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Re: This Weekend in Minneapolis: Central States VHF Society Meeting


At 11:44 PM 7/29/2006 -0400, Andrew Glasbrenner wrote:
>Jim and all,
>If I read things correctly Eagle will still carry a S-band beacon? It seems 
>to me if we go to the trouble of including a transmitter and antenna, we 
>might as well provide a little passband for those who don't have the 
>interference issues? Even say 25 khz?

When I proposed this to Bob McGwier, he responded that they would not be
providing S-band downlinking.  All I can guess from this is that no
provision is being considered for linear transponding.  Perhaps the beacon
is psk digital, only?

>I read with interest accounts of people with interference on S-band, and I 
>notice that there may be a common thread. Many of the antennas used for 
>reception on AO-40, and even more used for AO-51 are not very effective at 
>blocking sidelobes and thereby mitigating interference. It may be (and 
>certainly is in my own experience) that successful weak signal S band HEO 
>operation is going to require more than a BBQ dish and unprotected feed, or 
>a helix wound on some PVC pipe. My own AO-40 downlink antenna was nearly 
>immune from interference when above 15-25 degrees, including from the WAP 
>and video sender in my own house. This was in an urban environment where I 
>routinely could see 5-6 local WAPs on a wifi PC in the yard, and over a 
>dozen with a gain antenna. My dish was very simple. 36" prime focus, with a 
>homemade helix feed in a cup to reduce sidelobes. All of this was mounted 
>with 70cm and 2m CP yagis on a G5500 on a roof tripod. The dish and homebrew 
>feed and mounts cost less than 100$. Just another anecdotal data point for 
>your consideration.

I do not live in urban America so cannot guess how bad WiFi is or will be,
but your reasoning seems logical to me.  What I am hearing is the subject
of L or S-band is closed for Eagle.

>I understand that Eagle II is being considered as a close follow-on for 
>Eagle I? Maybe there can be some diversity of modes between the two 
>satellites, say U/V and S/C on I and UL/S and C/X? on II?

I asked about mode-X and got no response to my question, so I gather that
it is not being included on Eagle-I.  If I were to guess it may be an
attempt to not repeat trying to build a satellite with everything on it
(like AO-40).  So the choice is for one VHF/UHF transponder and one mw
transponder; one analog voice and one digital voice/video.

But if I have any assumptions wrong I hope a member of Eagle design team
will correct or clarify.  Really, I should not speculate as too many folks
will read this as "fact".  
Ed - KL7UW 
BP40iq,  Nikiski, AK      http://www.qsl.net/al7eb
Amsat #3212
Modes: V - U - L - S
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