Circularly Polarizing C1PLL LNBF

[cyberham]

I am trying to receive 22W C-band. Transponders are circular.

On the C1PLL, do I simply insert the provided board into the LNBF? What orientation? How far does it need to be inserted down the throat of the LNBF?

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[Titanium]

Place the dielectric slab into the slot positioned at 45 degrees between the Horizontal and the Vertical probes. The dielectric slab depth into the slot will be set to optimize with your specific dish F/D. Slide it into the slot about 1/2 way then increment 1/4" to optimize. Use the amalgamated rubber tape to secure the slab position in the slot when the signal is optimized. Other materials can be used as a dielectric and may provide better results. Some dielectrics have been fabricated out of CD jewel cases, PCB boards (with or with out etching), etc.

 

[cyberham]

I think I understand. I notice now there are two sets of guides inside the LNBF. One of the sets of guides places the dielectric 45 degrees between the V and H probes.

My chance of success on this attempt is maybe 5%. I have the LNBF cable-tied to the LNB arm. I am using a small 1m dish. I don't really know which is the best tp to try for. I am also moving the LNBF around looking for any hint of a signal. The only good thing in my favour is I know azimuth and elevation of the dish is exactly correct since I peaked it on a 22W Ku tp.

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[Brct203]

I think I understand. I notice now there are two sets of guides inside the LNBF. One of the sets of guides places the dielectric 45 degrees between the V and H probes.

My chance of success on this attempt is maybe 5%. I have the LNBF cable-tied to the LNB arm. I am using a small 1m dish. I don't really know which is the best tp to try for. I am also moving the LNBF around looking for any hint of a signal. The only good thing in my favour is I know azimuth and elevation of the dish is exactly correct since I peaked it on a 22W Ku tp.

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there should be 2 sets of guides at 90 degrees. One set will match RH with H and LH with V, and the other set will match RH with V and LH with H (which is what you want). But rather than going straight to the unknown with 22W, maybe try some other birds? I find 47.5W to be quite strong. Also in the past I was able to receive the AFN transponder on 34.5W with a 1.2 meter dish, but that was back when it had a lower SR. Also, I was able to get Rede Genesis on 40.5W

It's worth a shot, and your estimation of chances of success at 5% seems quite realistic . Still fun to try. And definitely try 11W too

 

[Inclined Orbit]

With a spectrum analyzer you can get it perfect. Look up the beacon frequencies for the 22W satellite and tune to one, they should be frequency specific per polarity. Once the dielectric card is inserted as mentioned above, change polarities so you can see one of the beacons and choose the polarity that gives the lowest signal. Then carefully take some needle nose pliers and rotate the card a little then check the beacon level again. You would be going for the least amount of signal and when done right the beacon will disappear on one polarity and be full strength on the other polarity. I've set up a number of commercial linear feeds this way to receive circular polarity.

I prefer to use Teflon sheet about .015 to .030" thick for the dielectric card.

 

[Brct203]

With a spectrum analyzer you can get it perfect. Look up the beacon frequencies for the 22W satellite and tune to one, they should be frequency specific per polarity. Once the dielectric card is inserted as mentioned above, change polarities so you can see one of the beacons and choose the polarity that gives the lowest signal. Then carefully take some needle nose pliers and rotate the card a little then check the beacon level again. You would be going for the least amount of signal and when done right the beacon will disappear on one polarity and be full strength on the other polarity. I've set up a number of commercial linear feeds this way to receive circular polarity.

I prefer to use Teflon sheet about .015 to .030" thick for the dielectric card.

I agree that a spectrum analyzer is the ideal tool, and when it comes to narrow signals like beacons, that can even be done with a cheap SDR and a laptop. There is however one very common problem with using the beacons: very often they are using the "other" polarization type. For example, on 22W, according to what's published, the C-Band transponders are circular, but the beacon is linear. And on Ku, the TPs are linear but the beacons/telemetry are circular. There does not seem to be any hard rule about it, some satellite use the same type and other use the opposite type and some use a mix of both. They can still be used to peak the dish, but might not always be useful for peaking the dielectric,
It might be better to look for a transponder that the spectrum analyzer can display together with the surrounding noise floor (so if using a cheap SDR, a very narrow TP that would be at most 1 MHz wide. Not every satellite has that though)

where do you find such Teflon sheet?

 

[Inclined Orbit]

If there is no circular pol beacon then you can try nulling out transponders on the opposite polarity, but its less accurate. Usually transponders overlap in frequency between polarities so you can set the analyzer to see two transponders on the desired pol and one in the middle of the opposite pol, then tweak the dielectric card to null the middle or opposite transponder. With small dishes you may only have 10-15dB of carrier sticking out of the noise floor so that's about the best you can see to null the opposite pol. With a CW beacon you can have enough range to null 30dB or more although you won't get that much with a home made dielectric card modification.

I have an amount of Teflon sheet I've used for replacing feed horn windows in big transmit antennas. Years ago I did a search online and found it but I forget the company name. I believe it was in Los Angeles. Now you can probably find it on Ebay.

I agree that a spectrum analyzer is the ideal tool, and when it comes to narrow signals like beacons, that can even be done with a cheap SDR and a laptop. There is however one very common problem with using the beacons: very often they are using the "other" polarization type. For example, on 22W, according to what's published, the C-Band transponders are circular, but the beacon is linear. And on Ku, the TPs are linear but the beacons/telemetry are circular. There does not seem to be any hard rule about it, some satellite use the same type and other use the opposite type and some use a mix of both. They can still be used to peak the dish, but might not always be useful for peaking the dielectric,
It might be better to look for a transponder that the spectrum analyzer can display together with the surrounding noise floor (so if using a cheap SDR, a very narrow TP that would be at most 1 MHz wide. Not every satellite has that though)

where do you find such Teflon sheet?

 

[cyberham]

So I discovered that my 1.2m motorized dish can actually swing as far east as 18W without physically hitting the tree beside it. It could go even further east physically, but the tree horizon stops its visibility of the sky at about 30W anyway.

This means I've increased chances of finding C-band signals on this portion of the arc. I can use the bigger dish (1.2m) and I can use USALS so at least I know I'm pointing in an identifiable azimuth and elevation. However, I am looking through a forest of tree trunks so there are specific azimuths that are blocked. I've blind scanned in both linear and circular modes. I've checked all tps that might have a receivable signal according to popular charts.

End result: I still haven't found any signals while looking from 58W to 30W.

brct203: I tried each of your suggested tps but came up with nothing.

 

[Brct203]

So I discovered that my 1.2m motorized dish can actually swing as far east as 18W without physically hitting the tree beside it. It could go even further east physically, but the tree horizon stops its visibility of the sky at about 30W anyway.

This means I've increased chances of finding C-band signals on this portion of the arc. I can use the bigger dish (1.2m) and I can use USALS so at least I know I'm pointing in an identifiable azimuth and elevation. However, I am looking through a forest of tree trunks so there are specific azimuths that are blocked. I've blind scanned in both linear and circular modes. I've checked all tps that might have a receivable signal according to popular charts.

End result: I still haven't found any signals while looking from 58W to 30W.

brct203: I tried each of your suggested tps but came up with nothing.

I checked the various footprints for coverage of NS, and I think your best bets might be SES14 @47.5W and SES6 @40.5W.

47.5 is strong here but its transponders need at least 6dB to lock, so that might be a challenge

40.5 is not as strong for me, but it has so many small transponders with a variety of FEC, and some might be quite forgiving

31.5W Linear might give you some data signal, for what that's worth. It does have good coverage of NS

Unfortunately 55.5W and 58W , while fairly easy targets here, are about 4dB weaker in NS. Certainly still reasonably easy on a large dish, but probably too weak for a mini BUD. Still, the BBC radio mux on 55.5W might be a possibility. NHK on 58W might be worth checking

 

[cyberham]

Success! A little...

I snagged the BFBS tp on 40.5W with 5.1 dB. This is well above their C/N threshold of 2.2 dB so it will serve as a good 24/7 reference. Tuning this tp told me I must move the dish 1 to 2 degrees to the west from the USALS direction. This is not surprising since I've never had a reference in the eastern sky for USALS adjustments. This will help when searching for other satellites. Being my first circular satellite, this also confirms the dielectric plate in the LNBF is working.

My C1-PLL only tunes 3.7 to 4.2 GHz so I can't try for the extended C-band tps below 3.7 GHz.

Sources indicate 31.5W Intelsat 903 is in an inclined orbit. The Intelsat website doesn't show this as an available satellite.

 

[c-spand]

Success! A little...

I snagged the BFBS tp on 40.5W with 5.1 dB. This is well above their C/N threshold of 2.2 dB so it will serve as a good 24/7 reference. Tuning this tp told me I must move the dish 1 to 2 degrees to the west from the USALS direction. This is not surprising since I've never had a reference in the eastern sky for USALS adjustments. This will help when searching for other satellites. Being my first circular satellite, this also confirms the dielectric plate in the LNBF is working.

My C1-PLL only tunes 3.7 to 4.2 GHz so I can't try for the extended C-band tps below 3.7 GHz.

Sources indicate 31.5W Intelsat 903 is in an inclined orbit. The Intelsat website doesn't show this as an available satellite.

Always good to find something to work with. Fine tune that there and maybe fined more. And upgrade maybe to universal lnb. Thanks for sharing. Hope you find more.

 

[cyberham]

...Also in the past I was able to receive the AFN transponder on 34.5W with a 1.2 meter dish, but that was back when it had a lower SR.

Found the AFN tp on 34.5W. Its threshold is only 1.0 dB which is about the level I'm receiving. TV and radio channels are encrypted. But at least its another satellite.

Also found a data tp at similar level.

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[Brct203]

Success! A little...

I snagged the BFBS tp on 40.5W with 5.1 dB. This is well above their C/N threshold of 2.2 dB so it will serve as a good 24/7 reference. Tuning this tp told me I must move the dish 1 to 2 degrees to the west from the USALS direction. This is not surprising since I've never had a reference in the eastern sky for USALS adjustments. This will help when searching for other satellites. Being my first circular satellite, this also confirms the dielectric plate in the LNBF is working.

My C1-PLL only tunes 3.7 to 4.2 GHz so I can't try for the extended C-band tps below 3.7 GHz.

Sources indicate 31.5W Intelsat 903 is in an inclined orbit. The Intelsat website doesn't show this as an available satellite.

31.5W also has Intelsat 25, which is more recent and Linear. But I've only seen data TPs on that one. I have in mind that there's a strong TP on 3500 MHz, so your LNBF might not receive it.

 

[cyberham]

31.5W also has Intelsat 25, which is more recent and Linear. But I've only seen data TPs on that one. I have in mind that there's a strong TP on 3500 MHz, so your LNBF might not receive it.

Nothing seen blind scanning. Any SR?

 

[Brct203]

i'm seeing 2 TPs on 31.5W now:

3919 H 29686. Getting it with about 10.7 dB on a 10 foot Winegard. It seems to be a 16apsk with a 5/6 FEC. A data service scans in as "Satnet4_UNAMID --- UnKnown Service Type E:"
3705 QPSK 4341 - not sure about FEC. I'm getting about 7dB on that one. Nothing scans in.

I guess the one at 3500 is gone

not very auspicious for a mini-BUD. but the 3705 might be worth a shot

 

[cyberham]

I locked the one at 3919. It scanned in as you said. So that nails down the 31.5W direction which is good. The C/N reading is a screwy 64.3 dB. We saw this on 115W Ku. Maybe it is 16APSK signals that cause this type of erroneous reading. I think the signal on 115W Ku was also 16APSK.

Nothing seen on 3705.

 

[Brct203]

now that we're getting colder weather (27F right now and clear sky), I'm able to get 27.5W with my side-car circular LNBF
'DVB-S2 8PSK 4152L / 1500 / 3/5' > Tp# 1
< (1)NntecHDTV1 /> 1:0:16:1:1:1:CFC1038:0:0:0:<
It's NTA1 from Nigeria, same as on 97W Ku. Getting about 6dB

Of course if I put the dielectric in the prime-focus LNBF I get a better signal, but I need that one for linear sats...

 

[cyberham]

No luck here on 27.5W.

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[cyberham]

...Slide it into the slot about 1/2 way then increment 1/4" to optimize....

Reading old posts can teach you. I have always just pushed the circular dielectric plate in as far as it will go into the LNBF throat. It works fine like that. But today I tried different positions of the dielectric plate. I found I could get up to an extra 1.4 dB on a tp when using my mini-BUD. This is big! Signals are often just above threshold when using a small dish so 1 dB can mean the difference between locking or not locking a tp. Or the difference between a visually perfect picture and one that is always breaking up and is unwatchable.

But...I also discovered the best placement of the plate varies depending on satellite being received. For example, 40.5W is received best with the plate fully inserted. But 47.5W is best with the plate much closer to the mouth of the LNBF. There is no easy solution to this on a motorized dish short of running outside every time you move the dish. Is there a solution for this?

 

[Titanium]

I would confirm that the dish tracking, focal length setting, skew and feedhorn alignment with the reflector are correctly placing the convergence point of each target satellite at the same point within the feedhorn. From your description, I would guess that there is a misalignment, resulting in the convergence point not remaining constant across the arc.

The purpose of a dielectric slab for polarity conversion (circular to linear or linear to circular) is to delay the AB to XY components by .25 of the wave length. The circular wave travels along the slab until, at a specific distance, the phasing delay produces a linear wave. Moving the slab fore and aft changes the point that the dielectric slab interacts with wave and optimizes the conversion.

The slab provided with LNBFs is a good generic or universal starting point. You may find other dielectric materials or phasing techniques to provide more efficient polarity conversion.