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tkrandall said:
I'm just curious what signalling mechansim is used by the receivers and sent to the b-band converter to tell it to pass the b band instead of the a band.
I don't believe any signaling takes place. All the BBC does is "shift" the frequency of the inbound Ka signal to that of the Ku band. It's not an 'either/or' situation - the receivers are expecting a signal in a band from x to y mhz, and the BBC takes the a to b mhz signal and shifts it up to the x to y range.

Forgive the vagueness - I forget the actual ranges.
 

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Because the HR20s were designed and shipped before the commitment to the Ka band.

If you get a Single Wire Multiswitch solution, the frequency shift is taken care of in the multiswitch and BBCs aren't required. There's also a possibility that future units (the rumored '23' series) have the circuitry built-in.
 

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dbmaven said:
I don't believe any signaling takes place. All the BBC does is "shift" the frequency of the inbound Ka signal to that of the Ku band. It's not an 'either/or' situation - the receivers are expecting a signal in a band from x to y mhz, and the BBC takes the a to b mhz signal and shifts it up to the x to y range.

Forgive the vagueness - I forget the actual ranges.
I don't think that is how it works. As I understand it, the receiver can only receive/process signals in from the coax cable in 2 bands: the band traditionally allocated to the Ku signals (950-1450mhz?), and the band (1650-2150 mhz?)allocated initially just to the Ka A-band signals. The B-band signals are sent down the coax in the UHF range, and then have to be upconverted to the the same range as occupied by the A-band signals prior to being sent in to the receiver. I don't think you can have both a-band and b-band sginals occupying the same input range at the same time, so there has to be a switching mechainsm to choose which one.
 

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The linked thread is correct, is is a DiSEqC signal that causes the BBC to switch.

The newest HD units, the H23 series, have wide band front ends that are able to receive the b-band directly, thus they do not require the BBC.

Carl
 

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I've posted in the other thread, so I'll summarize here. DiSeq commands activate the BBC.

BTW, the BBCs were necessary because wideband tuners didn't exist or were too expensive at the time--at least that is my guess.

Now, wideband tuners are available and economical so I expect all new receiver and dvr models will no longer need BBCs. :)

Cheers,
Tom
 

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dbmaven said:
I don't believe any signaling takes place. All the BBC does is "shift" the frequency of the inbound Ka signal to that of the Ku band. It's not an 'either/or' situation - the receivers are expecting a signal in a band from x to y mhz, and the BBC takes the a to b mhz signal and shifts it up to the x to y range.

Forgive the vagueness - I forget the actual ranges.
Signaling/switching absolutely does take place. If it didn't, the BBCs functionality would either be built into the LNB assembly, or just one set of BBCs would be installed before the multiswich. The reason that every (non-SWM) line into every tuner needs a BBC is because each tuner signals the BBC to either shift or not shift the "b" frequencies depending on what channel is being tuned.
 

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Adding to cartrivisions correct analysis just a tiny bit--the BBC either shifts or blocks. If it didn't block, diplexed OTA couldn't work.

Cheers,
Tom
 

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My apologies - I was working from (obviously defective) old memory/information.

You learn something new every day - thanks.
 

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I learned something today too--I realized that the BBCs had to block or shift. So I'm glad it came up. :)

Cheers,
Tom
 

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Tom Robertson said:
Now, wideband tuners are available and economical so I expect all new receiver and dvr models will no longer need BBCs. :)

Cheers,
Tom
I always figured it was actually that the tuners could handle those frequencies now more than the BBC functionality was built in. It's a minor difference but it means there won't be any bbcs dying in the H23 and other similar receivers.
 

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Tom Robertson said:
I learned something today too--I realized that the BBCs had to block or shift. So I'm glad it came up. :)

Cheers,
Tom
Why would they have to block? you can't diplex OTA between BBC and dish anyway.. seems they could just ignore it since the tuner can't see that freq anyways..
 

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houskamp said:
Why would they have to block? you can't diplex OTA between BBC and dish anyway.. seems they could just ignore it since the tuner can't see that freq anyways..
The two modes of the BBC are:
allowing A-band signals to pass and blocking b-band
blocking A-band signals and converting b-band signals to a-band.
 

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houskamp said:
Why would they have to block? you can't diplex OTA between BBC and dish anyway.. seems they could just ignore it since the tuner can't see that freq anyways..
But blocking the OTA frequency range that B-band comes on from the dish allows you to diplex OTA on the line between the BBC and the receiver. If the BBCs didn't block B-band when they weren't shifting it, you couldn't diplex on the output side of the BBC for the same reason you can't diplex between the dish and the BBC input.
 
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