PAGE 1...VHF/UHF TV Signal Distribution ____________________________________________________________________
PAGE 1 DISTRIBUTING SIGNALS AROUND THE HOUSE
Once you get your satellite system installed, most people find it
necessary to have the signal available in other parts of the house
besides the primary viewing location next to the satellite receiver.
Several methods are available: I prefer to run direct video and
audio on RG-6 coax, with RCA to F type adapters, and send top quality
video signals to a monitor, and stereo audio to the tape inputs of
a "ghetto blaster" or other stereo receiver that allows auxiliary
inputs. Most situations demand the capability of multiple locations,
so unless you want to buy an expensive audio/video distribution sys-
tem and run lots of separate cables everywhere, signals will be best
distributed via RF modulator. Inexpensive channel 3 or 4 mixers are
the least costly way to mix one signal into an existing TV system,
provided one of those channels is free to insert programming. Most
mixers are of borderline quality, and it usually takes an experienc-
ed technician with a field strength meter and a knowledge of exact
levels and how to "tweak" filter pots. to make things watchable.
In most cases, you will degrade either the existing adjacent off-
air channel or the satellite signal. If you are connected to a cable
system, the use of one of these mixers is usually not an option, as
all channels are normally in use. In this case, using the built-in
channel 3 or 4 VHF modulator, and running a parallel cable to each
location plus an A/B coaxial switch is the cheapest conventional
method, but if you have multiple satellite receivers, or multiple
VCRs, and/or a lot of TV sets to feed, the economics quickly favor
using a low-cost UHF modulator for each device. This prevents having
MTS stereo in each location (unless your satellite receiver has a
built-in Ch 3/4 MTS stereo modulator). If that is the case, running
separate cables (one for existing off-air system, and one for your
"new" TV system) to each location in a "home-run" fashion; directly
to each location from a central power divider, is the wiring method
most often advised. My method of running video and audio directly
to a single location to get stereo is another option. If you don't
mind spending $300 or more, CHANNEL PLUS has some MTS stereo type
modulators that allow video plus stereo audio to be patched from
your satellite receiver (assuming it has these RCA jacks) to the
CHANNEL PLUS modulator. This allows you to leave your existing
TV distribution system pretty much undisturbed, and find an unused
UHF channel in which to place a satellite signal. If you have
cable-ready TV sets that tune cable channels between 65 and 100,
it is a little known fact that UHF modulators between UHF channels
14 and 35 will appear on cable tuners in the 60s through 80s.
If you have cable TV, and a mix of cable ready plus UHF/VHF tuners,
the best method of adding channels is to put them on channels above
existing cable signals. If you have off-air TV, and UHF channels
are in use, you can usually squeeze a few channels in between the
existing broadcast signals.
Let's talk budget! If you don't mind MONO audio, two relatively
inexpensive modulator types are available. PICO makes the USM-8
modulator, which can be tuned between channels 14 and 30 UHF;
sometimes up to Ch 32. If you have no existing signals on the
UHF band, seven of these boxes can be used to provide 7 channels
of in-house programming, provide you set them on channels 14,
17, 20, 23, 26, 29, and 32. We suggest maintaining three-channel
spacing to minimize interference. If you have existing off-air
channels in this range, you can probably insert signals 2 channels
above or below an existing TV signal without much interference.
If you have a need for even more signals, two products come to mind.
[Please see next page]
PAGE 2 UHF DISTRIBUTION IDEAS
PICO has a medium powered Digital modulator called the CAM-25,
which changes channels with front panel buttons, and can be set
anywhere from CH 14 to CH 69. Its digital design makes the unit
more stable than the USM-8, which tend to drift slightly if the
temperature in the room is not maintained at a steady level.
This is not generally a problem, but slight drift is a possibility.
We also have a couple of other vendors supplying 2-channel devices
similar to the CAM-25, allowing CH 14 to CH 69 selection and
the ability to provide two channels of programming from one box.
These are the higher-quality digital tuning variety, and are
proportionately more expensive.
The CAM-25 and other digital modulators can be set by pushing
buttons...something even the novice can do. The PICO USM-8 has
three adjustments that are tuned with a fine flat head screwdriver.
Video and audio level plus channel frequency. Units are shipped
from the factory at no particular frequency. For an additional
$5.00 per unit, GLOBAL COMMUNICATIONS will set individual USM-8
modulators to the channel of your choice, and get the video and
audio levels close to specification using one of our test satellite
receivers. You may have to make slight adjustments when connecting
to your own satellite receiver, but at least you will have more to
work with than an un-set unit.
Here is an approximate conversion chart for viewing of UHF signals
from these devices on cable ready sets, or cable converters:
UHF/CATV UHF/CATV UHF/CATV UHF/CATV UHF/CATV UHF/CATV
14 65 15 66 16 67 17 68 18 69 19 70
20 71 21 72 22 73 23 74 24 75 25 76
26 77 27 78 28 79 29 80 30 81 31 82
32 83 33 84 34 85 35 86 36 87 37 88
38 89 39 90 40 91 41 92 42 93 43 94
Here are some rough drawings showing system configurations...
a lot more can be designed with a little bit of imagination.
ADDING A UHF MODULATOR FOR SATELLITE OR VCR SIGNALS
ON SAME WIRING SYSTEM AS EXISTING CABLE TV SERVICE
! NOTES: USM-8 may
__________ ! Existing CATV require slight
USM-8 UHF ! Input inside amplification with
Modulator ! house Distribution Amp
__________ ! such as PICO TA-25.
! CH 18 = ! CABLE CHs 2 to 62
! CABLE 69 ! This may need to be
! ___________ "padded" down to
!............! DSU-2 ! achieve an exact
** ! Combiner! level match with
Optional ___________ existing cable
Dist. Amp. ! service. If there
! To existing splitter is any interference
If interference serving house to VHF or cable
affects any cable channels, additional
reception, add a UHF/VHF combiner at filter is advised.
output of amplifier [PICO UVSJ] and
terminate VHF output with F59T terminator.
PAGE 3 UHF DISTRIBUTION Continued
Please be advised that if you cause interference to your local CATV
service (to yourself, requiring a service call from the cable co.,
or to other subscribers), you will be responsible for eliminating
any problems. Do NOT hook up additional equipment such as this,
find a problem, and call them for help. You will very likely be
asked to remove the offending device, and possibly pay for a service
call. When in doubt, call a competent service technician that is
experienced in television distribution systems.
ADDING MULTIPLE UHF CHANNELS:
________ ________ ________ ________
USM-8 USM-8 USM-8 USM-8
Ch 14 Ch 17 Ch 20 Ch 23
________ ________ ________ ________ ___________
! ! ! !...... ! !
! ! !................... ! DSU-4 ! Out
! !................................ ! Combiner !....
!.............................................. ! !
Please note that DSU-2, DSU-4 and DSU-8 units are sold as combiner/
splitters, and labelled for use as splitter (power divider). In the
above application, 4 ports labelled OUTPUT are actually used as
inputs, with the single INPUT port being used as an output.
When adding 2 or more modulators, the output should definitely
be amplified with PICO TA-25 or equivalent Distribution Amplifier.
Normal output of USM-8 Modulators is about dBm. Losses from
insertion into DSU-4 typically approach 7 to 8 dB. If your level
gets below dBm, resulting signals will appear more grainy, so
it is important to amplify before degrading signals. You COULD
use an 8-way combiner such as the PICO DSU-8, but are starting to
approach a 0 dBm level, which will probably appear on upper
frequencies used. If adding multiple channels, especially above
Ch 32, use signal units such as the PICO CAM-25, which has a
dBm output. This will compensate for cable losses at higher
frequencies, and might even need to be padded with a small fixed
attenuator (, or db devices) if levels are objectionable.
Please call, write, fax or Email us for advice on designing
a UHF distribution system.