Best C-band lnbs for offset dishes?

kippysat

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310
Hello All,

Does anyone have any thoughts and/or recommendations on the best/top of the line C-band LNBs
for an offset dish?

I want to do some testing and investigation on various transponders with some of the western satellites.

Thanks.
 

moonbase

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There are two structural types of LNB(F) for offset dishes.


1. LNBF which has the feed waveguide as part of the barrel, these are generally dual probe for both polarities (simple, easy to use).

2. WR229 flange LNB which has no feed waveguide and attaches to a separate waveguide. These are single probe LNBs for single polarity. Dual polarity is achieved by attaching a pair of them to an OMT.
These are not for dreamers or tyre kickers, some of the higher spec models such as Norsat with 5G filtering can be expensive but they are top of the line.


For testing and a basic introduction, my recommendation would be to buy an LNBF such as a Titanium C138 with 1 cable output or Titanium C238 with 2 cable outputs.
In addition, for an LNBF on an offset dish you will need a hooded scalar. These can be bought separately or sometimes as a kit with the LNBF. The flat scalars used on prime focus dishes are no good for offset dishes.

Lastly, if you are using circularly polarised satellites you will need to use either a dielectric plate in the waveguide feed or use a polo pipe as waveguide feed.
The circular polarity signals need to be converted to linear polarity for the LNB(F) to receive them or there will be signal level reduction. The dielectric plate or polo pipe performs the circular to linear conversion.
 
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kippysat

Donating Member
Messages
310
There are two structural types of LNB(F) for offset dishes.


1. LNBF which has the feed waveguide as part of the barrel, these are generally dual probe for both polarities (simple, easy to use).

2. WR229 flange LNB which has no feed waveguide and attaches to a separate waveguide. These are single probe LNBs for single polarity. Dual polarity is achieved by attaching a pair of them to an OMT.
These are not for dreamers or tyre kickers, some of the higher spec models such as Norsat with 5G filtering can be expensive but they are top of the line.


For testing and a basic introduction, my recommendation would be to buy an LNBF such as a Titanium C138 with 1 cable output or Titanium C238 with 2 cable outputs.
In addition, for an LNBF on an offset dish you will need a hooded scalar. These can be bought separately or sometimes as a kit with the LNBF. The flat scalars used on prime focus dishes are no good for offset dishes.

Lastly, if you are using circularly polarised satellites you will need to use either a dielectric plate in the waveguide feed or use a polo pipe as waveguide feed.
The circular polarity signals need to be converted to linear polarity for the LNB(F) to receive them or there will be signal level reduction. The dielectric plate or polo pipe performs the circular to linear conversion.
Hello @moonbase,

Thank you for this information. I've decided to buy an entry level one to start my testing. Seems a sensible
option just in case the signal reception is not what I hoped it would be. I am literally dipping my toes in
the water with C-band.

If the entry level goes well, then I will defo upgrade to the Titanium C138 for improved signal reception.

As soon as it arrives I will be moving the dish to 8W and then 40.5W to see what transponders actually
appear. Will update this thread with my testing results.

Exciting stuff...(y)
 

kippysat

Donating Member
Messages
310
Hello All,

This is what arrived in my c-band lnb package. From what little I know, the blue conical ring is designed for an offset dish like mine,
as opposed to the light brownish ring which is designed for a prime focus dish.

There is a small rectangular piece of "tile". I believe this is the dielectric plate and has to be inserted into the lnb if I want to convert
signals to circular left and right and improve the strength of the signals.

I have been reading lots of old threads from @amdade, @empb, @RimaNTSS, @moonbase , @ArloG and others regarding C-band
escapades from 2013 onwards.

Someone referred to another website that has c-band set up information. It said that when setting up the lnb, it is critical that
I insert the dielectric plate at a 45 degree angle to the probes inside the lnb to maximise signal reception.

I know I have a lot of initial work to do to get the lnb to fit on my offset lnb arm, but that is DIY stuff and I am not afraid to do that
work.

May I kindly ask those of you with C-band experience and who have done this before, if I have understood what I read correctly or
should I be doing something else?

Any advice and/or comments on how to do this properly is appreciated? Thank you in advance.



IMG_7171.jpgIMG_7172.jpg
 

moonbase

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@kippysat

Yes, you have understood things correctly.

1. Blue hooded scalar for your offset dish.
2. Green rectangular slab is the dielectric plate.

If you look into the barrel of the LNBF you will see the two detector probes, one for horizontal polarity, one for vertical polarity. These probes are at 90 degrees to each other.
If you think of the two probes aligned to a clock face and they are at approximately 10 o'clock and two o'clock respectively, the dielectric plate needs to run vertically between them at 12 0'clock and 6 o'clock.
In other words, the dielectric plate bisects the 90 degree angle between the probes.

Get strapped up and aim for 40.5W or 40.0E, they are both strong satellites with circular polarity, you should easily lock a good few channels.
Once you have bimmed in a few channels check their parameters with Lynsat to be sure you are on the correct satellite.

Use the signal level to peak the dish setup including the position of the hooded scalar along the LNBF barrel. The signal level should change as you move the hooded scalar along the barrel.
You can probably lock channels without the hooded scalar from these two satellites as they have strong signals, then place the scalar on the LNBF and watch the signal level increase by a couple of dB.
 
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kippysat

Donating Member
Messages
310
@kippysat

Yes, you have understood things correctly.

1. Blue hooded scalar for your offset dish.
2. Green rectangular slab is the dielectric plate.

If you look into the barrel of the LNBF you will see the two detector probes, one for horizontal polarity, one for vertical polarity. These probes are at 90 degrees to each other.
If you think of the two probes aligned to a clock face and they are at approximately 10 o'clock and two o'clock respectively, the dielectric plate needs to run vertically between them at 12 0'clock and 6 o'clock.
In other words, the dielectric plate bisects the 90 degree angle between the probes.

Get strapped up and aim for 40.5W or 40.0E, they are both strong satellites with circular polarity, you should easily lock a good few channels.
Once you have bimmed in a few channels check their parameters with Lynsat to be sure you are on the correct satellite.

Use the signal level to peak the dish setup including the position of the hooded scalar along the LNBF barrel. The signal level should change as you move the hooded scalar along the barrel.
You can probably lock channels without the hooded scalar from these two satellites as they have strong signals, then place the scalar on the LNBF and watch the signal level increase by a couple of dB.
Thank you @moonbase for the detailed description of the dielectric positioning.

I am going to position it as I have understood the description and then post my picture.
 

kippysat

Donating Member
Messages
310
Here is a pic with the dielectric plate in a 12 o'clock to 6 o'clock position vertically dissecting
the 2 thin probes. It seems to sit roughly 45 degrees between each probe.

One question though....

Do I have to insert the dielectric plate as far as it will go into the lnb or leave it half-way or
very near to the top?

IMG_7187.jpg
 

moonbase

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Donating Member
Messages
575
Here is a pic with the dielectric plate in a 12 o'clock to 6 o'clock position vertically dissecting
the 2 thin probes. It seems to sit roughly 45 degrees between each probe.

One question though....

Do I have to insert the dielectric plate as far as it will go into the lnb or leave it half-way or
very near to the top?


The dielectric plate is positioned correctly at 45 degrees angle to each probe.

Let the plate go in as deep as it is allowed by the internal side grooves, there should be some type of stop such as the barrel narrowing
If you gonna do it, go in deep, if its deep it must be good.

Don't overthink this, it is simple, it aint rocket science or a gas plant.
 

kippysat

Donating Member
Messages
310
The dielectric plate is positioned correctly at 45 degrees angle to each probe.

Let the plate go in as deep as it is allowed by the internal side grooves, there should be some type of stop such as the barrel narrowing
If you gonna do it, go in deep, if its deep it must be good.

Don't overthink this, it is simple, it aint rocket science or a gas plant.
Thanks @moonbase. I got it to fit as deep as possible with some effort.

Now, if the weather would just give me a full weekend day without rain, then I
can make some more progress.
 
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