Path loss is 15 dB less at 435 MHz than 2400 MHz
and antenna gain is 13 dB less. However, the noise figure is 5 dB
higher, so almost twice the EIRP wll be required on a U uplink
than an S uplink. The 70 cm receiver has a 200 kHz bandwidth so some class
2 (4800 bps) uplinks could be accomodated. Since they will be BPSK and use
FEC, I assume that they will occupy at least 15 kHz each and will have to be
spaced at least 25 kHz apart. This could allow 4 uplinks. It's not good to
increase the receiver bandwidth as it will let in more PAVE PAWS
interference.
73,
John
KD6OZH
----- Original Message -----
Sent: Saturday, September 16, 2006 22:06
UTC
Subject: [eagle] Re: [Advisors] [Fwd: Re:
S band and Eagle: an appeal for ahigher level discu...
Hi all,
As discussed with Bob McGwier at
this weekend's TAPR conference in Tucson, I believe that the current frequency
recommendations for the Eagle digital payload somewhat underestimate the
inefficiency and time lags of the international regulatory process, as well as
the inconsistency of application from one country to another.
While
amateurs in some countries may well find themselves unable to use 1.2 GHz
uplinks for the reasons stated, that situation may not apply to others.
Some countries, such as many in Region II, may continue to permit 1.2 GHz
uplinks because their navigation systems will continue to be GPS-based.
In some other countries, in and out of Region 2, there is effectively little
or no telecommunications regulation at all, or such regulation is ineffective
in practice.
Similarly, as Robin has pointed out, some countries may
well prohibit uplinking on 2.4 GHz for whatever reasons, such as interference
with Wi-Fi etc., irrespective of whatever the ITU Radio Regulations might
say.
So, depending on where he is located and the RF environment in his
area, an individual user may find that:
1. He may not use 1.2 GHz
but may use 2.4 GHz.
2. He may not use 2.4 GHz but may use 1.2
GHz.
3. He may use both.
4. He may use
neither.
Since the actual regulatory environment on the ground is
unpredictable, Eagle's uplink configuration needs to take all four
possibilities into account.
The first three may be accommodated by
flying BOTH 1.2 and 2.4 GHz uplinks, which I am recommending. Planning
for the fourth, however, is a little more complicated.
As has been
discussed previously, the link budget argues strongly against the use of 10
GHz or higher frequencies, and we cannot realistically fly a 5 GHz uplink
since it would be too close in frequency to our 5 GHz downlink. The use
of 3.4 GHz is prohibited in Region 1.
My suggestion, therefore, is to
fly a digital uplink at 70 cm in addition to those at 1.2 and 2.4 GHz, and
also in addition to the 70 cm analog SDX uplink already planned. Since
the amateur-satellite service allocation there is only 3 MHz wide, the uplink
bandwidth would be limited accordingly. My "straw man" suggestion for
that would be 435.5-437.5 MHz, with 435.0-435.5 used primarily for SDX and
other such systems (e.g., P3E if it is still up and working by then), and
437.5-438.0 used, as now, primarily for human spaceflight applications, i.e.,
whatever succeeds ISS.
A 2 MHz bandwidth would not be as good as the 10
MHz envisioned for L-band and S-band, and the uplink EIRP requirement (and
thus ground antenna size) would be higher than I would like, but remember that
the 70 cm uplink would be primarily for those who cannot use 1.2 and 2.4
GHz. For them, such an uplink would make the difference between being
able to use the Eagle digital payload or not.
My 2 cents worth,
anyway.
73,
Ray
P.S. I am speaking here only for myself
and not for the IARU Panel, which has not considered this matter.
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