It has been a while since I was busy with a ground station for the geosynchronous (geostationary) satellite Es'hail-2 also known as Qatar Oscar 100 or QO-100.
The major delay in the beginning of the project was to receive an assortment of coax adapters. Finally, those were in, now, the down-link was sorted rather quickly. There was a disused 35cm dish, which I used to analog ASTRA reception. When ASTRA satellites turned digital, I lost interest in watching those, so I never upgraded the equipment. Although, I never dumped any of that stuff either.
So, here was my down-link receiver, PLL-LNB with the old 35cm dish in a FUNcube SDR dongle. That worked perfectly. I later replaced the FUNcube dingle with an SDRplay RSP1A, so that I could receive the entire bandwidth of QO-100's narrow band transponder, allowing for locking on the mid-beacon for frequency stabilization.
Concerning the up-link, I decided to go for a DXpatrol converter. I like the possibility to select the baseband, although, I will probably stick with 432MHz.
To amplify the 2.4GHz signal, I went for the omni-present chinese 8W WiFi-PA.
Then came a long struggle of what to do about the up-link hardware.
Initially, I considered an RHCP helical antenna, something in the realm of 15 to 20 turns.
Then I found a 60cm offset dish in the trash. So, what about a 4 to 6 turn LHCP feeding helix? And yes, I wound that thing. But, the mechanical details of holding the thing in place put me off again.
Finally, I decided on a K3TX LHCP patch feed for the 60cm dish.
I know, 60cm is rather small for a 13cm wavelengnth... 10 lambda upwards make the deal... I know. However, 60cm is what I got.
The dish I got had not LNB/feed mounting hardware, so this is what I came up with.
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| K3TZ LHCP patch, PCB over Al |
You may wonder what the strange structure to the left is, this will be the mount to the dish.
Something not obvious from the above picture, I am using a F-connector for this feed.
Please note that this picture was taken before I filed down the edges to of the reflector to the circle seen scratched into the aluminium sheet.
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| The patch feed added to the up-link dish |
Winds can be pretty strong over here, so I mounted the dish to a concrete parasol stand.
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| Up-link (grey) and down-link (white) |
Note that both channels are using 75Ohms satellite cable. While for the down-link this is fine, the up-link will experience this as an attenuator, in particular over the length I am using for this experimental setup (about 20m).
Having done some experiments, I could hear my signals in both CW and SSB (USB). While CW was easy, single side band was somewhat challenging. I would not count for any SSB QSO with the attenuator in place.
However, CW should be just fine. Have a look how the signal compares to the lower beacon:
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| Lower beacon and pa1gsj carrier |
This was my first day of bouncing signals from QO-100. I know what I need to do now, i.e. building an outdoors cabinet next to the up-link dish.
I hope to be QRV as an audible station on Es'hail-2 soon.
Update
After further improvements, I can now provide relative signal strengths from my receive setup:
- transponder noise about 32 dBuV
- CW beacon 58 dBuV
- my own signal 41 dBuV
