[opendtv] Re: White paper from CEA

  • From: Richard Hollandsworth <holl_ands@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Fri, 4 Nov 2005 15:10:27 -0800 (PST)

The low-cost STB RFP released by MSTV included a requirement for the 
CEA/EIA-909 Smart Antenna interface.  So maybe we'll finally start to see more 
than one STB implement this capability.
 
I haven't spent the $75 to look at the detailed spec, so I only know a few 
highlights re the serial control data exchange (uplink controls at least the 
individual antenna element gain controls in DTA-5000).  But it is supposed to 
be readily expandable for future requirements.  Most ATI, Broadcom and 
STMicroelectronics chips (and some Tuner Modules) claim to support EIA-909 
interface, although it appears to require additonal external circuitry to use 
the AGC setting and decoder "quality" signal from the ATSC Decoder chip and 
then do "something" with the antenna uplink controls.
 
Super channels might be a good choice for "IF" downlink freq, if it is 
integrated with a matching STB.  However, I would prefer something in the 
normal VHF/UHF band so that it would work with any STB equipped with 
CEA/EIA-909 to provide Smart Antenna controls and associated tuning frequency 
as one of those "enhancements".
 
This could also permit use with ANY TV/HDTV by adding some sort of channel 
selector control.  [Hmm, you could probably detect the TV's Local Oscillator 
freq to determine the selected channel...)
Watching/Recording two different programs currently requires a Dual Tuner 
arrangement.
No reason why a Dual Tuner Masthead Preamp couldn't be designed to output on 
two different "IF" frequencies.
 
                     <holl_ands>
 
/////////////////////////////////////////////////////////
Allen Le Roy Limberg <allimberg@xxxxxxxxxxxx> wrote:
A very good reason to have the tuner(s) at the antenna is that you come down
the down lead at a predetermined VHF intermediate frequency for each tuner.
The down lead can be properly terminated, so there are no reflections. This
lightens the load on the equalizer considerably. Also, the signal level to
the house is regulated. Therefore, proper termination is easier to maintain
since receivers can be close to optimal point in AGC range.

The cable-only super channels are good IF choices.

Tuners belong with antennas. The reason they didn't do this in the old days
is that they used mechanical tuners that could not be remotely controlled.

Al


Bert Manfredi wrote:
>
> > If it's so easy and so obviously needed, why doesn't
> > anyone make such a Preamp????
>
> Seems to me that to design an RF amp that is tuned to
> a specific frequency band, in tandem with the IF stage,
> to improve selectivity, requires either that this
> more expensive beast be incorporated in the receiver
> itself (increasing cost) or that it be added as an
> external device, used as needed. But such an external
> device would then require a signal from the receiver.
>
> If done as such an external device, it becomes
> cumbersome or even unusable for any setup that
> incorporates recording devices or multiple receiver
> hookups of any type. Unless the multiple receivers are
> contrained to receive the same channel at all times.
>
> So bottom line, in my view, tuning a masthead or
> similar external antenna amp is not the right way to
> go.
>
> Anything wrong with dual conversion tuners? They can
> accept wide band RF amps without paying the
> consequences. Or just build the fancy RF amp into the
> receiver.
>
> Bert
>
>
>
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