Newsnet on Ka Band A

s-band · Nov 17, 2017

John said:
Nice going, looking at those results makes your installation just a tad under to what my dedicated Hughes lnb / xmw cone feed / 1.25 gibby gives me Graham. I did a bit of searching on my modded Gilat the other day and it's still working lol.

Thanks, managed to scrape an extra 1/2dB from somewhere! Now all lock except 18535 and that hasn't got a chance as there's an internal spurious near it.

New test cards on 18511 (SIS 91) and 18531 (SIS Plymouth)

Edit: another feed on 18523 H264 test card

Llew · Nov 17, 2017

No lock here with 18535, despite a few extra dBs.

Hughesnet LNB+XMW Feedhorn on Triax 1M dish.

tony smith · Nov 17, 2017

Hi Folks
Some of the problem with the Newsnet feeds of ITV and ITN operated by SISLive
is that the levels are low, and that the separation of channels is next to nothing not unlike the DVB S2X, plus channel bandwidth is very small,so without a narrow bandwidth IF receiver, with AFC to match, it always going to be a problem
to separate the channels.
Also the likes of ITN receiving at Grays Inn Road has bigger antennas than the 2.8 metre at many ITV regional news centres,
so can cope with lower eirp's, ITV GRA use SISLive at Media City to downlink for them, on a much bigger antenna maybe.

Channel Hopper · Nov 17, 2017

Tony

You need to look back through the earlier Ka band threads to understand that bigger is not always better at these frequencies.

s-band · Nov 18, 2017

@tony smith Interesting info. Whilst the dish is good to 30GHz, I am using a modified Gilat 19.2-20.2 LNB from an ODU so it droops a bit at the bottom end. I have bodged the Gilat feed directly on to it (It's wrong for the dish, f/d 0.6 not the 0.8 needed). That's losing something due to mismatch at the transition and probably over-illumination. In fact, it's a wonder it works at all! I get a total system noise figure (sky/ground measured) of 2dB at >19GHz and 2.4dB at 18.6GHz. My LO is 18.25GHz. The TBS6983 can separate the lower 2 TPs which are 4MHz apart but here's a pic showing the spurious that blocks 18535:

I don't know why @Llew can't lock 18535 as the spacing is the same as the lower pair. I also note that 18557 is about 5-6dB down this morning compared to last night. I can only just lock it at times now.

Edit at 10:50: 18515 is back just below threshold at 5.9dB

tony smith · Nov 18, 2017

@ Channel Hopper, my comments were only ref this particular satellite Astra 19 1L, She's a Lockheed Martin 2100
with 14 Ka transponders, 30 Ku Transponders
Her architecture for Ka up and K down is zoned ,with very limited cross strapping to change zones,she was intended for
IP operation that's VSAT up and Earth station Hub down around 9 metre dia hub.Not DVB S2
SISLive have the UK lower 50mHz, and part of the upper 50mHz downlink, so are limited for space, so hence my comments
ref guard bands( see DVB S2x ref levels/saturation/guardbands.) not just frequencies.

@s-band if your headend is working then your rocking and rolling. Sis Live can run the lower 50 Mhz with 10 scpc channels
they normally only run max 7 or 5 , then move up to the upper 50 Mhz, on top of this we have a data carrier at 18502 MHz
which is uplink truck's to base comms, with another data link at 18562 MHz, which is base comms to truck, as well as ITN to ITV news regions 18556 mhz.
So the unwanted rf carrier, is either local to you or lower level channel break through

s-band · Nov 18, 2017

tony smith said:
So the unwanted rf carrier, is either local to you or lower level channel break through

I had a look at another LNB and the spurious is at 285.15625MHz which is 10x the reference crystal. The 9125MHz PLL uses 5 x xtal as its reference. I could shift the LO to 17920 by using a 28.0MHz xtal which would move the spur to 18.2GHz. This is the LNB arrangement Ka with Prodelin/Viasat 1.2m Band B

tony smith · Nov 18, 2017

Hi s-band
yes sounds a plan lets know how you get on

Channel Hopper · Nov 18, 2017

tony smith said:
@ Channel Hopper, my comments were only ref this particular satellite Astra 19 1L, She's a Lockheed Martin 2100
with 14 Ka transponders, 30 Ku Transponders
Her architecture for Ka up and K down is zoned ,with very limited cross strapping to change zones,she was intended for
IP operation that's VSAT up and Earth station Hub down around 9 metre dia hub.Not DVB S2
SISLive have the UK lower 50mHz, and part of the upper 50mHz downlink, so are limited for space, so hence my comments
ref guard bands( see DVB S2x ref levels/saturation/guardbands.) not just frequencies.

I was talking about this position only though I had forgotten about the type of bus (Astra 1KR is of similar manufacture but without the Ka band kit installed - allegedly).

The active transmissions at 18GHz are provided by two transponders and from memory they are on opposite linear polarities. In order to improve the reception by a margin, one could use a dedicated single polarity LNB and matched rectangular port transfer from the feed, or perhaps a dedicated one piece feed/transfer if one can be constructed. The other option would be to rotate the offset dish by 90 degrees, so that the elipse is better at removing the side lobes in the orbital plane, and possibly aligning the dish at the correct skew angle of the equatorial arc to peak the cross-pol rejection mechanically.

Since the orbital slot around 19E is rather crowded, not only with the official commercial satellites, but a couple of classified/military birds, it might be the incoming noise from the thousands of different transmissions are swamping the tuner input, and the filters at the band stops let some of it through.

In the second case, increasing the dish size, whilst narrowing the beamwidth, is unlikely to remove the unwanted signals unless you are talking about diameters of above 5m to limit this below 0.5 of a degree or so.

tony smith · Nov 18, 2017

Hi Channel Hopper
First yes Astra 1KR she is a Lockheed Martin 2100 running Ku band.
Going back to Astra1L SISLive lease on about a 7 year lease the lower UK one, and some & plus ad hoc lease on the upper
frequency one, they are all Vertical polarity, there is one more that can be strapped (beam focus mostly) for France or UK
zones, this is all for ITV/ ITN News operations, SISLive have many other leases on other satellites for their other activities,
mostly Ku band. Sky News etc.
The another Ka transponder which is active around 183xx MHz again Vertical polarity was used for Playboy TV, still running.
The only Horizontal transponder that could cause any opposite transponder cancellation, is the one that did have the Italian
horse racing on, but as it's not in UK zone, and very much higher in frequency, it's not a problem, very easy to skew out.
Any side lobes are not a big problem if as most of us are running prime focus antennas, this comes more of a problem with dual optics antennas this is all to try and reduce the beam width, so your tx or receive 1st order are with in the 32 Log theta
shape.

The K band down link at the 19.2 east Astra orbit is very clear, as in it's 18/19 Ghz spectrum only Astra 1L is using it, nothing else.

The only problem downlinking K band here, is if you have any local high power cellular telephone transmitters . that's one of the reasons why this spectrum slice at K band is so clear, all or most other Ka band uplink satellites have higher downlink frequencies.

PS Satellite term's " Bus" is it's electrical power platform, the rx/tx is it's" Payload"

s-band · Nov 18, 2017

@tony smith So, it's on Ka 10 as page 2 here?: http://frequencyplansatellites.altervista.org/Astra/Astra_1L.pdf with Unire at the lower edge of Ka 19?

There is a strong carrier on 18794.749MHz V ~42dB SNR in 1kHz (TP 19?) and a weaker one on 18794.755MHz H at ~15dB SNR in 1k. (TP20, France/Finland?) Frequencies are +/- few kHz but the weaker on is ~6kHz above the stronger. At first I thought that my x polar rejection was poor (it's actually around 29dB ).

tony smith · Nov 18, 2017

Hi s-band
It's beam 8 Italy(Ka 19) this can be strapped as beam 10 Ukraine, it's H polarity, so need to check your skew to reduce this to min
Beam(s) 4(Ka 10 &12) are the uk ones.
I can reduce this H carrier no problem, also can see it at high level like you if I cross polarise my feed but below + 35dBm

Having said that, it does look a little higher today, maybe to help with rain fade

s-band · Nov 18, 2017

tony smith said:
Hi s-band
It's beam 8 Italy(Ka 19) this can be strapped as beam 10 Ukraine, it's H polarity, so need to check your skew to reduce this to min
Beam(s) 4(Ka 10 &12) are the uk ones.
I can reduce this H carrier no problem, also can see it at high level like you if I cross polarise my feed but below + 35dBm

I can null out the strong H carrier 18794.749 or the weak V carrier around 18794.755 but I was curious to know which TP the weak carrier is on i.e TP20? I see you have an analyser, can you see them both on that? I have to use <1kHz RBW to separate the 2 carriers.

Do you have definitive beacon frequencies for Ka?

Channel Hopper · Nov 18, 2017

tony smith said:
Hi Channel Hopper
First yes Astra 1KR she is a Lockheed Martin 2100 running Ku band.
Going back to Astra1L SISLive lease on about a 7 year lease the lower UK one, and some & plus ad hoc lease on the upper
frequency one, they are all Vertical polarity, there is one more that can be strapped (beam focus mostly) for France or UK
zones, this is all for ITV/ ITN News operations, SISLive have many other leases on other satellites for their other activities,
mostly Ku band. Sky News etc.
The another Ka transponder which is active around 183xx MHz again Vertical polarity was used for Playboy TV, still running.
The only Horizontal transponder that could cause any opposite transponder cancellation, is the one that did have the Italian
horse racing on, but as it's not in UK zone, and very much higher in frequency, it's not a problem, very easy to skew out.
Any side lobes are not a big problem if as most of us are running prime focus antennas, this comes more of a problem with dual optics antennas this is all to try and reduce the beam width, so your tx or receive 1st order are with in the 32 Log theta
shape.

The K band down link at the 19.2 east Astra orbit is very clear, as in it's 18/19 Ghz spectrum only Astra 1L is using it, nothing else.

The only problem downlinking K band here, is if you have any local high power cellular telephone transmitters . that's one of the reasons why this spectrum slice at K band is so clear, all or most other Ka band uplink satellites have higher downlink frequencies.

PS Satellite term's " Bus" is it's electrical power platform, the rx/tx is it's" Payload"

The offset comment was for S-band, who I recall was using a dedicated Prodelin offset in 'out of the box' vertical configuration (and I think a circular scalar feed). Reception at his location could be improved with turning the reflector on its side and upgrading the feed to an elliptical type.

I was talking about the bus being the same - virtually - for both 1L and 1KR which would include the TTCandR including the kit that provides the beacon frequency via its own high gain antenna (though I would have to check through old notes if this has changed with 'modern' communications satellites) . But yes the payload is the bit that includes the profitable part and reason for putting them up there, the communication antenna(s) and the repeaters/transponders.

Channel Hopper · Nov 18, 2017

Beacon detail comes from the bus, which would make sense in the event a payload antenna fails to deploy, or the satellite experiences trouble with orientation.

Aeneas - eoPortal Directory - Satellite Missions

s-band · Nov 18, 2017

CH, the dish is from a Viasat VSAT terminal and its original feed is difficult to adapt to other LNBs. It originally used a round feed and I can only see round feeds on the GD site (but can't see the scalar structure). It is a 3122 but with custom feed supports for the Viasat ODU. https://gdmissionsystems.com/produc...antennas/vsat-antennas/1-2-meter-vsat-antenna.

I found another horizontal beacon on 18405.260MHz (+/- few kHz). This one is almost as strong as 18794.75H and my LNB is way below its best there. Interesting (to sad people like me) that the x polar rejection is about 33dB at that frequency. None of the beacons seem to have data. I thought that the TT&C was on Ku but haven't checked for myself. It's hard to separate them on Ku, anyway.

Channel Hopper · Nov 18, 2017

s-band said:
CH, the dish is from a Viasat VSAT terminal and its original feed is difficult to adapt to other LNBs. It originally used a round feed and I can only see round feeds on the GD site (but can't see the scalar structure). It is a 3122 but with custom feed supports for the Viasat ODU. https://gdmissionsystems.com/produc...antennas/vsat-antennas/1-2-meter-vsat-antenna.

The only elliptical antenna (in the correct plane) from Prodelin has been the 1950/51 system which
1) is too small for your requirements, and
2) is not Ka compatible.

There might be a 3000 series that does meet the needs, but as Tony has mentioned, many will have gone and bought a prime focus antenna to cover the lack of elliptical equipent out there for civilian needs

You might find something on a military surplus auction site though. US334 compatibility would fit the bill.

US 334

tony smith · Nov 18, 2017

Hi s-band
I would say that the vertical signal you can see at18.794 is part of your block down convertor process showing up as low level image like old heterodyne receivers did.
Otherwise it's as the satellite frequency plan.
Satellite beacons as not the most reliable part of the space crafts kit, I have not seen one on any of the Lockheed Martin
2100 birds at 19.2 east, even with the R&S spectrum analyser, they can be very narrow, band none modulated of course, also by nature low level, unless you need them for your beacon receiver, then all identification can be taken from satellite's data.

The 18.405 frequency you called as a beacon, I think again is locally generated, as it's part of Ka 5 Germany zone beam 5, so would not have a beacon there, if it was active

Also looking your antenna, it's fine for Ku and K bands, I would make your own oblong feed horn, as your made for Vsat feed, is not helping with all it's stud filters. they are very easy to make out of tin plate, to get all the size info and details just look up some made up units on internet and many makers give the measurement details, I have made quite a few this way, they work fine fitted to WR75 type flange or smaller flange.

s-band · Nov 19, 2017

Hi Tony, The 2 strong horizontal CW signals have been reported by a many. I have convinced myself the the vertical one 6kHz above 17894.75H is real since;

As far as I can tell , they peak at the same point in the sky. It could be from another position but I can't find it elsewhere. I'm only using a 1.2m so the angular resolution is limited.
They are present on 2 different receivers, an HP analyser and an SDR
I can't see any strong vertical signals that might cause a spurious (that's not to say that there is not one out of band, but it still has to be from the same position).
I can null the H one to peak the V and vice versa. The feed skews look orthogonal. The plots are in an effective BW of ~3Hz hence nearly 60dB SNR on the H one. The frequencies on the plots are a bit out as I did not re-calibrate this morning and the reference in the LNB wanders a bit.

Can you look, using vertical pol, 6kHz above the H carrier in <<1kHz, please?

The VSAT feeds I'm using are simple ones and don't have the filters included. There were chokes and filters in the ODU so the only filter left is the microstrip one in the LNB. The circular polariser has been removed. I've got another WG adapter so I can try the Viasat feed which should be matched to the dish. I've made feeds for X band but Ka is more fiddly;-)

Back to the thread title, The GS on 18561V seems very stable in level (12-13dB SNR) but the ITN ones vary a lot. At the moment 18515 & 18557 are both about 7dB SNR but 18557 has peaked 12dB over the past few days.

tony smith · Nov 19, 2017

Hi s-band
If your Local Oscillator of your LNB is 17.250Ghz then the IF of your 17.894 signal will be about 644 Mhz the lowest broadcast
off Astra 1L K band on H pol would be 1.05 Ghz, so it's not off the bird, I have looked at my site at narrow band down to 1Khz
can see nothing like this at my site, it's also outside my LNB pass band filter, (Norsat 18.2 19.2 Ghz dia stab L.O 17.250 Ghz)

Surprised that you have no wave guide filters they take the form of small threaded screws along your wave guide, most Vsat feeds normally have them.

Look at Astra 1L K band at GMT 13:52 K has ITN K90 at 18.514, plus usual comms carriers, with ITN main Newsnet feed at 18556 ,otherwise she is quiet, and stable

Newsnet on Ka Band A

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