[amsat-bb] Station decisions re. upcoming Geosync bird
jim at k6ccc.org
Thu Mar 24 14:25:41 UTC 2016
Sure. Remember that AO-40 at apogee was WAY beyond the Clark belt. Took a
little bit of getting used to, but was not a real problem.
Jim - K6CCC
From: "Joe" <nss at mwt.net>
Sent: Thursday, March 24, 2016 5:32 AM
To: amsat-bb at amsat.org
Subject: Re: [amsat-bb] Station decisions re. upcoming Geosync bird
Full Duplex on a Geo Bird,,,,?
What is the delay lag time on such a distance?
The Original Rolling Ball Clock
On 3/23/2016 11:17 PM, John Toscano wrote:
> Details on the satellite are still quite sensitive, but details on
> 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
> 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
> 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
> 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>
>> 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
>> 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
>> that pattern will be at my location. My 144 and 440 MHz antennas will
>> 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
>> know and I'll shut up. :-)
>> --Peter, KD7MW
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