About
Us
Contractor
specials
Fire
& Rescue specials
Institutional
specials
Manufacturer
specials
Police
specials
Financing
Repairs
Warranty
What's
New!
Home
Other
US Products
American quality at prices
below the imports!
Here
is an example
of INFRASTRUCTURE!
Infrastructure is a term that was seldom used until just recently. In the traditional sense, infrastructure defines something that supports something else. For example, a railroad track is infrastructure. Without the track, the train goes nowhere!
Another example of infrastructure is hydroelectric power such as that generated by the Hoover dam as shown in the picture at the above left. Without the dam, there can be no generators and no power. For what it's worth, I am standing on Interstate 93, the only Interstate highway in the USA with a stop sign (actually on my right) as it passes across the dam from Nevada to Arizona (A bypass is under construction to eliminate this major bottleneck across the Grand Canyon at this time.
So what does all of this have to do with wireless communications systems? Actually quite a lot since wireless communications systems also depend on infrastructure for all applications except simple direct communications between personal and or mobile radios. In this section, we will introduce you to the infrastructure of trunked radio systems.
Conventional repeater radio systems generally consist of four basic elements - the radio transceiver (known as a repeater), an antenna, a coaxial transmission line, and a rarely discussed gadget called a duplexer. Since most of us have a general idea of the functions of transceivers, antennas and cables; we won't spend a lot of time of these subjects. For those who would like more information on repeaters, you may wish to visit www.usa-radio1.com/repeaters. Most of us are not so familiar with duplexers. If you are planning a migration to a trunking radio system, it is important that you have at least a basic understanding of a duplexer.
The thing that makes a repeater different from an ordinary 2-way radio is that the transmitter and receiver operate at the same time, unlike a conventional radio where it is either in the transmit or receive mode (controlled by a PTT button), but never both at the same time. In order for the transmitter and receiver to operate simultaneously, a duplexer has proven to be the most cost effective solution. In essence, a duplexer is a set of filters that keeps the transmitter from interfering with the receiver. The output of the transmitter and the output of the receiver are connected to the duplexer which in turn is connected to the station antenna. If you would like to know more about duplexers and how they work, our old friend Jack Daniel (not the one in the bottle) has prepared an excellent white paper on the subject. Click here for the full report.
Duplexers work well with single channel repeaters. They can also be used with trunked systems if the duplexer and antenna system is already in place. On new trunked systems, we don't use individual duplexers for each channel. We take the output of all the radios dedicated for use on each channel and feed all the transmitters into a gadget known as a Combiner. The output of the Combiner is then connected to a single transmit antenna. We then take the output of all the receivers and feed them in another gadget known as a Multicoupler, and then connect between the Multicoupler and a single antenna. Combiners and duplexers are primarily used for purposes of improving receiver sensitivity, reducing size, and in some cases reducing cost. A four channel trunked system would require only two coaxial feed lines and antennas versus four antenna and transmission systems if duplexers were used.
We will assume for now that you already have UHF frequencies licensed by the Federal Communications Commission (FCC). If not, we will assist you in applying for the required frequencies. As a general rule, UHF frequencies should have a 5 MHz separation between the transmit and receiver plus a 2 MHz separation between frequency pairs. If you already have antennas and transmission lines installed, you may elect to use your current duplexers and antenna systems. Conversely, if the existing antenna systems are over five years old, it may be to your long term advantage to build your new system utilizing a combiner and multi-coupler.
On of our favorite manufacturers of receivers and multi-couplers is EMR Corporation of Phoenix, AZ. EMR produces a complete package that will handle four trunked repeater stations for only $4,735 complete. Better yet, it takes only five and a quarter inches of vertical space on a standard 19 inch rack. Complete information is available by clicking here.
As we get into trunking systems, we learn that many of the theories used when original conventional radio systems were installed are not applicable in planning for today. First, high power is OUT! We don't use 100 watt repeaters. We never go higher than 20 watts. Why? First there is the logic of equality. The highest powered UHF hand held personal radios are rated at 3 to 4 watts. You can assume that you will lose about half your transmitter power through the losses associated with a combiner. That means that a transmitter power output of 8 watts should be acceptable. A good antenna can easily make up for any combiner losses, and in fact exceed the original transmit power efficiency as well as improving receiver efficiency. We'll discuss antennas in more detail shortly.
We could use more power, but there are technical issues to address. One of them is licensing. The FCC rarely hands out high power licenses any more, mainly because it isn't needed. The Europeans learned over fifty years ago that a low powered transmitter coupled with a high spec receiver can actually outperform a standard receiver used with a high powered transmitter. The second consideration is cost. A combiner capable of handling 100 watts can easily cost up to three times more than one capable of handling up to 20 watts. Physically, a combiner capable of handling 100 watts can be quite large which can be a major consideration. The bottom line is that the EMR SYS-20 four channel combiner with multi-coupler used in conjunction with four Ritron 8 watt trunking radios (we call them Exciters) and a pair of good antennas should be capable of providing all the performance required for hospitals, manufacturing plants, warehouses, and other on-site high volume wireless communications uses. Now, let's look at the actual repeaters that are used to make up a trunking system.
This is the HEART.......
of a trunking system. We call it the Exciter. Technically it is a high spec, American made 8 watt UHF transceiver that provides that transmit and receive functions of your trunking system. In a four channel system, four of these are used. Each is connected to the aforementioned combiner (transmit) and multi-coupler (receive) which in turn are connected to separate transmit and receive antennas. You can learn more about the Exciter by clicking here.
Now our system is starting to come together. We have our combiner and multi-our Exciter RF transceivers (4 of them for our packaged system). The next item is the controller. Each Exciter transceiver is connected to it's own LTR trunking controller. There are a lot of people who make good LTR controllers including IDA, Trident, and Zetron being the major providers. As good as these other products may be, the best value in terms of performance, price, and compatibility with our needs is the Flex controller by Connect Systems, Inc. (CSI) To be sure we may be a little prejudiced since we have known some of the key people for a couple of decades. This is a company that has consistently done more and cost less. And, like our other channel partners, this is an American company, employing American workers, just like Ritron and EMR (we've been working with the family owned EMR organization for close to three decades).
This is the BRAIN.......
that does the controlling that makes LTR trunking so efficient. It's called a Flex III-A. There are four of these in our system, each one controlling it's associated RF transceiver. This technology is very similar to telephone switching technology. Actually trunking is an outgrowth of telephone switching technology that has long been used to allow just a few "real" phone lines to serve up to hundreds of individual phone users, each of who thinks they have a private line. In reality, down at the phone company (or cell phone company as the case may be), there are a number of dedicated circuits (lines or numbers if you prefer) that are available for on demand dynamic switching and connection. In some cases as few as ten phone lines can adequately serve up to 100 subscribers with dial tone instantly available over 99% of the time.
A typical 2-way radio channel can generally handle up to 75 users. Any more than that, are people find themselves waiting to get on the air. Realistically, the maximum number should be closer to 50. So, it we have four channels, each being used separately by administration, maintenance, security, and transportation, we could reasonably serve a total of around 200 users. If we pool those frequencies and dynamically assign use as required, our four channel system could easily serve over twice as many users. There are some very sophisticated calculations used to support the fact that pooling and dynamically assigning resources causes an increase in general availability. Interestingly, the benefits tend to peak, at least for communications circuit at around five inputs. Four units seems to be the ideal number for the majority of our users, but theoretically, there is no upper technical limit. The major limiting factors are cost and availability of frequencies. Suffice it to say that the Flex III-A can DOUBLE the efficiency for a typical four channel system user.
Now,
we rack it all up in a protective (and attractive enclosure available in IBM
Blue or White as well as gray or black). Our cabinet choice is 36"
tall with up to 32" of vertical mounting space and an interior depth of up
to 16" using standard 19" panel mounting. This is sufficient to
mount our EMR combiner and multi-coupler (5.25" vertical), four each
Exciter transceivers (1.75" x 4 for a total of 7"), four Flex III-A
controllers adds another 7" for a total of just under 20". That
leaves us room for a good Transformer based AC power supply plus panel mounted
coaxial and AC lightning protection.
So, what's left? The antenna system! Existing users can often user the antennas and cable systems already in place. For those that want to make a clean sweep, we offer special high gain antennas with maximum down tilt for on site use. Pricing for all elements of our recommended trunking system follow below:
Are you ready to move up to trunking? It's as easy as clicking on the Buy-Me buttons below. You will be instantly transported to our web store when you can order using your American Express, Discover, MasterCard, or VISA (We also Net 15 day terms with approved accounts). We'll set it up, check it out and send it to you, ready to operate. You can fax your programming instructions to 205.853.6178 or email to sales@falcondirect.com. If you prefer on-site installation, this can also be arranged.
|
Product |
Description |
Your Price |
Buy Now |
|
|
|
$4,735 |
|
Exciter |
The
Exciter is a high
spec, American made 8 watt UHF transceiver that provides that transmit and
receive functions of your trunking system. Four
of these, priced at just $1,495 each) are included in our four channel trunking package. Each is connected to the aforementioned combiner
(transmit) and multi-coupler (receive) which in turn are connected to separate
transmit and receive antennas. You can learn more about the Exciter
by clicking here.
Order Code TR102.
|
$5,580 |  |
Flex III-A |
This is the
brain (actually four of them in our recommended package) that does the
controlling that makes LTR trunking so efficient. It's called a
Flex III-A. There are four of these in our system, each one priced at
just $995 each for controlling
it's associated RF transceiver. Order Code. TR103
|
$3,980 | |
CAB-36 |
This
is the cabinet that houses the components of a UHF trunking
system. Available in IBM Blue or white, gray or black, the cabinet
also includes a continuous duty AC power supply with battery back up,
coaxial transmission line and AC lighting protection. Price
includes system integration cost. Order Code TR104. |
$2,495 |
|
 ANT-2 |
This
is the standard antenna system for a four channel UHF trunking
system. Two of these co-linear high gain antennas are used with maximum
down tilt setting for in-building saturation. Price also includes
coaxial transmission line and connector kit. Order Code TR105. |
$1,995 |
|
|
|
Doing business with USA Radio is easy! You can charge to American Express, Discover, MasterCard, VISA, or we will accept Purchase Orders from approved customers. | |
User information. Products sold by USA Radio are warranted to be technically compliant with the manufacturers specifications. No other warranty relative to use of the equipment or related service, when applicable, is expressed or implied. USA Radio makes no claim for suitability or fitness of users purpose or application. USA Radio is not responsible for claims arising from the use of equipment or services provided by or through USA Radio in which there are losses attributed to the use or application of equipment and/or related services. User agrees to these terms as a condition of purchase.
Be sure and insert your desired frequency and tones in the comments section if you are ordering on line. If you prefer, you can fax your programming information to 205.853.6178. If you have questions, give us a call at 1.800.489.2611.
Thanks for visiting with us!
The USA Radio Team
At your Service!
Copyright 2007 - USA Radios of
Alabama Inc.
This page was last updated on 10/27/2007
American quality at prices
below the imports!
36 - 20th Avenue NW - Birmingham, AL 35215
Phone Toll Free - 1.800.489.2611