[amsat-bb] Station decisions re. upcoming Geosync bird
n8hm at arrl.net
Thu Mar 24 12:39:20 UTC 2016
Remember that AO-10, AO-13, and AO-40 at apogee were all at about
geosynchronous altitude or higher, so hams have experience operating
full duplex with such a delay.
On Thu, Mar 24, 2016 at 8:31 AM, Joe <nss at mwt.net> wrote:
> Full Duplex on a Geo Bird,,,,?
> What is the delay lag time on such a distance?
> Joe WB9SBD
> The Original Rolling Ball Clock
> Idle Tyme
> On 3/23/2016 11:17 PM, John Toscano wrote:
>> Details on the satellite are still quite sensitive, but details on ground
>> station requirements are much more readily discussed due to the lack of
>> ITAR restrictions there.
>> One approach to the ground station would be to add a 5G and a 10G
>> transverter to your existing radios, using them for IF radios. Though many
>> 5G and 10G transverters use a 144 MHz IF, some are available with a 432
>> IF. Getting one of the two transverters with a 432 MHz IF and one with a
>> 144 MHz IF would probably facilitate full-duplex operation, unless you
>> two 144 MHz IF radios available.
>> This sort of approach might be preferred by an operator who plans to add
>> those two bands to BOTH terrestrial and satellite operation. But if you
>> were adding these two bands for satellite use only, there is significant
>> opportunity for financial savings. You only need a 5G transmitting
>> converter and a 10G receiving converter. On the receiving end, a modest
>> satellite dish and an inexpensive LNBF designed for for satellite TV will
>> convert the satellite downlink to a signal somewhere near 700 MHz, which
>> easily within the RF range of many software-defined radios. The ground
>> station team has been hoping that an under-$20 satellite TV PLL-LNBF
>> coupled with an inexpensive RTL-SDR dongle MIGHT suffice for the heart of
>> the 10G receiver. For the uplink, it is possible that a $300-ish HackRF
>> SDR (which can transmit at up to 6 GHz), coupled with appropriate
>> and a suitable power amplifier might form the heart of an inexpensive 5G
>> transmitter. The ground station team is looking at other, more expensive
>> solutions, as well, and we can't yet promise that the rock-bottom-price
>> solutions will work until they have been well-tested.
>> In any event, digital modes are going to be the order of the day, so if
>> are using a pair of all-mode radios as IF's, they will need to support a
>> digital interface to a computer. That's one of the reasons why we are so
>> excited about the possibilities of SDR to get us from RF to digital data
>> and back at affordable prices.
>> \I hope that helps at least a little bit.
>> John Toscano, W0JT/5
>> On Wed, Mar 23, 2016 at 7:44 PM, Peter Klein <pklein at threshinc.com> wrote:
>>> I've been casually following the discussion of the upcoming
>>> satellite. I currently have a Mode B , J and A analog setup that I've
>>> on Oscar 10 and 13, and on some LEOs. This includes crossed Yagis on 2m
>>> 70cm, and an all-mode radio for those bands. LEOs and flying mailboxes
>>> longer interest me, so in recent years that setup has only been used for
>>> occasional terrestrial VHF SSB/CW, plus local repeater activity.
>>> I will need to make some decisions on my general station setup soon.
>>> Antenna space is limited, and I want to take the possibility of the
>>> bird into consideration. From what I've read and seen on video, the
>>> uplinks and downlinks to the satellite will be microwave. The satellite
>>> track will make a figure-8 pattern in the sky, but I don't know how large
>>> that pattern will be at my location. My 144 and 440 MHz antennas will not
>>> be compatible with the new bird. But will the 144/440 radios be useful,
>>> perhaps as an IF after the digital gymnastics happen in a converter?
>>> So, my questions:
>>> - Are any "dummy" Keplarian elements available for the geosynch bird's
>>> planned (or likely) orbit? That would let me do some "what-iffing."
>>> - If the above are not available, could someone tell me the approximate
>>> range of azimuth and elevation I might expect from CN87 (Seattle area)?
>>> - What is the physical size of the required dishes?
>>> - Will the radio for the new bird be self-contained, or require another
>>> radio as an IF? If the latter, what frequency band or bands are being
>>> contemplated for the IF?
>>> If I've asked things that are too sensitive to discuss right now, let me
>>> know and I'll shut up. :-)
>>> --Peter, KD7MW
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>> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
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> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
> to all interested persons worldwide without requiring membership. Opinions
> are solely those of the author, and do not reflect the official views of
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
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