[opendtv] Re: White paper from CEA
- From: "Allen Le Roy Limberg" <allimberg@xxxxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 3 Nov 2005 19:45:32 -0500
An IF derived AGC control voltage is OK if it is a wideband IF amplifier
driving the AGC detector. One that responds to Adjacent Channel
Interference (ACI). A narrowband IF amplifier using a SAW filter will drive
the demodulator.
Al Limberg
----- Original Message -----
From: "Richard Hollandsworth" <holl_ands@xxxxxxxxx>
To: <opendtv@xxxxxxxxxxxxx>
Sent: Thursday, November 03, 2005 6:53 PM
Subject: [opendtv] Re: White paper from CEA
> I've also installed/replaced my share of roof-mounted "stick" antennas.
But most people don't feel comfortable dealing with heights (and
tools)....which means a healthy nick in the wallet.
>
> I think a properly designed EIA/CEA-909 SMART ANTENNA system is the
solution for not only reception in the 'burbs, but also for high signal
level environments, like Schubin's location. [Two birds, one stone.]
>
> The DX DTA-5000 SMART ANTENNA Preamp/Combiner Modules appears to use
varactor attenuators (0-10 dB) prior to the LNA chips, which will reduce the
gain in a high signal environment. Unfortunately, the Funai/Sylvania
6900DTE (with ATI NXT2004) is still using an IF derived AGC control voltage,
the same as every other ATSC Tuner on the market. My principal gripe is
that it only uses an overly small 2-element Yagi, with no external
connections for decent sized roof-mounted antennas, as are usually needed in
the 'burbs. [Subject of a future hacking exercise....]
>
> I have yet to run across an ATSC Tuner that claimed overload
characteristics that were even close to that of the Winegard Preamps, which
in turn is greatly exceeded by expensive GP Preamps like the NuWaves
HILNAV1, et al.
>
> DX didn't specifiy overload for DTA-5000, but their similiar (manual)
DTA-3000 stipulates a maximum output level of 95 dBuV (presumably for 24 dB
gain setting), which may imply 105 dBuV for 14 dB gain setting. That's
about the same as the Blonder-Tongue UHF Preamps and is 6 dB less than is
specified for the CM7777.....give or take some ambiguities wrt how many
input signals are active. So it may or may not have difficulty in a high
signal level environment.
>
> A SMART ANTENNA automatically combines mulitple antennas to form a beam in
the desired signal direction for each of the desired stations. Note that
with dispersed tower locations, and multipath signals coming from unexpected
directions, the arrival angles are typically NOT in the same direction for
all stations (as must be assumed for conventional antenna installations).
>
> A properly designed adaptive antenna array algorithm should perform a
joint optimization: maximizing the SNR and minimizing the residual error
rate. Nulls would be directed towards undesired directions and beams toward
the "best" desired direction. Sometimes maximizing the beam will yield
acceptable results, but nulling out strong multipath pre-echos and
post-echos can sometimes be even more important. The ATI patent disclosure
discussed discarding certain results identified as being caused by adjacent
interference....and multipath:
> http://gauss.ffii.org/PatentView/EP1484847
>
> I think that Mark might want to consider doing a test, even though the
Funai/Sylvania 6900DTE is the first SMART ANTENNA controller and probably
has a sub-optimum implementation, esp given the small size of the DX
DTA-5000.
>
> <holl_ands>
>
> //////////////////////////////////////////////////////
> "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx> wrote:
> Richard Hollandsworth wrote:
> > White paper from CEA IMPROVE THE PREAMP VICE THE TUNER:
>
> Certainly Mark Schubin's reception problems are not
> caused by a lack of antenna preamp.
>
> > Many people don't want to invest in an outdoor antenna
> > that is prone to being blown away in a storm, has to be
> > properly grounded, requires frequent maintenance, looks
> > ugly and costs perhaps as much as 6 to 12 months of
> > cable service.....each time it has to be replaced.
>
> Knock on wood, but this has certainly not been my
> experience. E.g., installed one reasonably priced yagi
> in 1972, at a friend's place in Baltimore, while I was
> going to school. It's still there. No, it didn't cost
> anywhere close to a year's worth of cable. Maybe two
> months worth of cable. (The RS double bowtie costs less
> than one month of cable for many people.)
>
> Of course, my preference is to avoid the fancy stuff,
> such as mast-mounted amps. They make good sense in some
> ways, but not in other ways. I have a small RS antenna
> amp inside, where the down-lead enters. Been there
> silent, cool, and ignorable since 1983.
>
> Bert
>
>
>
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