Antenna's

[justin00]

So I'm trying to understand antenna's and all that stuff.. I have been reading wiki's and various pages on the internet
to get a better understanding.. I'll admit I am having a tough time understanding and taking it all in.

A question I do have.... In a lot of the pages I have read (and in a few threads here) people mention if you go from say
LHCP to Linear you will get a 3db loss... Now my question is.. What sets the Phantom as LHCP ?

Is it the 5.8GHZ TX transmitter that is configured for LHCP ? Or is the aerials on the Phantom that are LHCP
and that is why the change to linear gets 3db loss ? Or is it something else I am not understanding ?

Reallly just trying to get my head around this... :/

Thanks heaps

 

[Happyflyer]

I could put my 2 cents worth of info on your question(s) but my knowledge is mostly with circular and linear polarization with satellite TV. I am sure one of the antenna people will give you some qualified answers soon.

 

[SteveMann]

It's the same in any medium. Receiving a CP signal on a linear antenna is at least a 3dB loss.
Signal polarization is determined by the antenna.

 

[Happyflyer]

It's the same in any medium. Receiving a CP signal on a linear antenna is at least a 3dB loss.
Signal polarization is determined by the antenna.

Interesting it is only a 3dB loss. Because if you try a linear LNB on your dish and try to get a CP signal from a satellite, you will get "0" or nothing.

 

[N017RW]

Here's an article with some graphics that may help in understanding polarization and losses:

http://www.fpvuk.org/equipment/circular ... -antennas/

 

[Happyflyer]

Purrrrrfect N017RW, well done.

 

[SteveMann]

Interesting it is only a 3dB loss. Because if you try a linear LNB on your dish and try to get a CP signal from a satellite, you will get "0" or nothing.

I said "at least" 3dB. That's what the pure lab math would indicate barring all other losses. In real life I wouldn't be surprised to see a 6dB loss. Your satellite LNB is already so close to a signal dropout that a few dB from a rain shower will cause a temporary interruption.

What satellite service uses linear LNB's?

 

[justin00]

edit.. n/m can't delete post.

 

[justin00]

If that is the case, why do I read there a 3db loss going from LHCP to Linear ???
I don't get it.. or is the RX antenna (on the phantom) determining the polarization ??

*edit* read articles and I think it says TX antenna needs to match RX antenna or there will be loss..sooo is the RX on the phantom not Linear ?? thought those 2 little cables dangling would be linear ?? are they LHCP ??

Thanks heaps all for the responses

It's the same in any medium. Receiving a CP signal on a linear antenna is at least a 3dB loss.
Signal polarization is determined by the antenna.

 

[Happyflyer]

.....Your satellite LNB is already so close to a signal dropout that a few dB from a rain shower will cause a temporary interruption.

What satellite service uses linear LNB's?

F.Y.I
It is called Free To Air or FTA. There are more channels coming from the satellites than you would ever believe that are not scrambled and 100% legal to receive if you have the correct equipment. They use linear transmission. I can receive programs from my dish farm that you can't even get from the popular providers. I also subscribe to Dish network.
Providers like Dish and Direct use circular polarization.

 

[Buckaye]

Purrrrrfect N017RW, well done.

oh no you didn't LOL LOL :lol:

 

[justin00]

Can anyone tell me if 2 antenna's on Phantom are linear or polarized ?

I'm still not getting this..... the page N017RW posted up said the tx/rx decide if its linear or polarized.. which makes sense... but then why do I lose 3db if I use my linear antenna ???
Is the RX polarized ??

 

[SteveMann]

I'm still not getting this..... the page N017RW posted up said the tx/rx decide if its linear or polarized..

No, it doesn't. The only mention of the TX/RX was: "All antennas sold with video transmitters and receivers are linear polarized."

 

[justin00]

Errrm so what is it then that decides?

Im guessing the 2 wires dangling down legs are LHCP and that means the TX should also be LHCP ??

 

[N017RW]

Justin00,

The short answer is the both the transmitter and the dual antennas on the receiver of the P2s are linear and which ever way the are oriented at any given time determines their polarity. They are intended to be oriented as vertical polarization. For best results keep both the Tx and Rx antennas parallel to each other.

Please go to this link at RCGroups:
http://www.rcgroups.com/forums/showthread.php?t=1494024

It is well written and will save us a lot of typing :lol: