 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Microcontroller and PC projects : A question of 433MHz antennas
| Author | Message | ||||
bigmik Guru  Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Hi there, I am looking to get some 433MHz antennae, those short rubbery black ones that pivot in all directions as well as folds down when not in use. Looks like this one.  But reading the specs confuse me and I am wondering if some sellers are falsely advertising their products (shock horror) For example here are the quoted specs.  Note that they say suitable for wireless lans. Aren’t wireless lans 2.5GHz or 5GHz? Some even state these as well as 433MHz in their specs. I wouldn’t have thought that the antenna could be optimised for all of those frequencies. Or am I wrong in that assumption? Kind regards, Mick (the big one) Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
||||
Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
Probably almost as effective as 6" of wire pushed into the socket. :) They state 7 dBi (gain of 7dB relative to omnidirectional) so these are obviously directional yet they are also omni? Lovely new invention! The cavalier attitude to resonant frequency is merely icing on the cake. :) They do look like the ones normally supplied with wifi LAN cards and routers. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
NPHighview Senior Member  Joined: 02/09/2020 Location: United StatesPosts: 200 |
Antenna design is largely black magic (and I was trained as a physicist by a WWII radar engineer who taught an antenna design class). Do you want this to be directional? See the Wikipedia article and enjoy a can of Pringles while building. My son was in high school when he decided to run a LAN party for 31 of his gaming classmates. We couldn't handle all in our garage, so I suggested that he and a friend up the street build cantennas to link our local WiFi networks. We scrounged BNC connectors from my junk box, Pringles cans from our pantries, and before long, the networks were linked successfully, and the split LAN party went off without a hitch. Live in the Future. It's Just Starting Now! |
||||
lew247 Guru Joined: 23/12/2015 Location: United KingdomPosts: 1702 |
You want one for 433Mhz  Antenna length calculator This is the best without spending a fortune on yagi antennas, or stupid fake ones on ebay Edited 2023-10-25 02:28 by lew247 |
||||
| Andy-g0poy Regular Member  Joined: 07/03/2023 Location: United KingdomPosts: 59 |
Antennas can be constructed to do all sorts of frequency ranges, some work better than others. There are very specific relationships between the length of an antenna and the frequencies that it works on. The basic length is 1/4 of the wavelength A helical antenna which is what these rubber things are, the wire wound into a spring like form, which shortens it. The shorter the less effective. You cannot beat "wire in the sky" The gain is another matter. 7dbi is the gain measured against an isotropic radiator, a fictional antenna that radiates in all directions. Antennas don't just radiation in a linear line along the ground. They radiate in a bubble sort of. So if you design the antenna with multiple phased elements in it, you can pull the radiation that would normally squirt up into the sky and push it out in a horizontal direction. The antenna is still omni directional, but rather than a bubble of RF all around it now has a pattern more like a ring donut and the horizontal radiation extends much further, so it gives gain in that direction Such designs are usually of the co-linear format. where several 1/4 wave sections are stacked and phased together. The bad news is that most of the antennas you see on ebay and such like are no good, and without the correct test equipment you will have no way of knowing. The m0ukd design is fine, but not foldable. However 433 Mhz is in the bottom section of the Amateur Radio 70cm band so if you visit an Amateur radio store and get a 70cms (432Mhz) antenna that will work fine for your requirements. It will also be a lot better than a multi band unit. Note that a lot of such antennas do dual duty as 144Mhz and 432Mhz antennas which are the two most common VHF/UHF bands. So you might have to get one that does both. Andy |
||||
PeteCotton Guru Joined: 13/08/2020 Location: CanadaPosts: 368 |
I'm not sure if it's exactly what you want - but I did a bunch of research on various antennas recently (sorry I can't share the raw data - it was for a client). However, the consensus was that yes - the cheap antenna are absolute garbage. One's marked for 433MHz where actually 915MHz etc. However, these ones topped our testing by a long way. They're the only ones I buy now. https://www.mouser.ca/ProductDetail/TE-Connectivity-Linx-Technologies/ANT-433-CW-HD?qs=K5ta8V%252BWhtbmK0n9GHtzxQ%3D%3D They're not mounted on a swivel - but there may be an option for that in the same product range. Edited 2023-10-25 04:14 by PeteCotton |
||||
OA47 Guru Joined: 11/04/2012 Location: AustraliaPosts: 926 |
Mick, I have tried using this type of antenna in the field and I think the gain should be expressed as 0.7 dBi and the SMA connector should not be reversed as in a WiFi antenna. Unfortunately the antenna did not stand up to the wildlife and the birds dismantled them to reveal that they only consist of a length of wire in a plastic tube. I replaced them with stainless steel whips and in cases where I needed more gain small yagis. Hope this helps OA47 |
||||
| DaveJacko Regular Member Joined: 25/07/2019 Location: United KingdomPosts: 76 |
Anyone know anything about sleeve dipoles? seem to recall a nice donut shaped field around these. simple to construct, and possibly easier to deploy than the quarter wave ground plane have I seen these atop taxi ranks ? |
||||
TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6099 |
Wet blanket time. Last time I checked, in Australia the regulations for these types of transmitters was based on EIRP or Equivalent isotropic radiated power. This means that if you use an antenna with any reasonable gain, you are likely to be putting yourself over the legal limit. Not a problem if the antenna is only used on a receiver, but transmitters are a no-no. As an aside, a yagi style TV antenna (UHF band IV) can often be used 'as is' with good results. For omni directional, I like 3 5/8ths in phase. Jim VK7JH MMedit MMBasic Help |
||||
| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Hi All, Thank you for the responses, it seems that I was correct with my suspicion that these sellers are taking us for fools to suggest the antennae can work (and perform) on bands as far apart as 433MHz and 5GHz. To fill in the blanks, what I am working on is a hand held unit that has an HC12 inside the module that will be ‘sandwiched’ between the PCB and a TFT so I want to poke the antenna outside of the enclosure. I could have the little spring antenna sticking out but it would be prone to catching on things (and possibly snap off) so I was thinking one of these will be more robust but if they are crap then there is no point in using them. @PeteCotton, Thank you for the mouser suggestion, that might be my best option. Another thought is mounting the spring antenna flush along one edge of the enclosure but how much would adding 10mm or so (maybe a bit less) of ‘extension’ wire from the HC12 module (at right angles) to the antenna attached to the external spring, or should I use shielded coax from the module to the antenna to minimise the extra length on the antenna.? Sorry for what may be dumb questions but radio is all relatively new to me. Kind Regards, Mick Edited 2023-10-25 22:09 by bigmik Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
||||
| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
Amateur radio antennas for the 70cm band are what you want to look for. They will be close enough in the "rubber duck" format. You won't get great range with this design, especially when handheld. Expect to pay a bit more than typical ebay / AliExpress prices though. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
||||
| Andy-g0poy Regular Member Joined: 07/03/2023 Location: United KingdomPosts: 59 |
|
||||
phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
... or let it dangle from the bottom of the box for a bit more range. A vertical antenna doesn't have to point up. Start with 5/8 wavelength and if that gives more range than needed trim it to 1/4. |
||||
| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
Hi Andy, All, I am sure, for MY use the included spring antenna would be fine but I was looking for a more rugged (and ‘professional’ look) and I am sure the spring antenna would get snapped off with my box lying on the desk. But I am also looking to have the PCB on offer for others and want to include ideas and options for the antenna. Others may want to use it in locations that are much larger than my modest home. I looked seriously at Pete cottons mouser antenna but I found THIS ONE on RS and I trust them to not lie about the specs like the fleabay sellers. They were only about $8AU ($5-6US) each so I purchased a couple to play with. It is not the fold down I would have preferred but it is only 58mm long and is indeed very rugged. @Andy, My device (currently has the moniker of UtilMite) is in a clam type case 125mm x 80mm x 32mm and I have designed a PCB that neatly fits to this case. I also have a 4” ILI9488. TFT that almost fits in between the four shell securing posts. When I say almost, I had to sand the 4 corners down at 45 degrees so that the flat is about 3mm across. You can just nip them with side cutters. As I said it almost fit as it was. But once the corners are sanded it fits in snugly and no sideways movement can occur. I have milled out the top half of the clam shell to create an opening for the screen. Between the PCB and the TFT there is no/little clear area to hide the antenna in that the innards wouldn’t screen to one extent or other. That aside a 17cm length of wire could be run around the inside of the shell and may be one option for future builds. For this first build I will use the 58mm stubby antenna listed above. Thank you for all of the advice, it proved that what I thought about the online sellers on Fleabay was correct and they were effectively lying about the specs of their antennas. It reminds me of the early(er) days of wifi when I bought a bunch of USB dongles that had a rubber stick ‘antenna’ sticking out of the module, as I thought these would be better than the plain units. I broke one apart and there was nothing in this antenna, it was a plain rubber sleeve with no electronics at all. SCAMMERS. Thank you all again. Kind Regards, Mick (the big one) . Edited 2023-10-29 08:08 by bigmik Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
||||
 Print this page |
