Project : Ubitx go box with batteries (topic will be updated upon works done)


adrien.grelet@...
 

Hi there,

I'm waiting for my Ubitx to be shipped and my project is to make a small go box to be portable with no risk of breaking something on the move.

I create this topic because I'll post updates on this project to share and to give ideas for others.

The goal of this box is :

  • to be not so big to be carriable easily in a backpak
  • to have it's own energy to last about a day
  • to be also ergonomic and fun to use in the QRA (so, I'll keep some comfortable knobs)
  • to have a connection for a RTL SDR when used at the QRA
  • to be installed in a cookie metal box or something similar, but with no holes at all in the box (so you need to open the cap to use the radio, like SOTA boxes for example)
  • if possible and if it's not to big, to be able to carry also small materials like earplugs, mic, notebook + pencil, etc.
  • with an internal speaker which can be switched on or off to be able to share the contacts with my family or friend
  • with USB panel connector to connect CAT on computer a clean way

I'll use this radio at the QRA, but also for SOTA or SOTA like activations (on hills around my QRA for example) and when moving for work (that I do often) to use in hotel rooms for examples.

Box

Why do I want to use a metal cookie box ? 
 
  • it's cheap
  • it can be small (or you can find lot of different sizes at the supermarket)
  • it's lightweight
  • you can eat the cookies inside before ;-)
  • it's open source friendly, to keep the philosophy of the global project
  • it can be watertight quite easily (if there are no holes, you can use electrician tape all around the cap to have it protected from water)
  • with a metal box, you can shield the whole radio
I've in first thought thinked about a Pelicase or something like that. It's so  badass and look like terrific ! But the main problem is the size of the global case (could be difficult to fit in a bag for a 25x25cm box), heavy (beetween 800g and 1200g for the size I speak about) and could be quite expensive.

I've laying around a very nice cookie box which is about 230x230x50mm inside. I think everything should fit and the box is really not to big to fit inside my backpak I use all the time.

Battery

I've some experience with 18650 lithium cells (I've already built several e bikes with lot of them). It's quite cheap, very reliable, and easy to solder (with a point to point soldering unit that I've built).
Also, you can configure the battery pack shape as you to fit in tiny spaces.

As the ubitx is about 10W output, I think the global power should not exceed 20W when transmitting.

I'll make a 3S battery pack (3x 4.2V fully charged, so 12.6V), and I've ordered 3300 mAh cells. I'm thinking about making a 3S4P battery pack, so the capacity will be 13200 mAh.

It will give about 8 hours of transmitting time with that very simple calculations. It could be maybe a bit overkill but with that you can last a whole WE if needed. Also, you don't have to check everytime before you go if the battery is still OK.

Mics and speakers

As the idea is to have something to use at the QRA as my main rig, and also as a go box, it needs to be quite versatile on the things you can connect.

At the QRA
  • I'll often use I think a CB mic with a 6 pins connector with the PTT, so the rig should have a 6 pins CB socket
  • As I won't have some weight limitations, I'll use an aircraft headset I already have, with 6.35mm and 5.23mm jacks. I'll certainly use adapters to fit the 3.5mm standard jack sockets to avoid overloading the panel with too much sorts of sockets. That kind of headset should give a good audio quality for the ears
  • If I use the mic of the headset instead of the CB mic, I'll also need a PTT button directly on the panel to transmit

When moving
  • I'll also have the 2x 3.5mm jacks on the panel, to connect maybe a very light and small mic made from the supplied electret mic of the kit and not having to carry the CB mic if it can't fit inside the box (I don't really want to choose a bigger box just to carry that mic)
  • The internal speaker could be used outside (I've salvaged a 8ohms 5W something like 60x60mm speaker from an old CB radio)
  • Or I can connect earplugs on the 3.5mm jack and switch the internal speaker of if needed

Antenna

The main panel will have a PL259 socket to install all sort of cables or antenna.

At the QRA

I'll certainly use an endfed antenna system, connected with a coax cable like the QRPguys end fed system which is simple : https://qrpguys.com/qrpguys-end-fed-wire-antenna

When moving

  • I've ordered a Watson ATX Walkabout MK2 which should give me (even it's not the best efficiency) a simple way to connect directly the antenna on the PL259 socket and have it attached to the rig
  • maybe a small tuner for wire antenna like this one if I can deploy wire antenna : https://qrpguys.com/multi-tuner

So, what do you think about that ? It's not easy and also not a good idea to think about making a "do everything" rig, it's matter of compromise.

I think with this setup it will be still quite carriable and also fun to use at the QRA.

Stay tuned for the next part : the CAD design to fit everything in the box !

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