[amsat-bb] Link budgets for upcoming HEO/GEO sats

Sun Apr 10 17:39:21 UTC 2016

Information is hard to come by, so I will test my own to know for sure,
once they arrive. I did find one web site listing specs for a visually
identical unit:

Specification:

Model Number: TXPA58002W5
MAX input power: 600mW/27.8dBm
Frequency Band: 5-6 GHz
Power Supply Voltage: 12-16V
Cooling mode: active magnetic fan
Lithium battery: 3S 4S
Weight: 50 g
Power dissipation: 20W
Box Size (L * W * H) : 10 * 10 * 4 cm

Battery operating time reference:

3S 2200mAh 30 minutes
4S 5200mAh 90 minutes

Output connector type: RP-SMA jack
Input connector type: RP-SMA plug
MAX output power: 2500 mW/+34dbm
Temperature: andlt; 80℃

As you can see, they specify a maximum input of 600mW, but don't specify
the gain, so I'm not sure what is the minimum power needed to drive it to
full power output. The other interesting thing is that the listings call
them a "...Booster Amplifier 3W 4.5W for FPV " but the specs say that the
maximum power output is 2.5 watts, so I'm not sure what the "3W 4.5W"
refers to...

I'm not sure what you mean about a mount/rotator specifically designed for
these satellites. There are az/el rotators out there already that should do
the job. And there are folks out there who are writing code for Arduino
controllers to take over control of Yaesu (and maybe other) rotators...

John

On Sat, Apr 9, 2016 at 5:54 PM, Jim Barbre <jbarbre at xmission.com> wrote:

> Thanks John for your responses. How much power is needed to drive the
> "drone" linears? Will a HackRF provide enough power to run one?
> Anyone working on a mount/rotator specifically designed for these
> satellites?
>
> 73
> Jim
> KB7YSY
>
> On 4/9/2016 3:34 PM, John Toscano wrote:
>
> Estimates suggest aiming for 8 watts of RF and a re-purposed
> 3-foot-diameter satellite TV dish to be able to get into the bird. It would
> be nice if only 3 - 4 watts were enough to do the job, because there are
> inexpensive 3 - 4 watt linear amplifiers designed for First Person Video on
> radio-controlled "drone" aircraft like this:
>
> http://www.ebay.com/itm/262249565979?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
>
> So, time will tell. It is possible that with a slower digital transmission
> rate the bird might hear well enough for the lesser power.  I expect I will
> try one of these low-power amps, and might even consider driving a pair of
> them into an appropriate combiner to get twice the power if one by itself
> does not make the grade. They are small and light, but would require
> protection from weather. On the other hand, I should have 10 watts
> available if I need it, once I perform these modification on a much bigger
> and heavier surplus power amplifier:
>   http://www.g4fre.com/avantekpa.htm
> (In fact, I have two of these beasts awaiting modification. I think they
> are much too large and heavy for my tripod-mounted rover station, but one
> of them might be doable on a fixed station.)
>
> It would be hard to equal the gain of a dish by using a helix. Once upon a
> time, I thought that the helix was the greatest antenna in existence, just
> make it longer and longer to get outrageous amounts of gain. But the more I
> investigated the less excited I got about building a humongous helix
> antenna. (In fact, at one point, I was dreaming about a 2x2 quad array of
> helices of great length, but I never actually attempted to build one.) On
> the other hand, I have been amazed by the ability of a scrap-heap satellite
> TV dish (less than 3 feet in diameter) and a couple of watts of power to
> make terrestrial 10 GHz SSB QSO's over distances of well over 100 Km, at
> least when I stopped using a dish that was bent like a Pringles Potato
> Chip, causing it to lose 10-20 db of its gain! I expect even greater things
> when an un-damaged dish is pointed up into the sky, away from trees and
> hills!
>
> For the 10 GHz downlink, a possible low-cost scenario might work out to be
> a direct-to-home satellite TV dish of approximately one meter in diameter,
> and a PLL-based LNBF, which would mix the 10.5 GHz satellite signal down to
> the 600 MHz or so range, and the  receiving that with some sort of SDR,
> possibly even a RTL-SDR USB dongle, though perhaps a better SDR might be
> required. The downlink is going to be DVB-S2x which is NOT the native
> format of the inexpensive USB dongles. DVB-S2x requires a bit of
> computation ability on the computer controlling the SDR, especially if the
> VLSNR (Very Low Signal to Noise Ratio) extensions are needed. It is also
> possible that we can find (and suitably modify) an inexpensive
> direct-to-home satellite TV receiver. AMSAT also expects to have a familiar
> USA company building complete ground station transceivers, but those will
> likely command a bit of a (well-deserved) premium price. We are actively
> pursuing a lot of different choices, so stay tuned!
>
> From what I have heard, the bird will be in a geosynchronous orbit, NOT a
> geostationary orbit, so periodic dish re-positioning of some sort will be
> necessary. Since the primary payload onto which we get to piggyback is
> owned by a government agency that likes to keep secrets, an exact proposed
> orbit is not widely discussed, if at all. So it is hard (for me, at least)
> to give more specifics at this time. You won't need the
> horizon-to-zenith-to-horizon pointing ability needed to chase a satellite
> in Low Earth Orbit, but some positioning in both azimuth and elevation will
> be needed. High precision will be more valuable than a wide range of
> pointing directions. In other words, being able to tweak the position by a
> degree at a time to fine-tune the pointing would be more helpful than being
> able to move the dish by 30 or 40 degrees. I wish I could be more specific,
> but I can't at this time. On the other hand, one of the other projects in
> the works is the NASA-sponsored CubeQuest Challenge, and for that bird you
> would need to be able to point at any part of the sky where you observe the
> moon, since the package is going to be headed for lunar orbit! We are
> trying to make these two birds compatible with the same ground station
> equipment.
>
> Sorry for the vagueness, but I hope it helps a little bit.
> 73 de W0JT/5, EL09vu
>
> On Sat, Apr 9, 2016 at 12:42 PM, Jim Barbre <jbarbre at xmission.com> wrote:
>
>> Hi all,
>>
>>     Given that people are currently working on groundstations for the
>> upcoming HEO/GEO sats, I am in hopes that at least some of the following
>> questions can be answered.
>>
>> What kind of power will be required on the 5GHz uplink?
>>
>> Does anyone currently make a linear amp or upconverter that can be
>> mounted at the antenna for the 5GHz uplink?
>>
>> Will I be able to use a helix antenna on the uplink or will I be limited
>> to using a dish?
>>
>> Same question with regards to antenna usage for 10GHz downlink.
>>
>> What size dish?
>>
>> With AO-10 and AO-13 I could point my antennas at the satellite and not
>> have to move them for an hour or longer. These new sats will be using
>> microwave frequencies. What kind of realistic expectation do I have of
>> being able to point a dish at the satellite before having to tweak it?
>> Otherwise said, will a rotator be absolutely necessary?
>>
>> Thanks for the info. Looking forward to working the next generation of
>> HEO/GEO sats.
>>
>> 73
>> Jim Barbre
>> KB7YSY
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>
>
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