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Re: AMSAT has a SECRET: why not 10m instead of V band



Hello to ALL,
my 2 cents,worth or not:

- I started with the birds for the first time around 1974 with AO-6 copying the
bea-
con on 10 meters and passing the readings through the weekly Amsat Net on 20
meters, using dipoles and verticals.Later I returned with AO-10 and AO-13 plus
RS series and the Leo's. So far mode B for me is still the preferred operating
mode for a very simple reason.I do not have access to tools to which garants to
me
the correct tuning/setting of equipment working in the 2.4 range and above, also
I do not have the availability of low priced parts you have in the USA, for us
these
are very expensive.I'm dreaming with a down converter set from DEM plus the
helix, because I think I can rely on DEM.This setup will cost me here at least
US$800,00, a lot of money.Therefore a new project, for me, has to have a mode
B transponder build in.
73's
Nicolaus Sallay-PP8DA
E-mail : n.sallay@internext.com.br

----- Original Message -----
From: <rdwelch@swbell.net>
To: <sco@sco-inc.com>
Cc: "Douglas Cole" <n7bfs@qwest.net>; <amsat-bb@AMSAT.Org>
Sent: Sunday, June 03, 2001 2:28 PM
Subject: Re: [amsat-bb] AMSAT has a SECRET: why not 10m instead of V band


> My 2 cents worth:
>
> I can recall operations on the early satellites with mode A (2M up & 10M
> down) and on those with mode B (70cm Up & 2M down).  Mode A was never as
> satisfactory as mode B, mainly because I never could hear the mode A 10M
> downlink until it was well above the horizon, sometimes as much as 25
> degrees above.  I could always hear my own mode B downlink signals within
> 20-30 seconds after AOS.  I assume the mode A 2M uplink was able to access
> the satellite very shortly after AOS similarly.  The 10M downlink however
> was poor or non-existent at my receiver.  The 10M antenna was a vertical
> which had most of its gain near the horizon with very little gain
> vertically.  However, I could hear the satellite on this antenna when the
> angle of approach of the signal was high but not when the satellite was
> below that elevation
>
> I think the reason for this was that the satellite was above the ionosphere
> layers and that the angle of incidence of the arriving signal was low
> enough that the ionosphere absorbed or reflected the signal back out into
> space.  When the angle of incidence became high enough, the signal began to
> penetrate the ionosphere and reach my 10M vertical.  This was born out here
> by the fact that this effect was more noticable during daylight hours and
> less so at night.  It also varied with the sunspot cycle.  In other words,
> when 10M was open to the world for terresterial DX, the mode A downlink
> access was pretty limited.  When the old 10M band folded up, the 10M
> downlink was much improved.
>
> Another effect of this situation was that the 10M downlink might be poor at
> one station when the satellite was in range.  However, other stations well
> outside of the acquisition circle could often hear the 10M downlink due to
> multiple refraction paths in the ionosphere.  This was of no use to them
> because their uplink signals could not be heard by the satellite.
>
> When mode B came along on AO-7, I jumped at the chance to build something
> to make use of it.  I cobbled together an old Motorola 2C39 final box as an
> amplifier and drove it with a transverter kit and 18 watt intermediate
> amplifier kit, using my Heathkit HF rig.  The difference was remarkable.  I
> could work stations horizon to horizon.  It was with this arrangement I got
> my satellite WAS.
>
> As a result I have never gone back to operating on mode A.  In my opinion
> it is not a very satisfactory arrangement, probably for more reasons than I
> have listed here.
>
> --
> 73, Roy
>
> Internet: w0sl@amsat.org
> Home Page: http://home.swbell.net/rdwelch
>
>
>
> sco@sco-inc.com wrote:
>
> > I do not see what is so hard about putting a 10m downlink on "Project JJ".
> > Then using a V band uplink with it. That combination (would it be called
> > "V/A"?) I assume would work great at and near perigee (if an AO-40 type
> > orbit is used for Project JJ). It would certainly help to attract new hams
> > and current non-satellite hams to our hobby and to AMSAT. Anyone with a
> > general coverage receiver and long wire antenna could hear the satellite at
> > perigee.
> ----
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