Body mount "puck" antennas 433MHz

[nali]

I'm looking to source a body-mounted "puck" type antenna for use at 433.92MHz. These are often used for M2M use, about 50-80mm diameter, and look like this:

Trouble is, most of them are rubbish! They are more often than not a helical spring wound to be resonant, but drift massively and generally perform about the same as a wet piece of string. I know that cramming a 70cm wavelength antenna into such a small form factor is a compromise in the extreme, but these really are dire. Here's one I cracked open:

This one is sold as a true omnidirectional. My ass!

I've only found one to date that really works, which is made by Linx. But that's now obsolete which is a real shame as it looks like some effort has been put into the design, and as I say it actually works and is fit for purpose.

So does anyone here use such a thing? This is for a commercial offering so not interested in DIY. Whip, stubby, rubber duck not suitable because of vandalism concerns. From the generally-availiable brands (from Mouser, Digikey etc) I've so far eliminated RF Solutions, Siretta, Taoglas.

[Gribo]

Look for NMO Base antenna, something like this (I don't know this one):https://www.2j-antennas.com/antennas/single-external-antennas/2j7715b-433-mhz-ism-screw-mount-ground-plane-dependent-antenna/390]

[richnormand]

Interesting Gribo. I get this message clicking on your link... from Ontario
"about:blank#blocked"

But using VPN in the US its OK.

Anyway note that the antenna is ground plane dependent. OP talked about body-mounted.

Unless I misinterpret the use of "body-mounted" in that context of machine to machine communications it might depend a lot on its location.

[nali]

The URL tag is broken, it resolves to "http://[url" here (Firefox, Win11)

Anyway, this is a very small (compared to wavelength) GP. It's receive-only and would be fitted to electronic displays such as kiosks or more commonly small TFT  or LED matrix displays fitted in bus stop shelters or terminus gates. The flat "puck" form factor is pretty much a requisite unfortunately as anything which protrudes significantly isn't suitable. The whole thing is a compromise, but it's a legacy system and we need to live with it the best we can.

The Linx pictured above (and a long-defunct Abracon which is similar) look like they've been designed with a ground plane in mind as they are stood off from the mounting surface by 20mm or so, so I'd say the GP is also acting as a tuning capacitance in this case. I'd vaguely heard of 2J but hadn't considered them, so I'll get in touch with them thanks.

[A.Z.]

https://www.2j-antennas.com/antennas/single-external-antennas/2j6510b-433-mhz-ism-anti-rotation-mounting-ip67-ip69k-ik09-antenna/162

is the antenna this one (original link broken) ?

if not start from base site

https://www.2j-antennas.com

[nali]

This one https://www.2j-antennas.com/antennas/single-external-antennas/2j7715b-433-mhz-ism-screw-mount-ground-plane-dependent-antenna/390

...though the one you posted looks better (I've already had a browse)

[A.Z.]

Notice that the company is from Slovakia but has offices in US, UK and other countries

[nali]

Well I had a good chat with one of the guys at 2JUK and they kindly sent me a sample to look at. Unfortunately it doesn't fit this particular application, but I would say it looks like a really good product. Nice hefty heavy duty construction and from a quick test on a small groundplane (a baking tray commandeered from the kitchen) has a pretty decent performance.

[LaserSteve]

If you need a custom batch,try MP Antennas in Elyria, Ohio, USA  https://www.mpantenna.com/antenna-products/
I don't see one of the compact ones  on the web site for 434,  but shoot them an email.

Steve

[A.Z.]

Well I had a good chat with one of the guys at 2JUK and they kindly sent me a sample to look at. Unfortunately it doesn't fit this particular application, but I would say it looks like a really good product. Nice hefty heavy duty construction and from a quick test on a small groundplane (a baking tray commandeered from the kitchen) has a pretty decent performance.

Let me start by saying that I've no kind of relationship with "2J"; that being said, I'm curious now, what will you use the antenna for ? See you wrote that it "doesn't fit", so maybe some other on the forum may jump in and suggest a better antenna for a given, particular application

[nali]

So they go on to public transit displays like this one for example (random Google image)


It's to receive a signal from a key fob transmitter to make the display talk for blind travellers.

Options are quite limited for mounting antannas depending on the internal construction of the actual display; the particular unit I was looking at last week was a clamshell design so the diameter of the antenna couldn't really be any more than 60-70mm else it would prevent the case from opening. They also need to be low-profile if mounted underneath as there is normally a strict requirement height clearance to minimise the chance of injury to tall people. Whip antennas would be ripped off sooner than later by vandals.

All in all it's a set of conflicting near-impossible requirements. To date the Taoglas Hercules is the best I've found but they're expensive.

[A.Z.]

I see, now; I don't know if it's feasible, but looking at the display enclosure it seems made with some kind of "plastic" so, did you consider placing the antenna inside the enclosure, possibly near the bottom side ? In such a case the antenna would be more "protected" and will still work, plus you'd have more choices regarding the type of antenna, heck, even a dipole may fit

[nali]

I see, now; I don't know if it's feasible, but looking at the display enclosure it seems made with some kind of "plastic" so, did you consider placing the antenna inside the enclosure, possibly near the bottom side ? In such a case the antenna would be more "protected" and will still work, plus you'd have more choices regarding the type of antenna, heck, even a dipole may fit

Ah if only life was that easy. No they're all made of metal, normally pressed steel sometimes diecast aluminium. Even the display window itself has either a TFT panel which normally has aluminium cladding or even the older LED matrix panels will invariably have PCB with ground pour.

Mind you that doesn't stop some people putting antennas inside... (we don't fit the things by the way, we make the fob TX / RX boards)