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Question About A Yagi Antenna


Razor512
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On a recent episode of hak5 (10x11), Darren was using a yagi antenna but I noticed one issue. it looked very close to those found on ebay, and I have actually purchased one a long time ago which looks the same.

But there was an issue, It performed significantly worst than the coat hanger + cardboard yagi that I made

Then I also noticed why, the driven element, as well as the boom and reflector and parasitic elements were all more or less linked and conductive with each other, essentially turning the entire frame into a large antenna. Which poses another issue of the irregular shape no longer being tuned to 2.4 GHz

This caused a very low gain and the antenna performed better pointed straight up functioning as a omnidirectional antenna rather than a yagi (directional)

It also, regardless of how well I aimed it and regardless of direction, not get anything better than -90 -85 signal for the open access point for the near by coffee shop, but with a 5dbi omnidirectional antenna , I can connect with a signal in the -70 range.

PS, I was able to get a refund on the antenna.

Has Darren done any testing with his antenna to see what kind of gain it actually gives?

I am interested in seeing what kind of gains he is actually getting in order to see if I should probably try getting another

Edited by Razor512
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Do you know what kind of model antenna Darren was using on the show?

Not sure which model he was using, so I was basing it purely off of looks

The one I got from ebay looks very close

UCH0x.jpg

BtNRz.jpg

The only issue is that it lacked the directionality that he seems to be getting. When i took mine apart, the connections looked fine in terms of there being no breaks in the wire, but I also noticed that all of the elements including the reflector and mounting bracket were all electrically conductive with each other (which from what I have seen with many tutorials and insanely overpriced ones is that they all followed a model where everything was not electrically conductive with each other)

The end result was an antenna that did better than a 2dbi but worst than a 5dbi.

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I'm not sure, yeah I think Darren said in the show he was doing like 16dbi on his yagi. If it a matter of conductivity, maybe somehow the mounting brackets etc are interfering with the tuning of the antenna. It could be that it's not operating on the 802.11 b/g frequencies.

I'm going to try and get a hold of a yagi antenna to play around with it, got any suggestions?

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Quote: "from what I have seen with many tutorials and insanely overpriced ones is that they all followed a model where everything was not electrically conductive with each other"

I think its OK that the director and reflector elements are connected as at the characteristic frequency the connections are at node points, the crucial thing is that the driven element (the folded dipole) is insulated from the rest.

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hard to recommend anything. The only yagi that i ever purchased was from ebay and turned out to be crap and I cant possibly recommend it causing someone else to go through the same trouble of wasting money.

Quote: "from what I have seen with many tutorials and insanely overpriced ones is that they all followed a model where everything was not electrically conductive with each other"

I think its OK that the director and reflector elements are connected as at the characteristic frequency the connections are at node points, the crucial thing is that the driven element (the folded dipole) is insulated from the rest.

For the one I got, the driven element was not insulated. The housing of the driven element was conductive with the driven element it's self, it was also conductive with the boom and all other elements.

In the tutorials that I have seen, they generally stressed the importance of exact measurements along with the proper shape of the driven element in order to maximize performance.

Edited by Razor512
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