| Q. |
What distance or range can I expect
with a Video Transmission system? |
| A. |
Unfortunately it depends
on a huge number of variables such as transmit power, antenna type,
building construction, height above ground and surroundings. Inside, metal
shelves, filing cabinets and other metallic objects may greatly reduce
the range.
INSIDE:
You can expect a range of between 50 to 200 ft. inside a modern steel building,
depending on the antenna type and location. You may have better results
in brick, wood and other non-metallic buildings. The number of floors or
walls the signal will penetrate is dependent on their composition and antenna
type and placement.
OUTSIDE: Coherent
has tested its transmitter and found that in an urban area, about 1000
ft (328 m) is realistic with a Yagi antenna on the receiver. In a
more rural setting, a one mile (1.6 km) range is reasonable. Using
only the Rubber Duck antennas supplied, 200 ft (66 m) is possible
in an urban area and about 2000 ft (660 m) in a rural one. NOTE:
For applications outside the US, our Export Transmitters have 4 switchable
power settings and range will be considerably greater
Our advice is to borrow a
Coherent system from your local dealer and see if it works for you.
Call us and we will assist you with the set-up assistance you may need. |
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| Q. |
I have seen Video Transmitters priced
from less than $100 to over $15,000. What are the differences? |
| A. |
For professional applications
you want reliability, stability, a quality picture, and good sound.
The cheap "Video Senders" you may have seen usually have poor picture quality,
may not pass a color signal and will not stay tuned since they are not
crystal controlled. They also use AM transmission for cost reasons.
Just as FM radio sounds better than AM, FM Video has a 15 dB advantage
in signal reception over AM Video. It is also immune to interference
from many more sources than AM.
Even some of the wireless
video systems selling for $2000-5000 use AM. Avoid all non-crystal
controlled and all AM Video systems.
The Professional video transmitters
used by broadcasters for short range transmission cost up to $25,000 and
are all FM. Coherent is using clever design and the latest highly
integrated, surface mount ICs to give you virtually this level of performance
for a fraction of this price. |
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| Q. |
What frequencies should I use? |
| A. |
If you do not fit in an
FCC regulated service such as broadcast, public utility, etc., or, you
don't want the hassle and expense of applying for a license, then you currently
have two choices.
Under FCC part 15, low powered
video transmission is allowed between 902-928 MHz and 2.4-2.483 GHz.
The 900 MHz band will yield better range than the 2.4 GHz band and
has fewer dropouts due to multipath reception problems. The 2.4 GHz
is now the standard band for Wireless computer networks (WLANs) and also
Microwave ovens.
A frequency selector switch
is a must on any Video Transmitter used in an urban area. Coherent
transmitters and receivers are equipped with a 10 channel selector switch. |
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| Q. |
Do I need to worry if a Video Transmitter
and Receiver are FCC approved? |
| A. |
Yes! You and /or your
customer may be liable for severe penalties and fines if caught.
NOTE: If you
see a Video transmitter for sale that can be received by an ordinary TV
set or tuner without its own receiver, it is not FCC approved. |
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