| Author |
Message |
Jo
Guest
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 Posted:
Mon Oct 24, 2005 2:37 am Post subject:
Digital transmission/reception |
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I don't understand how stations transmitting from the same exact
location don't all come through. In the NYC area the major networks
transmit their DTV signals from the Empire State Building. However only
some of the signals are dropout free 50 miles away in Bridgeport, CT.
CBS 2, NBC 4, FOX 5, ABC 7, UPN 9, WB 11, WXTV 41(Univision)transmit
from the ESB. Of those channel only 5,7,9,11 are dropout free on fair
weather days. 2 is barely ever visible, 4 teases you with a good signal
then drops out, and 41 on some days is perfect and on other days is
unwatchable.
Channel 5, according to the FCC, is transmitting its digital signal at
246kW, while channel 2 at 349kW, yet 5 is the most solid, dropout free
signal of the ones transmitted from the ESB, at least in Bridgeport. I
was always under the belief that tv signals worked similar to radio
signals, in that the higher the transmission power the farther the
signal travels and the stronger it is at the point of reception. Have I
been mistaken or is something not right.
For OTA reception I have an LG LST 3100A stb, a Channel Master 4228 8
bow tie UHF antenna, a 17 db gain Winegard pre amplifier and a remote
control rotor with compass. I wouldn't be so perplexed if the
transmission sources were from different locations, but they all come
from the exact same location but with greatly varying consistent
strength. I'm just confused and would be appreciative of anyone who
could explain this. BTW I got the transmission strength information
from http://www.fcc.gov/mb/video/tvq.html
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Doug McDonald
Guest
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| Posted:
Mon Oct 24, 2005 3:01 am Post subject:
Re: Digital transmission/reception |
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Jo wrote:
| Quote: | I don't understand how stations transmitting from the same exact
location don't all come through.
|
There are several possible explanations.
First is that the transmitting antennas are not all
100% nondirectional. The ESB antenna farm is a complex beast,
and some of the digital TV antennas are lower down than others.
Lower height is very important.
Second, and likely a problem for you, is that some channels
may get interference. The Northeast is seriously overpacked
with channels. At 50 miles, you may very well get
temporary interference from much more distant stations ...
or from ones off the back of your antenna. You need
to check where all the stations (both digital and analog)
are located within 150 miles of you on all the problem
channels.
Third, there is the possibility of overload on some channels
due to strong local stations. These can be on any channel.
The only cure is filters before the preamp, as you really
cant get narrow frequency band UHF antennas.
Doug McDonald |
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Dennis Mayer
Guest
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| Posted:
Mon Oct 24, 2005 3:03 am Post subject:
Re: Digital transmission/reception |
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Jo wrote:
| Quote: |
I don't understand how stations transmitting from the same exact
location don't all come through. In the NYC area the major networks
transmit their DTV signals from the Empire State Building. However only
some of the signals are dropout free 50 miles away in Bridgeport, CT.
CBS 2, NBC 4, FOX 5, ABC 7, UPN 9, WB 11, WXTV 41(Univision)transmit
from the ESB. Of those channel only 5,7,9,11 are dropout free on fair
weather days. 2 is barely ever visible, 4 teases you with a good signal
then drops out, and 41 on some days is perfect and on other days is
unwatchable.
Channel 5, according to the FCC, is transmitting its digital signal at
246kW, while channel 2 at 349kW, yet 5 is the most solid, dropout free
signal of the ones transmitted from the ESB, at least in Bridgeport. I
was always under the belief that tv signals worked similar to radio
signals, in that the higher the transmission power the farther the
signal travels and the stronger it is at the point of reception. Have I
been mistaken or is something not right.
|
Power level for an Analog TV station vs a new Digital TV station
channel
on the same Network is never the the same KW rating..
UHF vs VHF TV stations have different reflection properties depending
on a Chan 2 Freq vs a Chan 59 Freq...
Not all Antenna patterns are circular for many reasons....
Not all NYC TV stations are operating at full Power... Maybe now??
However most TV transmitters were knocked out on 9-11-01..
| Quote: |
For OTA reception I have an LG LST 3100A stb, a Channel Master 4228 8
bow tie UHF antenna, a 17 db gain Winegard pre amplifier and a remote
control rotor with compass. I wouldn't be so perplexed if the
transmission sources were from different locations, but they all come
from the exact same location but with greatly varying consistent
strength. I'm just confused and would be appreciative of anyone who
could explain this. BTW I got the transmission strength information
from http://www.fcc.gov/mb/video/tvq.html
|
Using an Antenna amp on a Strong TV signal makes the signal 'weaker'.
And recent large Sun Spots have caused communication Problems...
Plus on Sunny Fall days in the afternoon, Satellite uplink
communication
relative to the sun position can be affected adversely. |
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Sal M. Onella
Guest
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| Posted:
Fri Oct 28, 2005 3:52 am Post subject:
Re: Digital transmission/reception |
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"Doug McDonald" <mcdonald@SnPoAM_scs.uiuc.edu> wrote in message
news:djh17a$ddv$1@news.ks.uiuc.edu...
| Quote: | Jo wrote:
I don't understand how stations transmitting from the same exact
location don't all come through.
|
< snip>
| Quote: | some channels
may get interference. The Northeast is seriously overpacked
with channels. At 50 miles, you may very well get
temporary interference from much more distant stations ...
or from ones off the back of your antenna. You need
to check where all the stations (both digital and analog)
are located within 150 miles of you on all the problem
channels.
snip |
I have a similar problem in San Diego, involving stations from LA. I have a
7-foot
parabolic UHF antenna that gets good signals from LA (~122 miles) most of
the time.
However, KNBC-DT (Channel 36 OTA) gets interference from a low-power
analog transmitter nearby, so I suffer dropouts even when my desired signal
is,
perhaps, 20 dB or more out of the noise. Luckily for me, the interfering
transmitter
is 90-degrees off axis from LA, so I have a separate antenna that consists
of two
antennas spaced a half-wave apart at Ch 36, nulling out the local nuisance.
Since you've established the known UHF DT channels at the FCC's tvquery, try
tuning a UHF analog TV to those channels and see what's on.
Interference nulling by stacking antennas is dealt with on many websites.
See the
pictures, recall your HS geometery and start experimenting.
Good luck.. |
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numeric
Guest
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| Posted:
Thu Nov 10, 2005 5:32 am Post subject:
Re: Digital transmission/reception |
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|
"Jo" <Rosariom@prodigy.net> wrote in message
news:EoT6f.1370$Kv.1327@newssvr22.news.prodigy.net...
| Quote: | I don't understand how stations transmitting from the same exact
location don't all come through. In the NYC area the major networks
transmit their DTV signals from the Empire State Building. However only
some of the signals are dropout free 50 miles away in Bridgeport, CT.
CBS 2, NBC 4, FOX 5, ABC 7, UPN 9, WB 11, WXTV 41(Univision)transmit
from the ESB. Of those channel only 5,7,9,11 are dropout free on fair
weather days. 2 is barely ever visible, 4 teases you with a good signal
then drops out, and 41 on some days is perfect and on other days is
unwatchable.
Channel 5, according to the FCC, is transmitting its digital signal at
246kW, while channel 2 at 349kW, yet 5 is the most solid, dropout free
signal of the ones transmitted from the ESB, at least in Bridgeport. I
was always under the belief that tv signals worked similar to radio
signals, in that the higher the transmission power the farther the
signal travels and the stronger it is at the point of reception. Have I
been mistaken or is something not right.
For OTA reception I have an LG LST 3100A stb, a Channel Master 4228 8
bow tie UHF antenna, a 17 db gain Winegard pre amplifier and a remote
control rotor with compass. I wouldn't be so perplexed if the
transmission sources were from different locations, but they all come
from the exact same location but with greatly varying consistent
strength. I'm just confused and would be appreciative of anyone who
could explain this. BTW I got the transmission strength information
from http://www.fcc.gov/mb/video/tvq.html
|
Your location may be terrain blocked. Lat 41.18235, Lon -73.1919 which is a
general coordinate for Bridgeport Ct, is terrain blocked to the ESB
antennas; not by much however. The received signal to noise ratio is less
then the 15db threshold required for digital reception, as calculated using
the Longley/Rich irregular terrain point to point method. Reception in a
terrain blocked area produces greater variability in the transmission path;
which may explain your reception anomalies.
If you have terrain mapping software, you can check out the path between
your location and the ESB to determine what antenna height will give a clear
path.
The 9250 phemt preamp provides a 0.4 db noise figure, 20 db gain and very
high overload capability, may improve the signal margin. See
http://www.researchcomms.com/hdtv.html I currently have this preamp
connected to the UHF antenna. It does seem to make an improvement over the
Channel Master 7777 preamp; however I do not have the equipment to verify
the manufactures specification claims. |
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