[opendtv] Re: White paper from CEA
- From: Richard Hollandsworth <holl_ands@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 4 Nov 2005 09:36:49 -0800 (PST)
If it's so easy and so obviously needed, why doesn't anyone make such a
Preamp????
And don't forget the RF bandwidth derived AGC....and considerably more than
just 10 dB.
FYI: Fol. is "Digital Television Tuner Design" presentation by Max Muterspauch
(TTE/Thomsen) that addresses RF Front End bandwidth, varactor Q, "typical"
Noise Figure and even the double conversion tuner design found in the Grand
Alliance ATSC Receiver:
www.ieee802.org/22/Meeting_documents/2005_Jan/
22-05-0006-00-0000_Digital_Television_Tuner_Design.ppt
The fol app note for the Infineon TUA6043T when used for ATSC is about the only
info I've found on-line re RF Front End bandwidth:
https://www.infineon.com/cgi-bin/ifx/portal/ep/programView.do?channelId=-64222&programId=32784&programPage=%2Fep%2Fprogram%2Fdocument.jsp&pageTypeId=17099&BV_SessionID=@@@@0730106163.1131125461@@@@&BV_EngineID=ccckaddgeedkmkfcflgcegndfifdfoi.0
Good luck with that link!!!!
Or go to Infineon site, find TUA6043T and click on Documents under TUA6043T for
the product sheet and then Documents under Digital Terr. Tuner for the app.
note.]
<holl_ands>
///////////////////////////////////////////////////////////
Allen Le Roy Limberg <allimberg@xxxxxxxxxxxx> wrote:
You shouldn't use a wideband LNA. The preamp should be tuned also, easy to
do with electronic tuning, even at masthead.
Al
----- Original Message -----
From: "Richard Hollandsworth"
To:
Sent: Friday, November 04, 2005 2:55 AM
Subject: [opendtv] Re: White paper from CEA
> But an IF derived AGC only responds to on-channel and adjacent channel
signals.
>
> A typical RF Front End might have a 3 dB bandwidth that is not much more
than three channels wide. I've only seen a few claims re RF bandwith,
mostly in the 15-30 MHz range, depending on the operating frequency (Q less
than 40). Very few Tuner manufacturers include this (or overload) in their
posted spec sheets. [Probably because they are just too embarassed...]
>
> With only a single stage of L-C tuning and the relatively low Q of typical
varactors, I wouldn't expect very much suppression several channels away.
> These are the "other" signals that can drive a LNA into non-linearity,
preventing reception of weak signals.
>
>
> ////////////////////////////////////////
> Allen Le Roy Limberg wrote:
> 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
>
>
>
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