George Smart - M1GEO

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Receiving EsHail-2 GeoSat

Posted: 19 Feb 2019 11:00 PM PST
https://www.george-smart.co.uk/2019/02/eshail2-rx/



First of all, let me say that I am in no way an expert with regard to
satellites, microwave operations, or anything else. This is meant to be
more of a crude beginners guide. Experts will probably cringe thats fine!



A little bit about EsHail-2




EsHail-2 (QO-100) is a geostationary satellite at 25.5° East which carries
transponders (devices for receiving and re-transmitting signals) usable by
radio amateurs. These two transponders are the first amateur radio
transponders to be put into geostationary orbit and are expected to link
radio amateurs from Brazil to Thailand.




Es’hail-2 will carry two such transponders, operating from the 2400 MHz
band into the 10450 MHz band. A 250 kHz bandwidth linear transponder
intended for conventional analogue operations (SSB, CW, etc.) and an 8 MHz
bandwidth transponder for experimental digital modulation schemes and DVB
amateur television. The operating guide provided by AMSAT-DL asks that
users refrain from using FM on the narrowband transponder.



Narrowband Linear transponder
2400.050 - 2400.300 MHz Uplink
10489.550 - 10489.800 MHz Downlink (Vertical Polarisation)
Wideband digital transponder
2401.500 - 2409.500 MHz Uplink
10491.000 - 10499.000 MHz Downlink (Horizontal Polarisation)




Image taken without permission from Amsat-UK/DL [source]




With these linear transponders, any signal that the satellite receives in
the input frequency range will be linearly translated to the output
frequency range. As a signal power increases, so will the signal at the
output; as the signal frequency increases, so will the output signal. And
so it goes.




You can find out lots more information about the EsHail-2 satellite (and
others) from the AMSAT-UK EsHail-2 website.



Why this page?




Following Noel G8GTZs talk on EsHail-2 at the RSGB Convention 2018, I
started collecting the parts required to put together a receive system. At
the time of Noels talk, I remember thinking how hed made the process sound
simple. It wasnt until I started playing with the setup that I actually
found how simple the process was. More on this later




Yesterday, I stumbled across a link to the BATCs Eshail-2 Ground Station
website which has links to their wideband (think HD TV) and their
narrowband (think SSB, CW) web receivers. The hardware is located at the
Goonhilly Earth Station in Cornwall (IO70JB). More details can be found on
the EsHail-2 BATC website.




If you have used a WebSDR online before, then the narrowband SDR will be
familiar to you. The wideband monitor will probably not be familiar, but it
is very useful if you are looking to experiment with digital amateur
television (DATV) transmissions more on this later. Since were interested
in doing the receiving ourselves, we just note is that such web SDRs and
monitors are a fantastically useful resource. There are of course many
other similar resources.




Ultimately, this is the page that I wish I had found when I started out on
this path a couple of days ago You are welcome to contact me if you spot
errors, etc.



Antenna talk: Dishes, LNBs & Feeder




A satellite dish is a type of parabolic antenna that is highly directive
and therefore has a high gain. In simple terms, the dish collects incoming
radio-waves over a large area and focuses them towards a central point.
This point is usually the front of an low-noise block (LNB). The larger the
dish diameter the more gain the dish will have but the sharper the beam,
and so the more critical the alignment. Common dish sizes for receiving
EsHail-2 are in the range 80 centimetres to 1.2 metres diameter. My dish,
pictured below, is 1.2 metres diameter. Because the dish is highly
directive (i.e., its beam is very sharp, like a laser pointer is with
light), it requires careful adjustment.



Where do I aim the dish?




The AMSAT-UK EsHail-2 website tells us that the satellite is at 25.5° East.
This means that the satellite is at 25.5° East of the meridian line. You
will need to find the azimuth and elevation, i.e., the direction and tilt
of the dish, yourself, since this depends on your longitude (distance from
the meridian line) and latitude (distance from the equator). I have used
the SatLex tool (below image), but many other online tools exist
(DishPointer, SatSig) to help you. When using such tools, if they dont have
EsHail-2 in their index, BADR4/5/6 or EutelSat25B are close enough for now.



Satellite location calculated by SatLex for EsHail-2 from Norwich, UK.




As you can see, the top half of the above image shows you a view due south,
and the satellite location in your field of view. Youll see the elevation
angle of 25.88°, which Ive rounded to 25.9°. Youll have to tweak a little
for maximum signal, regardless of how well you do this step, but it really
helps to get the alignment as good as you can before you start. You will
also see the true azimuth angle, here 150.50°, which is the angle your dish
should point to, and corresponds to a simple calculation between your
longitude, the satellites position in space, and the meridian line.




The only other point to note in the above figure is the LNB Tilt of −17.4°
(note, minus). Without proper knowledge, it is tricky to set the LNB skew
without the LNB receiving a signal, so for now, lets press on with getting
the dish mounted. Well come back to LNBs later.





Getting the dish pointed at the satellite is, without doubt, the hardest
part of the entire undertaking. On the right, you see Chris G8OCV helping
to align the dish holding a spirit level. Since it is my policy to only
ever do antenna work in the dark, on a cold evening, preferably in rain,
hes very enthusiastic! But he always helps!





For my QTH in Norfolk UK, the elevation worked out to be 25.9°. This is the
elevation, i.e., the angle of the dishs beam to the horizon. The dishs beam
points upwards 25.9°. We also know the azimuth of the satellite is 25.5°
East, which corresponds to a true heading of 150.5°. These are the two
coordinates we need to know to aim the dish.




Once the dish support pole was absolutely vertical, the elevation
adjustment on the satellite dish can be done using the angle markers on the
dish bracket. The azimuth 25.5° East is translated to 150.5° as taken from
the satellite pointer website. I used a compass to initially align the
dish. Some warning/disclaimer about the difference between true North and
magnetic North belongs here. It didnt cause me any trouble, but your
experiences may be different. If youre using a temporary post in the
ground/umbrella stand, make sure it is heavy enough not to blow around in
the wind. Mine wasnt until we added some concrete weights.



Satellite dish mounted on an aluminium pole in an umbrella stand. Scrap
metal was slid under the stand to help achieve the optimal angle.



Some words on LNBs




This section may sound a little scary, but I have tried to explain some of
what is going on inside the LNB dont be put off! The low-noise block (LNB)
is something that sits at the focus point of many commercial satellite
dishes. The dish focuses the radio signals to a point usually into the
LNB. The LNB has a low noise amplifier to increase the level of the weak
signals received by the dish. Since satellite downlink frequencies are well
over 10 GHz, that would require some very fancy coax to get the signal into
your house. So the LNB also mixes the received signal with a local
oscillator (LO) frequency that it generates itself, in order to reduce the
frequency of the received signal this LO frequency is switchable to allow
different frequency ranges to be received. Finally, the LNB has a
polarisation switch, changing between horizontal and vertical polarisation.
This is, of course, a gross simplification of what is going on, but is
enough for now.




Without going into too much detail beyond what feels strictly necessary,
the switching of LO frequency and polarisation are controlled by signals
fed to the LNB from the shack-end of the coax. The LO frequency defaults to
9.75 GHz, but is switched to 10.6 GHz when the LNB receives a 22 kHz tone
on the feeder. Since the LO is outside in the cold, the frequency reference
is prone to thermal drift. You are strongly recommended to find an LNB that
has its LO frequencies derived from a phase locked loop (PLL) as opposed to
an dielectric resonator oscillator (DRO). A more advanced configuration is
to purchase a dual-port LNB, and use one port for the feeder return to the
shack, and hack the LNB such that the second port serves to accept a
frequency reference that can be provided. You do not need to do this, an
off the shelf LNB will work, but a PLL variant is strongly recommended. If
you hear very garbled or warbling sounding sideband or it is unresolvable
altogether, it may be that your LNB is using a DRO as the frequency
reference.




The polarisation is either vertical when the LNB is powered at 12V DC, or
horizontal when powered at 18V DC. Often hams will only use the 9.75 GHz LO
frequency, since then no 22 kHz tone is required. Some hams rotate the LNB
physically to change polarisation, while others set the LNB between
vertical and horizontal, thus receiving both simultaneously but with
losses. I opted for supplying either 12V or 18V to the LNB and switching
polarisation electronically from inside the shack. I have not, as yet,
needed to change the LO frequency.



Goobay 67269 Single Universal LNB retails at under £6 with free postage




Everything on this page was done with a Goobay 67269 Single Universal LNB.
There is lots and lots of information on LNBs if you search around online.
The BATC has some information on LNBs, as does UHF-SatCom Ku Band PLL LNBs
page. The key point is get a PLL based LNB, as recommended by others. Some
of the recommended ones carry a heavy price tag as at the time of writing
there is a huge demand, and relatively small supply. A few years ago I
bought an Octagon PLL-based LNB for less than £10 delivered; now they cost
over £130! I would have used that, but it was in boxes packed for moving!
Unfortunately for radio hams, sellers have realised that PLL based LNBs are
more valuable to us, and so their price is gradually increasing.



Feeder




I had a bit of discussion with friends online about what feeders were being
used. Most people have, I guess obviously, opted for satellite coax. This
is RG6 coax, and has a solid centre pin suitable for use in F-connectors.
This is also available cheaply on eBay, often kitted with ten F-connectors.
I paid around £9 for 50 metres. In an early instance, I got away with using
RG213 (which is 50 Ohm, not 75 Ohm) and some F-connector adaptors, but the
LNB gain makes up for a lot of small misdemeanours. RG6 satellite coax is
the way to go! The image below shows my mash of connectors and adapters to
overcome my lack of a solid centred feeder such as required by F-connectors.



How not to do it. My first attempt worked perfectly but isnt best practice!



Connecting it all up




Terminate the LNB end of the feeder with an F-connector, and seal it up to
keep the rain out. Mount the LNB in the dishs LNB mount. You need to be
able to twist the LNB to adjust the LNB tilt, but dont want anything to
move of its own accord.




The next obstacle is to power the LNB. I did this by hacking about with an
RTL-SDR dongle and building in a bias tee inside details in the LNB Bias
inside an RTL-SDR Dongle section, below. If you have a bias tee already,
you may be able to use that provided it is suitable for use at around 740
MHz. Power the LNB with 12V to select vertical polarisation with 9.75 GHz
LO, ideal for the narrowband transponder of EsHail-2.




The centre of the EsHail-2 narrowband transverter downlink is 10.489675
GHz. If we use the 9.75 GHz LO, we expect to see an intermediate frequency
(IF) of 10.489675 − 9.75 = 0.739675 GHz = 739.675 MHz.




We are expecting to see signals in the 250 kHz bandwidth centred on 739.675
MHz. On an RTL-SDR dongle waterfall, you should see an increase in the
noise floor between when the LNB is powered and when it is unpowered. If
you do not, check your wiring. My LNB draws around 100 mA.



Tweaking the dish




As we alluded to earlier on in the dish section, we need to tweak the dishs
alignment. But to do this, we need to be receiving signals, and then take
an opticians approach, of better or worse with very tiny adjustments each
time.




If you have followed these notes so far, you will have a receiver, or
spectrum analyser or similar centred on 739.675 MHz, with your LNB in
horizontal polarisation and a 9.75 GHz LO frequency.




The EsHail-2 narrowband transponder has will appear as a wide lump of
raised noise floor, similar to what you see below. The raised bump is the
transponder bandwidth, and the two signals present are the upper and lower
band markers. They send CW and binary data, too. The transponder bandplan
is outside the scope of these notes, but you can find it on the
AMSAT-UK EsHail-2 website. It roughly follows the usual bandplans for
all-modes, with CW at the lower end, then digital modes, then SSB at the
top.



EsHail-2 Narrowband Transponder Downlink





When tweaking the satellite dish, adjust for the largest (highest) bump
above the noise floor. You equally want the two beacons to be high above
the transponder noise floor. Very slowly, in small steps, adjust the
azimuth (rotation) of the dish stopping at the point that maximises the
signal. Then adjust the elevation (tilt) of the dish to further maximise
the signal. If you do not see anything on the waterfall, then you may need
to make larger sweeps of the dish to find the satellite in the first place.
This is where your care previously helps. As mentioned before, this is the
trickiest step.



LNB Tilt/Skew




Once you have a good signal-to-noise (high bump above the noise with large
beacon signals), you should adjust the LNB within the dish mount.




If you can electrically switch polarisation to horizontal (by feeding the
LNB with 18V) then you should do this. With the antenna now cross-polarised
to the narrowband transverter, rotate the LNB to receive the minimum signal
you can. What you are doing is looking for the maximum amount of
cross-polarisation. It is easier to adjust for the null than for the signal
itself, and you will achieve a better adjustment this way. If you cannot
switch the LNB polarisation electronically, then you should adjust for the
maximum signal with rotating. Rotate the LNB towards the LNB tilt angle
(for me this was −17.4°), going past that angle to ensure you find the
minimum or maximum as appropriate.




You may also like to adjust your LNB backward and forward in the mount to
try and find the optimum focal point, although this point is usually
specified pretty clearly on the dishs paperwork. Either way, with the LNB
now in the correct polarisation (12V feed, vertical for the NB
transponder), move the LNB backd and forth looking for the largest signal.




These steps may be difficult to do, as your body will cast an shadow on the
dish either hide out of the way as you adjust, or, tweak and step back.
You get the idea.




Youve youve done that, bolt everything up tight. Youre good to go!



Receiving Narrrowband Modes




If we zoom in a little from the spectrum display we saw when aligning the
dish; such that the markers are now on the outsides of the waterfall, we
see more of a band view, and the transponder frequency response looks
relatively flat. This screen-grab was also taken with several signals
visible.



EsHail-2 NB transponder, showing 2 beacon signals, 4 SSB signals and a CW
signal




As with any other SDR you may have used, clicking on the signals will allow
you to demodulate them.



G4EML calls CQ and OZ2OE answers signal variability caused by my error




Below, OH1ZAA calling CQ:



OH1ZAA calling CQ




OH1ZAA calling CQ and UN6PD returning



Receiving Digital Video Amateur TV




The EsHail-2s wideband DVB-S2 beacon on 10.492,500 GHz is always
transmitting video. This beacon was my very first reception of DATV. I am
still finding out about this, so my experience here is minimal, but perhaps
it is of some use. You should defer to the BATCs Receiving DATV guide for
detailed information.




Digital television has many different standards, as you might expect. The
key factors are the modulation type (how data is encoded onto the RF
carrier), sample rate (in samples per second), picture mode (DVB-S, DVB-S2,
etc) and FEC (or forward error-correction). As well as this, streams have a
PID (packet identifier) which identifies the program all we need to do is
set this correctly. The standard is set out in the ETSI EN300-468
specification if you want to learn more. You dont need to.




Most amateur signals vary in the above listed parameters to what is used
commercially. While a standard digital TV multiplex may be 8 MHz wide,
radio amateurs typically use much smaller bandwidths, and what is called
Reduced Bandwidth TV (RB-TV). Commercial receivers usually do not support
these configurations, so a special receiver (the MiniTiouner by F6DZP and
others) was developed from modules and allows fine control over all of the
parameters associated with digital video transmission.




This remainder of this section concentrates on the MiniTiouner. However,
there are two SDR based options available. I cannot offer any words on
these, except to highlight their existence:



Lean SDR: A lightweight, portable software-defined radio (C++)SDRAngel: SDR
Rx/Tx software for Airspy, Airspy HF+, BladeRF, HackRF, LimeSDR, PlutoSDR,
RTL-SDR, SDRplay RSP1 and FunCube (C/C++)DATV Express: Software and
(discontinued?) hardware



The MiniTiouner Receiver




The MiniTiouner by F6DZP and others is a USB tuner designed specifically
for Amateur TV use which natively covers 143 MHz to 2450 MHz and is
suitable to receive EsHail-2 and a number of other amateur bands with no
modifications or additional up-converter. It is available from the BATC and
other sources. See the BATC MiniTioune page for more details.




As a short note, the term MiniTiouner with an R at the end refers to the
hardware PCB; the term MiniTioune (no R) refers to the software.





Most amateur TV transmissions are made using Reduced Bandwidth DATV (RB-TV)
with a bandwidth below 1 MHz. To date, 90% of the DATV transmissions on
EsHail-2 (QO-100) have used RB-TV.
The MiniTiouner comes as a kit from BATC, and took me roughly an hour to
build. Follow the build notes on the BATC website.





I then had to register on the VivaDATV forum to obtain F6DZPs MiniTioune
software (post link here) Im not sure why I had to register, but, I did.
At the time of writing, this is software version 0.8s. For instructions on
how to install this, visit the BATCs MiniTiouner Software page. Dont forget
to install the accompanying USRC and LAVFilters packages, too. I did; you
get no video!




An issue that I faced is that the USB connection between my computer would
drop randomly causing the MiniTioune software to crash. This is supposedly
solved by using a Lindy Cromo Lindy cable USB 2.0 type A/mini-B 1m long,
but after spending £10, the issue still persists.




Before you fire up the software, open the minitioune.ini file and edit the
following fields: OM_ID (callsign), ForumPassword (forum password), Locator
(QRA locator), Ville (location) and anything else you see fit. Youll
probably want to come back to this file from time-to-time.



The MiniTioune Software




When the software first starts, youll see something like the image below
just wait a few seconds:



MiniTiouner Splash Screen




After a few seconds, you will see the main MiniTioune program window:



MiniTiouner in Expert mode receiving EsHail-2s main beacon.





My advice would be to make sure you can receive the beacon before you move
on to anything else, since the beacon has known parameters.



Receiving the EsHail-2 DVB Beacon




The first thing to note is that the wideband transponder is horizontally
polarised, so you will need to supply 18V to your LNB to switch
polarisation, or, rotate the LNB 90° in either direction. The MiniTiouner
hardware has two jumpers which allow you to feed the input DC supply
voltage into the LNB F-connectors via the Serit module. These are labelled
LNB_A1 and LNB_A2 on the PCB, and can be found between by the DC input
power jack. Then the whole MiniTiouner receiver is powered from either 12V
or 18V as required.




Next look to the top-left of the main MiniTioune window; youll see a place
to enter the sample rate (SR) and a frequency (in kHz). The beacon
frequency is centred on 10.492,500 GHz, and transmits DVB-S2 with 2 MS/s
QPSK modulation using 2/3 FEC forward error correction.




If we enter 10492500 kHz into the frequency box, we also need to tell the
MiniTioune software to accommodate for the frequency translation the LNB is
performing. It is enough to say that the LNB provides a frequency offset of
−9.75 GHz, so we indicate −9750000 kHz (note, minuses).




Were told the sample rate is 2 MS/s, so we can enter this as 2000 KS/s in
the SR box at the top left. Make sure you have selected either AUTO or
DVB-S2 for the mode, and that you have the checkbox for 2/3 FEC enabled.




Looking at the BATCs Wideband Transponder Monitor, it is possible to see
the beacon transmission on the left at 10.492,500 GHz. You may also see
other transmissions besides the beacons and well look at that those in the
next section.



EsHail-2 wideband transponder monitor with beacon clearly visible on the
left




As you enter the sample-rate and frequency, you should start to see some of
the indicators at the bottom left of the MiniTioune window turn from red to
green. Once the Viterbi decoder error goes to 0% (bottom centre-right), you
should see video and hear sound! If you do not, then toggle the Auto PID
button in the top right. This makes MiniTioune decode the incoming stream
to find the video and audio transport streams and understand their codecs.








The clip below is a short section of the EsHail-2 DATV beacon:



Clip from EsHail-2 DATV beacon from wideband transponder



Receiving the EsHail-2 DVB Beacon




The process of receiving an amateur transmission is very similar to
receiving the beacon. The only difference is that you may not know the
properties of the signal being transmitted. In this case, I have found that
using the BATCs Wideband Transponder Monitor to look at the signals can be
very useful to help guess. You can see from the spectrum that the signal is
much narrower than the beacon, so we can take a guess at the sample rate by
knowing a few commonly used values. 125, 333, and 500 kS/s seem to be
common, while some use 1000 kS/s in the simplex DATV window.



BATC wideband transponder monitor




If you leave the common FEC options ticked and use AUTO mode selection, the
MiniTioune software will magically recognise things after a few seconds, if
you have chosen the right combination of options. There is, of course,
another way:



BATC wideband transponder monitor also includes a chat window




The BATC wideband transponder monitor page also includes a simple chat
system, where users can advertise their settings. Above you can see F8CED
and M0DTS advertising their settings.




Using a mixture of trial and error, as well as watching others talk in the
chat, I have been able to observe a considerable amount of amateur test
transmissions via EsHail-2.



Mike G0MJWCharles G4GUODave G8GKQ



LNB Bias inside an RTL-SDR Dongle




In order to tweak the dish alignment and also to receive narrowband
transponder signals, I needed to power the LNB for use with an RTL-SDR
Dongle. I had heard that some dongles have a bias tee included, and I was
hoping to repurpose some of this since clearly it would only supply 5V.




I opened the New Gen RTL2832 SDR I had to look inside and noticed a DC
bypass inductor to ground for static discharge, with capacitors leading to
a DC blocking capacitor, limiting diodes and on into the receiver.




By standing the DC bypass inductor on end, and adding a decoupling
capacitor on the now unused pad, I could create a very crude bias tee. I
used a 1000pF and a 47nF capacitor to create some further blocking and add
mechanical stability, and then I soldered on two power wires.



RTL-SDR Dongle modified to have a bias tee for LNB power




It doesnt look pretty at all, but it does work, and is small!