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HF Radio for data communication

brains93

Hello Guys & Girls,

 

I have an allotment which I am in the process of "making smart" i.e humidity, temperature and moisture sensors, this is all going well and to plan for the moment, but I had a thought it would be nice to have the data sent back to my house where it could be stored and processed, I was even thinking i could make a basic app to show the current or past data. This is not essential as I want the loop to be self contained i.e if it needs water it will auto-magicly open the valve to the rain water tank and pump water out to the plants without my interference needed.

 

The data collections is just a "Lets see if I can" scenario but I am quite new to the electrical building world, so I thought I would get some advice from the experts before I blow anything up. I think the easiest option would be to use a USB data dongle and a sim card to get 3/4G connectivity and send the data back that way, but where is the fun in that.

 

In one of my jobs I use a lot of radio equipment and I am fairly o fay with it, my thinking was I could set up a small radio transmitter (it would have to be 4W or below in power output in order to stay on the correct side of the law) and have it transmit Morse to a receiver at the house which will be hooked up to a raspberry pi to decode the Morse (Transmitting Morse means it should be able to go further on smaller power levels), My house is about 5 mile or so away from my allotment which I think with a bit of tinkering and testing I should be able to get a signal to the house using a sky-wave propagation method which means I need to use between a 3Mhz and 30Mhz frequency range (HF).

 

As I said I am far from an expert on any of these fields so any words of wisdom, advice, warnings or manic twitching would be appreciated. image

Parents

  • It's a great idea and you've at least thought about some options before posting ...great.

     

    Firstly I think you'll find many of the 'max power' regulations are written around radiated power which includes the aerial system.

    Having said that, you can do an awful lot with a good quality yagi antenna at both ends and UHF (433MHz) lends itself very well to that.

    Eric showed a few good examples using the RFM69 series transceivers in the Forget-Me-Not Challenge. They have a much lower receiver threshold and all the hard work is done for you.

     

     

    HF is not very useful in short distances.

    It relies on bouncing a signal off the ionsphere and varies depending on day/night. The antenna tend to be quite large as well.

    I'm not sure how you'd get on splattering the band with morse code to pass data, but I'm predicting it won't be positive.

     

    The 3G solution is also an idea. We use a similar system for getting data from remote sites. I know that TP-Link MR3020 takes a USB dongle for data, and has great features. Portable 3G/4G Wireless N Router - TP-Link

    I suspect that once it's up and running you'll want to add motion dection camera and then the 3G comes into it's own, and with the WiFi aspect you can probably link directly and whenever you're on site.

     

     

    Having your system automatic is ideal, but be aware that you might want to ensure you have a belts and braces approach to detecting that the instruction did actually work.

    I have known a simple watering system continue to water when it quite happily thought the valve was off image

     

    Mark

Reply

  • It's a great idea and you've at least thought about some options before posting ...great.

     

    Firstly I think you'll find many of the 'max power' regulations are written around radiated power which includes the aerial system.

    Having said that, you can do an awful lot with a good quality yagi antenna at both ends and UHF (433MHz) lends itself very well to that.

    Eric showed a few good examples using the RFM69 series transceivers in the Forget-Me-Not Challenge. They have a much lower receiver threshold and all the hard work is done for you.

     

     

    HF is not very useful in short distances.

    It relies on bouncing a signal off the ionsphere and varies depending on day/night. The antenna tend to be quite large as well.

    I'm not sure how you'd get on splattering the band with morse code to pass data, but I'm predicting it won't be positive.

     

    The 3G solution is also an idea. We use a similar system for getting data from remote sites. I know that TP-Link MR3020 takes a USB dongle for data, and has great features. Portable 3G/4G Wireless N Router - TP-Link

    I suspect that once it's up and running you'll want to add motion dection camera and then the 3G comes into it's own, and with the WiFi aspect you can probably link directly and whenever you're on site.

     

     

    Having your system automatic is ideal, but be aware that you might want to ensure you have a belts and braces approach to detecting that the instruction did actually work.

    I have known a simple watering system continue to water when it quite happily thought the valve was off image

     

    Mark

Children
  • in reply to mcb1

    Hi Mark,

     

    Thanks that Challenge is an interesting read and definitely gives rise to a few ideas.

    I had a chat last night with the amateur radio society in the area, lets face it these guys know more about radios than anyone at my job! They had said about the Yagi Antenna and it is definitely an option. I will probably go down the VHF or UHF route after hearing everyone's advice but in case it is useful to anyone I thought I should expand on what I was planning with the HF.

     

    The HF antenna I was intending to use was going to be a more passive approach to sky-wave i.e not a full dipole while that would be an option using 1/4λ and keeping the frequency high to shorten the antenna length there are also devices i could acquire from my work which can be set to move the height of the antenna in order to adjust for night time atmospheric changes. BUT the way I was thinking was to use an inverted V antenna.

    image

    Now Keeping the Antenna length small would be key but with a bit of fiddling and the help of a coupler this could be mounted on top of a shed and be "relatively" low footprint, I can then bring the two 'Legs' closer to narrow the beam and make it very directional (a poor mans Yagi) and due to where I live any "overshoot" of the signal would be out the Sea (and is Isle of Man/England's problem after that **Joking of course***)

     

    As I said it sounds like VHF and UHF would be far better plans but I thought I should share my thought process in case it could be of help to others image