2.4GHz Antenna  - Page 1
Forum section: electronics / rf-microwave

author: Randy222
author_rank: Frequent Contributor
timestamp: August 29, 2024, 09:23:45 pm
content: 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.

author: shabaz
author_rank: Frequent Contributor
timestamp: August 29, 2024, 10:08:59 pm
content: I don't know if it meets your need, but raspberrypi.com have a low-cost antenna. It's RP-SMA (even though thedatasheetdoesn'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).

author: Randy222
author_rank: Frequent Contributor
timestamp: August 29, 2024, 10:44:22 pm
content: I see many places just list it as VSWR <= 2.0That'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.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: August 29, 2024, 11:08:46 pm
content: Amazon is thewrongplace 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.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 03, 2024, 04:23:47 pm
content: 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.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 05, 2024, 01:49:43 pm
content: Two new items from amzon tested out badly. 2.66 and 3+ vswr in 2.4G band.I have some Bigfu dual bands that are near 1.2 in 2.4G and 2.0 in 5G, I only use those for 2.4G.I am waiting on Inventek stuff to arrive.

author: David Hess
author_rank: Super Contributor
timestamp: September 05, 2024, 03:01:14 pm
content: Quote from: Randy222 on August 29, 2024, 10:44:22 pmThe physical environment has an overwhelming affect on VSWR, so low VSWR of the antenna in an ideal environment has little importance.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 05, 2024, 05:55:43 pm
content: Quote from: David Hess on September 05, 2024, 03:01:14 pmI am certainly not testing in an "ideal" environment.You mean my amp-line-antenna will vswr one way, but my same amp-line-antenna moved to your location will vswr another way?That's true. I guess when I make comparisons it's only the delta that tells us one is better than the other, because for my testing the amp-line-environment is constant.However, I don't expect a 3.0 vswr antenna on my side to suddenly become a 1.2 vswr when you test it.I do however believe that when I test these cheap antennas the 1.2 is doing better than the 3.0 one. Calibrated VNA shows VSWR and Smith that makes sense, so I don't use the ones that cannot get down below 1.5.We should be able to test individual components to best of ability, then tune the connected "system" (amp-line-antenna in environment) to best we can get. In the context of this thread, it's wifi, not high-end long distance license band.Am I off base?

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: September 06, 2024, 04:24:19 am
content: Quote from: Randy222 on September 03, 2024, 04:23:47 pmOf course, the amp only wants to deliver power somewhere. You were talking about antennas before, not amplifiers.QuoteNo, it's not. It's vital for doing a link budget among other things. Probably a moot point though, because the type of companies to sell you junk antennas are also lying about their gain.Are your antennas assuming a ground plane, and if so what size are you providing? Or are they "ground-plane independent"? Makes a lot of difference to VSWR.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 06, 2024, 04:13:13 pm
content: Quote from: Geoff-AU on September 06, 2024, 04:24:19 amI explained it in more detail, look at each component, then all connected together as a system. We do usually tune the antenna to some favorable characteristics, and then attach it to the line.If it's +6dbi gain in a stick antenna and the vswr is 3.2, gain means little. If it's +2dbi and vswr is 1.2, great.Gain means little by itself. Gain means little unless we know where that gain is achieved. If the gain is all vertical and my receiver is horizontal, that gain does not help me.I testing the antenna as they are to be used in application, which are devices that basically have no well defined ground plane. I am testing some of my own 1/4 stick 1/4 legged antenna, but these are not simple sma sticks in terms of construction.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 06, 2024, 09:58:07 pm
content: Tested another bingfu dual band, amazon B082SH6QH6Not great, 1.53 in 2.4G, 1.7 in 5GI cannot seem to find <1.5 in both bands of any dual band antenna.Some dual bands do really well in 2.4G but crappy in 5G.I have other bingfu, about 2x the length of the one above, is good in 2.4G but crappy in 5G.Inventek 2.4G should arrive tomorrow.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 09, 2024, 10:16:00 pm
content: Inventek results are in.Not good.W24-SSMA-MAcross the 2.4G wifi band, 1.8vswr on the low end of band, 1.9vswr on the high end of band. Adding a metal ground plane of any kind did not help.I'll ask Inventek to provide VSWR chart to back their claim of <1.5vswr.

author: shabaz
author_rank: Frequent Contributor
timestamp: September 09, 2024, 10:49:37 pm
content: Hi Randy,It could be worth showing a photo of your test setup, just in case there's any issue. Also a quick explanation of how you're doing the calibration.I'm not suggesting mistakes are being made, it is just in case anyone spots anything that might make a difference.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 09, 2024, 11:50:38 pm
content: LiteVNA64, freq band selected, then calibrated, antenna attached directly to the VNA S11, then test run. Very simple process.I also have a mini tripod that has a 3" diameter copper disc as a gnd plane with a SMA bulkhead in the center, I use a short 8" cable to connect that to VNA.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 16, 2024, 02:36:34 pm
content: Sadly, Inventek replied to my inquiry, they said the published spec was wrong and it should be <=2.5In other words, my tests seem to be correct, and even though testing is better than their new" spec, the antenna is good for filling up my trash can.

author: ftg
author_rank: Frequent Contributor
timestamp: September 16, 2024, 03:52:37 pm
content: I don't think an antenna with repeatable performance will be found on Amazon.Pasternack's PE51018 promises <1.5:1 VSWR across the 2.4GHz band, but it's a discontinued product. And most else promise <2.0:1 VSWR.And there's no charts about the VSWR.There are also others, PE51133 with promises of 1.45:1 maximum VSWR.PE51OM1024, PE51OM1023 and PEANOM1149 also come with promises of 1.5:1 VSWR.I guess you'd have to contact them about more detailed parametrics.

author: Randy222
author_rank: Frequent Contributor
timestamp: September 16, 2024, 09:36:22 pm
content: Quote from: ftg on September 16, 2024, 03:52:37 pmI don't think it's a true statement.I have found some decent items from amzon which have good test results.I also found very good sma attenuators from a vendor on alliexpress. My VNA test results matched theirs. A surprise find.I do agree that most of the items from both market places have poor test results. Hence my original question.

author: radiolistener
author_rank: Super Contributor
timestamp: September 17, 2024, 01:52:18 pm
content: Quote from: Randy222 on August 29, 2024, 10:44:22 pmIdeal antenna has VSWR=1 at center frequency and VSWR=2.681 at left and right borders of it's bandwidth. It corresponds to -3 dB attenuation and this is ok.Antenna with more flat VSWR will be more wide bandwidth and as result less sensitive and less selective which is not good.The equation is:BW = (VSWR - 1) / (Q * sqrt(VSWR))orVSWR=(Q^2 * BW^2 + sqrt( Q^2 * BW^2 * (Q^2 * BW^2 + 4) ) + 2) / 2whereBW => relative bandwidth ( BW = bandwidth / center_frequency )Q => Q factorIf you get better one parameter, it leads to worse another parameter.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: September 18, 2024, 03:07:07 am
content: Quote from: Randy222 on September 16, 2024, 09:36:22 pmOk then. Good luck with it

author: Randy222
author_rank: Frequent Contributor
timestamp: September 18, 2024, 03:53:19 pm
content: Quote from: Geoff-AU on September 18, 2024, 03:07:07 am