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Joined: 31/12/2012
Location: New ZealandPosts: 9995
| Posted: 01:28am 01 Nov 2022 |
Yes, I have used the external antenna socket on the HC12 a couple of times, and it can allow for stella performance range-wise.
If you have a node outside, up a pole in a weatherproof box, just a standard helical soldered to the usual ant connection will still provide excellent performance, simply cost elevation will do wonders for your range.
I do have one install where I specifically used those little sockets and adaptor cables etc, so I will try to find the photos I took, and upload them here so you can see the arrangement.
As far as antennas per-se', it really is something of a designer/builders choice to some extent. Pretty much any 433MHz antenna will work well, so long as you keep the HC12 module inside the 433MHz band they are designed for.
I have found through trial and error, that the longer length ones work SLIGHTLY better inside then the shorter ones do, and outside up a pole, even the short ones work superbly well - basically cos you have a matched antenna connected to the module, with all but the enclosure material removed in way of obstructions.
For external(to the module) antennas, I use IPX-to-SMA adaptor coax leads, which allow you to easily fit any of the plethora of SMA antennas to the HC12. Leads such as these ones - be VERY sure you get the correct type of SMA connector. Most SMA antennas have a male plug on them, so you should be looking for a IPX-to-SMA female adaptor lead, naturally, but SOME antennas use a female plug and a male socket, so you need to be careful not to get caught by that. The link I supplied allows you to buy either gender and various lengths of coax.
If your transmit AND receiving nodes are outside up poles, more then 2km can be expected if you use FU4 mode. I got out to well over 5km using that idea, with the base station receiver node on a pole on the roof coupled to a standard UHF masthead TV amplifier, and then into the HC12(base was receive only), and me with the transmitting node on a pole I was holding on the side of the hillside overlooking my town. To get the SMA into the masthead amp, I used SMA-to-F adaptors(link), allowing me to connect the HC12 directly to the output of the masthead amp, and the input to the amp was fed from a 434MHz base-loaded-whip antenna with SMA plug and low-loss RG58 coax. LINK
This test was line-of-sight though, with no obstructions at all between them - just the airwaves.
The HC12 is a really amazing little module though - provided you get the genuine article!!!
If I can be of any further help, please do post back. I have done lots of work with the HC12's now, including the above kinds of setups, so if I can give back anything of use to others wanting to do this kind of thing, I would love to help.