The New "goTenna"

[W0AJA]

So,

I just got done talking with the brains behind the "goTenna". Let me just say it didn't go very well.

But first, let me explain this new invention out if you never seen it before. Its a device that acts like a portable Hotspot or WiFi (But it don't connect to the internet) but connects you to the other paired device. Like ham radio, radio to radio, without internet, and no strings attached.

Back to the story,

I asked them how many watts and what frequency. The designer said they selected 151-154 MHz and when it came to the wattage, he was VERY hestient, but said 2 watts.

My next question was, "On an internal antenna with no real gain, on 2 watts for VHF, I can get 50 miles on mountaintop to mountaintop? They then wanted to end the conversation, tell me to "Checkout online RF calculators" (Which I have done in the past and no where did you get 50 miles)

It sounds like our friends at "gotenna" are to much over there head in this feeding people "You can be 50 miles apart" when in-fact it will almost (And I say almost) never happen without some nice propagation.

My question to you guys:

So, I was told the higher in frequency the higher transfer rates for data, and the lower frequency lower transfer rates, is that true?

If so, how are they doing this (Or projecting they can do it)

[KC2UGV]

Well, 2W VHF, 50 miles is unlikely. But, then again I've gotten used to the wild exaggerations of the hand held radio companies like Motorola.

Yes, as a rule of thumb, the higher you go in frequency, the faster your data rate. The only reason is a matter of channel bandwidth available, however. More bandwidth? More information.

[W0AJA]

Thanks! Thats what I thought, but they should not be bragging about this uploaded photo, with one 500 feet and one 4 feet off the ground.https://forums.hamisland.net/attachment.php?attachmentid=12743&stc=1

[N2CHX]

50 miles on 2 watts TPO is quite doable, if you have perfect line of site. Back in 2003, I built an 80 milliwatt 1 mbps data link on 2.4 gHz that went between a transmitter site and a studio in Martinsville Virginia and it worked pretty well. I sent four mp3 audio streams and a UDP link for satellite relay closures and time sync data across it.

As for frequency vs data rate, obviously a higher data rate requires more bandwidth. I restricted my link to 1 mbps because higher bitrates require more bandwidth and hence, more transmitter power to maintain the same signal to noise ratio. On VHF and UHF frequencies, there simply isn't enough bandwidth available to make it practical for anything greater than maybe 1200 baud. There are only a couple of small segments of spectrum where Part 15 regs would allow it in the US anyway. The lowest band available for high speed data would be 2.4 gHz, and there you have 11 spread-spectrum channels but they overlap. Each channel is 20 mHz wide (only channels 1, 6 and 11 don't overlap each other) and now the newer data rates require 40 mHz of spectrum and a lot more transmitter power to maintain a reliable signal.

Try finding 20 or 40 mHz of spectrum below 2400 mHz... Not gonna happen-- legally or otherwise.

[NQ6U]

I can kerchunk the Palomar Mountain 2m repeater using my 2-watt VX-2R HT. That's about fifty miles so, yes, it's possible, although I wouldn't want to rely on it in an emergency. Of course, that's with an aftermarket external whip antenna that's undoubtedly superior to whatever the goTenna is using.

[W0AJA]

Right, PERFECT line of sight im sure you can do it on 100 milliwatts, but I definitely would not rely on it for an emergency.

I would doubt there is any gain on the "goTenna", atleast no dBd gain.

[W0AJA]

That was the other thing that made me upset, is that they told me they "tested" it and it wasn't projected, but then in the same paragraph they said "we use RF calculators".

This is what is on their site:

NOTE: The ranges calculated above use industry-standard RF propagation calculators that assume ideal conditions. They are not guaranteed ranges, and can vary greatly in either direction, depending on a user’s specific environment.

[N2CHX]

That was the other thing that made me upset, is that they told me they "tested" it and it wasn't projected, but then in the same paragraph they said "we use RF calculators".

This is what is on their site:

NOTE: The ranges calculated above use industry-standard RF propagation calculators that assume ideal conditions. They are not guaranteed ranges, and can vary greatly in either direction, depending on a user’s specific environment.

OK. So why are you mad about this? Pretty much every radio manufacturer puts out specs like this. It's up to you to figure out if it will work for your application. I will say this though... This uses the MURS band and 2 watts into an antenna that short isn't going to be very efficient. 50 miles is definitely a stretch. If you notice though, the calculator they use shows 50 miles if the unit at one end is at 500 ft AGL and the device at the other end is 4 feet AGL. That's quite possible with the right modulation scheme, narrow bandwidth and line-of-sight, even with shitty antennas. Not likely to happen in the real world, but look at the packages in FRS and GMRS radios. All manufacturers advertise like this. You just have to use your head.

[N2CHX]

BTW this...

http://www.fcc.gov/encyclopedia/multi-use-radio-service-murs-0

[W0AJA]

Right KKM but what made me and my other friends sketchy is that they said they tested it in real-world applications but then use the projection to "CYA"

It sounds (To my friend and I) they cannot trust it themselves and they have to use the "Projection" as a safety net, which isn't right to the customer.

[W0AJA]

BTW this...

http://www.fcc.gov/encyclopedia/multi-use-radio-service-murs-0

That would make sense, but here is another question. Are they allowed to use MURS for a product that is CONSTANTLY transmitting data signals, because that means the MURS frequencies will just be jammed with data signals (Assuming they use FM like they should).

[N2CHX]

Right KKM but what made me and my other friends sketchy is that they said they tested it in real-world applications but then use the projection to "CYA"

It sounds (To my friend and I) they cannot trust it themselves and they have to use the "Projection" as a safety net, which isn't right to the customer.

Like I said, no different from any other device manufacturer. How many times have you used an FRS radio that is advertised to work "up to 15 miles" and actually EVER had one work up to 15 miles? Theoretically, they should work up to 15 miles under ideal conditions... Ideal conditions would be two mountaintops 15 miles apart in the middle of the desert. They're not lying, but most people won't be using them under those "ideal conditions."

[N2CHX]

That would make sense, but here is another question. Are they allowed to use MURS for a product that is CONSTANTLY transmitting data signals, because that means the MURS frequencies will just be jammed with data signals (Assuming they use FM like they should).

I would assume these devices won't be transmitting constantly. You can't send voice over them, they're just for text messaging. They're going to send packets back and forth to each other, presumably using some type of QAM modulation. I would assume that if the FCC gives them type acceptance, they will work within the regulations for that band.

[KC2UGV]

That was the other thing that made me upset...

Not wanting to burst the enthusiasm bubble, but take a chill pill man. No need to get up in arms at every perceived conflict. Choose your battles, and save your anger for better targets. Then, you'll be much happier :)

That, and you have access to huge slices of spectrum in the microwave range, and plenty to play with in the VHF/UHF band.

[NQ6U]

It's possible to take the power supply and tube out of a cheap microwave oven and use it in the 2.4 GHz amateur radio allocation. You can send a shit-ton of data at that frequency.

[K7SGJ]

It's possible to take the power supply and tube out of a cheap microwave oven and use it in the 2.4 GHz amateur radio allocation. You can send a shit-ton of data at that frequency.

While cooking your weenie.