Reverse Band LNB

Discussions about low-noise blocks, waveguides, horns and other components used at the prime focus of your reflector dish.
Foxcreek
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Reverse Band LNB

Post by Foxcreek » Thu Mar 02, 2017 5:32 pm

Hey all,

Has any one seen a "reverse Band" ( 17.3 to 17.7 Ghz. ) LNB ?
Of course the Direct TV RB unit is beginning to show up on ebay
but I'm looking for something more FTA.

I'm very curious about what might be going on in this new band.
DTV is transmitting 4k stuff from 99W/103W and D/N is transmitting
in this band at 110W. Since it's brand new it might be ITC.
DTV of course is DSS as oposed to DVB so I'll only be able to see the carrier.

foxcreek :cool2

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Re: Reverse Band LNB

Post by elko » Thu Mar 02, 2017 9:01 pm

More info on RDBS and 4K DTV

https://en.wikipedia.org/wiki/DirecTV-14

Haven't heard of an RB LNB for fta yet...what is wrong with using the ones sold by dtv?

Foxcreek
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Re: Reverse Band LNB

Post by Foxcreek » Thu Mar 02, 2017 9:25 pm

elko,

I'll try one of the DTV LNB's if I can't find anything else.
I'll have to figure out the switching because they have the
Ka band @ 99/103, and the Ku band @ 101 in them too.

foxcreek :cool2

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Re: Reverse Band LNB

Post by Foxcreek » Fri Mar 03, 2017 10:20 am

All,

Well it looks like at this point the only reverse band LNB available is
the direct TV unit. I ordered one this morning from ebay.

Of course I don't have the unit in hand but I have a pretty good idea
of it's design. It looks like DTV uses the same L. O. ( 18.05 Ghz. ) that
is used for the Ka band which down converts the reverse band ( 17.3 to 17.7 Ghz. )
to an inverted I F of 750 to 350 MHZ. This I F is then upconverted with the "B" band
upconverter to 1650 to 2050 Mhz. which is inputed to the DTV receiver.
The "B' band upconverter that used to be inserted at the receiver input is now in
the LNB. The LNB also has a Ku band downconverter in it for 101W it's L. O. is the
standard 11250 Mhz. as in the previous LNB's. It probably switches between Ku band
and Ka/RB with 22khz.

Thats my educated guess.
foxcreek :cool2

rusty
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Re: Reverse Band LNB

Post by rusty » Sun Mar 05, 2017 8:30 pm

So foxcreek, the 17Ghz band will be exlusively 4K?

Do let us know if you find anything in the clear...
12' Cosmos Primestar (refurbished)36" SuperJack Actuator
Chaparral Corotor Feed (Norsat 8115, 4106A)
ZGemmaH7 UHD, OctagonSX88 HD, Edision UHD, DSR-6000, DSR-6050
Clarke Belt: 22W - 133W

Foxcreek
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Re: Reverse Band LNB

Post by Foxcreek » Mon Mar 06, 2017 9:11 am

rusty,

I believe thats the plan at least for DTV.This could really
kick start a stalled 4k world ! If successful I can see D/N
jumping on board too.

I've been hoping that this would happen...... time to buy
that 4k TV !

foxcreek :cool2

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Re: Reverse Band LNB

Post by elko » Mon Mar 06, 2017 9:23 pm

Foxcreek wrote:...... time to buy
that 4k TV !

foxcreek :cool2
I wouldn't get too excited just yet. :wink Even if the 4K content is fta, how do you plan to decode it? :sweating I believe DirecTV uses DVB-S2D (custom in-house standard) for all HD content and probably the same (or something more advanced???) for UHD?

Just for the record, I haven't come across a single tuner card that can decode DVB-S2D, although the Skywalker works fine for the older DSS stream.

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Re: Reverse Band LNB

Post by Foxcreek » Tue Mar 07, 2017 11:35 am

elko,

As you know the main problem with 4k UHD has been the lack of
interesting programming. It's hard for most people to justify the
expense if their not going to view it no matter how dazzeling it is.

It appears now that DTV is planning to offer much more appealing
programming. This is what will motivate me ( and lots of other people )
to take the plunge even if it requires a SUB !

To answer your question I'll decode it with a SUB !

foxcreek :cool2

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Re: Reverse Band LNB

Post by elko » Wed Mar 08, 2017 10:47 pm

Foxcreek wrote: To answer your question I'll decode it with a SUB !

foxcreek :cool2
That's one way of doing it...but kinda defeats the purpose of our hobby, no? :thinking

You can still get around the proprietary DVB-S2D stuff by using a genuine DirecTV receiver (no need to sub). Tune the 17GHz signals within the meter section of the menu settings and then probe the motherboard of the receiver for the transport stream bus lines. If the bus lines are not accessible, find the I and Q signals after the tuner. You'll have to interface these signals to your PC somehow (or another 4K FTA receiver) and then go from there...kind of an odd setup, but it may just work!

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Re: Reverse Band LNB

Post by Foxcreek » Thu Mar 09, 2017 11:04 am

elko,

I'm glad that your on this forum I appreciate your support for my
goofie projects ! I already have a DTV receiver and a sub !
What your suggesting is a little bit more effort than I want to put in.
I'm stumped at the moment with the switching protocol of the LNB.
Perhaps you can help me with this. In the previous ( prior to reverse band )
LNB's the Ka band L.O. ( 18.05 Ghz ) is presented with 18.3 to 18.8 Ghz
( the low Ka band ) which produces an inverted I. F. of 250 to 750 Mhz
which is fead to the B band upconverter ( 2400 Mhz L.O. ) that produces
an inverted 2150 to 1650 Mhz I. F. to the IRD. This L.O. ( 18.05 Ghz ) is
also presented 19.7 to 20.2 Ghz ( the high Ka band ) which produces a
noninverted 1650 to 2150 Mhz I.F. ( no up conversion required ) to the IRD.

Now the reverse band ( 17.3 to 17.7 Ghz ) is also presented to the mixer with
the 18.05 Ghz L.O. producing an inverted I.F. of 750 to 350 Mhz which again
requires the B band upvconverter which produces a noninverted 1650 to 2050 Mhz.
I.F. presented to the IRD. Unlike the Ka band where you have 2 different frequency
bands one requiring the B band converter and the other not you can see that on the
reverse band the B band converter has to be on for both satellites ( 99W, 103W ).
The B band converter is turned on with a 22khz tone.

Now with my current test setup I can either have the 22 khz tone on or off. In both
cases in looking at the LNB output on the spectrum analyzer I see transponders above
1650 Mhz but I can't tell if their Ka band or RB. In other words I need to turn off the
Ka band in order to see the reverse band. How do I do that ?
The feed horns for 99W / 103W are used for both Ka band and RB .

I'm considering building my own LNB for RB using Mini Circuits modules. This could be
a rather expensive proposition however !

foxcreek :cool2

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