Radio Modem Telemetry System (APRS?) - Page 1
Forum section: electronics / rf-microwave

author: rvalente
author_rank: Frequent Contributor
timestamp: August 14, 2019, 10:45:36 pm
content: Hello Friends,so this need came to me. There will be shelter for water quality analyzes in a tailing dam, the results + alarms make around 60 bytes packets, the data needs to be sent 10Km away, in a forest and mining environmenthttps://www.google.com/maps/dir/-6.0832673,-50.1469525/-5.9768152,-50.1412973/@-6.0238625,-50.1404607,17156m/data=!3m1!1e3There is no gsm coverage and I do not want to use satellite comms (expensive). I've checked some campbell scientific spread spectrum radios, but they need to be on visual levels to workSo as an HAM operator that never used APRS, thought about using some motorola or icom commercial radio to send this data over.I have local power, there is no problem supplying the radio, my first thought was on motorola DGM5000 VHF radio. I do no want to develop anything, but apply FCC/Anatel approved stuff.Does anyone have a experience with this?

author: fourfathom
author_rank: Super Contributor
timestamp: August 15, 2019, 01:17:31 am
content: Do you have solid line-of-sight between transmitter and receiver? If not, VHF will be a challenge. If you do, you might look into commercial 900MHz wireless bridges used to deliver internet to remote locations. 10km is easy if you have a good path, and you get a simple ethernet interface at both ends. This gear is also available on higher frequencies that should still cover the distance. Generally no licensing is neededIf you need non-LOS radio, you will be looking at HF radios. Your data is 60 byte packets, how often are these packets be sent? Do you need guaranteed delivery (implies some sort of ACK/NAK transceiver protocol) or can you lose the occasional packet without causing trouble (implies one-way transmission with forward error correction or simple redundancy)?(I've got some ham radio experience, but nothing commercial.)

author: rvalente
author_rank: Frequent Contributor
timestamp: August 15, 2019, 05:53:59 pm
content: Hello,i'm not sure if I have a line of sight or no, I've not yet been in the location, can google maps help me with this Isopleths?The 60 bytes packet will came every 10s or so, the results from the water quality are ready every 40 to 60 minutes, them the 10s interval is for alarms.For the 900Mhz modem, do you have suggestions? Ive checked some stuff from DIGI, other makers?As for using the commercial radios, do you have any experience with telemetry on Motorola Mototrbo or similar?

author: fourfathom
author_rank: Super Contributor
timestamp: August 15, 2019, 06:28:09 pm
content: Quote from: rvalente on August 15, 2019, 05:53:59 pmGoogle maps has (somewhere) a feature you can use for line of sight mapping, but I haven't played with it in a long time. Beware of trees though, and diffraction from intervening hilltops, as these can all impact the signal. At some point you will have to do an on-site survey (just eyeballing it may be good enough).Your data transmission requirements are very easy. If you do have good LOS, you might consider the wireless radios from Microtik or Ubiquiti for an ethernet connection:https://mikrotik.com/products/group/wireless-systems(all 2.4 GHz and up, but many of these can easily support your range.https://www.ui.com/products/#airmaxI've not used these myself (at least not the current generation of products), but I do see them in use.But for non-LOS links these aren't going to help. I know how to set up a ham radio HF data system, but am not familiar with the commercial options.

author: denverpilot
author_rank: Regular Contributor
timestamp: August 15, 2019, 10:51:33 pm
content: When you say 60 byte packets, in what format do they leave the monitoring system?Definitely doable if you have the RF path. Don’t even need the full path. MAX.25 “technically the A isn’t right since its not amateur but the protocol is the same” over cheap-ish commercial radios at low data rates and half duplex is commonly done for all sorts of serial data alarms.One local security alarm company in my area uses an ingenious little converter that takes a MODEM input from GE burglar alarm panels that used to need a phone line, tosses those into serial format and shoved them into a typical AX.25 packet and out to a UHF radio.The receiving end is a mountain top (more than one for coverage and reliability/redundancy) that’s just digipeating the packets down to the actual receive point in the city which does the reverse and sends the data into the alarm monitoring company.I don’t know brands or whatever on the gear but you don’t even need the simulated telephone modem, and there’s a ton of commercial radio shops who could design this for you with whatever gear they’ve been using for decades and trust.Not a “new” problem I guess is what I’m saying. Just a niche so you’d need to talk to a commercial radio engineer at a decent sized shop. All sorts of alarms that need to be passed off of mountain top radio equipment sites, etc. Your dam monitoring “telemetry” project will be quite familiar to them.

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 16, 2019, 01:50:42 am
content: What about LoRa?

author: fourfathom
author_rank: Super Contributor
timestamp: August 16, 2019, 02:33:01 am
content: Quote from: NiHaoMike on August 16, 2019, 01:50:42 amI hadn't really looked at that. Really cool! Here's a little 900MHz LoRa card from Adafruit:https://www.adafruit.com/product/3231They claim 20km range using a good antenna. And the board costs $20. Still, at 900MHz you're going to need line-of-sight or close to it anyway.There are 433MHz units available but these will not be license-free in the USA. Still LOS needed at 433MHz

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 17, 2019, 03:50:16 pm
content: Quote...So he is from Brazil what kind of Freq are there for such ISM are available?

author: coppercone2
author_rank: Super Contributor
timestamp: August 17, 2019, 03:55:45 pm
content: Quote from: denverpilot on August 15, 2019, 10:51:33 pmCheyenne mountain??

author: fourfathom
author_rank: Super Contributor
timestamp: August 17, 2019, 03:58:51 pm
content: Quote from: Lord of nothing on August 17, 2019, 03:50:16 pmApologies for my USA-centric response. The LoRa documents say there are allocations in the 900MHz band for Brazil:

author: denverpilot
author_rank: Regular Contributor
timestamp: August 17, 2019, 04:48:35 pm
content: Quote from: coppercone2 on August 17, 2019, 03:55:45 pmI believe that may be one of their sites but don’t have details.

author: coppercone2
author_rank: Super Contributor
timestamp: August 17, 2019, 06:37:51 pm
content: lol, if they are working with home security companies, maybe you can get office space to run the equipment for scientific applications like telescopes at low rent?

author: geggi1
author_rank: Frequent Contributor
timestamp: August 17, 2019, 06:43:07 pm
content: I would consider a serial port extender with a frequency range approved in your country.There are several manufacturers of this kind or equipment.