8 replies to this topic

[robyr1]

I found this ebay seller:
http://cgi.ebay.it/w...em=180295073576

he sell a normal patch 2,4ghz antenna to fit on a satellite dish of 90cm diameter.
I have a lot of these dish, so i can test it, but i have a question:

I would like to test it fitting a smallest camera+tx 2,4ghz ( 500mW) on an eagle (i tested already!).
And with 2 dishes and these smallest patch antennas should i got a high db?
I will use the oracle diversity.
Should a 8db patch antenna become a 24db on a 90cm diameter dish?? Will works better fitting 2x??

Edited by robyr1, 07 December 2008 - 10:39 AM.

[Kilrah]

Well, the seller says 27dB with a 90cm dish, how he calculated that and whether that's right I have no idea.

However, beware that such a high gain results in a VERY narrow beamwidth - you'll have to aim at the transmitter with about +/- 2° precision to make advantage of an antenna like this one.

Edited by Kilrah, 07 December 2008 - 11:29 AM.

[robyr1]

Well, the seller says 27dB with a 90cm dish, how he calculated that and whether that's right I have no idea.

However, beware that such a high gain results in a VERY narrow beamwidth - you'll have to aim at the transmitter with about +/- 2° precision to make advantage of an antenna like this one.

Thanks Kilrah!! you are everytime present!!

What's your suggest for my project??
what kind of antenna should i use?
I would like to use the same antennas for wi-fi, in my next experiment, is possible?

Edited by robyr1, 07 December 2008 - 12:23 PM.

[Mr.RC-Cam]

This might help: http://my.athenet.ne...abolic.main.cgi

I agree with Kilrah that the narrow beamwidth will be a burden. With mobile applications like yours, it is usually more convenient to keep the antenna gain under 10dB so that the beamwidth is easier to accommodate. Otherwise, be prepared to precisely aim the high gain antenna at the moving target.

[Kilrah]

I'd say that if you really need that much gain and have someone who can aim pretty accurately you could use those 12dB panels, but on their own without a dish.
If you then want to experiment long-range, fixed WiFi then yes you could add the dishes for that. Just make sure you get the correct connectors/adapters (SMA for video and usually RP-SMA or BNC for WiFi).

[robyr1]

I'd say that if you really need that much gain and have someone who can aim pretty accurately you could use those 12dB panels, but on their own without a dish.
If you then want to experiment long-range, fixed WiFi then yes you could add the dishes for that. Just make sure you get the correct connectors/adapters (SMA for video and usually RP-SMA or BNC for WiFi).

Thanks Kilrah,

so i can try it, because i can use the antenna only (2x )for receiver the tx from the eagle, and the same set up + dishes for the wifi, really? I have all the connectors! (I sell it!)

As you know, i can't use big antennas on an eagle, so i have a good receiver stations on ground, what's your suggest? What's best result?
The BBC team, wich tested already this "on board camera on an eagle", have a big dish, and 2 cameras on the eagle!!

[Kilrah]

The BBC team, wich tested already this "on board camera on an eagle", have a big dish, and 2 cameras on the eagle!!

Well I never said it was impossible, just not practical and possibly not needed/worth the effort.
If I were to use a parabolic antenna for such a thing, I'd rent a professional grade video camera tripod, heavy, sturdy and with adjustable resistance fluid panhead, fix the dish on it, and attach binoculars or another kind of scope perfectly aligned with the antenna's beam because without this it would be pretty much impossible to follow the bird at a distance without losing track of it. And if you do lose it, with the high gain you'd have a hard time finding it again. Maybe a diversity RX with a 2nd lower gain antenna (same one without dish) would help with that.
With such a setup you could possibly follow the eagle for a few km, or until he goes and hides behind something

I'd already try maybe just a single patch, if clearly not enough go for the full set...

Edited by Kilrah, 08 December 2008 - 05:12 AM.

[robyr1]

Yes kilrah,

but the eagle is always near to me, around 500 mt maximum.
i will try with a low gain antenna setup, can you suggest me a good reseller in europe (to pay in EURO)?I need to buy also some STEP UP and STEP DONW power supply..

[Kilrah]

but the eagle is always near to me, around 500 mt maximum.

Oh... well, then don't worry too much, with a 500mW TX you should not need anything more than a stock omni antenna on the RX side at such a short distance... You can just get yourself a 8dBi panel for safety and as it will also pick less interference from outside its coverage.