Wireless HC-12 what is the best antenna for following use

Thread Starter

dcbingaman

Joined Jun 30, 2021
493
I have two HC-12 modules being used for wireless communications at 433Mhz. One station is in a building (wood frame house) and the other is stationary in a small enclosure made of plastic about 400 feet away. This is for a wireless weather station app. Both the transmitter and the receiver are at fixed locations. I had trouble using the included 'coil' antenna that came with the module. I replaced it with an 8 inch wire standing up vertically on both units connected to ANT2 through hole pad on part. This allowed for communications but still had some fairly significant error rates. When I move the outside module to within say about 200 feet everything works properly.
My question:
What is the best antenna option for a setup like this? There is a mini-coax antenna connection also available on the part. Would it be better to use that with an external antenna and if I can is there a limit to the length of the coax to get to the antenna? I was thinking of placing the antenna on the outside of the house with a more direct line of site, but I am not sure how to use the onboard mini SMA connector and what antenna to use? Any help appreciated! I have attached the datasheet for the HC-12. I am using FU-3 mode at 9600 baud.
 

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Yaakov

Joined Jan 27, 2019
3,735
Something like this: https://www.amazon.com/433mhz-Antenna-Connetcor-Female-Cable/dp/B07DDF5YCJ/ could be good but you have to be sure the antenna is actually resonant on 433MHz. A lot of these antennas are simply not operational in the frequencies they are labeled for.

It's a bit of a rabbit hole, but you might want to invest in a NanoVNA https://www.amazon.com/【Upgraded】AURSINC-Analyzer-Measuring-Parameters-Standing/dp/B07Z5VY7B6/ to actually measure the VSWR over the band in question. I have the one linked and it works quite well. It's surprisingly cheap given what it can do, and while there is a learning curve you don't need to know or use all the functionality to get a lot out of it.

There is a lot online about NanoVNA, how it works and how to use it, so you can learn it pretty quick. It could also help you build your own antenna, including a small Yagi-Uda directional antenna that might work very well for you.
 

nsaspook

Joined Aug 27, 2009
8,894
The standard normal mode helicals should work with a clear radio path using good transceivers. Be sure you have good modules.
 

Yaakov

Joined Jan 27, 2019
3,735
The standard normal mode helicals should work with a clear radio path using good transceivers. Be sure you have good modules.
A lot of the supplied antennas are trash and a mismatch will completely take the modules transmitter, so it could just be the antenna.
 

Yaakov

Joined Jan 27, 2019
3,735
I have two HC-12 modules being used for wireless communications at 433Mhz. One station is in a building (wood frame house) and the other is stationary in a small enclosure made of plastic about 400 feet away. This is for a wireless weather station app. Both the transmitter and the receiver are at fixed locations. I had trouble using the included 'coil' antenna that came with the module. I replaced it with an 8 inch wire standing up vertically on both units connected to ANT2 through hole pad on part. This allowed for communications but still had some fairly significant error rates. When I move the outside module to within say about 200 feet everything works properly.
My question:
What is the best antenna option for a setup like this? There is a mini-coax antenna connection also available on the part. Would it be better to use that with an external antenna and if I can is there a limit to the length of the coax to get to the antenna? I was thinking of placing the antenna on the outside of the house with a more direct line of site, but I am not sure how to use the onboard mini SMA connector and what antenna to use? Any help appreciated! I have attached the datasheet for the HC-12. I am using FU-3 mode at 9600 baud.
By the way, it you want to put the antenna outside you would be better off putting the module and antenna outside and run data in. The losses in the feed line would eat up any gains from a "better" antenna. You really want to keep the feed line as short as possible. The losses in miniature coax are prodigious.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
493
Something like this: https://www.amazon.com/433mhz-Antenna-Connetcor-Female-Cable/dp/B07DDF5YCJ/ could be good but you have to be sure the antenna is actually resonant on 433MHz. A lot of these antennas are simply not operational in the frequencies they are labeled for.

It's a bit of a rabbit hole, but you might want to invest in a NanoVNA https://www.amazon.com/【Upgraded】AURSINC-Analyzer-Measuring-Parameters-Standing/dp/B07Z5VY7B6/ to actually measure the VSWR over the band in question. I have the one linked and it works quite well. It's surprisingly cheap given what it can do, and while there is a learning curve you don't need to know or use all the functionality to get a lot out of it.

There is a lot online about NanoVNA, how it works and how to use it, so you can learn it pretty quick. It could also help you build your own antenna, including a small Yagi-Uda directional antenna that might work very well for you.
By the way, it you want to put the antenna outside you would be better off putting the module and antenna outside and run data in. The losses in the feed line would eat up any gains from a "better" antenna. You really want to keep the feed line as short as possible. The losses in miniature coax are prodigious.
In that case I have two options:
1. Run a USB 2.0 cable from inside the house to outside to the module. The module includes a USB 2.0 UART powered by USB power then connected to HC-12 also using USB power.

2. Send only the TX/RX along with 5V USB power and ground via a cable from the USB 2.0 Module to the HC-12 module. Being that it is only running at 9600 baud, I would not think the cable would cause much of an issue.

Not sure which is better. Appreciate the help. I do believe I am going to end up running a cable to the antenna and module which could be on the roof of the house. Where the cable would carry USB 5V power, TX/RX and ground.
 

Yaakov

Joined Jan 27, 2019
3,735
In that case I have two options:
1. Run a USB 2.0 cable from inside the house to outside to the module. The module includes a USB 2.0 UART powered by USB power then connected to HC-12 also using USB power.

2. Send only the TX/RX along with 5V USB power and ground via a cable from the USB 2.0 Module to the HC-12 module. Being that it is only running at 9600 baud, I would not think the cable would cause much of an issue.

Not sure which is better. Appreciate the help. I do believe I am going to end up running a cable to the antenna and module which could be on the roof of the house. Where the cable would carry USB 5V power, TX/RX and ground.
I do think remoting the module is the best bet. A weatherproof enclosure should be pretty easy. A good antenna is still important, but it will work better outside.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
493
Something like this: https://www.amazon.com/433mhz-Antenna-Connetcor-Female-Cable/dp/B07DDF5YCJ/ could be good but you have to be sure the antenna is actually resonant on 433MHz. A lot of these antennas are simply not operational in the frequencies they are labeled for.

It's a bit of a rabbit hole, but you might want to invest in a NanoVNA https://www.amazon.com/【Upgraded】AURSINC-Analyzer-Measuring-Parameters-Standing/dp/B07Z5VY7B6/ to actually measure the VSWR over the band in question. I have the one linked and it works quite well. It's surprisingly cheap given what it can do, and while there is a learning curve you don't need to know or use all the functionality to get a lot out of it.

There is a lot online about NanoVNA, how it works and how to use it, so you can learn it pretty quick. It could also help you build your own antenna, including a small Yagi-Uda directional antenna that might work very well for you.
If I continue to have issues after placing the module on the outside of the house, I may consider ordering that item. You are correct that specific model is reasonably priced for my budget.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
493
I do think remoting the module is the best bet. A weatherproof enclosure should be pretty easy. A good antenna is still important, but it will work better outside.
Thanks! I am going to proceed to implement that. I plan to use CAT-6 cable for the cable. I will run 5V USB power and ground along with TX/RX to the module. The cable could end up fairly long. But should not hurt anything at 9600 baud.
 
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