Re: Front End (TUNER)
- From: "Michael A. Terrell" <mike.terrell@xxxxxxxxxxxxx>
- Date: Sun, 25 Mar 2007 06:12:39 GMT
Joerg wrote:
Phil Allison wrote:
"Joerg"
Easy to buy, yes. But don't always expect a whole lot of dynamic range.
With some tuners that I wanted to use I got the impression that their
designers didn't know what a dynamic range is.
** Do tell us more.
It's been too long ago since I gave up on TV tuners (mid 90's) because
of dirt poor 3rd order IP. After hearing from other engineers that is
has gotten even worse I never looked back.
The TV and FM tuner modules I have used seemed well optimised for their
jobs.
If you find a really good one again please let us all know. One of them
I investigated further and I found a wimpy dual-gate running at 5mA or
so in front. That won't hold any water with strong signals.
Maybe you expected something more.
Yeah, probably. But what really miffed me was this: Placed the antenna
on a mast after re-roofing the house. So, I equipped it with a nice
preamp, splitter, postamps with eight outputs and a home-run style
wiring closet. It cost a bit but I wanted to do it right. I was very
diligent with the gain distribution plan as well.
Hooked up a professional grade receiver to see how FM and stuff comes
in. Sweet, could now get Bay Area stations etc. Listened to the audio on
a few TV channels and found that I had now lots more than ever. Then I
turned on the TV and it was pandemonium. Utter disappointment. All
channels pumping with noise like crazy, not even the local stations
showed clearly, audio either not there or completely garbled. Tried the
downstairs TV, same thing. Then through the VCR's tuner, same thing. I
had to attenuate by more than 10dB plus place a notch on a strong local
channel 29 station, plus another channel I don't remember, plus notch
out the complete FM band. It was pathetic. The result is that we don't
have a single additional station from when the antenna was on the roof
(with a shot preamp). Oh well, most TV programming ain't worth it anyhow.
--
Regards, Joerg
http://www.analogconsultants.com
TV tuners used to be built to accommodate the wide range of signal
levels from over the air TV reception. Now, they "Assume" that every TV
will be connected to Cable, DVD, VCR or SAT, all of which have a higher
than 0 DBM signal level, and never over +10 DBM, so they don't give a
damn about the dynamic range. Also, some TVs had an extra IF stage that
would help in far fringe areas. That was why a cheap portable would
give a better picture than a console. Portables were expected to have a
wider range of signal levels to deal with, and the design reflected
this.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
.
- References:
- Front End (TUNER)
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- Re: Front End (TUNER)
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- Re: Front End (TUNER)
- From: Joerg
- Re: Front End (TUNER)
- From: Phil Allison
- Re: Front End (TUNER)
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