Electronics > RF, Microwave, Ham Radio

2.4GHz Antenna

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Randy222:
Anyone have good source-site for 2.4G wifi sma stick antenna with verified VSWR? I am looking to avoid just buying stuff and testing VSWR myself. I think over past year I had bought 20 or 30 different items from amzon but only a handful had acceptable VSWR.

shabaz:
I don't know if it meets your need, but raspberrypi.com have a low-cost antenna. It's RP-SMA (even though the datasheet doesn't make that explicit) and comes with a cable to convert that to U.FL.

The data specifies the worst-case VSWR amongst other data. I have bought a few, they seem fine, I have not measured them. Main benefit is that they are cheap and performance hopefully is fairly repeatable with subsequent purchases. They also seem reasonably well made (nothing special).

Randy222:
I see many places just list it as VSWR <= 2.0

That's a sad stat. I prefer to see <= 1.5, but would rather see an actual VSWR sweep across the wifi band. I have these charts for my attenuators, should have them for antenna too.

Geoff-AU:
Amazon is the wrong place to buy anything decent.

50R resistor has great SWR, ergo SWR is a poor indicator of performance.  It *may* show how much effort a designer has gone towards impedance matching, it may not.

You need to buy from a reputable vendor, ideally one that provides a chart.  A good antenna should have sharp, well defined tuning.  A poor antenna will be "broadband" but terrible radiation efficiency.  If a vendor is not trustworthy, their datasheet isn't either.

Another tip is to pick an antenna with a high power rating.  You can't hide inefficiency in an antenna that handles a good amount of power.

A final tip is to look at antenna gain.  Inefficiency kills gain.

A quick look on Digikey produced a few "stubby whip" type WiFi antennas 1) with SMA connectors (making them "not consumer" gear like all the RP-SMA stuff), 2) with a 50W (!!!) power rating, and 3) low price ($4).  Company is Inventek Systems, a USA LLC.  They are far too sue-able to risk lying on their datasheet.

Why would you shop grey market? Such a waste of time.

The Raspberry Pi whips seem to handle about 10W and claim 2dBi gain, which is also fine.

Randy222:
Geoff,

SWR is everything when it comes down to the amp stage. Must evaluate the transmission line, the antenna, and then transmission line terminated at antenna (aka "amp load"). Individual pieces, and then all connected together.

Pure resistance is gonna be obvious on the Smith chart. ;)

Gain is a number of trickery. The antenna cannot produce more power than what is delivered, but directional radiated power density can increase (gain), but that changes the shape of radiated power. Plenty of better options than stick to get directional gain, like corner, yagi, circular.

I ordered some Inventek, will compare it to two new items from amzon.
I am also testing out some homemade 1/4 wave antenna.

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