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Most of the antennas I've seen advertised have 5.875 Ghz as the upper end of efficiency. 

Has anyone done any testing on 5.9 Ghz (channel 180) to see what effect there might be on SWR?  Are there any suggested antennas that appear to have a wider bandwidth for the upper channels?


Additional information - there is a dual band antenna on eBay (Alfa) that lists the SWR at 5.85 Ghz as being almost 1.7:1.  While most people accept less than a 2:1 as being OK, I'm trying to be more conservative in case specifications vary a bit between items of the same model.

Well I can't say that I have
Well I can't say that I have done any testing on them though it certainly is much cheaper to do so now as higher GHZ SWR analzyers have come out at an affordable price but I haven't done it.

Most WIFI antennas stop their specs at the end of the Part 15 band since they have no reason to specify higher (just like many ham antennas only call out the full ham band and ignore everything else) this doesn't mean they will 'die' right there.

I will put into perspective however you can go up to 2.6:1 SWR and have only around 1db loss per chain. From experience the gain of being "out of the noise" makes up for any loss of RF coverage to date.

Traditionally yes 2.0:1 is the recommended limit for ham antennas, however that has also generally been when talking 100w of output power, where (at a 2.6:1 SWR) your radio PA has to burnoff 20w of reflected power as heat.  With the power outputs we are putting out here on the microwave band your talking closer to .05w of additional heat to be burned off by the power chip in reflected energy.  While no reflected power could ever be ignored in any design circuit and the area for heat dissipation will be different between the two examples, it is still much easier to dissipate .05w than it is 20w.
k1ky's picture
SWR Analyzer suggestions?
What SWR Analyzer models (cheaper) are available that cover 5Ghz?  I bought a 2.4 Ghz 1W slug and a peak power kit for my Bird wattmeter that works very well in that band, but no good at 5 Ghz as far as usable Reflected Power / SWR measurements are concerned.
Ah you are correct,  I was
Ah you are correct,  I was thinking RIGEXPERT's had one for each band, but they only have 2.4GHz in the IT-24.

Guess next option is an RFE6GEN and either the RF Explorer 6Gcombo or RF Explorer WIFI   and a Directional Coupler ( around $550 for the RFExlorer Generator + G6Combo and not sure how much for the Directional Coupler)

Don't own either RFExplorder device but I heard they work decent enough for Amateur Use. I keep saying I'm going to buy them some day, just haven't gotten to it yet (Part of me keeps hoping a 3.4GHz support model will come out I think)
KE2N's picture
boat anchor

I have had good luck with a big old 2-18 GHz signal generator from HP and a power meter with the same frequency range.  There are tiny integrated circuit based units that have made these "boat anchors" somewhat obsolete and hence priced so that they sometimes sell for less than the shipping charge. Needless to say, you bring the antenna to the equipment, not the other way around. 

Anyway - the key is a directional coupler for the frequency range in question and a good 50 ohm microwave terminating resistor.  You need to verify that you can get 20-30 dB of return loss on the terminating resistor then any antenna measurement you make will be good to a few dB less than that, plus or minus the uncertainty of the coupler.  Your signal generator needs to have enough excess signal over your power meter minimum readable level to account for the 30 dB, plus the coupling coefficient of the directional coupler (which may range from 6-30 dB).

A dual-directional coupler costs a lot more than single one, but saves you from having to reverse the connections to measure forward and reverse power.  I think you should be able to find a suitable surplus directional coupler for less than $100 on the auction web sites or UHF/microwave conference flea markets.  I got a single-direction unit that covers 5.4-11 GHz and cost $30.

If you are feeling flush, you could find a boat-anchor 6 GHz vector network analyzer (by HP or Anritsu) that would read out the antenna characteristics directly,  A friend of mine has one for his ham antenna business.  These can be had for as "little" as $2K - $4K  - a bit out of my league ....


KE2N's picture

Very interesting.  The Ubiquiti Rocket-Dish 5G30 does indeed seem not to like frequencies above 5.85 GHz.  The problem I suppose will be that the output power will be turned down once you go above a certain reflected power and you may get signal distortion before that happens, if you try to run full power.

However, I have used my RD at 5.9GHz / 13 miles without obvious problems.

I note that the Light Weight (5G30-LW) version of the dish has a much flatter SWR characteristic and the return loss does not appear to take off vertically at 5.9.


I just wanted to get an idea of what to expect.  I read all the responses, and agree with the idea.  We're normally going to be at a lower power, so heat dissipation won't be such a problem.

I'm part of a group in Sacramento that is forming to put up a mesh in the area.  I'll be starting with an omni for the moment, then will look at directional when we start putting together our foundation.

Again, Thanks to everyone.
zl4dk's picture
It's not strictly correct to believe that the reflected power is dissipated as heat in the output stage. In fact much of it is actually reflected back towards the antenna again. What actually happens instead is that the output stage sees a load that is not 50ohms resistive and this creates higher than normal ac voltages and/or currents in the output stage. These usually prevent the output stage from producing full output and may cause damage. However I would expect in this case damage would be unlikely. 

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