[amsat-bb] Re: Redundant geostaionary birds?
Edward R. Cole
al7eb at acsalaska.net
Tue Jan 30 02:16:55 PST 2007
Dave and all:
I wonder what all of you were thinking? If a commercial communication
satellite were channeled on one of our mw ham bands, then we would be
C-band satellites used approx. 37-MHz wide channels with alternating linear
polarity to afford more adjacent channel isolation. On most of the TVRO
units one could manually adjust polarization angle for optimizing the
signal. If you adjusted 90-degrees off then one often got a ghost of one
of the adjacent channels. The feedhorns had a rotating probe with the
motor on the backside of the feedhorn.
Typically in the mid-1980's these TV sats cost over $100M before launch.
Your not going to convince the satellite company to include ham radio in
AS has been hashed out many times previous on this reflector the path loss
to the Clarke Belt orbit is prohibitive.
This topic is going no-where!
73, Ed - KL7UW
At 04:04 PM 1/29/2007 -0800, Dave hartzell wrote:
>It looks like the commonly adopted block conversion for C-band
>transponders wouldn't land in our bands. There seems to be a delta
>for 2.2 GHz for the block conversion (e.g. 5.9 GHz up, 3.7 GHz down).
>We'd need more like a 4 GHz conversion to land in our S-band, given a
>5.8 GHz uplink. I'm sure the filters aren't quite tuned to go below
>out of band, either.
>Another issue I just realized is that these transponders use polarized
>signals (left, right, vertical, horizontal, polka-dotted)....this
>again makes using an old communications sat a bit more difficult (but
>not impossible) for us hams.
>Looks like this was not meant to be!
>On 1/28/07, Karl Bullock <karl at bullock.org> wrote:
>> Dave hartzell wrote:
>> > 3) Most of the uplink freq's are in the 5.9 GHz range (out of our
>> > allocation) and downlink in the 3.7 GHz range, again, (out of our
>> > allocation).
>> That may be _the_ problem. I don't know the current capabilities of
>> these birds, and if they have any capability of either "retuning" to a
>> close amateur band, or if there are other assets on board, but inability
>> to transmit/receive on one of our bands would probably make this a non
>> sequitur. Those with more intimate knowledge of current flying
>> technology would need to speak to this.
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