Alright, so, basically everything that I know about satellite, I learned in the military, working in SATCOM, in the 8GHz range (no, that's not classified). When it comes to amateur radio satellite, I know, well, nothing. That leaves me with quite a few questions, but to keep it short, I'll start with two: Q1: This thing is going to be geosynchronous. What's the polarization? Because if this bird is going to be spinning like a top, then the claim that a Dish Network dish and LNB is going to work comes with a big asterisk - you'll need the "cat eye" type LNB for right-hand (clockwise) polarization from Dish Network. There goes DirecTV, Hughes, Wild Blue, you name it. Given its intent for use by the amateur radio community, I'm going to. . . hope. . . that it's not spinning. That's for the receive side. Easy cheesy. Q2: For the transmit side, not so much. What does it take to push a 5GHz transmit signal out in the civilian world? Supposing I wanted to go "all out" and purchase a 5GHz transmitter, where could I even find one? I read about an interesting idea from W1NPP on using a router to accomplish this task, as 802.11a covers 5.660 - 5.905GHz. I suppose from there, it's all about amplification. But of course, somehow modifying a satellite internet antenna is going to give us the biggest head start. This is the scenario that I said to myself years ago, that I would dabble around in the amateur satellite world if, and only if, someone launched a geosynchronous repeater. I mean, I'm sure it's neat to build an inexpensive system and load computer programs that correct for Doppler via servos and so on and so forth, but my interest stopped at the fact that I get maybe 5 seconds to get my call out and confirmed, because there's hundreds of others out there that want to get their shot too. Now that those days are about to be over with, I guess "I'm in". Just imagine. A real QSO, via satellite! The receive side is no problem at all. You can find cheap satellite TV receivers from Europe, which allows you to manually enter in specific frequencies. It's the transmit side of this project that I'm concerned about. And looking at many of the other posts here, I'm not the only one.
One of the transmitters being used for development is the Ettus Research B200 Software Defined Radio. https://www.ettus.com/product/details/UB200-KIT It's capable of about 10 milliwatts of transmit power (from 50 MHz to 6 GHz), so an amplifier(s) will be required. Here's my B210 (the MIMO capable version of the B200) transmitting a 6 MHz wide DVB-S2 signal at 429 MHz. I also have a 40 dB amplifier in line, so the average power being shown is 2 watts. There's 60 dB of external attenuation, and the RBW compensation is 23 dB. So -50 dBm + 83 dB = 33 dBm, or 2 watts. The -70 dBm carrier at 432 MHz is the DC offset of the IQ modulator shifted out of the passband.
It's the DC offset of the IQ modulator. On the B210, they're just using the built-in compensation of the AD9361 transceiver chip. It's adequate, but certainly not perfect. Usually, it would be right in the center of the signal (0 Hz baseband), but on the B210 you can use the on-board FPGA to shift the modulated signal in frequency. In this case, I've shifted it down 3 MHz. On other SDR transmitters, you can manually compensate for DC offset and IQ imbalance. You can tweak it to be perfect, but only for one frequency and temperature.
I know that Quisk can be calibrated at many frequency’s (that are relatively close) and make linear scale I/Q adjustments based on frequency ... temp iv never had an issue with .... drift, yes, but not I/Q balance ...
I first started out with Satellite when I got my license and loved it, after the best birds died I went to HF, I like HF but love the birds for certain reasons. I would love to return to my roots so to speak. Regarding prices, you are right, its cheap to start up now, but I wonder what will happen when the bird is officially up and running, and the exact freqs are announced. What will happen to the prices, I say they sky rocket to new heights (no pun intended), THIS I GUARANTEE! All the best to probable satellite operators, I can hardly wait to do this again! hi hi. Tom in Ca.
DEM has been providing affordable VHF to microwave gear for several decades and adds items as needed. Their customer base is the various weak signal groups of which satellite is a small part since very few are capable of building those kits or integrating into a working system.
When did this happen, a geo satellite????? I work the birds, but heard nothing about this until today, September 7, 2016.
Im wondering what you would use for an amp for the 5Ghz uplink ... ill be able to produce 10mW at 5ghz or so ... but id like 500mW or 1W ... What's modifiable etc ...
Not just one, but TWO. Both still future works-in-progress, but look promising. Here is some more data, http://www.hume.vt.edu/geo/ AMSAT-USA is involved with that one; and AMSAT-UK and others are involved with Qatar’s Es’hail 2 bird, which unfortunately, will not cover North America (but perhaps some day they could be linked? ;-), https://amsat-uk.org/satellites/geosynchronous/eshail-2/ The ham geo-sat space race is on !
Pardon me, but you need to do your own reading. The questions you ask are covered in this thread and the supplied links. Start with my Post #4 and work your way through the thread. Super short cut: Watch the PARC presentation video: https://forums.qrz.com/index.php?threads/amsat-phase-iv-palomar-arc-presentation.501187/
Part of the passband should be open as a standard linear transponder for SSB/CW communications. How much will be available is TBD. The idea of the use of analog modes on this project is somewhat controversial since the digital protocols being used will be far more efficient. The digital channels will certainly require less power output and a smaller antenna for the same quality of link compared to using SSB on the linear transponder. Also, keep this project in mind. It should be usable with the same equipment: https://amsat-uk.org/2016/09/07/5-ghz-to-10-ghz-lunar-transponder-mission/ AMSAT is developing 5/10 GHz digital ground terminal equipment suitable for use with projects in GEO, HEO, and lunar orbit. All of the documents relating to the ground side are available here: https://github.com/phase4ground/documents There should be no worries about the availability or cost of equipment for future 5 GHz / 10 GHz satellites. By the time these missions fly, it will be available at a reasonable cost.
That's the beauty of using an SDR on the spacecraft. Here's a test waveform showing a wide band DVB-S2 signal and a narrow band SSB signal being transmitted simultaneously. The spike at 1278.125 MHz is the SSB signal. I've actually transmitted this signal into an Icom IC-7300, but centered at 52 MHz instead. There is absolutely zero interference to the SSB signal on 50.125 MHz from the big DVB-S2 signal up the band.
The reason i was wondering about the digital only ... was that i can output more power ... and could use a smaller antenna .... for the uplink Iv been looking at a FPV transmitter 1W and just remove the modulator and just use the RF amp section .... like a TX51W (its 40$$) ... FM(CW) its 1W but for linear its less than 1/3 im sure ....
