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Re: Up and dwnlink polarization of HAMSAT



No...RHCP matches RHCP. Think of it this way. Take two bolts, both with the same threads. Think of them like helixes. Put a nut on one bolt. Point them at each other like antennas would be. Move them close enough together that the ends touch. Notice how the nut (the wavefront) will thread off the first bolt right onto the second! If a LHCP transmit antenna required a RHCP receive antenna this would not be true. 

It's a simplistic analog, but always one that helped me understand circularity.

The part about defining what constitutes RH or LH is true though. Groups disagree on which way the thumb points for which one, LOL. Been too long for me to remember who's on what side of that fence.

73, Drew KO4MA

-----Original Message-----
From: Charlie Schlieper <n5td@vvm.com>
Sent: Jul 1, 2005 2:29 PM
To: "Don, w7das" <w7das@cox.net>, amsat-bb@AMSAT.ORG
Subject: Re: [amsat-bb] Up and dwnlink polarization of HAMSAT

By golly, I think you're right Don.

You just reminded me not only of that, but the fact that Optical theory
denotes the polarization (polarisation) opposite from us radio guys, or
as the twist is seen coming into the RECEIVE antenna, instead of the
TRANSMIT antenna relationship.

Thanks for that refresher!

Charlie, N5TD

----- Original Message ----- 
From: "Don, w7das" <w7das@cox.net>
To: <amsat-bb@amsat.org>
Sent: Friday, July 01, 2005 9:18 AM
Subject: Re: [amsat-bb] Up and dwnlink polarization of HAMSAT


>I may have read incorrectly, but I thought polarisation was determined by 
>the rotation of the electric field about the axis as the wave moved AWAY 
>from the source.  If this is true, wouldn't the polarisation be opposite as 
>it arrived on Earth?  i.e. transmitting with an LHCP antenna in space would 
>be best received with an RHCP antenna on Earth?
>
> 73,
> Don
>
>
> ----- Original Message ----- 
> From: "William Leijenaar" <pe1rah@yahoo.com>
> To: <amsat-bb@amsat.org>
> Sent: Friday, July 01, 2005 2:37 AM
> Subject: [amsat-bb] Up and dwnlink polarization of HAMSAT
>
>
>> Hi AMSATs,
>>
>> This morning I received the answer from ISRO about my
>> question for the uplink polarization, and why they
>> used LHCP on the downlink.
>>
>> The uplink of HAMSAT is in RHCP, opposite of the 2m
>> downlink that is in LHCP.
>>
>> I was also supprized to hear that the downlink is in
>> LHCP, as most amateur sats use RHCP.
>> The reason that ISRO used RHCP and LHCP is to avoid
>> interaction between the uplink and downlink signals.
>>
>> By using opposite polarizations the output of the
>> satellite would less interact on its 70cm input.
>> Personaly I think the antennas are at such close range
>> that this will not really help...
>> At least we know the right polarizations, and the
>> reason why it is done.
>>
>> Myself I have fixed RHCP antennas, and actually have
>> had never any problems with the HAMSAT.
>>
>> On the other hand the signals are that strong that it
>> should be no problem, and most of the hams I hear on
>> HAMSAT are in aligator mode and can use some
>> polarization attenuation on the uplink :o)
>>
>> 73
>> William
>> PE1RAH
>> ---
>> ----
>> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
>> Not an AMSAT member? Join now to support the amateur satellite program!
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> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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