RE: [amsat-bb] Re: HEO naïveté

[Gary "Joe" Mayfield]

My observations...

I miss the HEOs too, and I believe our AMSAT-DL friends have an HEO
basically waiting in the closet if a ride were to show (I know that's an
over-simplification).

I think a phase IV shared space satellite would/could be a great boon to
emergency communications!  And our public relations!  But I fear it would be
about as much fun to work as dialing my cell phone, no tracking, no Doppler,
100% predictable propagation.  Okay, more reliable than my cell phone.

The microwave thing always gets me though.  If the antennas are too big how
come they can get them on cube sats?  I know the correct statement is
high-gain antennas are too big.  The problem is gain antennas need some
pointing mechanism (complicated and expensive) and they need to be pointed
no matter what band they are designed for.  When using omni antennas the
lower frequency will yield higher performance due to lower path loss....

The bottom line is to keep building what ever we can get up there, and make
sensible use of reasonable frequencies.  I'm still glad AMSAT-NA built and
orbited AO-51 as opposed to dumping all of our resources in Eagle which I
believe would still be on the ground anyway.

73,
Joe kk0sd


At 04:28 PM 2/6/2009, Rocky Jones wrote:

>Bob...Your "rant" strikes me as pretty close to right on the 
>money.  I read the missive in the latest journal about 3.3 and 5.6 
>ghz links and thought "thats nice, It will never happen".
>
>A baseline requrement  for ANY Amateur satellites should be that 
>they work on frequencies and modulation methods which are consistent 
>with radios that are already commercially manufactured for the bands 
>in question...or can use some very easily (think the MDS converters) 
>commercial gear for other services.
>
>The instant the "bird" is designed with some type of radio in mind 
>that does not exist now and is limited to that bird...then the 
>entire adventure is nice but has little practical value.
>
>Why on earth is the AMSAT community wasting time on a design which 
>requires a ground station that is (by the latest Amsat Journal) 
>"beyond the scope of most hams".  Instead of spending time working 
>on  making an 'acp capable earth station within the reach of most 
>radio amateurs".
>
>Because if the equipment has little value beyond a satellite which 
>could do an Oscar 40 at any time how many are going to shell out the money?
>
>I dont have a clue why the AMSAT design folks seem to think that it 
>isnecessary to drive up into the microwave frequencies.  They never 
>seem to answer the question why a 2meter 70cm translator is not a 
>good solution...and the one that we really need.
>
>Meanwhile AO-7 flies on.
>
>Robert WB5MZO life member

Well, there are a few reasons:
1- 2m & 70cm antennas are large and it takes a large satellite to support
them
2- Microwave antennas are physically smaller and yet will provide more gain
3- Microwave frequencies are quieter (low sky noise) so they work 
better with low noise receivers; some mw freqs. are less impacted by 
interference and/or pirate stations.

When such a mw satellite can be launched, many sources of equipment 
will surface.  Downeast Microwave and Kuhne Electronics will come out 
with equipment when there is a market for them.

73, Ed - KL7UW