RHCP OMNI log spiral helical antenna

[dalbert02]

It seems that some of the professional AP'ers using full scale aircraft use log spiral antenna for video. Any thoughts? This company seems a bit expensive, http://www.covert-systems.com/airborne/pdf/KSS-ATS-4b.pdf http://www.covert-systems.com/airborne/heli_equipt.html perhaps one of you really smart people could make a tutorial on how to make one (like the patch antenna tutorial) for us not-so-smart people? Do you think it would be worth the effort? Thanks,

-dave

[ThomasScherrer]

the spiral antennas works like a beam antenna with tons of gain

but CIRCULAR polarized, so that is a good idea for receiving antenna.

(you know a horizontal and vertial signal path adds attenuation of max 26dB,

when they are exactly worst, so that is why it is SMART to use one of them circular)

radioamateurs have constructed them spiral antennas for ages,

they even use same band, so drawings must be out there.

higher antenna gain = more signal if pointed right !

but if not pointed right = less signal, so you need a tracker system or a helper to do the tracking :-)

see here a picture of me flying longdistance :

http://www.webx.dk/rc/uhf-link3/booster-in-action.htm

I use a LONG yagi, it is not circular so not uptimal, if we was getting near distance margin,

the helper would have to both point right, and also rotate the antenna right,

in our case this antenna have so much gain so we did not get even near critical distance.

circular is the way to go, why not try a tiny patch first to see if this solves your range and drop out issues ?

if you dont have access to RF measure equipment you have to purchase ready made antennas to be sure they perform uptimal.

Edited May 29, 2008 by ThomasScherrer

[dalbert02]

Currently I am using tri-versification (1 black widow diversity rx and a regular rx all connected to RC-CAM's diversity) with (2) dipoles a (1) 8db circular polarized patch. For hight altitude I swap the dipoles for 14db patches at right angles to eachother. At x miles out and at x feet high I start to get dropouts. I would like to eliminate the drop outs. I'll send you a pic of what I mean. Thank you for your input.

-dave

the spiral antennas works like a beam antenna with tons of gain

but CIRCULAR polarized, so that is a good idea for receiving antenna.

(you know a horizontal and vertial signal path adds attenuation of max 26dB,

when they are exactly worst, so that is why it is SMART to use one of them circular)

radioamateurs have constructed them spiral antennas for ages,

they even use same band, so drawings must be out there.

higher antenna gain = more signal if pointed right !

but if not pointed right = less signal, so you need a tracker system or a helper to do the tracking :-)

see here a picture of me flying longdistance :

http://www.webx.dk/rc/uhf-link3/booster-in-action.htm

I use a LONG yagi, it is not circular so not uptimal, if we was getting near distance margin,

the helper would have to both point right, and also rotate the antenna right,

in our case this antenna have so much gain so we did not get even near critical distance.

circular is the way to go, why not try a tiny patch first to see if this solves your range and drop out issues ?

if you dont have access to RF measure equipment you have to purchase ready made antennas to be sure they perform uptimal.

[eickst]

Currently I am using tri-versification (1 black widow diversity rx and a regular rx all connected to RC-CAM's diversity) with (2) dipoles a (1) 8db circular polarized patch. For hight altitude I swap the dipoles for 14db patches at right angles to eachother. At x miles out and at x feet high I start to get dropouts. I would like to eliminate the drop outs. I'll send you a pic of what I mean. Thank you for your input.

-dave

There's only so much you can do. If you want more gain on the receiving end you either need to get a more directional antenna or a more sensitive receiver. If you're using 2.4ghz....maybe get a license and go to 1.3 or go to 900mhz without a license. The antennas are much larger but the signal propagates farther. Kind of sucks but I think the blackwidow is 2.4 only?

Another option is a LNA as close as possible to the antenna. Or mount the receivers directly to the antenna/lna and don't use coax at all.

Unfortunately, there's no magical antenna that will do 180 degree beam width and 20db gain. Would be sweet if there was....maybe there's one in this list...

http://www.ece.uiuc.edu/about/history/antenna/photos.html

My vote is about 3/5ths of the way down, the quad array of conical log spirals.

[dalbert02]

Thank you for that link! I find those antennae very fascinating!

-dave

There's only so much you can do. If you want more gain on the receiving end you either need to get a more directional antenna or a more sensitive receiver. If you're using 2.4ghz....maybe get a license and go to 1.3 or go to 900mhz without a license. The antennas are much larger but the signal propagates farther. Kind of sucks but I think the blackwidow is 2.4 only?

Another option is a LNA as close as possible to the antenna. Or mount the receivers directly to the antenna/lna and don't use coax at all.

Unfortunately, there's no magical antenna that will do 180 degree beam width and 20db gain. Would be sweet if there was....maybe there's one in this list...

http://www.ece.uiuc.edu/about/history/antenna/photos.html

My vote is about 3/5ths of the way down, the quad array of conical log spirals.