Banana Pi BPi-M2 Ultra antenna

I have found specs for the Wifi antenna, but I’m wondering if Wifi/Bluetooth operations without an add on antenna will harm the device.

I do understand a 3db or 5db antenna may be attached.

The RF power levels with WIFI/BT are not enough to cause damage to components due to RF reflection - such concerns are the domain of HAM radio rigs and higher - generally a HAM transceiver will cut transmission power to 5 watts without any load in order to protect components.

WIFI power levels are restricted to (I believe) 36dBm for 5GHz WIFI (EIRP levels = combined line output power + antenna gain) - that equates to about 4 watts EIRP - but that’s with an antenna - line output power is usually less than 1 watt.

Basically - don’t worry about it :slight_smile:

Thanks! Apparently, it does require an additional antenna to properly work, nothing on the board.

Oh yes - you’ll need an external antenna but certainly don’t worry about damage if an antenna isn’t connected - there are antennas available online of course and I imagine BPI can hook you up with the right gear too.

I’d reccomend a high quality RG178 IPX U.FL to SMA connector - you’d be surprised at the losses in cheaper cables over even short lengths - you’ll want RP-SMA for most WIFI gear - I went with standard SMA as I already have SMA SDR radio gear and cables so it was convenient for me.

You can of course get antennas that have a wire that connects directly to a U.FL connector - however this will give you far less mounting options over a separate connector and RP-SMA antenna.

For legal reasons - be careful with the ultra high gain WIFI antennas - they could result in exceeding the EIRP level limit in your country for AP WIFI - governments are pretty hardcore when it comes to cracking down on radio regulations.

Well, I located an ipx to SMA dongle locally, but can’t find a SMA wifi antenna in retail stores. I reside in Asia and rf equipment is hard to come by due to government regs. Having studied ham radio as a kid, I decided to search the web for DIY wifi antenna solutions and was delighted with several easy alternatives.

A. One can make a flat dipole out of copper, possibly using printed circuit board. This is a nice compact design for an interior use.

B. One can make an extremely directional Yagi antenna for outdoor use where one might even be a mile away from one’s wifi modem. VERY INTERESTING!

The trade off is omni-diectional antennas are low gain; whereas, the high gain one are narrow beam diectional.

I have not provided DIY links, but search “DIY wifi dipole” or “DIY wifi yagi antenna”.

So a Banana Pi might be adapted to be a long distance wifi computer to be used by your swimming pool.

I can modify the dongle to fit whatever I choose to build.

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WIFI antennas like a lot of radio gear have an input impedance of 50 ohms - a little dipole will be fine but the more accurately you can get the length and symmetry the better - mismatched impedance will cause you to lose some power and thus range.

I’ve once used a couple of yagis I purchased off e-bay that were designed specifically for WIFI frequencies and achieved one mile easily (wireless G) - quite obtainable if there aren’t many obstructions causing reflections/multi path issues with the waves.

With a tuned dish and presumably some form of low noise amplification - a technician in Venuzuala managed 237 miles!

Actually, television and less than Gigahertz antennas usually have 50ohm impedance. Wifi is 75ohm impedance and uses different coax along with recalculation of all the maths in designing a DIY antenna.

I’m making a simple dipole with a circular ground plane for starters. It’s almost finished, but it’s likely to be a basic 2db omnidirectional antenna. Only good for use in the same room as the wifi router.

Getting into all the maths and design details for over 10db directional gain will have to wait until I have the BPi m2U wifi software installed.

Material choices require reengineering. Aluminum, copper, and brass all have different conductivity. It usually easiest to copy an all copper antenna with brass coax fitting. But an all brass antenna would not get easy damage from bending as the copper is softer.

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