. You need a proper charger, one available at Amazon is $32. One positive is the 12V power adapter can be used to power the DHAP. You may want to get a plastic case for them as well since if the short they can cause a fire as well — i.e. the case of the Samsung 8 Cell phone.
- 2 or 4 Lithium Ion (LiON) 18650 batteries.^[8] It’s your choice the Mini DHAP will hold 4, required is two in series to get 6.8VDC or more. Four simply connects two series pairs in parallel for greater operating time. There is a link on Hardened Power Systems’ MiniMega Page at the bottom to Amazon to order the batteries. The ones he shows are the correct size for the enclosure and are reliable. I strongly recommend you order these, as 18650 LiON Batteries vary in size and top profiles, and may not fit in the case or the contacts. These will definitely fit the DHAP enclosure, and should give 8 to 10 Hours of operating time. A Four pack of 18650 batteries runs $18.99. LiOn Batteries can be dangerous! Do not dispose of them in the Trash, use a safe and environmentally safe disposal method.
- A 117VAC adapter^[9] to run the DHAP can be purchased for about $8, a useful but not a required accessory. Also, any power source with a 5mm coaxial plug that delivers between 9 and 36 VDC will work, if you have an old laptop brick laying around that will work.
- Having an adapter cable with Anderson Power Poles on one end and a 5 mm x 2.1 Coaxial connector is handy as well^[10] for about $1
- A 12VDC Plug also known as a cigarette lighter adapter on one end, with a 5 x 2.1 coaxial adapter on the other allows you to run the DHAP mobile without using its batteries.

If you have to purchase everything the total is about $305 complete for all the parts, including Batteries and chargers, portable 12V power, antenna, and $316 with optional Power Pole Cable. You may not want some of the accessories, or have stuff laying around in your junk drawer which will save additional funds.

Note: I had older DVMega which needed the firmware updates to work with Brandmeister instead of just D-STAR. To upload the firmware into the DVMega requires an extra step, and a patch to the DVMega Board adding a wire from the Flash Memory Write enable to an unused GPIO pin (GPIO4 pin 7 of the RPI Bus). If you order the DVMega from the link provided they will solder the wire to the board for you if you check the option box (at no additional cost).

Continue to Part 2: Programming the Raspberry Pi Click Here

73’s

Barry, K0BSB