Weather Ready Relay Node


#1

Good morning from Kansas City!

Last night, I acquired a few of my Amazon Wish List items for my birthday, and upon returning home, immediately got to work on a little project. This project was inspired by very similar ones I’ve seen here on the forums, but I wanted to share.

Build Time
About 20 minutes, most of which was spent getting the foam cut correctly.

Product List

Construction

  • The only thing that really requires any work is the foam, which must be cut down to snuggly accommodate the battery, the charge cable, and the goTenna mesh node (behind the battery).
  • I left the perimeter foam in place, and pulled out the section I needed for the battery first. Since the battery is only about half as thick as the foam, I cut the battery foam section in half length-wise. This left a “bed” of foam the battery would sit on.
  • In the new “battery bed” and remaining foam, I removed space to run the charge cable, and space for the goTenna unit itself. This took a little eyeballing, but was simple enough.
  • Once the foam was ready, I placed the goTenna mesh node with charge cable attached, then the solar battery over the top, and that’s it! The foam keeps everything in place very nicely.

Note
I have not had the opportunity to do range testing on this setup yet, but expect decent performance once I get it mounted above the roof of the Emergency Operations Center (EOC) where I volunteer.

Reasoning
This is just a simple, relatively inexpensive, weatherproof housing that can be quickly deployed (or permanently mounted). With that in mind, I put this together to share with our Emergency Manager (EM) and Emergency Communications Services (ECS) team to see if we could put together some money to build these out! Hopefully, we can get some placed strategically around the city, or at least have them as Go Kits for volunteers for various deployments; like shelter operations, damage assessment in the field, storm spotting, public safety events, operational exercises, just to name a few.

Here’s the completed unit with top open to better see how it fits together.

This is the goTenna mesh unit displayed atop the pelican case for size reference.

This is what the section under the solar battery looks like.


#2

Nice.

I’m putting one together this weekend for deployment this week. I’m using goTenna’s weatherproof pouch (free with a 4-pack), a Voltaic V15, and a Voltaic 3.5 watt panel. The plan is to hang the unit in a tree at least 75 feet off the ground. I won’t be using relay mode, as I need the ability to ping it for range testing and check battery charge from the ground. Hardest part right now is finding a drone that can lift it.

With nodes in the right places, it should be possible to get comms between downtown Pittsburgh, Canonsburg, Washington, Scenery Hill, and Uniontown, but that’s still a ways away.


#3

Nice! I’d love to see any pictures you might take, to use those for my proposal to my EM when suggesting we have some of these around.


#4

KD0WNE,
Nice work!:eyes: The clear top on that Pelican case solves a couple of problems, how to mount a solar panel and how to avoid needing the holes in the cases when mounting a panel outside.

Any idea how much output you’ll get from the panel on the battery pack? I’m experimenting with these sorts of battery packs right now. I concluded most were limited in how much charge they could add to the battery pack, but that number seemed to be about as large as the GTM’s needs so it could work. Since I was using the Harbor Freight cass, no clear tops so I was concentrating on adding solar panels to the ones I’ve been playing with and not worrying about the inboard panel. Ideally, what you have there could save some expense and hassle, while making for a nice clean installation.

In thinking more about installing the GTM in such cases, I wonder if there’s a difference in RF attenuation in the plastics used that might make one type case better than others?


#5

I plan to manually charge the battery and goTenna to full, then set the entire unit in the dark to see what my Max run time is. From there, I can compare the dark run time with the device’s manufacturing specs and estimate how much the goTenna drains it. Then back to testing in outside sunlight conditions!


#6

Bbwr10’s observation about the usefulness of the PVs on those battery banks is inline with what I have found. It seems that the tech info on them is written by the PR team.
An ad hoc test for radio transparency is to microwave the case. If it gets hot, then it is absorbing RF @ 2.4GHz anyways. Be sure to put a cup of water in with it to sink the energy that the box does not absorb. Use a time and power about right for heating the water to cuppa tea temp.
KD0WNE, nice looking unit.


#7

My concerns.

  1. Heat. There is a lot of black in that sealed box.
  2. I’m not sure about that solar pack. I’ve heard most of the PV cells in those battery packs suck. You may have got a good one though.

Let us know how it goes. Battery charging will stop when the Gotenna gets too hot but hopefully even if it gets that hot during the day it will cool down enough at night to accept a charge again.

Please let us know what kind of time you get out of it and the solar region it’s placed in. Valuable info for the rest of us.


#8

I will definitely try to follow up. Got a busy work schedule ahead of me, but I’ll try to science it up as soon as I can spare the time, for sure.


#9

Updated: Put a third picture that I forgot to upload previously. Should help with understanding the basic layout I went with.


#10

“Science it up”.
LIKE.


#11

Total Dark Run Time testing began at 08:15 Central Time on Sunday 02/11/18


#12

@KD0WNE great effort.
Placing goTenna Mesh directly behind a battery pack will affect performance. The battery pack will block RF.
To maximize range performance, I’d recommend placing goTenna Mesh next to the battery pack.


#13

@Rahul_Subramany If I can find a better battery / case pairing, I intend to do exactly that. Since this is my first go, I substituted longevity versus distance. Thank you and others for the RF considerations! I’ll definitely be tinkering in the coming weeks & months to see what ways I can improve.


#14

Wouldn’t below the Mesh be the ideal spot? Possibly even a 1/4 wavelength or more.


#15

@giqcass do you mean to use the battery+Solar panel to reflect RF?
This may make performance better in one direction.


#16

I mean the battery and panel should be over 9cm below the Mesh unit. A little offset so the shadow doesn’t hit the panel. Any closer and I suspect it will affect angle of radiation but without computer modeling I don’t know if it would effect it positively or negatively.


#17

@Rahul_Subramany I’m not that sure how much effect there is at this wavelength but the solar panel and battery could act as a ground or reflector depending on position. Either way if it’s too close I expect it to mess with radiation patterns and antenna impedence matching.

http://www.qsl.net/aa3rl/ant2.html

EDIT: Not sure about the ground effect there would definitely be a reflection effect.


#18

I am contemplating installing a weather protected relay on my roof.
So far my relay node has been installed inside, by a window, but I would like to increase coverage, hence the roof.
I don’t need to go solar just yet, a big enough battery that I charge regularly would do the trick.
“Always on” battery packs are not so easy to source in Europe, so I have experimented with a Power Practical 4400 pack that I had, with an actual physical “on” switch on it.

It is rated 4400 mAh at 3.6V and was able to maintain the relay up for 7 days under the following conditions:

  • GTM and battery pack fully charged

  • Relay mode (I was able to check regularly if it was still on by pressing the switch)

  • Temperature close to 20°C (~68°F), probably close to optimal for battery chemistry

  • Not many GTM users here, so little traffic to relay

YMMV

I am planning to use a similar setup as @KD0WNE, with a waterproof box for battery and GTM.


#19

Unfortunately my testing hasn’t gone super well because there’s virtually no other GTM users in my area for my Relay to get usage. I do have to say, the battery pack that I ordered has kept my unit going in complete blackout conditions for a very very long time, so I’m confident it could deal with low-light/cloudy conditions for days on end even under use.


#20

Are you using the same setup? Any issues with heat with all of that packed nice and snug inside the Pelican Case with the Foam?