> In practice if the signal is above the digital cliff it is 100%. What
> make life more complicated?
The digital cliff is the perfect vehicle for sloppy design since it
allows a system to show a generally perfect picture one moment and
nothing the next. It simply hides sloppy system design. Working
with marginal antennas when a proper system (e.g. adding a 29" dipole
in parallel with a UHF only bow tie) is easily obtainable with no
overall impact to the installation only opens the door to unreliable
operation when the station drops power, absorption/scattering increases
due to weather or the front end gain drops due to HF overload, etc..
> I have been working with DTV for 15 years and learned what works.
> It is necessary to think differently.
I have designed and built TV reception systems for more than 35 years.
Cutting corners is simply sloppy and unprofessional whether one was
using about vacuum tube preamps and converters or working with modern
ATSC/DTV systems. Two or three dB above the digital cliff may work
for 80% of the cases 80% of the time but the extra three to six dB
from doing the job right will raise the reliability to 99+/99+ .
While 80% may be "good enough" for some in the big city, it's not the
way the rest of the world works.
73,
... Joe, W4TV
On 7/7/2012 2:55 PM, W2XJ wrote:
> That is what the theory says. In practice if the signal is above the
> digital cliff it is 100%. What make life more complicated? Many people
> have height, space and covenant restrictions. They in practice do what
> works. I have been working with DTV for 15 years and learned what works.
> It is necessary to think differently.
>
>
> On 7/7/12 2:44 PM, Joe Subich, W4TV wrote:
>> On 7/7/2012 1:54 PM, W2XJ wrote:
>>> Most people report acceptable results on VHF with a UHF bowtie if
>>> the V is relatively local.
>> If you are going to erect an external antenna, use the right antenna
>> for the job. In mixed U/V environments, that's a U/V antenna - not
>> a UHF bowtie that just "might" work on close-in VHF signals. If you
>> are going to accept whatever signal is there, the FM folded dipole
>> produces signals even though it is a resistive short very close to
>> one of the channels in use in the particular market.
>>
>> With a UHF bow-tie in a mixed U/V market, at least install a splitter
>> backward as a combiner and connect a high VHF bow tie or at minimum
>> a dipole cut for about 195 MHz in parallel with the UHF antenna.
>>
>> 73,
>>
>> ... Joe, W4TV
>>
>>
>>
>> On 7/7/2012 1:54 PM, W2XJ wrote:
>>> Most people report acceptable results on VHF with a UHF bowtie if the V
>>> is relatively local.
>>>
>>>
>>> On 7/7/12 12:03 PM, Joe Subich, W4TV wrote:
>>>> > *** And from my original question. Is it a good bet to install this
>>>> > well-regarded amplified TV antenna? Bearing in mind that I will be
>>>> > helpless if the internal amp suffers fundamental overload at HF?
>>>>
>>>> Also far removed from amplifiers and their operation - more appropriate
>>>> for a DTV antennas list.
>>>>
>>>> > bearing in mind that we are getting very decent - but not 100% -
>>>> > reception with a mere 300-ohm folded dipole "FM Antenna" tacked to
>>>> the
>>>> > wall.
>>>>
>>>> A twinlead folded dipole "FM Antenna" (88-108 MHz) is not very good
>>>> on UHF TV (450-900 MHz). It has a widely varying pattern and on some
>>>> channels appears as a resistive short across the receiver input.
>>>>
>>>> If you get any where near acceptable signals with the FM dipole, all
>>>> stations are in a single direction (+/- 45 degrees or so), and all
>>>> stations are UHF (actual channel - not the virtual channel they ID),
>>>> then a two or four bay bow-tie antenna will be more than enough and
>>>> probably far more reliable than the amplified omni. On the other
>>>> hand if you are in one of those places "between" transmitter sites
>>>> (with clusters in opposite directions) you're likely stuck with an
>>>> omni (or multiple directional) antennas.
>>>>
>>>> Start your search at:
>>>> http://www.antennaweb.org
>>>> http://www.antennapoint.com
>>>> http://transition.fcc.gov/mb/engineering/maps/
>>>>
>>>> Your area has two high VHF channels and many UHF channels (19-47).
>>>> Fortunately, other than one distant independent, they seem to be
>>>> clustered in two directions with less than a 30 degree spread.
>>>> You would probably be best served by a small VHF/UHF dualband
>>>> log-periodic - a UHF "bow tie" antenna would be questionable for
>>>> the two VHF stations.
>>>>
>>>>
>>>> 73,
>>>>
>>>> ... Joe, W4TV
>>>>
>>>>
>>>>
>>>> On 7/7/2012 11:19 AM, Jerry Kaidor wrote:
>>>>>> In any case, all of this is rather far removed from amplifiers.
>>>>>>
>>>>> *** And from my original question. Is it a good bet to install this
>>>>> well-regarded amplified TV antenna? Bearing in mind that I will be
>>>>> helpless if the internal amp suffers fundamental overload at HF? Or
>>>>> should I just pack it off back to Amazon and install something like a
>>>>> bowtie - bearing in mind that we are getting very decent - but not 100% -
>>>>> reception with a mere 300-ohm folded dipole "FM Antenna" tacked to the
>>>>> wall.
>>>>>
>>>>> - Jerry Kaidor, KF6VB
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> 73,
>>>>>>
>>>>>> ... Joe, W4TV
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 7/7/2012 7:18 AM, W2XJ wrote:
>>>>>>> You got what you got. In most cases the antenna had to be adjusted for
>>>>>>> each channel. With DTV this is not very practical as the TV must scan
>>>>>>> the channels seen by the antenna at that instant.
>>>>>>>
>>>>>>>
>>>>>>> On 7/7/12 7:01 AM, Bill Turner wrote:
>>>>>>>> ORIGINAL MESSAGE:
>>>>>>>> On Fri, 06 Jul 2012 22:19:21 -0400, you wrote:
>>>>>>>>
>>>>>>>>> I disagree. No one in their right mind would have used an omni to
>>>>>>>>> receive NTSC.
>>>>>>>> REPLY:
>>>>>>>> What about those hundreds of millions of portable TVs with "rabbit
>>>>>>>> ears" or
>>>>>>>> monopole verticals?
>>>>>>>>
>>>>>>>> 73, Bill W6WRT
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