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DIRECTV Satellite Discussion D-14 @99W


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#801 OFFLINE   veryoldschool

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Posted 14 July 2013 - 01:54 PM

No;

 

DIRECTV is downlinking between 18.3-18.8 GHz for the Ka-lo (or the Ka "B") band. This is then converted by a receiver circuit with a 18.050 GHz L.O. injection in the LNBF to output at 250-750 MHz.

"Mr Smith" has seen Ka-lo be inverted from Ka-hi, which happens with a low side conversion so "something" isn't tracking.

 

If the LNB was using a high side conversion for Ka-lo, the 17.3-17.8 RDBS would require another LO.

 

"Seems like" we might need one of these:

 

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#802 OFFLINE   HoTat2

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Posted 14 July 2013 - 02:29 PM

"Mr Smith" has seen Ka-lo be inverted from Ka-hi, which happens with a low side conversion so "something" isn't tracking.

 

If the LNB was using a high side conversion for Ka-lo, the 17.3-17.8 RDBS would require another LO.

OK, I'll let P. Smith comment to confirm that;

 

Since from everything I remember reading on the issue in the past, even from P. Smith, was that both the satellite Ka-lo downlink at 18.3-18.8 GHz and Ka-hi at 19.7-20,2 GHz use the same 18.050 GHz L.O. for low side conversion in the LNBF to 250-750 MHz and 1650-2150 MHz respectively.   


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#803 OFFLINE   P Smith

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Posted 14 July 2013 - 06:00 PM

yes, all Ka LNBFs using just one LOF=18.05GHZ for both Ka ranges,

 

but for old school tuners (950...2150) DTV made SUP-2400; another converter with a LOF=2.4 GHz to move 250...750 into 1650...2150 with an inversion

 

wideband tuners just fine for all three L ranges coming from LNBFs: 250...750, 950...1450 and 1650...2150 MHz


Edited by P Smith, 14 July 2013 - 06:05 PM.


#804 ONLINE   bobnielsen

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Posted 14 July 2013 - 06:36 PM

OK, I'll let P. Smith comment to confirm that;

 

Since from everything I remember reading on the issue in the past, even from P. Smith, was that both the satellite Ka-lo downlink at 18.3-18.8 GHz and Ka-hi at 19.7-20,2 GHz use the same 18.050 GHz L.O. for low side conversion in the LNBF to 250-750 MHz and 1650-2150 MHz respectively.   

This brings up something I wondered about a while ago:  With RDBS at 17.3 - 17.8, what is there to keep the existing mixer from combining that with the 18.050 L.O. to make a 750 - 250 MHz  output which would interfere with Ka-lo?  Or does Ka-lo go away, which would allow the 250-750 MHz i.f. to work for RDBS without any new receiving hardware?



#805 OFFLINE   HoTat2

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Posted 14 July 2013 - 06:58 PM

yes, all Ka LNBFs using just one LOF=18.05GHZ for both Ka ranges,

 

 Thanks for the confirmation P. Smith, as I thought.

... but for old school tuners (950...2150) DTV made SUP-2400; another converter with a LOF=2.4 GHz to move 250...750 into 1650...2150 with an inversion

 

And perhaps this might be the past mention of a "Ka-lo band inversion" which VOS is confusing with the what's taking place inside the LNBF. That is, the high side frequency conversion used in a B Band Converter (SUP-2400)?  

... wideband tuners just fine for all three L ranges coming from LNBFs: 250...750, 950...1450 and 1650...2150 MHz

 

Yes, as used in the H/HR23 models I suppose.


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#806 OFFLINE   HoTat2

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Posted 14 July 2013 - 07:20 PM

This brings up something I wondered about a while ago:  With RDBS at 17.3 - 17.8, what is there to keep the existing mixer from combining that with the 18.050 L.O. to make a 750 - 250 MHz  output which would interfere with Ka-lo?  Or does Ka-lo go away, which would allow the 250-750 MHz i.f. to work for RDBS without any new receiving hardware?

Bob, as with the example cited by James Long earlier in the thread;

 

For years now the Dish 500+/1000+ LNBFs simultaneously receive two adjacent bands at 11.7-12.2 GHz and 12.2-12.7 GHz from approximately the same orbital slot without mutual interference.

 

Shouldn't it be possible then to design for sufficient selectivity in the LNBF between the 17.7 and 18.3 GHz band edges in the same manner to prevent such adjacent band interference?

 

Note: For the CONUS, the RDBS band is only 17.3-17.7 GHz as authorized by the FCC to prevent possible interference to terrestrial microwave systems operating between 17.7-17.8 GHz.      


Edited by HoTat2, 14 July 2013 - 07:25 PM.

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#807 OFFLINE   veryoldschool

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Posted 14 July 2013 - 09:10 PM

Bob, as with the example cited by James Long earlier in the thread;

 

For years now the Dish 500+/1000+ LNBFs simultaneously receive two adjacent bands at 11.7-12.2 GHz and 12.2-12.7 GHz from approximately the same orbital slot without mutual interference.

This doesn't look to be the same, and is more like how I suggested more bandwidth by adding to Ka-hi.

 

To address Bob's question: image rejection mixers can be used for only one "side band".


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#808 OFFLINE   harsh

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Posted 15 July 2013 - 08:30 AM

I suppose if you have your mind set on a certain opinion any post could be twisted to be considered supportive of your side of an argument ... but your assertion that RDBS cannot be received on an OTARD compliant dish is not supported.

You've left out an important consideration in your "they simply must have figured this out" argument. This isn't a discussion of whether RDBS will work with an OTARD dish but whether it can work with a dish assembly that is set up for Ku or Ka from the same or relatively nearby slots.

The experts have been relatively silent on the technical details of how it could be done.

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#809 OFFLINE   HoTat2

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Posted 15 July 2013 - 10:05 AM

You've left out an important consideration in your "they simply must have figured this out" argument. This isn't a discussion of whether RDBS will work with an OTARD dish but whether it can work with a dish assembly that is set up for Ku or Ka from the same or relatively nearby slots.

The experts have been relatively silent on the technical details of how it could be done.

But as I've stated repeatedly harsh;

 

If the current Slimline Ka/Ku dishes can successfully receive the Ka band on one end of the spectrum, and the Ku band on the other end. Then what technological barrier can popup to prevent receiving the RDBS band somewhere near center of the two?   


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#810 OFFLINE   P Smith

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Posted 15 July 2013 - 10:21 AM

no barriers here,

we are guessing if RF engineers will make new LNBF with different LOF or we will continue using old LNBF if they will cleanup 250...750 from Ka-Lo signals



#811 OFFLINE   HoTat2

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Posted 15 July 2013 - 10:22 AM

This doesn't look to be the same, and is more like how I suggested more bandwidth by adding to Ka-hi.

 

 

Oh, I agree it's indeed not the same as to the deleterious effect the RDBS band will cause if it manages to reach the Ka band mixer with sufficient signal strength since it falls in the image frequency range of the Ka-lo band.

 

But I cited it as an example of how good selectivity can be designed into two very nearby microwave RF bands this way to prevent either from entering the receiver circuitry of the other at a sufficient level to cause any sort of significant spurious response.     


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#812 ONLINE   bobnielsen

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Posted 15 July 2013 - 11:33 AM

Bob, as with the example cited by James Long earlier in the thread;

 

For years now the Dish 500+/1000+ LNBFs simultaneously receive two adjacent bands at 11.7-12.2 GHz and 12.2-12.7 GHz from approximately the same orbital slot without mutual interference.

 

Shouldn't it be possible then to design for sufficient selectivity in the LNBF between the 17.7 and 18.3 GHz band edges in the same manner to prevent such adjacent band interference?

 

Note: For the CONUS, the RDBS band is only 17.3-17.7 GHz as authorized by the FCC to prevent possible interference to terrestrial microwave systems operating between 17.7-17.8 GHz.      

 

It's been a while (~50 yrs) since I have designed any microwave filters but the kind of selectivity needed isn't easily achieved in something that will be mass-produced (good grief, I AM getting old).

 

This doesn't look to be the same, and is more like how I suggested more bandwidth by adding to Ka-hi.

 

To address Bob's question: image rejection mixers can be used for only one "side band".

 

Image reject mixers would work, but would that have been a design criterion for the existing Ka band LNBFs?  I recall seeing some photos of the insides of the Slimline feed assembly several years ago which might provides some insight.



#813 OFFLINE   veryoldschool

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Posted 15 July 2013 - 12:18 PM

For years now the Dish 500+/1000+ LNBFs simultaneously receive two adjacent bands at 11.7-12.2 GHz and 12.2-12.7 GHz from approximately the same orbital slot without mutual interference.

Oh, I agree it's indeed not the same as to the deleterious effect the RDBS band will cause if it manages to reach the Ka band mixer with sufficient signal strength since it falls in the image frequency range of the Ka-lo band.

 

But I cited it as an example of how good selectivity can be designed into two very nearby microwave RF bands this way to prevent either from entering the receiver circuitry of the other at a sufficient level to cause any sort of significant spurious response.     

 

:confused:

I don't know what Dish does, "but" if their LO was 10.7 GHz, the output would be between 1 and 2 GHz.

I don't see this being any different than DirecTV 8 & DirecTV 4S at 101 that makeup the TPs.


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#814 OFFLINE   veryoldschool

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Posted 15 July 2013 - 12:25 PM

It's been a while (~50 yrs) since I have designed any microwave filters but the kind of selectivity needed isn't easily achieved in something that will be mass-produced (good grief, I AM getting old).

 

 

Image reject mixers would work, but would that have been a design criterion for the existing Ka band LNBFs?  I recall seeing some photos of the insides of the Slimline feed assembly several years ago which might provides some insight.

"My guess" is that DirecTV isn't using image rejection mixers due to cost, and for the same reason they haven't added another LO for RDBS as if it cost only $1, it would be tens of millions for the LNBs in service, for something that is only in the testing/proving stage.


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#815 OFFLINE   HoTat2

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Posted 15 July 2013 - 02:34 PM

For years now the Dish 500+/1000+ LNBFs simultaneously receive two adjacent bands at 11.7-12.2 GHz and 12.2-12.7 GHz from approximately the same orbital slot without mutual interference.

 

:confused:

I don't know what Dish does, "but" if their LO was 10.7 GHz, the output would be between 1 and 2 GHz.

 

Well AFAIK the Dish 500+/1000+ use perhaps four L.O.s;

 

Due to their frequency stacking approach, two (10.75 and 11.25 GHz) using low side conversion for the lower blocks (950-1450 MHz) of the two received bands, and the remaining two (13.850 and 14.350 GHz) to form the upper frequency blocks (1650-2150 MHz), using high side conversion.

 

But that's beside the point which I was trying to make which was to simply show that two close satellite bands can be successfully received, with each having sufficient out of band rejection of the other to prevent mutual interference, and I see nothing to prevent the same for separating the 17.3-17.7 GHz RDBS band from 18.3-20.2 GHz Ka bands.

 

... I don't see this being any different than DirecTV 8 & DirecTV 4S at 101 that makeup the TPs. 

 

D8, D9S, and D4S, all operate within the same 12.2-12.7 GHz band and are separated into odd and even transponder sets with high isolation by being of both offset frequencies and opposite polarities.

 

The two adjacent bands received by the Dish 500+/1000+ both use the same odd/even polarity and therefore separation can only be accomplished through their being in different frequency ranges.    


Edited by HoTat2, 15 July 2013 - 02:36 PM.

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#816 OFFLINE   HoTat2

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Posted 15 July 2013 - 02:46 PM

"My guess" is that DirecTV isn't using image rejection mixers due to cost, and for the same reason they haven't added another LO for RDBS as if it cost only $1, it would be tens of millions for the LNBs in service, for something that is only in the testing/proving stage.

While I can agree a L.O. and other necessary receiver circuitry for the RDBS band may not be in the current LNBFs, but "might" be.

 

If there is no image rejection type mixer for the Ka band , then how can DIRECTV power up the RB-2A payload on D12 or the upcoming RB-1 on D14 and future RB-2 without interfering with customers' reception of the Ka-lo band?     


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#817 OFFLINE   HoTat2

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Posted 15 July 2013 - 02:59 PM

It's been a while (~50 yrs) since I have designed any microwave filters but the kind of selectivity needed isn't easily achieved in something that will be mass-produced (good grief, I AM getting old).

 

 

Image reject mixers would work, but would that have been a design criterion for the existing Ka band LNBFs? ...

As I just asked VOS;

 

If the Ka band mixers aren't of an image reject type, how can DIRECTV power up any RDBS payloads at 99 and 103 without potential image interference to subscribers Ka-lo band reception?

 

... I recall seeing some photos of the insides of the Slimline feed assembly several years ago which might provides some insight.

 

They were, and I think they were originally posted by RobertE for a Andrews Ka/Ku SL-5 back in '06 here;

 

http://www.dbstalk.c...ialup-friendly/

 

Unfortunately all the images hosted by Photo Bucket except for 1 I think, have long been removed.


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#818 OFFLINE   veryoldschool

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Posted 15 July 2013 - 03:26 PM

Well AFAIK the Dish 500+/1000+ use perhaps four L.O.s;

 

Due to their frequency stacking approach, two (10.75 and 11.25 GHz) using low side conversion for the lower blocks (950-1450 MHz) of the two received bands, and the remaining two (13.850 and 14.350 GHz) to form the upper frequency blocks (1650-2150 MHz), using high side conversion.

 

But that's beside the point which I was trying to make which was to simply show that two close satellite bands can be successfully received, with each having sufficient out of band rejection of the other to prevent mutual interference, and I see nothing to prevent the same for separating the 17.3-17.7 GHz RDBS band from 18.3-20.2 GHz Ka bands.   

You've got me more :confused: with your "Well AFAIK the Dish 500+/1000+" as not much makes sense, but since "the point" was about the SAT downlink, 17.3-17.7 GHz and 18.3-20.2 GHz aren't any problem.

"The problem comes" when you're trying to use a 18.050 GHz LO which will "low side" the 17.3-17.7 and "high side" the 18.3-18.7 GHz into the same 250-650 MHz.

If you filter the unwanted sideband to [each] mixer, then you have two 250-650 MHz signals that can't be put on the same coax, if you're using the same LO.

"Seems like" we're running in circles [as in it's been posted before].


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#819 OFFLINE   P Smith

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Posted 15 July 2013 - 03:36 PM

if they will use different tpn's ranges for different sats and occupy upper 100 MHz part mostly for Ka-Lo ... but who knows



#820 ONLINE   bobnielsen

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Posted 15 July 2013 - 04:08 PM

You've got me more :confused: with your "Well AFAIK the Dish 500+/1000+" as not much makes sense, but since "the point" was about the SAT downlink, 17.3-17.7 GHz and 18.3-20.2 GHz aren't any problem.

"The problem comes" when you're trying to use a 18.050 GHz LO which will "low side" the 17.3-17.7 and "high side" the 18.3-18.7 GHz into the same 250-650 MHz.

If you filter the unwanted sideband to [each] mixer, then you have two 250-650 MHz signals that can't be put on the same coax, if you're using the same LO.

"Seems like" we're running in circles [as in it's been posted before].

Yup....

 

Hopefully someone "in the know" will jump in here eventually.



#821 OFFLINE   HoTat2

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Posted 15 July 2013 - 04:27 PM

You've got me more :confused: with your "Well AFAIK the Dish 500+/1000+" as not much makes sense, but since "the point" was about the SAT downlink, 17.3-17.7 GHz and 18.3-20.2 GHz aren't any problem. ...

 

Well, the Dish Plus L.O.description I gave was a side issue which perhaps I really didn't need to go into in any depth.

 

Just suffice it to say briefly AIUI, on the Dish 500+ and 1000+ LNBF each Dish Pro (DP) or Dish Pro Plus (DPP) LNBF actually uses two L.O.s due to the frequency stacking. 10.75 and 13.850 GHz to convert the 11.7-12.2 GHz FSS band and 11.25 along with 14.350 GHz to convert the 12.2-12.7 GHz BSS band.

 

But none of this is relevant to the issue. 

 

... "The problem comes" when you're trying to use a 18.050 GHz LO which will "low side" the 17.3-17.7 and "high side" the 18.3-18.7 GHz into the same 250-650 MHz.

If you filter the unwanted sideband to [each] mixer, then you have two 250-650 MHz signals that can't be put on the same coax, if you're using the same LO.

"Seems like" we're running in circles [as in it's been posted before].

 

 Again I agree, the RDBS band will need its own L.O. for reception 

 

The present 18.050 GHz one used for the Ka bands is useless for it. 


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#822 OFFLINE   James Long

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Posted 15 July 2013 - 04:28 PM

This isn't a discussion of whether RDBS will work with an OTARD dish


Funny ... because you're the one that made the claim a few pages back that a RDBS dish couldn't pass OTARD protection.

... but whether it can work with a dish assembly that is set up for Ku or Ka from the same or relatively nearby slots.

The experts have been relatively silent on the technical details of how it could be done.


They don't have to prove it to you now - just wait and buy the dish/LNB. :)
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#823 OFFLINE   veryoldschool

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Posted 15 July 2013 - 04:32 PM

Funny ... because you're the one that made the claim a few pages back that a RDBS dish couldn't pass OTARD protection.

"Funny" wouldn't be my first choice. Ignorant might be better since the current dish works from Ku thru Ka and it's the LNB where any work will be needed.


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#824 OFFLINE   studechip

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Posted 15 July 2013 - 06:13 PM

Virtually all of this is WAY over my head. From a "what makes sense" point of view, don't you all think the engineers at Directv figured this out a long time ago otherwise they wouldn't have started with RDBS in the first place? They can't reasonably replace all of the lnbs just to open up a new band. It has to work with what they already have in place. Make sense?



#825 OFFLINE   HoTat2

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Posted 15 July 2013 - 06:54 PM

Virtually all of this is WAY over my head. From a "what makes sense" point of view, don't you all think the engineers at Directv figured this out a long time ago otherwise they wouldn't have started with RDBS in the first place? They can't reasonably replace all of the lnbs just to open up a new band. It has to work with what they already have in place. Make sense?

My guess would be if RDBS is intended for mainstream service, then yes the current LNBFs likely have the receive capability already built in. If intended only for niche programming like moving the World Direct service from a separate dish aimed at 95w or something, then a new LNBF swap out program is feasible given the comparatively small number of subscribers needing to be converted. 


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