May 2009 - AMSAT-BB - mailman.amsat.org

ISS SSTV Active
by David Barber 26 May '09

26 May '09

ISS SSTV is active on 145.800MHz UK pass at 15.40UTC Pictures from camera looking out of the window. David G8OQW

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Iss digi rs0iss-4 today!
by Mr Jeffrey L Ross 26 May '09

26 May '09

hi folks, wondering why there changing the digi around from -3 to -4 again. just when i got a nice pass, hi oh well , try to reach it today 1600 pass. kc8gkf-5

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Calculation of foundation requirements for dish antenna
by Pieter Kotze 26 May '09

26 May '09

Hello all Anyone out there got a rough guide to calculate the foundation requirements for a parabolic dish antenna? We have acquired a 10m C-band dish which we would like to re-use. I am a bit rusty on undergraduate applied mathematics. Anyone with a nice tutorial? Regards Pieter -- This message is subject to the CSIR's copyright terms and conditions, e-mail legal notice, and implemented Open Document Format (ODF) standard. The full disclaimer details can be found at http://www.csir.co.za/disclaimer.html. This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. MailScanner thanks Transtec Computers for their support.

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Re: Antenna Polarization
by k9qho6762＠sbcglobal.net 25 May '09

25 May '09

This is what I would recommend. I do not have polarization switching for either of my antennas. My 11 turn helix on 435 MHz is RHCP My 14 element KLM on 144 MHz is LHCP K9CIS has studied the polarizations of the uplink/downlink signals from AO-7, VO-52, and FO-29 and this seems to be the best selection. Using his recommendation, I do remember switching my KLM from RH to LH because AO7's downlink was weak and switching did solve the problem. The helix (polarization cannot be switched) was constructed for AO-40 (which was RH) and easily hears FO-29. The optimum set-up is to be able to switch polarization, but you know how things go in the world of ham radio. All the best. Mike (K9QHO) AMSAT 33589

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Re: Gulf Alpha antenna
by vk5alx＠amsat.org 25 May '09

25 May '09

I use a homebrew 2x5 on a 2 metre long boom and it works very well with all current sats. 73s, Alex VK5ALX >One of the other questions I have, "2m Satellite 2x5 does it have enough >gain to work the birds? > > 73, > Norman. >73's Jan - PE0SAT

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Antenna questions
by Joe Hayes 25 May '09

25 May '09

Hello Everyone, I am new to the list (I'm sure you could have guessed that on your own) After 30+ years of being away from satellite work I have decided it's time to get back into it.. I used to work AO-6 AO-7,RS-15,ect.. Had an old Ameco TX-62 Xmit and used my "new" Kenwood 599D twins for downlink. I have looked for a week or better to find answers but still have several I can't find. I will be using the old (rebuilt) Cushcraft A144-T10 and a new homebrew 22 element 70 cm (11 vert, 11horz). 1. What circular polarization should I be using, LH or RH? I will not have polarization switching (at least not for a while) 2. What is good software for my Yaesu G-5400B rotator? 3. What is a good Interface for my Yeasu G-5400B rotator? 4. Need some good links for reference. thanks.. de wd9apy

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looking for Bob Twiggs
by Nick 25 May '09

25 May '09

Can somebody on the list please send me Bob Twiggs contact info \\\ Thanks nick

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Re: Optimal Distance
by Edward Cole 25 May '09

25 May '09

At 02:39 AM 5/25/2009, Norman W Osborne wrote: >Hello everyone, > >I am looking for suggestions for optimal distance between X yagi's >on a boom, so that there will be none or very little interaction with their >respective radiation fields. > >Also I will be adding a 24" dish between the two yagi's >on the same boom with the 70cm and 2 meter X yagi. > >Thanks to all in advance >Norman. Norman, Since I have not seen any response to you on amsat-bb, I will. First we need to know the aperture of the antennas. This will have to be calculated from the gain. Unfortunately, most antenna manufacturers are optimistic about the gain of their antenna. But if you have the gains in dBd: 1. Convert to dBi = 2.1 + dBd 2. Convert gain to a ratio G = 10^(dBi/10) 2. Use this formula G = 4*pi*Ae/lambda^2 to derive Ae 3. Ae = G*lambda^2/(4*pi) = G*4.33/12.56 = 3.45*G 4. Ae for x-yagi is assumed a circle: Ae = pi*R^2 5. R = sqrt(Ae/3.14), R is the width of your aperture so half that would be used for stacking distance. 6. The distance between 2m and 70cm antenna = 1/2 (R(2m) + R(70cm)) The dish will probably sit inside the 2m aperture but be outside the aperture of the 70cm antenna. I mounted my 436CP42 and 2m antennas five feet apart with the 33-inch dish set on the UHF side of the B5400 az-el rotator. This is probably closer than using the apertures for stacking.

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Re: tuning CP-6
by Alan P. Biddle 25 May '09

25 May '09

Mark, If you can get the CW at 1200 Hz, the following telemetry burst will be right on frequency, and decode every time. Using MixW is a great way to do this. You just need to be very quick with the mouse. ;) DK3WN and I have both found that 2009-028D, NORAD 35004, currently gives much better agreement, especially on Doppler correction, than the others, including 35002 which CalPoly had on their site. Based on the passes yesterday afternoon, my current DOPPLER.SQF file has this: 2009-028D,437364.3,0,LSB,,NOR,0,0 Mike finds a slightly lower RF frequency, but that may just be calibration. Except for one burst at an over the top TCA, the CW was within 200-300 HZ of predicted the whole pass, and the telemetry program has able to handle the slight deviation. 73s, Alan WA4SCA

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Optimal Distance
by Norman W Osborne 25 May '09

25 May '09

Hello everyone, I am looking for suggestions for optimal distance between X yagi's on a boom, so that there will be none or very little interaction with their respective radiation fields. Also I will be adding a 24" dish between the two yagi's on the same boom with the 70cm and 2 meter X yagi. Thanks to all in advance Norman.

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