In message , Paul
writes:
Mark Twain wrote:
I thought I had a balun and rabbit ears
In fact, I know I do, but damned if I can
find it. In any case, I decided to buy this:
https://www.ebay.com/itm/TERK-TVOMA1...idirectional-F
lat-Digital-HDTV-Antenna-/302565532675?_trksid=p5731.m3795
what do you think?
I found the HDMI input under Video
http://www.lg.com/us/tvs/lg-28LN4500-led-tv
[]
Thanks,
Robert
I couldn't find a good reference on the square antenna.
It could be hiding this sort of thing inside. A fractal
antenna. They don't have to use wire for those, and the
antenna could be made from FR4 with copper tracks on it
in the desired pattern. The phasing on some of these,
is intended to combine the signals and drop the characteristic
impedance. Which is how the antennas in the examples here,
manage to get a bit closer to 75 ohms. That's what the
two "rails" in the center are for. Impedance conversion.
http://www.instructables.com/id/How-...nna-for-HDTV-D
TV-plus-/
When I needed an antenna, I build a Gray-Hoverman. One with
extra elements for VHF. And that's because the bureaucrats
Is that better than a Yagi? (I once got hold of Yagi's original paper:
surprisingly long ago - 1920s I think. [When he wrote it, I mean - I'm
not that old!])
here thought it would be cool to give the TV industry zero
dollars to subsidize new transmission equipment. And a side
effect, is a couple transmitters just used the old analog
setup, on something like channel 6. They changed the
modulation of the transmitter, for the digital signal,
but the "power" part is just the old equipment.
It means our channels here, they could have all been placed
on UHF (simplifying things and making the square antenna
more practical), but instead the band remains split between
some stations being on VHF and the rest being on UHF. Then
it means a physically larger antenna to get VHF. UHF works
with smaller dimensions. If I only needed a UHF
antenna, I could have continued using my old one.
Whereas here in UK, things went the other way: VHF would have covered
the country with far fewer transmitters (and did), but we went to UHF
for 625 lines (what some call "PAL", though strictly that's the colour
method), so that the existing VHF network could continue to supply the
old 405 line system. (Which remained operating until I think 197x!)
My Gray Hoverman was designed "for the cottage" rather than
an urban setting. To use it in the city, I'd need a rotator
because it only has a 15 degree beamwidth. Since I have
TV transmitters on two major different vectors, it requires
rotating the antenna to either vector to get a signal.
Or two aerials. (I don't think I've ever seen a domestic TV aerial here
with a rotator; but, we are very fortunate that our networks were mostly
designed to co-site the transmitters.)
It the antenna is isotropic, and has a wide beam width,
then you hardly ever need to fiddle with it.
Though few, at least those with wire elements, are truly isotropic.
In one of the TV forums, the "experts" there never buy
an antenna, without seeing the beam pattern versus
frequency. And I was hoping to find a little backgrounder
on the square antenna, with some good pictures of results.
As that helps predict whether it'll be a practical
purchase or not.
Amplifiers are a good choice for distribution - if you're
driving 100 feet of cheap down-lead, then sticking an amp
on the head end, might help reduce the loss. Amplifiers
always have a "noise figure", and indiscriminate use of
amps leads to a degradation in the noise part of "S/N".
Yes, amplified room aerials aren't in general of that much benefit,
unless your TV is particularly deaf. In general, I wouldn't buy a
"by-the-set" amplifier (except for signal splitting between two or more
sets) unless it had a noise figure mentioned on the box, and few such do
have. As you say, other end of downlead is a different matter.
So a 60dB amp isn't "twice as good" as a 30dB amp,
or a loaf of bread baked for twice as long is burned,
rather than being "twice as good". So if you see
I like that analogy!
exaggerated claims for the amp, keep that in mind :-)
The TV has AGC (automatic gain control on RF) and
probably works from 10uV to 1V or so in amplitude.
The TV will turn up its own gain on a weak signal.
Indeed. A stated noise figure would be good there too, but again is very
rare; even a uV one is, I think.
One difference with DTV, is the response to the signal.
You can go from a crystal clear picture, to a black screen
(LOS) with only a 2dB drop in level. There isn't
nearly the graceful degradation as there was with
analog NTSC. A missing channel could be close to the
(And analog PAL.)
right level, or way way down and totally out of reach,
and you can't really tell.
This (combined with the more or less total decline in technical support
from the broadcasters from the general public) has also allowed other
near band - actually in-band for most equipment, as they keep
reallocating bits of the band to the ravenous mobile (cellular) section
- to increase with impunity; with analogue signals, viewers could see
that what was stopping them viewing properly was interference, but with
digital, they just suffer in silence (and frustration).
One amazing thing that happened here, was getting a
TV tuner card for the PC and comparing it to my
settop box. A world of difference. The STB could
only get three channels regularly. The TV tuner
card (using the same signal) gets everything known
to exist in the city. While propagation characteristics
change from month to month, the difference I'm seeing
really looks like the TV tuner does something different
from a DSP perspective. As I don't think this is
just "moar amp". It's not an amplifier effect.
Despite what I said above about room amplifiers, I was very agreeably
surprised recently when trying out a TV stick that came with an
"amplified aerial" (telescopic rod, but needed a separate USB socket to
power it); it got most of the channels available in the area, where I'd
expected to need to connect the roof aerial. (I _was_ trying upstairs.)
It even got usable signals - some breakup - from many of the channels
from an another transmitter site. (I was at NE6 5AD - main signals from
Pontop Pike, others possibly from one of its fill-ins [Fenham?].) I
_didn't_ try it without the aerial powered, to see if just the stick was
more sensitive than they've been in the past (it might not have worked
at all unpowered, anyway).
It's fun to play with. Too bad I'm not all that interested
in TV :-)
(-:
Paul
John
--
J. P. Gilliver. UMRA: 1960/1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf
The squeamish will squeam a lot.
(Barry Norman on the film "300", in Radio Times 30 March-5 April 2013.)