Xiegu X6200: Using the WR12 to Receive the QO 100 Ham Radio Geostationary Satellite

--By Ed Durrant DD5LP


This document does not describe the installation of the Xiegu WR12 add-on to your X6200 – please see the other guide from Radioddity for that.

Xiegu X6200

I will not be describing QO-100 in this article either, suffice to say it is the only current amateur radio geo-stationary satellite with a transponder using an uplink from the 13cm (2.3 GHz) band and downlink in the 3cm (10 GHz) band.

When I heard that a wide band receiver was going to be added to the X6200 radio with a coverage from 54 MHz to 1000 MHz, I initially thought, yes, nice you could then receive (but not transmit on) 4m, 2m, and 70cm bands but there are plenty of radios around that do that already. What became interesting was when I thought about the frequencies around 740 MHz.

Xiegu X6200 | frequencies around 740 MHz

Hmm, what band is around there you ask? Well there is none but… It is the Intermediate frequency that most people use to receive the QO-100 satellite. 740 MHz? Well, the satellite actually transmits on 10 GHz but using a standard TV satellite dish and LNB (Low noise block – the bit that sticks out in front of and points into the dish) signals from the QO-100 output of 10489-10500 MHz are converted down to around 740 MHz. You see an LNB is what we, as amateurs, would normally call a receive convertor. This one is built into the antenna and has a few unique requirements.

Q0-100/ Es'hail-2 Footprint

An LNB can have one, two or four coax cables going to it, this is for when multiple households share the dish for Satellite TV reception. In our case we only need to use one connection mine is an “universal LNB” with just one output for that I bought for €3 (special offer). I’ll talk later, why this might not have been the best choice.

universal LNB

The LNB and the dish are mounted it to a mast and the one coax cable (normally with the F-type connectors on each end), comes back to your shack. One coax cable – how does it get power from the preamp/receive converter? Well the DC supply is sent up the coax using what is called a Bias-T unit to inject the voltage and while some satellites use horizontally polarised antennas and others vertical (on several satellites some channels are horizontal and others vertical to get more stations in the available bandwidth) this voltage is also used to switch antennas in the LNB – 12v is vertically polarised and 18v is horizontally polarised.

LNBs also have two oscillators for the convertor. One is at 9.75GHz and the other 10.6GHz this enables one antenna to cover the complete band used by the satellite in two smaller blocks for the satellite TV tuner. As different voltages for signalling on the coax cable have already been used, the TV system designers changed to using an audio tone to switch between high and low bands in the LNB. No tone means low band and 22kHz means the high band oscillator will be used.

All of this signalling is taken care of within Satellite TV tuners (either stand-alone boxes or built into modern “Smart” TVs) but for our usage we need to provide this control when using the Satellite dish and LNB to receive QO-100. The good news is that we don’t use the high band oscillator so we don’t need to generate the 22 kHz signal. QO-100s narrow-band repeater (where CW/SSB/Digital data are used) uses vertical polarisation and so we just need to supply 12v. If you want to receive the digital amateur TV on QO100s Wide-band repeater, it uses Horizontal polarisation and so you will need to feed 18v to the coax.

No matter whether it is 12 or 18v, how do we get the DC voltage onto the coax without applying it across the input to the receiver? We use a Bias-T unit which capacitively isolates the RF in and RF out sockets while applying voltage (usually via an inductance) to the output socket. You could build one of these yourself but since they only cost €12-15 to buy, why bother?

Satellite TV tuners

The cable from the LNB on the dish has an F-Type connector on it. The Bias-T unit has two SMA connectors and the WR12 output is a BNC socket. Adapters to go between the connections are available via the usual sources. Please make sure you get the right one as using more than one to match connectors loses signal at 740 MHz.

The largest challenge once you have the hardware ready and connected is aligning the dish correctly. The dish has to point at the correct angle into the sky (elevation) and in the correct direction (azimuth). There are websites such as dishpointer.com and even Smartphone apps, such as Satfinder to help you align the dish antenna. There are also physical in-line signal meters that are supposed to help however unless you can afford one like the professional satellite installers use, they are not worth buying.

Dishpointer.com has you enter your location and selected the name of the satellite (in our case Es’hail-2 – which is the satellite, QO-100 is just one of its many payloads) and gives you accurate aiming information, it even shows you a satellite overhead picture indicating where your antenna needs to “see”. If you can’t simply mount the dish on a balcony with line of sight to QO-100 then the only option is to mount the dish on the top of the roof.

As well as Azimuth and elevation angles, we receive a “skew” angle. Remember I said TV satellites use either vertical or horizontal polarisation? Well, in this world (or out of it) nothing is perfect and the route from my location to QO-100 needs a slight twist on the polarisation and this is done simply by twisting the LNB in its mount to the required angle (there are marks on the LNB case) – I needed -13° your value will be different).

TV satellites use either vertical or horizontal polarisation

You can trust the values from Dishpointer, which is more than can be said for the smartphone app. In an ideal world you would put the phone side along the side of the dish mount and adjust to the correct azimuth. I did this to start with and could not hear anything from QO-100. It later turned out that the App’s direction was off by 10°. Once I knew this (by pointing the dish at the main TV satellite here) I could allow for the difference in reading and managed to hear one of the beacons on QO-100 and then fine-tuned by ear / S-Meter. It may sound obvious but pointing the dish is the correct direction is rather important!

One question you may be asking is how do you know the frequency in the QO-100 band plan when tuning the Intermediate Frequency (IF) around 740MHz as the signal is actually at 10 GHz. As we are only using the low band, we use the 9.75 GHz oscillator in the LNB. So, adding what the radio shows to 9.75 GHz will give the frequency you are receiving, right? In principal yes, however, as accurate frequency is not critical for TV reception, that 9.75 GHz oscillator may not be exactly 9.75 GHz indeed it often isn’t – so you need to calculate the difference from 9.75 GHz for your calibrated frequencies at 10GHz. How can you check what the real frequency against what you see displayed + 9.75 GHz? Well there are upper and lower beacons running constantly on QO-100 at 10489.5 and 10489.999 MHz and they are accurate, read off the frequency on the X6200, add 9750MHz to it and see how far you are away from the 10489.5 or 10489.999 MHz frequency and you have the amount your LNB oscillator is off.

Alternatively, you can find a station on the X6200-WR12 and then find the same station via the BATC WebSDR at eshail.batc.org.uk/nb/ and then see where the radio says it is (again adding 9750 MHz to the X6200 displayed frequency) to find the LNB oscillator error. These checks should be done after the LNB has warmed up and stopped drifting.

Once you know the actual frequency of the LNB oscillator you can put it into a spreadsheet to allow quick calculations, in my case I also have the QO100 Band plan as part of my spreadsheet.

Narrow band LNB frequency chart

Remember I said, I bought a “bargain basement” LNB? Well for €3 I wasn’t complaining however it drifts and there is a better option. One whose oscillator is closer to 9.75 GHz and that does not drift nearly as much as my LNB. This is one that is used, it seems, by the majority of people receiving QO-100. It is called the “Bullseye 10 kHz TCXO LNB” (that 10kHz refers to maximum drift and not frequency of operation). This, far better, LNB is available for under €30 if you shop around, After I replaced my standard LNB with this one, the receiver worked better and was stable enough for the X6200’s in-built FT8 Decoder to work.

X6200’s in-built FT8 Decoder

 


2 Kommentare

Ed Durrant DD5LP

Hi Reb – please explain how an IC705 can be used to receive QO100 when the max Rx Freq of the IC705 is stated by ICOM as 470MHz and 740MHz is needed for the dish IF? One might be able to use the IC905 but not the IC705.
D-Star is a Digital Voice modulation mode competing against DMR YSF, M17, NXDN, etc. It has nothing to do with satellites, despite the name.
Ed.

Reb

The Icom 705 does this with out all the wires and boxes .it’s called D star . U get what you pay for.

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