Hi again Andrew, Comments after your text. 73 OZ1MY Ib ----- Original Message ----- From: "Andrew Rich" vk4tec@people.net.au To: "OZ1MY" oz1my@privat.dk; "Amsat-Bb@Amsat. Org" amsat-bb@amsat.org Sent: Tuesday, January 01, 2008 4:54 PM Subject: Re: [amsat-bb] 70cm Yagi and AO-51
If I have this correct.
- LHCP recieved on a RHCP can knock your signal down by some 20dB
OZ1MY: In theory it will be compleately attenuatet - in practice more like you say.
- LHCP matched with LHCP will result in a good signal.
OZ1MY: Yes
So how does a linear antenna equate when receiving a circular signal ?
OZ1MY: In theory you loose 3 dB, which is not very much.
And the other way around, a circular receiving a linear signal ?
OZ1MY: Same as above.
BUT - all this is theory :-) For AO-51 the attitude of the satellite and the antennas in combination are fairly stabel, 435.300 MHz RHCP and 435.150 MHz LHCP. SO-50 have linear antennas on both up and downlink. In spite of that there can be a large difference between using RHCP and LHCP when listening to the downlink. That is one of the resons for at lot of us to have the possibility to switch between RHCP and LHCP.
Even satellites with RHCP antennas may change polarity if the attitude of the satellite is not right.
I can send you an article about it if you are interested.
--
Andrew Rich VK4TEC
So if I make x2 vertically polarised yagis, and then phase them together, I would gain roughly 3db.
The trade off is spose is the risk of the wrong sense, -20db or -3db (cp clash or linear)
---------------------------------------------------------------------------- Andrew Rich VK4TEC vk4tec@people.net.au mailto:vk4tec@people.net.au http://www.tech-software.net
-----Original Message----- From: OZ1MY [mailto:oz1my@privat.dk] Sent: Wednesday, 2 January 2008 3:08 AM To: vk4tec@people.net.au; Amsat-Bb@Amsat. Org Subject: Re: [amsat-bb] 70cm Yagi and AO-51
Hi again Andrew, Comments after your text. 73 OZ1MY Ib ----- Original Message ----- From: "Andrew Rich" vk4tec@people.net.au To: "OZ1MY" oz1my@privat.dk; "Amsat-Bb@Amsat. Org" amsat-bb@amsat.org Sent: Tuesday, January 01, 2008 4:54 PM Subject: Re: [amsat-bb] 70cm Yagi and AO-51
If I have this correct.
- LHCP recieved on a RHCP can knock your signal down by some 20dB
OZ1MY: In theory it will be compleately attenuatet - in practice more like you say.
- LHCP matched with LHCP will result in a good signal.
OZ1MY: Yes
So how does a linear antenna equate when receiving a circular signal ?
OZ1MY: In theory you loose 3 dB, which is not very much.
And the other way around, a circular receiving a linear signal ?
OZ1MY: Same as above.
BUT - all this is theory :-) For AO-51 the attitude of the satellite and the antennas in combination are fairly stabel, 435.300 MHz RHCP and 435.150 MHz LHCP. SO-50 have linear antennas on both up and downlink. In spite of that there can be a large difference between using RHCP and LHCP when listening to the downlink. That is one of the resons for at lot of us to have the possibility to switch between RHCP and LHCP.
Even satellites with RHCP antennas may change polarity if the attitude of the satellite is not right.
I can send you an article about it if you are interested.
--
Andrew Rich VK4TEC
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