Can't find Badr4 or Es'hailsat2 - Oscar 100

[g4hiz]

Finding Eshail-2 is not that easy as the Beacon is not strong. Aligning on Badr-4 first is a good first step. I think that the moral of this experience is, if its not too bad, don't fiddle with it ! On my receive system, the QO-100 WB beacon is about 8dB s/n, not a lot when compared to other broadcast signals. But is seems that adjustment was worth-while in this case.
I have a 1.2m prime-focus dish with a positioner (jack-arm). In this case, when I am close to the position I require, I disconnect the positioner controller and use a 13V DC supply through a changeover switch, to slowly creep East or West as required and optimise the level. The controller in my case usually generates ca. 36V, so 13V makes the DC motor go a lot slower. Note this may not work for all types of positioner. Once in the correct E-W position, I optimise the elevation. Lastly, I try to may sure the LNB skew is ok. Where I am located (Kent) the skew is about 19 degrees, ie looking into the dish with the LNB in front of you, twist the LNB clockwise about 19 degrees. It's not too critical but ensures you get the best result. In this case (EShail-2), we don't have a lot of channels on the opposite polarization, but Badr-4 has and by optimising the skew you reduce the adjacent channel interference, which can be seen on a spectrum analyser, in our case you are optimising wanted the signal power. If you optimised skew on Badr-4, you would be ok for Eshail-2 (for moderate size dishes).

I also have rotated my LNB 90 degrees, such that 12V gives you horizontal polarisation - ok for the WB transponder. But if you also want the NB transponder, then you will also need 18V to select this, as it's vertical polarisation. In my home-brew Rx, I had added a DC/DC converter to make 18V from 12V to achieve this and a switch to select.

Sun noise, yes it exists and twice a year the Sun passes the equator (spring and Winter Equinox) and aligns with the satellite. In this worst-case we have a varying degree of outage lasting minutes (few, tens, depends on dish size). Since our dishes have a non-zero beamwidth (1 to 2 degrees for 1.2m at this frequency) we will experience some Sun noise degradation around these dates more often - Spring Equinox next month.

73 Jen

[g8gtz]

Good point Nigel,

Now Oscar 100 is on I think the advice about aligning on BADR4 etc is out dated.

Use some SDR hardware (and £10 RTL dongle will do) on something like SDRconsole or SDR# and set for 1MHz bandwidth centered on 739 / 740MHz. Supply 12v to the LNB and look for a bump of around .5MHz bandwidth.

This is the easiest way as there are no other signals in that band, set the elevation to ~ 36 degrees and gently scan across in Azimuth until you see the bump.

The original article did refer to sunouts as being a very useful way to fidnexactly where Es'hail-2 is in the sky.

Also, near every equinox, the sun passes through the same position in the sky as a given satellite – using this website https://www.satellite-calculations.com/ ... erence.php you can calculate when the sun will be in the same position as BADR4 – this happens for a few days around the 10th of October 2018 for the UK and as long as it is sunny, you will be able to see where to place your dish by seeing where there is direct sunlight.

You can then use the TV beacon to tweak for maximum smoke - the types of MER yo should receive depending on dish size are listed on the bottom of this page: https://wiki.batc.org.uk/Receiving_Osca ... TV_signals

73

Noel

[g8ayc]

Do you mean an elevation of 25 degrees?

[radiogareth]

I've got my dish up and given it a tweak. I have the beacons, CW, SSTV and SSB around 20dB over the noise hump. Can't yet decode the DATV beacon. Do I need more signal? 1.1*1.0 dish. RF Pw showing as -39dBm MER 1-2. I guess I need to tweak it some more.
Gareth

Oscar100.PNG (512.43 KiB) Viewed 7087 times

[satdxer]

(jack-arm). In this case, when I am close to the position I require, I disconnect the positioner controller and use a 13V DC supply through a changeover switch, to slowly creep East or West as required and optimise the level.

Hi it might make it go slower but it will still turn a pulse, various ways to get a tighter pulse per degree one way is to add more magnets another way is to re-gear the gearbox another way is to use a different pitched acme thread.

Now Oscar 100 is on I think the advice about aligning on BADR4 etc is out dated.

Optimizing signal on Badr4 there would be very little gain on Es’hail-2 unless you are using a very large dish, unless your experienced setting dishes up Badr4/Astra is the best place to start.

[g4hiz]

Hi Noel,
indeed, the Eshail2 QO-100 beacon is the best option to finalise your reception system, especially given that it is receivable in all the coverage area visible on the Earth.

[g8lce]

I have made a video of me aligning my dish.
https://www.youtube.com/watch?v=wv1Srw6F8Bs
It is a 360 VR video and yes I mis-aligned the sound a tiny bit in the edit!!! It shows how you can hide the dish in a corner of the garden and how using a satellite positioner makes the job easier. Even easier if you have a satellite receiver that can control the positioner from your shack. The wire from the LNB goes through the satellite positioner to the shack (approx 30mtr of cable ) then into a satellite receiver set to give the 18v. Out from the through connection into a distribution type splitter. This gives 13dB attenuation or more on 6 outputs. The output from the LNB is very big and this attenuation does not seem to effect reception. One output goes to a Minitiuone V2, one to a Minitiuone V1 and one to a SDR.
The main thing when using a motorized satellite positioner is the get the motor's rotor pointing at the pole star which is therefore parallel to the Earths axis. Also start with the motor in its home position ( pointing due south ) and mount the dish pointing due south and vertical including the LNB. Once you have found Astra or any Satellite TV you can tweak the up/down of the dish for max signal. When rotating the dish looking for the Oscar 100 beacon with you Minitiuone set to all the right things, do it a step at a time if you have that with your controller and wait a few seconds at each step. Make sure the beacon is transmitting on the web site. You will pan through the satellites position at some point. I found I got a signal at 6 step positions and stopped at the middle of them. ( MER from 0.5dB to 6dB )
PS. This video can be viewed using VR goggles if you are brave!! Some of my 360 VR videos require a sick bag!!!

[g8lce]

Receiving Oscar 100 part two...
https://youtu.be/R8MSILdu2Hk

G8LCE

Martin

[M0NRD]

I know aiming at BADR-4 isn't the absolute optimal for QO-100 but have found if using a commercial receiver, or something like the V8 satellite finder (when trying to align dish away from shack) that if I can receive the TDM transponder on BADR-4 in addition to the usual one carrying BBC Arabic etc it correspondingly gives me a slightly stronger signal on QO-100. That transponder has a different beam (FSS) which is slightly more marginal in the UK.
Beam patterns at https://www.arabsat.com/english/the-fleet/badr-4
TDM Transponder is on 12563MHz V https://www.lyngsat.com/Badr-4.html (handy test cards and demo transmission)

73 Andrew

[g7ntg]

It took me ages but I now have two dishes accurately aimed and peaked up. For both dishes, I tuned for Maximum on Astra then moved west 2.5 degrees. I then used minitiouner at 742.5MHz 2000s/r DVBS/2 and fine tuned for maximum signal and minimum MER.Make sure you turn the LNB through 90 degrees! (or feed it with 18v)
I also used a PLUTO with SDR# to receive the narrowband segment using a bias tee to power the LNB.
80cm offset dish gives me 2dB MER and 55%signal
1.2metre dish gives me 8dB MER and 85% signal so far on the video beacon signal.
on the 1.2 metre dish I change feed voltage to change polarisation 12v fot TV and 18V for narrowband with the LNB sideways on + skew 17 degrees.
to receive TV on a digital receiver ,I use an ADX-plus to shift the frequency up by 500MHZ (allegedly - measure the frequency first - they can be 5MHz off) and then i GET A GOOD PICTURE. Make sure your receiver will decode DVBS2 - some older ones don't.
for narrowband I use a Technomate TM1 PLL which doesn't drift too badly once it has warmed up. A GPS locked LNB is being worked on.