January 2008 - AMSAT-BB - mailman.amsat.org

Re: Making your own rotator controller
by Henk, PA3GUO 01 Jan '08

01 Jan '08

Hi Andrew, Not exactly an answer to your question, but still: Some years (~1995..1996) ago I built my own tracker as well. Was the time when the LVB trackers etc were not available. Only the expensive Kansas City tracker (expensive). My system is still operational. Bertus, PE1KEH, wrote in PASCAL the tracking SW (input: kepler, output: sat position). I added to that the controlling of the rotors. All corrections mentioned below (overshoot etc) are done in PASCAL in the PC. That sends and integer value to the ST6 (like your PIC) which does only one thing extra: check if the integer exceeds the allowed maximum right or left position (in case max left is at 4.5V where your range maybe 0..5V). Items to consider next to straight degrees2voltage conversion: - overshoot (when you stop, the rotor actually moved still a tiny bit) - thresholds (to avoid oscillation & to much shaking) 8 bits give enough accuracy, I used a pot.meter to convert the voltage of the rotor voltage from eg 0..20V down to 0..5V. http://home.vianetworks.nl/users/hamoen/pa3guo/zb_rtr_ctrl.html (includes my poor PASCAL routines) Of course it took a terrible amount of effort/time, which I had only back then, so today I would buy an LVB tracker :-) Still - this was one of the most satisfying projects I ever did. Seeying you home-made system following the bright ISS in the darkness of the night is soooo cool ! Have fun & success Henk, PA3GUO http://www.qsl.net/pa3guo

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Re: 70cm Yagi and AO-51
by OZ1MY 01 Jan '08

01 Jan '08

Hi Andrew, That is exactly to be expected. 435.300 MHz is RHCP and 435.150 MHz is LHCP. Happy New Year 73 OZ1MY Ib ----- Original Message ----- From: "Andrew Rich" <vk4tec(a)people.net.au> To: "Amsat-Bb@Amsat. Org" <amsat-bb(a)amsat.org> Sent: Tuesday, January 01, 2008 10:12 AM Subject: [amsat-bb] 70cm Yagi and AO-51 > Gudday > > I tried a crossed offset yagi on the one boom. > > When I threw just one part of the yagi on the boom, AO-51 was really good, > > Now I am finding that with the second yagi on the boom I am seeing a big > drop between 435.300 and 435.150 voice / data. > > I think I might remove the second yagi from the common boom and add it to a > new seperate boom > > Comments ? > > I think I am getting -20db due to the cross polar RHCP LHCP with the data > > The voice is great , the data is down in the mud > > > -------------------------------------------------------------------------- -- > Andrew Rich VK4TEC > vk4tec(a)people.net.au > http://www.tech-software.net > > > _______________________________________________ > Sent via AMSAT-BB(a)amsat.org. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >

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Re: 70cm Yagi and AO-51
by OZ1MY 01 Jan '08

01 Jan '08

Hi again Andrew, Comments after your text. 73 OZ1MY Ib ----- Original Message ----- From: "Andrew Rich" <vk4tec(a)people.net.au> To: "OZ1MY" <oz1my(a)privat.dk>; "Amsat-Bb@Amsat. Org" <amsat-bb(a)amsat.org> Sent: Tuesday, January 01, 2008 4:54 PM Subject: Re: [amsat-bb] 70cm Yagi and AO-51 > If I have this correct. > > 1. 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. > 2. 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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New year
by CANDEBAT Christophe F1MOJ 01 Jan '08

01 Jan '08

Happy new year to all AMSAT members and all. Be well, be happy, be healthy, and be prosperous in 2008. 73 F1MOJ Christophe AMSAT-France Chairman

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Re: mode J filter / Comet CF416c
by K & R Yoksh 01 Jan '08

01 Jan '08

Thanks for all of the replies, both on and off the list. Happy New Year to all! 73, Kyle Yoksh K0KN Olathe, Kansas

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Detailed Information on Telemetry
by John Henderson 01 Jan '08

01 Jan '08

Happy New Year to the folks on the BB, Mike Rupprecht and others have given me quite a bit of info on understanding the telemetry from AO-16, but I am interested in learning more about the details of the raw info ( I understand the hex data) and what the acronyms are like MBL, etc. Can any one point me to a good source and tell me how much detail is in the digital book in the AMSAT book Store? Thanks and Best 73 John John Henderson N4NAB 212 Bayside Drive Cape Carteret, NC 28584 252-725-2744 <mailto:n4nab@amsat.org> n4nab(a)amsat.org <http://www.amsat.org/> http://www.amsat.org/

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70cm Yagi and AO-51
by Andrew Rich 01 Jan '08

01 Jan '08

Gudday I tried a crossed offset yagi on the one boom. When I threw just one part of the yagi on the boom, AO-51 was really good, Now I am finding that with the second yagi on the boom I am seeing a big drop between 435.300 and 435.150 voice / data. I think I might remove the second yagi from the common boom and add it to a new seperate boom Comments ? I think I am getting -20db due to the cross polar RHCP LHCP with the data The voice is great , the data is down in the mud ---------------------------------------------------------------------------- Andrew Rich VK4TEC vk4tec(a)people.net.au http://www.tech-software.net

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