I’m after either a commercial antenna or a design hint for a 2.4ghz antenna (It’s a zigbee system).
Main problem I have is it needs to be indestructible. It’s in a mining environment where it’s not uncommon for it to be hit by rocks.
Ominidirectional and a reasonable gain are important.
Leads me to ask. Has anyone characterised antennas that are built purely from stainless steel rod/tube? Does anyone make one?
Immune to falling rocks? Sounds like a job for a 1.21 inch wire mounted inside a bowling ball.
Problem is, what effect does a bowling ball (or any suitable lump of resin) have on the properties of the antenna? I guess what I’m after is a design that is relatively insensitive to it’s environment.
I’ve used some made for transit (bus) rooftops. Very rugged.
The ones for buses… what frequency? and where do you get one?
The antennas on continuous miners (JOY brand specifically) are a normal rubber duck style antenna, however they are encased in a solid tube of polycarbonate. Which is underneath the “lids”, nothing that will allow RF out will survive direct rock interaction. You may want to look at locating the antenna inside current housings, the light housings on a “pinner” or roof bolter come to mind as they are fairly rugged and pretty spacious.
some antenna vendors…
PCTEL - they acquired several antenna companies of late.
LAIRD Technologies - also, e.g., Cushcraft
Look for low profile/mobile/transit
Hyperlink Technologies, though maybe all generic
The polycarbonate tube approach is what I originally had in mind. That then begged the question, which antenna’s are least disturbed by being surrounded by that sort of material, and of course, nearby metal.
Steve, thanks for the leads. There’s a couple of interesting ones there. I’m particularly curious about this one. Would it behave itself encased in resin? http://www.lairdtech.com/downloads/NanoBlade-a.pdf
I’m also tempted by the cheap but easily fixed option like this one http://www.hyperlinktech.com/item.aspx?id=1932. At least if it does get bent it’ll be obvious and easy to fix 
Russel:
The polycarbonate tube approach is what I originally had in mind. That then begged the question, which antenna’s are least disturbed by being surrounded by that sort of material, and of course, nearby metal.Steve, thanks for the leads. There’s a couple of interesting ones there. I’m particularly curious about this one. Would it behave itself encased in resin? http://www.lairdtech.com/downloads/NanoBlade-a.pdf
I’m also tempted by the cheap but easily fixed option like this one http://www.hyperlinktech.com/item.aspx?id=1932. At least if it does get bent it’ll be obvious and easy to fix
to choose an antenna you need to define:
Tx Power into antenna
path loss (path length, obstructions, etc)
Antenna gain at far end
fade margin you want
How directional you can make the antennas, and if so:
high gain omni (highly directional in the vertical axis)
high gain horizontally directional (like a yagi or array-patch/panel)
And not the least: what is the max radiated power (Tx power + antenna gain) limit imposed by your regulatory authority (e.g., FCC), as a function of antenna gain. In Japan it’s limited to 10mW/MHz, far lower than the US.
Steve, the transmitter in question would be something like a 60mW Zigbee.
I also have issues with protecting my GPS antenna but that’s not quite as difficult. I am assuming there that the Sarantel antenna is fairly forgiving.
Oh, I should have added that reliable/even omni-directional coverage is more important than gain.
Linx makes a 7mm stub antenna that should be pretty indestructable if encapsulated. When I made dog trackers, we would encapsulate the RF components in parrafin wax before we would slather epoxy all over to protect it. Parrafin is a material that seems to be very nonreactive to RF. I would cast a parrafin “cap”, then cover it in resin. Actually making the transceiver in a ball shape will minimize stresses to the board and components. The 180 option is to make the antenna out of guitar string steel in heat shrink. It will be easier to tune(pun intended) and extremely flexible. To solder to it, get some thin wall brass tubing and crimp the wire into it. Solder to the tubing.
Thanks heaps for the leads guys. I’ll try to repost here when it gets up and running
those 1/4 in. square PCB mounted “chip” antennas for 2.4GHz are what’s used in WiFi dongles, bluetooth devices, some cordless phones, etc. -2dBi of gain though. XBee modules have them as an option.
And now for bonus points, Steve…
Try building a phased array out of those chip antennas…
yes, evil
And now for bonus points, Steve…
Try building a phased array out of those chip antennas…
yes, evil
Russel:
And now for bonus points, Steve…Try building a phased array out of those chip antennas…
yes, evil
that’s a black art I know nothing about!
Vivato did try to sell a phased array WiFi product. They demo’d it to us. But they went chapter 13.