goTenna Mesh community

Device- all in one?

Hey GoTenna,
Can you make an all in one texting device?
A simple 900mhz transceiver with a built in keyboard that’s compatible with the Go Tenna Mesh?

5 Likes

I agree. It should also have a GPS and WiFi chip built in so it can do network relay without a needing to be connected to a smartphone. Other must have features would be a replaceable battery, auto reboot capable firmware, and an SMA external antenna connector.

3 Likes

Sounds fun.

I’ve been looking at https://m5stack.com/products/face for a similar project.

If you could get the M5 to read the Bluetooth of the Gotenna you could maybe make a device?

I’d like to keep it small, but my preference would be for the next version of Gotenna to have an e-ink display that can display the device ID, so that even without being paired to smartphone, we can test ping the relay.

And if an SMA external connector can be added that’d be crazy terrific. :stuck_out_tongue:

I hate when I have to bring this up, but a SMA connection for a detachable antenna is pretty unlikely barring a change in FCC policy for the band (900 mHz ISM band) that the GTM operates in. The FCC requires that the device NOT have any easy way to swap in an alternate antenna. This is done to limit the effective radiated power to no more than specified. Adding an antenna with higher gain would allow that and thus is the reason why the FCC imposed this rule. It’s not specific to the GTM but to the classification the FCC certifies it under.

1 Like

Your post reminded me that I have heard this before as well. You’re right.

Ah well. If a version 2 comes out of Gotenna Mesh I certainly would want it to continue to mesh with the current model.

While annoying, the lack of a detachable antenna really doesn’t handicap the GTM. The fractal internal antenna helps with a compact form factor while limiting any damage from antenna connections, the leverage of an external antenna on that, etc. When placed at a high location that suitably overlooks the service area, coverage extends for miles.

People tend to think of an external antenna as greatly altering coverage. They can help. However, addressing issues like lack of range or coverage by swapping out the antenna doesn’t tend to work all that well with these issues with conventional radio coverage areas. I suspect that, like those, an external antenna really only helps with fringe coverage.

The two biggest factors affecting coverage with the GTM are height and adding relay nodes. Improve on those and the lack of an SMA is pretty small potatoes in comparison.

Um, a cheap Android phone (no SIM) and… duct tape?

1 Like

I built an all-in-one using a Moto Z play and the Mesh developer mod. The convenience factor was huge, but range suffered bad. Anything more than 1,000 feet relayed through the stock Mesh hanging nearby. I am willing to sell it if someone is interested.

For me, the ideal would be a classic flip phone with a retractable antenna (not removable, so should satisfy FCC regs), running a fairly basic goTenna firmware and not a full-blown OS. Lightweight, low-power, and small with an E-ink screen.

1 Like

instead of detachable antenna, it could have a extendable built in antenna like some Nextel phones to make it legal to the FCC.

2 Likes

It’s possible that an extendable antenna might pass FCC scrutiny. An external extendable antenna will likely cost more to produce than the internal fractal and is subject to being broken. Thing is an extendable antenna may perform no better than the internal fractal antenna. In any case, the FCC will limit it to the same ERP as the current design, so I suspect that it would yield pretty much the same results as the current design.

Which doesn’t mean it can’t happen anyway. I can see that for marketing purposes an extendible antenna could be perceived by consumers as more powerful, like the oftentimes fake hood scoops on certain cars, so thius could make the GTM more desirable.

That’s exactly what I had in mind. I think a weaker radio with a better antenna would perform better than a strong radio with a crap antenna, given the same ERP. It at least should receive better.

If not extendable, then at least a nub antenna as was common before antennas were fully internal to phones. I just know the fractal antenna on the GTM is significantly hampered by the phone itself.

The FCC has allowed many unlicensed devices with external antenna connections including SMA to operate on the 900MHz ISM band.

Here are a few examples:

Sonnet Mesh: (900mhz, 1 watt, removable antenna) https://www.indiegogo.com/projects/sonnet-game-changer-for-wilderness-communications#/

Helium Hotspot: (900Mhz, 1 watt, removable antenna)

https://www.helium.com/technology

Motorola DTR700 Licence Free Digital Two Way Radios: (900Mhz, 1 watt, removable antenna) https://www.motorolasolutions.com/content/dam/msi/docs/business/_documents/specifications/dtr600_700_spec_sheet.pdf

DuraFon long range SIP Phone System: (900mhz, 708 milliwatts, removable antennas)

All kinds of drone wireless controllers use 900MHz with SMA external antenna connectors.

Even old Nextel direct talk 900MHz walkie talkie cellphones had connectors for external antennas.

Heck there are even new cellphones that offer 900MHz license free walkie talkie modes that have 1 watt & external antenna connectors:

Sonim Direct Mode for XP5s (900MHz, 1 watt, external antenna connector)

It would seem that GoTenna Mesh could certainly get FCC approval for a device with a external removable antenna/connector considering so many other companies were able to secure such permission.

Well, maybe. There is no short, simple answer to this. The main issue is that ISM use of the 900 Mhz band is a secondary use and that there are other users on the band which these users (including goTenna) are secondary uses. Things like the restriction on removable antennas are intended to achieve this.

Here’s one reference:
https://www.itu.int/net/ITU-R/terrestrial/faq/index.html#g013

You have to read between the lines a bit here. Someof the cases you’ve cited are devices that were produced under an older set of rules - remember the MotoTalk or whatever that someone thought should justify a longer antenna? - or are currently produced under a different category of 900 Mhz licensure that permits it. The military, radio amateurs and others all have such access. But yes there are some that do state specifically that they are produced as 900 Mhz ISM devices.

So there could’ve been a recent change in this that might allow future iterations of GTM. That said, the current generation was produced under a restrictive set of rules that did not permit it.

That said, there are other reasons why a external antenna isn’t the first choice of designers even if permitted. An external antenna on a device of the same form factor as current GTM have would make for a rather ungainly near doubling of the device length and would be subject to breakage that might seriously affect the case. And as I’ve noted, a longer antenna produces more modest benefits than is expected and generally only on the edges of coverage.

In reading through some of the documentation, another solution is suggested at several points and that is that manufacturers may have managed to incorporate a way to effectively limit max ERP no matter what antenna is attached, which would satisfy the FCC. The Sonnet is a good example, as like the GTM it says it limits output according to the jurisdiction it happens to be in. In that case, an external antenna may suggest higher performance, but would be limited internally on how much improvement is achievable no matter what it’s attached to.

Perhaps the big takeway is that there are a number of competing devices that have either recently become available or will be soon that offer new and enhanced feature sets vs the GTM. As with most things in life, a little competition is good incentive to improve your own game. I can see such a change for a dedicated relay version of the GTM, if that is now permissible, but I still have a lot of reservations about this on units intended to have the same minimal form factor as the current GTM.

At one time the FCC rules allowed external antennas with “non-standard” connectors… typically “reverse polarity” TNC or SMA which by now are pretty… standard. Too easy to bypass, so the rules were updated. The intent is to limit ERP so as to share the band fairly, which I’d not quite what is being accomplished by using high-gain antennas.
Kinda like, “highway speed limits should apply to everyone… else.”

1 Like

At least 2 of the devices I mentioned above have external antenna capabilities, operate on 900MHz, output is 1 watt RF, & they have FCC approval for non license operation. Helium hotspot and Sonnet Mesh.

It’s possible some of the FCC’s boundaries have changed on this martter subsequent to their approval of the GTM. Check the FCC docs to see about the dates of test certification.

So this does make this possible as an option, presuming all others things between the devices being equal. Which they may not be.

Assuming it’s possible to now make the antenna removable, that’s only the first step. A new device would need to be engineered, submitted for testing and then be subjected to the FCC certification process. The process itself is not cheap. I would not think such costs could be justified simply to add this feature to the existing design. It would have to be part of a larger package of improvements/upgrades to redesign the GTM.

Beyond the need for certifying to suit the FCC, the device itself in its current form isn’t really suitable for supporting use of an external antenna. It would tend to be top heavy, if just sticking a new antenna on top of the current case. I’d imagine a rather short stubby antenna, given the band and concerns that it could make consumers feel it was a more clumsy package. Such a connector could potentially add a lot of leverage to the area around the SMA or whatever connector was used, making it easy to break.

For the vast majority of users, it might even be seen as a net negative, which could end up hurting rather than sustaining sales. As a radio geek myself, I understand the desire to fiddle with new antennas easily and can see the usefulness of having a detachable antenna. But I know that most folks don’t have that passion who are likely consumers. This is not a Ham radio.

Left unmentioned so far is another potential negative to a detachable antenna. That is the potential to destroy the radio’s output transistors due to high SWR if the antenna isn’t installed properly before transmitting. From failure to read and understand the instructions on purchase to simply forgetting to attach the antenna before use, this could vastly complicate a pretty darn good warranty program. Did the consumer properly install the antenna so it’s not a factor in a warranty claim?

Thus my position that, if it is possible to add this feature, it should be to a version specifically configured for use as a relay. It would be useful to have the option of adding a directional antenna to better link remote relays, for instance.

This is related to my concerns about the viability of such a feature for consumers. It may be perceived as a way to vastly expand the device’s range, but it’s not likely to be a very dramatic difference. Most antennas suggest a gain of ~3 dB or maybe a little more. That provides a gain that is about twice the original power. However, this is a logarithmic scale, so as one of my antenna theory books states, “there would be only a slight, barely noticeable increase in the loudness of the signal. The transmitter power would have to be increased ten times…before the signal would sound twice as loud.” That is why I argue that the improvements possible are mainly noticeable in a limited area at the fringes of a meshed area. This doesn’t help much when you’re well inside the mesh, especially in dense urban areas and places where the topography is a big factor in reducing signal strength.

For 30 years low end handheld Ham radios have had high swr protection circuits.

Directional antennas exist that go waaay beyond 3db gain. Also 5/8 wave and other omnidirectional antenna designs like a J-pole would vastly outperform the internal antenna for stationary nodes.

A much smaller antenna connection could be used that could fit inside the USB port area. Not for portable use antennas. Just for enhancing stationary relay nodes. By connecting the external antenna the internal antenna would be deactivated.

Yep, those are all potential solutions, but I think also design problems in order to put improvements in place that will retain the functionality of the current system, if the FCC is in fact now amenable to such changes. Some will add to production costs, but hard to say that they will significantly affect street price.

Certainly, there are plenty of antennas that go beyond 3 db gain. What I had in mind is what the average consumer would use/tolerate/not tend to break, which would be supplied with the radio, most likely something rather stubby. I like your idea of retaining and defaulting to the internal fractal antenna, while adding the option of using something else. In that case, no additional antenna need be supplied at OEM, while retaining the option.

.

But I still retain my somewhat pessimistic view of exactly how much improvement a detachable antenna option would provide most users. What would be good is if those who have done a hack to add a external antenna connectors did some range testing before and after the mod. and report back on what improvements can be expected. Perhaps I’m being too negative about the idea, but it matches my experience with using various consumer and business class handhelds. Alternative antennas make some difference, but to even get enough to notice usually requires substantially lengthier elements. But I have no experience with doing the same with freqs in the 900 mHz range and perhaops there’s more to “gain” there.

An issue with using a directional antenna on a relay is that this is good for linking longer distances on the fringes of existing mesh, but I think that when transmitting you’d want to still put a signal out on an omnidirectional antenna. Otherwise, the service area of that relay would be pretty irregular. One solution would be to colocate a node that provides this directional capability with another standard GTM that would rebroadcast the signals for the one with the directional antenna.