how do i find out how much db my antenna is

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Postby TheSovereign » Mon Jul 29, 2002 10:47 am

looks just like mine
very nice
yeah man take it out see what u get its meant to be lying down flat just like u got it in the pic
i dont know why u lost db mine goes up
hmm interesting
do like u said throw it on the dash and check it out
im pretty sure u will get much better signals
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Postby lincomatic » Mon Jul 29, 2002 10:58 am

just got back from driving w/ it on my dash. qualitatively, it seems to be decent...pulled in many of the AP's i usually see. but definitely not as powerful as having my collinear antenna on the dash. the positioning in my car was far from optimal, though...i think my wipers were blocking it a bit since it has such a low profile. i'll play with it a bit.
it's pretty near invisible inside the car... no one would even notice it.

thesovereign, so in your test, both the signal & SNR went up? weird. wonder what's the diff between our implementations.
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Postby TheSovereign » Mon Jul 29, 2002 11:35 am

r u using a cable?
the only cable i use is the one that plugs from the pigtail into the mail n connecter and directly into the bnc connecter for my ant
so im not using an inbetween cable

thats the only thing i can think of as a diffrence in the setups
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Postby lincomatic » Mon Jul 29, 2002 11:40 am

i have a 12" LMR100A pigtail w/ N-jack that goes into the orinoco. the antenna is soldered into an N-female jack that i screw directly into the pigtail.
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Postby TheSovereign » Mon Jul 29, 2002 11:45 am

really odd im stumped
do u have good connection between the copper i noticed a peice of it is cut to the left of the righthand coil
i used a solid peice of transformer coil - it looks like u just used copper wire, is their a copper quality diffrence?
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Postby lincomatic » Mon Jul 29, 2002 11:58 am

Originally posted by TheSovereign
really odd im stumped
do u have good connection between the copper i noticed a peice of it is cut to the left of the righthand coil
i used a solid peice of transformer coil - it looks like u just used copper wire, is their a copper quality diffrence?


i used a piece of romex...it was too short but since there are 3 conductors i just soldered 2 pieces end-to-end. it's a pretty solid connection. and my wire is pretty good stuff. but mine is #14 not #8 wire. are you sure you are using #8 wire? that is pretty damn thick stuff. pretty hard to coil i would think. what is the diameter?
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Postby TheSovereign » Mon Jul 29, 2002 12:11 pm

im using 16 LOL even worse

he told me 8 i dont know why i dont think its required
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Postby lincomatic » Mon Jul 29, 2002 12:21 pm

Originally posted by TheSovereign
im using 16 LOL even worse

he told me 8 i dont know why i dont think its required


oops. sorry missed the bit above where you said you were using #16 instead. anyway, if you build the multicoil one post your results. i'm not sure about decreased signal strength, but i still think my SNR gain seems more reasonable for an antenna of this size than your +12dB.

anyone else care to build one of these things? sparafina, are you game? pls post your results here.
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Postby TheSovereign » Mon Jul 29, 2002 12:31 pm

i know u didnt get great results but isnt it impressive for its size?

yes please someone else build one post your results
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Postby lincomatic » Mon Jul 29, 2002 12:39 pm

Originally posted by TheSovereign
i know u didnt get great results but isnt it impressive for its size?


yes, to be honest i was expecting it to not work at all. but the mobile mark mentioned in the homebrew antenna thread has about 5dB gain, so i rank it as similar, and it's even more simple than yours (and uses a helluva lot less wire ;)). but its 3" ground plane makes it hard to use. i like the way your antenna lays flat.
i think the wide tolerances like wire size etc may be affecting the performance...in the 2.4GHz range just a 1-2mm tolerance can really affect performance from what i've seen in my own experiments. is there a technical term for this style of antenna? i'd like to read up on them but can't figure out where to start.
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Postby sparafina » Mon Jul 29, 2002 8:11 pm

Originally posted by lincomatic
anyone else care to build one of these things? sparafina, are you game? pls post your results here. [/B]


Would love to but I'm on an extended trip with only basic tools. I saw a similar design at the FRARS site several months ago, I've searched but I can't find it. It was a coil wrapped around a CD spindle, it was mostly pictures. It was supposed to be an omni. I tried building it but it sucked. I've seen similar antennas described (for other frequencies) and they are horizontally polarized, however this antenna used a CD as a groundplane on the bottom of the CD spindle so it didn't make sense to me.

I'll give it a shot when I get a chance.
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bringin up old posts

Postby systemd0wn » Wed Aug 14, 2002 10:28 am

Bring up this older post, what ever happened? anyone figure this thing out? it looks easy enough to make?
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Re: bringin up old posts

Postby sparafina » Wed Aug 14, 2002 12:09 pm

Originally posted by systemd0wn
Bring up this older post, what ever happened? anyone figure this thing out? it looks easy enough to make?


I won't have time until October, guess I can't complain. I did follow up with trevor marshall about building a 2.4 gHz field strength meter. Here's his reply:

<Trevor Marshall>
I built mine by highly modifying an AIDC-3733 Down Converter I got from k5gna@aol.com

http://members.aol.com/k5gna/AIDC3733modifications.doc

I also reduced the gain of my converter, and improved its noise figure.

Then I built an IF box consisting of an AD8307, a few LM301A and an LM380 speaker driver. It is fed by 12V of NiMH batteries. The 301's function as a peak detector with variable slope (to average the pulses of the 802.11b signal). One drives an analog field strength meter 0-100 calibrated directly in dB. It has an 80dB dynamic range, and can sense far-field signals close to the thermal noise level.
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Re: bringin up old posts

Postby fordem » Wed Aug 14, 2002 3:31 pm

Originally posted by systemd0wn
Bring up this older post, what ever happened? anyone figure this thing out? it looks easy enough to make?


Are you referring to that antenna with the two coils? I tried building one - mine sucked big time - guess I didn't do something right.

Perhaps I started with a negative mindset - I remember thinking "those coils have way too much inductance for 2.4GHz" and that affected my results :confused:
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two coil antenna question

Postby paran0id » Tue Aug 20, 2002 9:54 am

I am finally attempting to build this "two coil antenna" (has anyone discovered the correct term for this type of antenna?), and i have a question. Please excuse my ignorance of the metric system, but when everyone stated that they wound this around a .75mm drill bit, is that - as in 3/4 of 1mm? That just seems awfully small to me. about the diameter of a small paper clip? It would seem to me that with #8 or even #14 wire, this would be about as small as you could turn it, and it just doesnt look that way to me in the pics. Thanks for your help, I will post my results when I finish.
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