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Questio about DirectV's new Ka Band Satellites

jim6201
03-30-2005, 04:50 PM
I understand Directv is all set to launch a bunch of Ka band satellites for its HD expansion. Ka band, as most of you know, is at a much higher frequency band than the Ku band currently used by Directv. My understanding is that Directv will position these new satellites near the existing Ku band satellites so that user satellite dishes will not have to be repointed to receive signals from the new satellites.
My question is: User dishes will of course operate at Ka band, but will have a much narrower beamwidth. The average user dish will be correctly pointed at Ku band frequencies, but will be mispointed at Ka band frequencies (the beamwidth is much narrower at Ka band).
How will Directv deal with this issue?

rbinck
03-30-2005, 06:02 PM
I must admit that is above my pay grade. Have to wait and see,I guess.

Then there is the question of LNBs and multiswitches, etc.

What is the freq range of Ka band anyway?

calicogang
03-31-2005, 12:15 AM
That's by me also. I will e-mail a friend of mine about KA birds. Will post his answer as soon as I receive it.

hdtv4me2
03-31-2005, 08:24 AM
The Ka-band of frequencies is generally in the 20 to 30 Ghz range. Directv has already announced that a new dish would be required to receive the new Ka-band feed. The new dish is required since, as pointed out, the old dish's beamwidth would be narrower therefore harder to point and the new LNB would need to be able to operate in the higher frequency range.

jim6201
03-31-2005, 06:24 PM
I believe the fact that Directv plans to change the satellite dishes solves my problem. The dishes will be smaller because of the higher frequency band used and, as was pointed out, new LNBs will also be needed because of the new frequency band. So it seems that we will be getting new HD receivers and new satellite dishes.

rbinck
03-31-2005, 08:23 PM
What about the RG6, I wonder?

RG6 goes up to about 1 Ghz.

DTV TiVo Dealer
03-31-2005, 10:57 PM
The antenna dish LNB, (Low Noise Block) amplifies the signal and beats down the KU frequency to 900-2150 mHz so it can run on coax. BTW RG6 coax can support up to 2200 mHz with very little degradation. So the coax is only transporting the MPEG-2 data stream at 900 - 2150 mHz.

DIRECTV will upgrade all HD customers with a new .66 meter dish with 5 LNBs, 3 KU receiving the current MPEG-2 101/110/119 satellites and 2 LNBs looking at the new KA MPEG-4 birds located at 99/103 degrees in the orbital slot. The 99 degree SPACEWAY 1 KU satellite is launching this week and the 103 degree KU SPACEWAY 2 satellite will go up later this year.

-Robert

beatboy77
04-01-2005, 02:14 PM
Robert,

So if I wanted to get ready for the Directv MPEG-4 Upgrade, should I run a 5th RG-6 cable from where my dish is mounted outside to where I will have the HMC?

Thanks,

Josh

rbinck
04-01-2005, 08:09 PM
I was going by Belden's tables that stop at 1 Gig. Shows between 6-8db loss per 100'. That beating down the freq. explains it. Thanks.

DTV TiVo Dealer
04-01-2005, 08:31 PM
Robert,

So if I wanted to get ready for the Directv MPEG-4 Upgrade, should I run a 5th RG-6 cable from where my dish is mounted outside to where I will have the HMC?

Thanks,

Josh

As MPEG-4 becomes available in every DMA, DIRECTV will be upgrading all HD customers’ dishes and HD receivers. They will run all of the coax required for the HMC. If you want to do it yourself, you are correct, 5 coaxes would be perfect, and one coax will be used for OTA.

-Robert

hdtv4me2
04-02-2005, 08:09 AM
So what are we to expect from D* tomorrow regarding the Yes channel?

hdtv4me2
04-03-2005, 07:12 AM
I see that channel 95 is showing Yankees/Red Sox game at 8:30 PM EDT. Anyone know who is eligible to watch it?

beatboy77
04-03-2005, 09:19 AM
Go Sox!!!!!!!!!!!!!!!!!!!!

jim6201
04-03-2005, 04:48 PM
Robert,

I appear to missing something here. Why do you need 5 coax feeds?
I have 4 coax feeds going to my main TV setup. Two coaxes feed my Standard Definition Tivo receiver, the third coax feeds my HD receiver, and the fourth coax feeds OTA signals to my HD receiver. My understanding is that unless I add another satellite receiver or upgrade my HD receiver to HD Tivo, I will not have to do any more coax installation for the Ka band system. I will have to swap my HD receiver for a new MPEG-4 capable receiver and install a new satellite dish.
Do I have this straight?
Thank you, Sir

Tony R
04-03-2005, 06:56 PM
Is it a known fact that the existing oval antennas will be replaced with 66 cm antennas? Dropping the gain of the antenna for SD services is not a good idea. That means lowering the outage threshold during rainy weather. The beamwidth issue isn't so significant. The -3dB beamwidth formula is: signal beamwidth x efficiency of antenna reflector (%) / diameter (meters). The signal beamwidth is calculated by: 300/frequency (MHz). 300/30,000=.01 degrees. .01x60% (typical efficiency rating/.8. The difference is between .75 and .9 degrees. It seems to me that optimizing the feed to operate efficiently at both bands would be difficult since the focal point will be different for the two wave lengths. It would seem to make much more sense to have separate antennas for the DBS and Ka bands to prevent compromising performance between the two.

hdtv4me2
04-04-2005, 09:08 AM
The focal point of a parabolic reflector is not a function of frequency/wavelength it is only a function of geometry.

Tony R
04-04-2005, 01:06 PM
Of course you're right with respect to parabolas and geometry. Though these antennas like most satcom antennas are not parabolas, but shaped antennas that have illumination tapers optimized for gain vs RFI rejection. And these offset prime-focus antennas are pretty forgiving with regards to set up. Having spent the past 25 years in the satcom industry working primarily with dual-reflector systems (Cassegrain and Gregorian feed types), I think of all the times I spent performing radiation pattern tests in the field and having to tweak 0.2 inches of movement of a subreflector to achieve acceptable patterns for FCC certification. One of the biggest hassles was trying to optimise a "hybrid" multi-band antenna (C/Ku/Tx/Rx) as the feed location relative to the main reflector was different so I would have to optimize one or the other. At Scientific Atlanta, we came up with a Dichroic system for our 6 and 7 meter antennas whereby the Ku-band was facilitated by a conventional Cassegrain feed/subreflector, but the subreflector was transparent to C-band RF so C-band was facilitated by a prime focus feed mounted on the back side of the sub at a focal point further out from the main reflector. Talk about a nightmare. Though technically challenged, I do love this stuff. Antennas were always my favorite part of the earth station build.

DTV TiVo Dealer
04-15-2005, 08:40 PM
The KA and KU bands are not that far apart that you can't use the same dish and offset feed arm. The 5 KA/KU LNB .66 meter truncated parabolic dish is what we will be upgraded to as soon as July ’05 in the top 12 DMAs.

Before I started ValueElectronics.com I was a TV Broadcast RF Systems Engineer for Ikegami, Nucomm and Hitachi Denshi America.

The dish will have 4 satellite down-converted and multiplexed signals. I recommend the 5th coax so we can have a home run for the OTA antenna, assuming you are trying to get ATSC.

-Robert

VE Advanced Digital Technologies Dealer

Tony R
04-16-2005, 05:37 AM
Thanks Robert. Do you know what the receive gain reduction will be at Ku-band between the two antenna systems?

T

DTV TiVo Dealer
04-16-2005, 06:59 PM
Thanks Robert. Do you know what the receive gain reduction will be at Ku-band between the two antenna systems?

T

Sorry, I don't, but one DIRECTV engineer told me 3 dB.

-Robert

VE Advanced Digital Technologies Dealer

stevek116
04-18-2005, 06:19 PM
Robert -

I just purchased a new 3LNB integrated multiswitch dish and was planning on running four new runs of rg-6 to a Terk 5/8 multiswitch to feed both OTA and DTV signals thorughout my house.

My house was wired for cable, so each time DTV has added a satellite, I've had to add wiring. I presently have a two LNB dish with four wires running to three different receivers in my house (one is an ultimate tv receiver with two feeds).

If I am understanding your previous post, this new dish will have five LNBs with a built in multi-switch and four "out" connections. Is that correct?

If so, does anyone want to purchase a brand new 3lnb dish? ;)

DTV TiVo Dealer
04-19-2005, 05:43 PM
Robert -

I just purchased a new 3LNB integrated multiswitch dish and was planning on running four new runs of rg-6 to a Terk 5/8 multiswitch to feed both OTA and DTV signals thorughout my house.

My house was wired for cable, so each time DTV has added a satellite, I've had to add wiring. I presently have a two LNB dish with four wires running to three different receivers in my house (one is an ultimate tv receiver with two feeds).

If I am understanding your previous post, this new dish will have five LNBs with a built in multi-switch and four "out" connections. Is that correct?

If so, does anyone want to purchase a brand new 3lnb dish? ;)


Yes, that's correct, but don't worry. DIRECTV will upgrade your dish system and HD receivers once MPEG-4 comes to your DMA.

-Robert

VE Advanced Digital Technologies Dealer

shellback
04-28-2005, 04:35 AM
So these satellite signal meters that are available at EBAY for under $20, are they compatible with KA band also? Or are all the installers going to jack up installation prices because of having to buy new test equipment? And does this mean that I can finally get HD and Direcway on the same antenna?