15 db whip 2.4 antennas

[Gary Mortimer]

Anybody had any experience with these?

http://www.jefatech.com/product/JTOD24-15/15dBi_24GHz_Super_Long_Range_Outdoor_Omni_Antenna. html

[c_matt92]

You wouldn't have much luck flying straight overhead with that guy, but if you are putting it on a diversity receiver with a 3 db omni then you should be fine.

[fnev]

The following is from a very good friend and top notch antenna designer:



Look at the radiation pattern called ‘E Plane’

This is a ‘slice’ of the radiation pattern of the antenna viewed from the side of the antenna. When they did the pattern plots the had the antenna lying on its side, instead of vertically up, probably how the antenna test chamber was set up. So, to understand the plot, just remember the antenna is sideways. Then the outer ring of the circle is the normalized reference for gain, and is the measured 15dB gain. The next ring in is a step down in the gain, by -10db, the next ring another 10dB down, ie, -20db, so the gain of the antenna at the -10dB ring = 15dB – 10dB = 5dB, etc. So now, at the antenna ‘horizon’, which is the 0 / 180 degree line in the E plane plot, the gain is 15dB.

At 15 deg up from the horizon (the 195 / 345 deg ref point) the gain is 5 dB less, ie, 10dB gain.

At 30 deg up from the horizon (the 210 / 330 deg ref point) the gain is 15 dB less, ie 0dB gain

At 45 deg up from the horizon (the 225 / 315 deg ref point) the gain is 20 dB less, ie -5dB gain

At 90 deg up from the horizon (the 270 deg ref point, ie, directly overhead) the gain is 25 dB less, ie -10dB gain.

So, as long as you wish to fly only knap of the earth, not more than 10 or so degrees above the horizon ,and remain line of sight, then it’s a great antenna, else USELELSSEELSSSLLESS

[rich smith]

While not an expert I experimented with XBee and RCCam type 2.4ghz antennas quite a bit and found that overhead is not as big a problem as expected. Not sure why I've had such good luck. Maybe because, unless you're flying at 20,000', the plane is closer when directly above. -10db sounds fine at 400'.

[spitfiremk9]

Gary, I got one here, fortunately i had mine for a tenner on ebay as it didn't perform much better than the small rubber ducks that come with the kit, i'm back to a yagi and paying an assistant to follow the plane

[Gary Mortimer]

Well I did wonder Spitfire, 15db gain for a whip seemed rather too much to me!!

I think maybe putting a repeater downrange with a yagi pointing at it might also be away to go with 2.4 or even, getting a repeater airborne with another aircraft and making an instant tower!

[Mick Molloy]

Try a couple of 9 xtend with the meshing on...

[Gary Mortimer]

Well I have the 900Mhz antennas, so that would be a plan!

Can you position several of those for network goodness Mick?

Which exact ones do you have?

[Mick Molloy]

9 Xtend
XTend OEM RF Modules containing firmware version 8020 (or above) now feature DigiMesh™
mesh networking support. Mesh networking allows messages to be routed through several different
nodes to a final destination. The DigiMesh firmware allows OEMs and system integrators to
bolster their networks with the self-healing attributes of mesh networking. In the event that one
RF connection between nodes is lost (due to power-loss, environmental obstructions, etc.) critical
data can still reach its destination due to the mesh networking capabilities embedded inside the
modules.
A Sample DigiMesh Network Topology

http://ftp1.digi.com/support/documentation/90000958_A.pdf

[Gary Mortimer]

Is it quick enough to support IP camera images??

Instantly thinks, several of these in a chain.

Big coverage for network.

Sorry Mick if I should just be RTFM

Cheers

G

[blue9]

What about an amplifier? (http://cgi.ebay.com/1-Watt-2-4-GHz-802-11b-Only-OEM-Amplifier-HA2401SFGI-10_W0QQitemZ220397458794QQcmdZViewItemQQptZCOMP_EN _Routers?hash=item3350b6556a&_trksid=p3286.m20.l1116)