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Guest Message by DevFuse

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DTVAHKaKu LNBF


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23 replies to this topic

#1 OFFLINE   tvhawaii

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Posted 28 March 2011 - 04:14 AM

What I have is a DirecTV Alaska Hawaii Ka/Ku Low Noise Amplifier/Blockdownconverter/Feed which was purpose made to work with a 1.2m offset reflector mfgd. by the same Co.
I need to modify it to work with a 2.4m offset reflector with a different f/D ratio.
I wrote to Eagle/PBI, the mfgrs., but have not received a reply, so I thought I'd just copy/paste the letter and see what folks here think.
~~~~~~~~~~~~~~~~~~~~~~
I have successfully used your DirecTV Alaska/Hawaii Ka/Ku LNBF on a variety of reflectors (Prodelin 1.2 and 1.8m) with satisfactory results, and now I need to fit it to an Andrews 2.4m reflector.
Appx. 4 years ago, I installed Ku LNBs at 101/110/119 (DirecTV) on this antenna. It was boresighted on 110 and I used a spectrum analyzer to find the focal points of 101/119 and attached those LNBs to a bracket I fabricated that was bent to the correct "tilt" angle which worked great.
Now that the Ka birds are being used, I need another solution in order to get HD into this SportsBar and there is a dearth of solutions available, especially with the requirement of switch outputs to be used with a SWM 16.
I estimate the new focal points for 99/103 to be around 2.6 inches from the 101, but I'll locate these empirically, exactly.
What I was planning on doing was to use a fine-kerf hacksaw and separating the Ka feeds down to 1/2 in. from the flange which screws to the LNB, then cutting them off.
Some Dremel tool grinding, etc. if needed to get both ends round.
Now all I need is a method to "extend" the end of the Ka feed in order to get the RF EM field into the remaining 1/2 in. tube of the feed attached to the LNB input.<grin>
Affix a WR-42 flange to both ends and use flexible waveguide? Bent copper tubing?

[snip]
~~~~~~~~~~~~~~~~~~~~~~~~~
Both the Ka and Ku feeds are 4 1/32" from throat to LNB opening.
Ka is from 18.3-18.8GHz and from 19.7-20.2GHz. Ku is from 12.2 to 12.7GHz and is Circular Polarized as is (I believe) Ka.

Many thanks to anyone who takes the time to look at the pics and comment here.
--Michael
http://www.flickr.co...in/photostream/

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#2 OFFLINE   texasbrit

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Posted 28 March 2011 - 06:36 AM

Can't answer your questions, but what's wrong with the standard Alaska/Hawaii dish? Works fine with an SWM16.

#3 OFFLINE   veryoldschool

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Posted 28 March 2011 - 08:23 AM

I've seen a few cobbled up large dishes with Ka/Ku LNBs used in Latin America.
I'm not sure how you're going to do what you're trying to. :nono:
Seems like you've just killed a good LNB. :eek2:
The SWiM-16 has four inputs:
13 volt: odd TPs from 101 & 99
18 volt: even TPs from 101 & 99
13 volt 22 Khz: odd TPs from 103
18 volts 22 Khz: even TPs from 103

If you connect a second LNB to the LNB, you also have 110 & 119, on the 103 coax.

Boresighting the dish to 101 and then locating the LNB for 99 should give you what you're looking for.
Using a second LNB for 103 and locating it at the focal point is how this has been done in Latin America.
A second dish would be used for the 110 & 119, if you need those, and connected to the 103 LNB.
A.K.A VOS

#4 OFFLINE   P Smith

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Posted 28 March 2011 - 09:42 AM

You are on right track - just keep new waveguide [tubes] smooth while bending the tube (copper is OK, with additional silver layer would better ;) ), if you could - expand open end to same or bigger diameter gradually to half length of the new tubes for 99W/103W- good luck with it.

#5 OFFLINE   tvhawaii

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Posted 28 March 2011 - 05:26 PM

Can't answer your questions, but what's wrong with the standard Alaska/Hawaii dish? Works fine with an SWM16.


Rain Fade margin. A highly localized 'squall' can roll through and take out the signal for 5 or 10 minutes.
During NFL season, it's not unusual to have ~150 football fanatics on Sunday morning.
"Fanatics" is the key word here. If their game is lost for more than a minute or two, they get on their cell-phones and call another 'SportsBar' to see if -they- have the signal, and if they do they'll get in their car and go there.

We installed this reflector back when the 'Sunday Ticket' moved from C-band to DirecTV in order to minimize these outages and it would be a shame, imo, not to try and take advantage of its capabilities.

#6 OFFLINE   tvhawaii

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Posted 28 March 2011 - 06:13 PM

Seems like you've just killed a good LNB. :eek2:

Naaa, I just removed the 8 screws that hold the feed assy. to the LNB/Switch. I haven't picked up the hacksaw yet. ;)

Boresighting the dish to 101 and then locating the LNB for 99 should give you what you're looking for.

Not quite sure what you're saying here. The existing feed spacing is 1.5 in. from Ku to Ka (centers) and using the dimensions from when I installed the 101/110/119 Ku feeds, I'm guesstimating the 99/101 spacing at 2.6 in.
Are you saying to use a separate Ku feed at 101?
This:
13 volt: odd TPs from 101 & 99
18 volt: even TPs from 101 & 99
has me concerned/confused.

Using a second LNB for 103 and locating it at the focal point is how this has been done in Latin America.


I really like this idea if for no other reason that the kluge I'm proposing will be a nightmare to weatherproof.

Thanks for the prompt reply, btw.

--Michael

#7 OFFLINE   tvhawaii

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Posted 28 March 2011 - 06:17 PM

You are on right track - just keep new waveguide [tubes] smooth while bending the tube (copper is OK, with additional silver layer would better ;) ), if you could - expand open end to same or bigger diameter gradually to half length of the new tubes for 99W/103W- good luck with it.


Thanks for the encouragement!
When I got into this business 27 years ago, I never dreamed I'd be heating copper tubing to almost Red Hot (annealing) and filling it with sand.:)

#8 OFFLINE   veryoldschool

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Posted 28 March 2011 - 07:47 PM

Not quite sure what you're saying here. The existing feed spacing is 1.5 in. from Ku to Ka (centers) and using the dimensions from when I installed the 101/110/119 Ku feeds, I'm guesstimating the 99/101 spacing at 2.6 in.
Are you saying to use a separate Ku feed at 101?

If you use 2 DTVAHKaKU LNBs, with the gain of the larger dish, the 101 LNB "more than likely" will have a good signal even off of the focal point, where the Ka would need to be at it.

This:
13 volt: odd TPs from 101 & 99
18 volt: even TPs from 101 & 99
has me concerned/confused.

The LNB has a switch in it and four outputs to the SWiM-16. Each of these carries a different voltage/tone and therefore different signals from the SATs.
"no tone" 13/18 volts carries the 101 & 99 SATs.
The "tones" carry the 110/119 & 103 SATs.
"The general idea" is to center the dish on the 101, then offset the LNB for the 99 SAT to be in the focal point. This would be slightly to the left of center [facing the dish]. The 101 LNB would not be directly at the focal point, but should still have good signal. Then connect two coax from this to the SWiM 13/18 volt inputs.
Use the second LNB and mount it to the right [facing the dish] at the focal point for the 103 SAT. Connect two coax to the SWiM-16 13/18 "tone" inputs.
The SWiM-16 now has all four inputs running to the right LNB(s).

I really like this idea if for no other reason that the kluge I'm proposing will be a nightmare to weatherproof.

Thanks for the prompt reply, btw.

--Michael


A.K.A VOS

#9 OFFLINE   P Smith

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Posted 28 March 2011 - 11:28 PM

I wouldn't so concise on "The 101 LNB would not be directly at the focal point, but should still have good signal" if remember he is using 2.4m reflector. What lead to bigger linear distance between 'focal' points for two sats. The size tend to make big drop in signal level for 101W sat using such method.

#10 OFFLINE   Davenlr

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Posted 28 March 2011 - 11:42 PM

Stupid question, but if Sunday Ticket is all transmitted on one KA satellite, could you not aim the dish at that satellite only (of course the other satellites would be 771). Then use an A/B switch between that dish/lnb and the standard slimline. If a storm is afoot, switch the A/B switch to the (KA only) sat. It would take several hours before you would get a guide data error I think. Unless DirecTv uses both 99 and 103 for Sunday Ticket HD, I would think this would work.

Given VOS's information, I think when it warms up, I am going to see if I can use two separate 36" dishes with SL3's, using one for 99/101 and the other for 103, routed to the SWM16. Just to see if it works, as I am curious how much longer the signal will remain on during a sqall line compared with the Slimline. If that configuration works, I could actually do side by side comparisons.

Tivo Premier XL4, Tivo Premier, Tivo HD whole home on Xfinity HD, DirecTv Whole Home with 39" high gain KaKu dish, Roku3,SageTv 8 TB Win8 Server -> DVDO Edge-> Denon AVR, Klipsch KB15's/Panasonic 55ST60 plasma"


#11 OFFLINE   P Smith

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Posted 28 March 2011 - 11:50 PM

Your 1m dish would be fine for two and (I posted, tested, did) will works fine for 99/101/103 sats.

#12 OFFLINE   tvhawaii

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Posted 29 March 2011 - 12:45 AM

he 101, then offset the LNB for the 99 SAT to be in the focal point. This would be slightly to the left of center [facing the dish]. The 101 LNB would not be directly at the focal point, but should still have good signal. Then connect two coax from this to the SWiM 13/18 volt inputs.
Use the second LNB and mount it to the right [facing the dish] at the focal point for the 103 SAT. Connect two coax to the SWiM-16 13/18 "tone" inputs.
The SWiM-16 now has all four inputs running to the right LNB(s).


" This would be slightly to the left of center [facing the dish]." Out here, it's actually 'above' and the 103 is 'below'.

At first read, I rejected this idea because it is a compromise which defeats the whole purpose of using the larger reflector. But then I got to thinking that the *real* objective here is to get HD on all the displays.
I just went out and covered my 101 feed with foil, and then went through all the ~27 sports channels we use and the only missing chs. were:
truTV-246(no HD channel, although during the NCAA BB playoffs, it was there.
ESPN Classic-614. No HD channel.
Mountain West Sports-616. No HD channel.
I assume the NFL HD channels will also be on 99/103 (assuming Billionaires and Millionaires settle.)

So in essence, only 3 channels which are rarely used are on 101. But the other problems are that the Guide data comes from 101 and this new software seems to check for proper signal strength on all the sats that are configured.(?)
Do you have any idea of what numbers are good vs. bad on the Signal Strength screen? Which specific xpndrs are checked?

As P Smith says above, these larger reflectors aren't too forgiving, and moving the 101 an inch away from it's FP might not work at all, it's still worth giving it a shot if I can get the minimal required numbers for the guide/test.
I tried to build this reflector (comes in two pieces) as accurately as I could in an effort to get the FP like a golf ball and not a softball, but who knows what it really is.:D

Thanks again to everyone for your help.

--Michael

#13 OFFLINE   tvhawaii

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Posted 29 March 2011 - 12:49 AM

I wouldn't so concise on "The 101 LNB would not be directly at the focal point, but should still have good signal" if remember he is using 2.4m reflector. What lead to bigger linear distance between 'focal' points for two sats. The size tend to make big drop in signal level for 101W sat using such method.


Exactly.

#14 OFFLINE   tvhawaii

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Posted 29 March 2011 - 01:07 AM

Stupid question, but if Sunday Ticket is all transmitted on one KA satellite, could you not aim the dish at that satellite only (of course the other satellites would be 771). Then use an A/B switch between that dish/lnb and the standard slimline. If a storm is afoot, switch the A/B switch to the (KA only) sat. It would take several hours before you would get a guide data error I think. Unless DirecTv uses both 99 and 103 for Sunday Ticket HD, I would think this would work.


Not a stupid question at all...I was thinking along the same lines.;)
When I was going through the channels with the 101 covered, I got the 920 Missing Guide Data about 20 minutes in. I reset it and finished before it came back again, so don't really know what the cycle time is.
Hard to predict where the Sunday Ticket games will be, but when I looked at the transponder maps at Lyngsat, the MLB HD channels were split between 99 and 103.
Does anyone know if Lyngsat is accurate or if there is a better source of where/how these channels are mapped?

#15 OFFLINE   Davenlr

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Posted 29 March 2011 - 06:40 AM

Does anyone know if Lyngsat is accurate or if there is a better source of where/how these channels are mapped?


http://www.dbstalk.c...ad.php?t=172899

Tivo Premier XL4, Tivo Premier, Tivo HD whole home on Xfinity HD, DirecTv Whole Home with 39" high gain KaKu dish, Roku3,SageTv 8 TB Win8 Server -> DVDO Edge-> Denon AVR, Klipsch KB15's/Panasonic 55ST60 plasma"


#16 OFFLINE   veryoldschool

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Posted 29 March 2011 - 09:13 AM

Exactly.

"Well" you are out there on the fringe. :lol:
The 101 LNB should output -19dBm to -15dBm, and needs to have around 10 dB CNR. An installer used his meter [who knows what the resolution bandwidth was] and measured the LNB [while in his truck] and got -40 dBm.
You might want to repeat this with your spectrum analyzer and see what readings you get.
A.K.A VOS

#17 OFFLINE   P Smith

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Posted 29 March 2011 - 09:33 AM

Not a stupid question at all...I was thinking along the same lines.;)
When I was going through the channels with the 101 covered, I got the 920 Missing Guide Data about 20 minutes in. I reset it and finished before it came back again, so don't really know what the cycle time is.
Hard to predict where the Sunday Ticket games will be, but when I looked at the transponder maps at Lyngsat, the MLB HD channels were split between 99 and 103.
Does anyone know if Lyngsat is accurate or if there is a better source of where/how these channels are mapped?

Lyngsat is not up to date, you must follow Sixto and gct's threads here if you want to use current map.

#18 OFFLINE   SomeRandomIdiot

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Posted 03 April 2011 - 01:22 PM

I found your original question very interesting in regards to several things I have been contemplating - and quite simply, I am curious to see how your experiment turns out, should you move forward with it.

Allow me to throw several things out.

As E* used to have HBO-HD and SHO-HD uncompressed on 148W (roughly over the big Island) and I am on the East Coast, for years, I experimented with pulling the signal in (Something E* maintained was impossible, especially given the elevation I needed was only 12 degrees above the horizon). You are roughly doing the same in reverse. The lower on the horizon the elevation, the more atmosphere the signal has to go through, so you have much more potential water vapor (and other potential items) to shoot through.

I finally ended up with a 1.2M dish pointed at 148W only pushed my Signal Quality into the mid 70s. With big storms 50-100 miles out to the West, I would have signal issues even if there was no rain within 10 miles of me.

Knowing that my signal quality went from the mid/high 40s with a 24" dish to mid/highs 50s with a 36" dish to low/mid 70s with a 1.2 dish, I got a feel for what type of difference dish size made.

Why go through all this? According to NASA and several other studies, Rain Fade on the Ka band is roughly 3x what it is with the Ku band. Yet, doubling the dish size does not give you 3x the signal quality.

I am sure that there is a formula that some regular dbstalk.com people can figure out exactly what the gain per increase would be instead of my rough real world experience, but give the issues aiming at 99W/103W slightly over 20 degrees on the Ka band, I am not sure how much BETTER it will be doubling the size of the dish. Perhaps you would get the picture back maybe 60 seconds sooner more or less?

Considering what you really want is to keep customers in the bar, might it be a better idea to go to the SD Ku band feed of ST when the signal starts going out as you have 3x less probability of signal loss than with the Ka birds (then try and go back to the HD feed at the commercial breaks?). And considering some of the rain storms I've seen out in the 50th state, I am not sure the Ku signal will survive.

In fact, even if you just used your bigger dish to get the SD feed with a single LNB that you could switch to during rain fade, that might be a win for you.

I will be curious to know how your experiment ends up. Also, I am sure P Smith will be one of your best sources of information as he was invaluable for me modifying some E* LNBs several years ago. In fact, fly him out to Hawaii and he'd probably do it for you :)

#19 OFFLINE   tvhawaii

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Posted 09 April 2011 - 09:51 PM

I found your original question very interesting in regards to several things I have been contemplating - and quite simply, I am curious to see how your experiment turns out, should you move forward with it.

Allow me to throw several things out.

As E* used to have HBO-HD and SHO-HD uncompressed on 148W (roughly over the big Island) and I am on the East Coast, for years, I experimented with pulling the signal in (Something E* maintained was impossible, especially given the elevation I needed was only 12 degrees above the horizon). You are roughly doing the same in reverse. The lower on the horizon the elevation, the more atmosphere the signal has to go through, so you have much more potential water vapor (and other potential items) to shoot through.


It was frustrating to have that 148 bird almost over our heads and not be able to access it. But in my experience, there is a big difference between 12 degrees and 22 degrees elevation in terms of atmospheric attenuation.

Why go through all this? According to NASA and several other studies, Rain Fade on the Ka band is roughly 3x what it is with the Ku band. Yet, doubling the dish size does not give you 3x the signal quality.

I am sure that there is a formula that some regular dbstalk.com people can figure out exactly what the gain per increase would be instead of my rough real world experience, but give the issues aiming at 99W/103W slightly over 20 degrees on the Ka band, I am not sure how much BETTER it will be doubling the size of the dish. Perhaps you would get the picture back maybe 60 seconds sooner more or less?


I use Satmaster Pro to get those numbers:
http://www.arrowe.com/index.html
Not exactly cheap at $270, but I bought it years ago when I needed to calculate the position of an additional off-axis dual feed on a 14ft. and 16ft. C-band reflector when the Sunday Ticket started using T301 in addition to G3.
And I hear what you're saying regarding the benefits of using this thing.
But put yourself in my place. Here we have a 9 ft high by 8 ft wide reflector (and the associated large mount) already on the roof (mount was originally made to support a 16ft C-band reflector and we tore off most of the roof to reinforce it.) and it would break my heart to cut all the cables and move them over to a 1.2m reflector (that's not even there yet) without at least trying to make it work.

Considering what you really want is to keep customers in the bar, might it be a better idea to go to the SD Ku band feed of ST when the signal starts going out as you have 3x less probability of signal loss than with the Ka birds (then try and go back to the HD feed at the commercial breaks?). And considering some of the rain storms I've seen out in the 50th state, I am not sure the Ku signal will survive.
In fact, even if you just used your bigger dish to get the SD feed with a single LNB that you could switch to during rain fade, that might be a win for you.


Yes, good points all, which is why I'm trying to come up with a way to have 100% efficiency at 99/103 -and- 101, not just "make 101 work good enough to get the guide".

I will be curious to know how your experiment ends up. Also, I am sure P Smith will be one of your best sources of information as he was invaluable for me modifying some E* LNBs several years ago. In fact, fly him out to Hawaii and he'd probably do it for you :)


Well, I've come up with another crazy idea, but I need to power an additional Ku LNB and I'm concerned about overloading the components in the existing switch built into the DTVAHKaKu LNBF, so I've ordered a 5SATPL from Sonora.
If this doesn't work, then indeed I'll need to 'modify' the DTVAHKaKu electronics internally, so he may be getting a call.:)

Thanks for your thoughts.

--Michael

#20 OFFLINE   AntAltMike

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Posted 10 April 2011 - 02:10 AM

A few years ago, when people here were kluging Sat B and C signals from separate dishes into DTVAHKaKu doiwnleads, I thought that those who combined them using an ordinaly, high frequency splitter had been successful. As long as the LNBs don't have AGC in them, you would just center the port of each LNB on the desired prime focal point and cover the other ports with foil.




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