[Ground-station] [amsat-bb] Update: Rent GEO bandwidth for US

[Wally Ritchie]

After a cursory glance it looks like a 1.2M Dish and 3W BUC would provide a
C/N at the transponder input of about 17dB. (That's based on an assumed G/T
of 8.5 dB - will have to look at the actual G/T footprint). This is based
on a 1MHz wide DVBS2 uplink (800Mbps). The downlink (to all CONUS) should
be very good. But there is a bandwidth issue that must be addressed in the
receive setup as the 1MHz DVB-S2 signal may have strong adjacent carriers.
Again, have to look at the actual allocation and guard bands for the
channels. Normal consumer tuners typically have 6 - 45 MHz tuner bandwidth
into the DVBS2 demodulator. So the the DVB-S2 receiver must be able to
reject the adjacent signals that are within the passband of the tuner. In
the receiver designs we've been working on we have additional narrow
bandpass filters to deal with this.

1.2M Tx/Tx Dishes, dual cross-polarity feeds, and 3W BUC's that are type
approved are cheap and readily available. These are standard high volume
VSAT components. LNB's with the appropriate waveguide inputs are also
relatively cheap. I'm not sure whether the Modem actually has to be type
approved. If the antenna, feed,  and BUC are type approved that may be
sufficient. If we need to gain type approval for the modem that is not an
insurmountable obstacle. There is also the option to use a commercial modem
that can accept a DVBS2 waveform.

This type of station can be viewed as an emulation of  a future P4X
transponder downlink. The emulation is almost identical to a real downlink
except it has two hops through a bent pipe rather one link from space to
earth. Otherwise the P4X transponder output on the ground (which feeds the
uplink) generates the exact same DVB-S2 signal that the future P4X
transponder will generate in space. The exact same approach can be used
through QO-100 on the Amateur Bands. The only difference is in uplink
frequencies and power and the absence of type approvals for the QO-100. The
primary motivation for using a commercial link is that it appears to be the
only way to provide downlink coverage for CONUS. There are no particularly
difficult issues in RO operation at 11.5GHz or 10.GHZ so modem equipment
suitable for either QO-100 or P4X is feasible.

Basically, a low cost earth station can receive the 11.5 GHz transponder
output and it will look very similar to a P4X repeater in space - except
that the future P4X downlink may be weaker. We might actually simulate the
expected C/N on the ground by purposely lowering the C/N on the uplink. In
any case, the received DVB-S2 signal will be demodulated by Earth Station
P4X modem to produce identical GSE streams for either case.

For the transmit side, the P4X Transponder uplink can be emulated through
the Internet. Instead of the modulator providing an RF signal transmitted
to the satellite, the modem sends a packet representing the modulated
signal through the internet to the P4X transponder on the ground (and
attached to the internet). The P4X transponder then combines these
simulated RF packets in a fashion equivalent to the output of the
multi-channel receiver in a space based repeater. These are then used as
the inputs to the narrowband and wideband multiplexors for the GSE streams.
The same protocol rules that will eventually apply to the real RF
transmitters will be applied to the emulated transmitters. Authentication,
Authorization, and Channel Allocation would all proceed in the same fashion
as it would for the P4X transponder in space.

The above configuration would a solid testbed for supporting the
development of the P4X transponder and modem. However, in the US it will be
dependent on the Internet. Hams could deploy a very low cost earth station
using a real 12GHz downlink for the DVBS2 signal and low cost dish and RNB.
The BUC would not be required. (The modem could even omit the modulator
although I don't think that would be necessary). In any case this would be
a fully functional station as long as there is internet connectivity. When
a P4X transponder is finally deployed in space, stations can be converted
to Tx/Rx by upgrading to a dual feed and installing a 5GHz Hamband BUC.

For disaster response, a second channel would be required to simulate the
uplink with a space segment rather than the Internet (presumed to be down
within the disaster zone). This would add delay in the uplink (greater than
the delay through the Internet). This could be accomplished by splitting
the 1MHz channel into two pieces or using another channel on the same
satellite in the same or different transponder. This type of configuration
is similar to that of using QO-100 for both uplinks and downlinks of a P4X
Transponder on the ground. Deploying VSAT's for disaster response is well
covered ground.

In any case, I think it worthwhile to explore this further as P4X
Transponder development moves forward. The QO-100 configuration for a
similar arrangement was presented at DCC 2017. A paper on this is availble
from here https://www.tapr.org/pdf/DCC1017-DVB-S2Repeater4GEO-WU1Y.pdf and
a youtube of Steve Conklin's presentation is here:
https://www.youtube.com/watch?v=sTprB3bUGCM

WU1Y
Wally




On Thu, Aug 22, 2019 at 9:38 PM Howie DeFelice via Ground-Station
<ground-station at lists.openresearch.institute> wrote:

> I don't recall seeing a requirement for a licensed installer in Part 25
> but I will check again because I'm curious and really should know anyway.
> $2K/mo. is a decent price for CONUS coverage, there is still allot of
> demand. You can often find deals on used BUCs and LNBs on EBay. I recently
> bought NJRC 4W BUC for $125 and it even worked. Each earth station would
> need its own FCC license which is a pain to file for and if I remember
> correctly has a filing fee around $400. You need a minimum antenna size of
> 1.2M to be "routinely" licensed. There are satellites every 2 degrees in
> the CONUS arc. Every time you move the antenna you need to contact the
> satellite operator to verify correct pointing and polarization adjustment
> and confirm you are not exceeding your contracted downlink EIRP. The only
> way this would make any sense would be if a group got an STA and got
> certified by the GVF.
>
> Howie AB2S
>
> Get Outlook for Android <https://aka.ms/ghei36>
>
> ------------------------------
> *From:* Ground-Station
> <ground-station-bounces at lists.openresearch.institute> on behalf of Phil
> Karn via Ground-Station <ground-station at lists.openresearch.institute>
> *Sent:* Thursday, August 22, 2019 1:25:51 PM
> *To:* ground-station at lists.openresearch.institute
> <ground-station at lists.openresearch.institute>
> *Subject:* Re: [Ground-station] [amsat-bb] Update: Rent GEO bandwidth for
> US
>
> On 8/22/19 08:17, KC9SGV via Ground-Station wrote:
> > Echostar 9
> > Here she is:
> > 32 FSS transponders in the Ku band.
> > 120 Watt...
> >
> >
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fspace.skyrocket.de%2Fdoc_sdat%2Fechostar-9.htm&data=02%7C01%7C%7C03927b4247e64c2c47bd08d727268214%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637020918654236654&sdata=XLDxnN0YqK92%2Be6i%2B4zgZgV7JdeixDcHfPSZuIMS1jw%3D&reserved=0
> >
> > KC9SGV
> >
> > Sent from my iPad
> >
> >> On Aug 21, 2019, at 8:34 PM, Michelle Thompson via AMSAT-BB <
> amsat-bb at amsat.org> wrote:
> >>
> >> An arrangement on Echostar9 for 1MHz of bandwidth for up to 4 years of
> >> USA+Mexico+Canada coverage is on offer for $2000 a month.
> >>
> This would not be in the amateur satellite service, so we'd need to use
> commercial type-approved ground equipment, or gain type approval for our
> own designs. That could get very expensive. Check out, e.g., Qualcomm's
> filings for its Omitracs service for what was required to get something
> novel past the FCC. The chief concern with commercial geostationary
> satellites is spraying adjacent satellites with uplink QRM. They're
> packed quite closely in longitude these days, close enough that the
> usual ground antenna patterns can't be assumed to roll off fast enough.
> So you have to analyze the system and show it's not objectionable. Also,
> assuming the satellite in question is also carrying other traffic, you
> have to show that your uplink transmitters are clean enough to not
> interfere with those signals.
>
> On the other hand we would not be subject to limitations on 3rd party
> traffic or encryption.
>
> I seem to recall that ground stations for retail Internet access have to
> be installed by professional installers, which could also get expensive.
> I don't know if that's a FCC requirement, or just a vendor policy.
>
> This is not an easy or cheap option. $2000/mo for the transponder would
> just be the beginning. It's not like QO-100, where the satellite
> transponder itself operates in the amateur satellite service (2.4 GHz
> up, 10 GHz down).
>
> Phil
>
>
>
>
>
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