Re: [amsat-bb] Re: HEO naïveté

[Michael Heim]

I usually tend to keep quiet during arguements such as this, but I need to chime in on this one.

I live in a location that frowns upon antennas.  I was able to put up a mode V/u as well as S band antenna to get me on AO-51.  This antenna has 3 ele on 2m, 6 ele on 70 cm, and the S band antenna is a 18 inch long yagi.

This system is way too small for a GEO or HEO bird.  I was on AO-10 + 13 when they were up.  My 2M was 22 ele crossed yagi, and a 10 turn 70 cm helix.  Very large antennas compared to what I'm using now.

I'm not certain, but I believe I would be able to receive an S band SSB signal with my current S band receive setup from a geo sync orbit.  

There is a law of physics that states that if the antenna size remains the same and the frequency increases, the signal strength will also increase.  Notice I said antenna SIZE not GAIN, because as the frequency goes up and the antenna remains the same size, the gain will overtake the increased path loss.  I understand the reason for having to use microwaves for rideshare birds.  Thing is, the microwaves give you a distinct advantage, and that is a stronger signal and less noise.  the cost for that?  some new equipment.

I recently bought myself a new laptop.  It wasnt a very high end unit, about $600.  I really didnt NEED it, but the same money would have bought me a new microwave band and had money left over.  Reason I didnt get the transverter?  lack of activity.  If a satellite would have been launched, hey, guess what I would have bought instead?  yep, you guessed it...  A new DX band!  

Lets say 5760 is used on an upcoming bird.  Ground station with a 19 inch dish with a simple homebrew feed will have almost 30 dB of gain!  thats 100 times more signal than your 2 meter arrow, and the antenna is a lot smaller!

By the way, I hold VUCC on terrestrial 10 GHz, so I think I have some idea as to what I'm talking about.

Michael Heim
ARS KD0AR
Amsat 36924


--- On Sat, 2/7/09, Jeff Davis <ke9vee at gmail.com> wrote:

> From: Jeff Davis <ke9vee at gmail.com>
> Subject: Re: [amsat-bb] Re: HEO naïveté
> To: amsat-bb at amsat.org
> Date: Saturday, February 7, 2009, 11:10 AM
> On Sat, Feb 7, 2009 at 10:50 AM, Gary Joe Mayfield
> <gary_mayfield at hotmail.com> wrote:
> > 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....
> 
> CubeSats buzz around 180 miles over your head. At apogee,
> AO-13 was
> 23,000 miles from the ground.
> 
> That's why the gain antennas were needed and when you
> add up the power
> required for a transponder to handle lots of stations at
> the same
> time, then the link budgets and antenna sizes (for more
> gain) at
> higher frequencies begin to make a LOT more sense.
> 
> The tightrope the developers walked was always how to
> deliver
> performance on frequencies that stubborn members demanded
> always be
> used. The S-mode stuff held much promise with AO-40. James
> Miller,
> G3RUH presented all the superior reasons for S-mode (the
> paper is
> still in the archives) but for a large percentage of
> members it was
> always "2 meters on the downlink or I will withhold
> funding".
> 
> Just like those who raise a stink now whenever almost
> anything is
> proposed requiring more than a fifteen year old dual band
> handheld and
> an Arrow antenna...
> 
> Sigh.
> 
> As has been hinted around this thread, our problems are
> almost 100%
> self-inflicted. We have shot our toes off until we have
> none left to
> shoot. I don't blame the leadership -- this
> "club" contains some of
> the most stubborn individuals in all of hamdom. Perhaps if
> AMSAT can
> stick around long enough, the naysayers will all eventually
> die off
> and we can move forward with reality instead of dreamy-eyed
> reminiscing about days gone by and what might have been.
> 
> Jeff, KE9V
> AMSAT-NA
> AMSAT-DL
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