Nova Scotia UHF Back Bone
Linking System
Bill Elliott
VE1MR
Introduction
We will introduce you to the UHF back bone system
as currently implemented.
1) explanation of some terms.
2) overview of system.
3) detail
4) uses and limitations
5) linking etiquette
We will also show how other means can be used to
pass traffic into and out of other areas.
Explanation of Some Terms
Repeater
A repeater is a Transmitter/Receiver on a
particular VHF or UHF band that immediately
transmits what it hears on the receiver.
Repeaters generally have a tail - that is the
transmitter stays on for a few seconds after the
received signal ceases.
There is usually a courtesy beep, identifiers
and sometimes messages on repeaters.
Explanation of Some Terms
Link
A link is generally a radio on a different
frequency than the primary repeater.
There are several types of links. Our
system uses 3 different types.
1 - UHF HUB Repeaters
2 - UHF Half Duplex links
3 - UHF Full Duplex Links
Explanation of Some Terms
UHF HUB Repeater
A HUB repeater is a true repeater in that it
immediately transmits what it hears on the
receiver.
These repeaters normally do not have any tail
- that is the transmit stops as soon as the
received signal ceases.
You will see later how these are used in the
linking system.
Explanation of Some Terms
Half Duplex
Half Duplex refers to a link radio that generally uses
different transmit and receive frequencies but at any
given time transmits or receives, not both at the same
time.
When a Half Duplex link radio is transmitting it cannot
receive.
When a Half Duplex radio is receiving it may go into
transmit depending on the situation.
You will see later how this may affect operation.
Explanation of Some Terms
Full Duplex
Full Duplex refers to a link radio that uses
different transmit and receive frequencies and
can transmit and receive at the same time.
When a Full Duplex link radio is transmitting it can
receive without affecting what it is transmitting.
When a Full Duplex radio is receiving it can also
transmit without affecting what it is receiving.
You will see later how this affects operation.
Explanation of Some Terms
Controller
A controller generally refers to a piece of equipment to
control a repeater or link or both. It takes care of things like
tails, courtesy beeps IDs, messages, timers and other
functions like connecting ports together.
The programming of a controller can be quite simple or
very complicated depending on functions required and
auxiliary equipment added to it.
Port
A Port refers to a controller input/output for controlling a
radio. Each port controls one radio for transmit and
receive functions. In general the more ports a controller
has the more it will cost.
Explanation of Some Terms
TIMERS
• Link activity timer is generally 3 minutes. Most controllers are set to
drop the transmitter after 3 minutes of continuous receive carrier - this
applies to both repeaters and links. So if you think your monologue will
be longer than 3 minutes take a short break to allow all timers to reset.
• Link inactivity timer is generally 5 minutes. This will ensure the link
will time out if there is no activity on the link for the set time. So if you
drive out of the coverage area of a repeater you up linked, do not
worry, the link will time out with no activity.
• Often the inactivity timer on the repeater side will be set to a longer
time typically 20 minutes. This allows listening to a net when no one is
checking in from a particular repeater. Not all controllers allow this.
Explanation of Some Terms
Duplexer
A Duplexer is a piece of equipment that allows one antenna
to be used for both receive and transmit at the same time. It
can be used on a Repeater or a Full Duplex Link.
Hard Link
A Hard link is one that is always up. This means that a
Hard Link between 2 or more repeaters allows what is
received on one repeater to be transmitted out all hard
linked repeaters simultaneously. Hard links can use UHF
HUB repeaters, Half Duplex links or Full Duplex links or
any combination that will work.
Explanation of Some Terms
DTMF SIGNALLING
DTMF is Dual Tone Multi Frequency, often called
touch tone.
For the linking system DTMF signalling uses a
touch tone key pad normally mounted on the
microphone or radio.
Our linking system normally uses a 4 digit code
according to a co-ordinated dialling plan. The
various system controllers respond to their own
code to link ports together, thus allowing control
of receivers and transmitters.
Why use different types of links
1 - Primarily due to equipment costs and availability
of antennas on a particular tower.
2 - A HUB repeater can service many links to different
sites with one antenna. The disadvantage is that
links to a HUB repeater must be Half Duplex.
3 - Half Duplex links require less equipment and space.
If a Half Duplex link does not go to a HUB repeater
then it can be easily made into a Full Duplex link in
the future with some modifications and the addition
of a Duplexer.
4 - A Full Duplex link is the preferred method of linking as
you will see later.
QUESTIONS
ON ANY THING SO FAR
??????
Overview
We will take a quick look at the complete system
more or less as it stands today.
You will see the complexity of the backbone
system but you actually do not need to understand
all the paths involved but knowing some of the
routes and the types of links involved will help you
understand why certain things happen.
I will then explain how some of the links work.
OVERVIEW
This map shows most of the
repeaters in Nova Scotia
Not all are linked
OVERVIEW
VE1BBC
Red lines = Hard linked
Yellow lines = UHF backbone system
White lines = under construction
OVERVIEW
VE1BBC
The white links under
construction will be
hard links
OVERVIEW
OVERVIEW
OVERVIEW
Now an overview of the types of
link sites.
1) Full Duplex
2) Half Duplex
3) Half Duplex with HUB Repeater
FULL DUPLEX TRUNK LINK SITE
UHF BACKBONE
VE1EFP
East Kemptville
VE1BO
Port 2
Port 3
Port 1
Controller
NRC
VE1AAR
DND
HALF DUPLEX TRUNK LINK SITE
UHF BACKBONE
VE1SAB
VE1MHR
Cochrane Hill
Jerusalem Hill
Port 2
Port 3
Port 1
Controller
VE1ESR
Marionette
HALF DUPLEX HUB LINK SITE
UHF BACKBONE
VE1CFR
VY2UHF
PEI
PEI
UHF HUB
Repeater
Controller Port 2
VE1SPR
VE1HAR
Port 1
Harmony
Sugarloaf
VE1BHS
Aliant
DETAIL
I will now explain how some of the link
sites work
First we will look at VE1PSR link site.
When the proper code is received it will connect port 1 to ports 2, 5 & 6
VHF
repeater
Main
Link
UHF
repeater
6M
repeater
VE1HNS
Link
VE1MHR
Link
ECHO
Link
Port 1
Port 2
Port 3
Port 4
Port 5
Port 6
Port 7
VE1PSR Controller
Note that
and66
Notice
thatport
port1 2isisconnected
connectedtotoports
ports2,55and
Notice the main link is Half Duplex
Main
Link
Controller path
VE1HNS
Link
While the VE1HNS link is Full Duplex
A signal coming in on the main link will be retransmitted out
to VE1HNS.
If a signal comes in from VE1HNS will cause the main link
radio to go into transmit and it will no longer receive.
Half Duplex
Main
Link
Full Duplex
Controller path
VE1HNS
Link
If you are listening on the main link you cannot reply until the
main link stops transmitting.
If you were to transmit on VE1HNS while the main link is
receiving, you will cause the main link to transmit and cut off the
incoming signal.
Remember - a Full Duplex link can receive while transmitting.
a Half Duplex link cannot receive and transmit at the same time.
DETAIL
Now we will look at some
general link sites.
VHF
repeater
VHF
repeater
Controller
Controller
Port 1
Port 1
Port 2
Port 3
Port 2
Port 3
Full Duplex
link
Full Duplex
link
Full Duplex
link
Full Duplex
link
This
Bothrepresents
sites have two
full duplex
link sites
links
in asosystem.
traffic
can flow in both directions at the same time
Note that the link ports are connected
This
together
is donebut
for the
technical
repeaters
reasons
are not
since
most users
connected
use a to
half
theduplex
links. radio.
There are 2 main technical advantages.
VHF
repeater
VHF
repeater
Controller
Controller
Port 1
Port 1
Port 2
Port 3
Port 2
Port 3
Full Duplex
link
Full Duplex
link
Full Duplex
link
Full Duplex
link
2. 1.
- the
time onwith
the alink
is much
- if turn
therearound
is a problem
stuck
less than or
if Half
Duplex
links
were
used.
transmitter
open
squelch
then
a signal
can be sent back down the system to turn
A quick example would be a set of links
off the offending radio.
using 5 link radios.
InThe
a half
duplex
system
lossover
of in
receive
Lets
number
say
each
of radio
link
radios
haswith
ainvolved
turn
from
a link
on the
radio
the
radio
should
be
transmit
our first
system
to receive
could
of 5th
200
be up
mstoand
25
or
it takes
more.
receive
in about 1000
ms.
100 ready
ms to to
bring
the transmitter
up to
power
Some will be full duplex some will be hub
Then
withduplex
a received
signal
on
theignore
5th
radio
In a
repeaters
full
andsystem
some
will
yoube
can
half
duplex.
the
the first to
radio
should
be around
up in full
transmit
in
receive
transmit
turn
time
and are
This is why it is recommended that you key
about
only concerned
with500
thems.
time it takes the
your microphone for about 2 seconds before
transmitters to come up to power.
Complete
turn around
is 1.5 seconds.
speaking
to allow
all the radios
to come up to
With a signal on thepower.
first receiver all 5 radios
should be up to power in about 500 ms.
The actual time lag is less than 2 seconds
User 1
VHF
repeater
User 3
Controller
Full Duplex
Half
link
Duplex link
HUB
REPEATER
Controller
Full Duplex link
VHF
repeater
User 2
User 1
VHF
repeater
User 3
Controller
Full Duplex
Half
link
Duplex link
HUB
REPEATER
Controller
Full Duplex link
VHF
repeater
User 2
QUESTIONS
ON ANY THING SO FAR
??????
SITE PHOTOS
Many of you may not have ever seen
a repeater site so here are some site
photos.
Springfield
NSIMRS Tower
Nuttby Aliant site
VE1OBN Site
VE1ESR
Other means of passing traffic
Some system repeaters have other types of links such as IRLP or
Echolink
IRLP is Internet Repeater Linking Project
This uses the internet as the voice and signal carrier between
repeaters. It is also accessed by DTMF signaling.
Echolink is another type of internet linking and may use either
radio or a computer - you are required to be a licensed Amateur
Radio Operator to gain access via a computer.
Both of these systems are world wide so as long as the internet is
working at a site that has this type of linking, you can pass a
message to any area of the province or world that also has this
type of link.
Other means of passing traffic
Some other types of messaging can be used in many areas.
There are VHF/UHF Packet systems existing in many parts of the
province. We are in the process of rebuilding and refurbishing
these networks. They fell out of general use but the emergency
applications are being recognized and utilization by emergency
agencies is increasing. Some of these systems exist in the
Provincial grid sites.
Packet is a slow form of the internet using radios and computers,
most traffic is passed using 1200 baud with some at 9600 baud
and a small portion at 19.2 K baud.
There is error checking and some encryption and depending on
how traffic is handled some messages cannot be read by
others listening on the same frequency.
Other means of passing traffic
A newer type of messaging is coming into emergency
communications use called Winlink or Packlink. These units are
more expensive but can be used without special training.
A Winlink station uses a standard e-mail program to send regular
e-mail messages. When you send an e-mail the system will first
try to use the internet, if unsuccessful or not available it will then
try VHF or UHF packet at 1200 or 9600 baud, If that is not
successful or unavailable it will then try to send the e-mail by
HF packet at 300 baud if HF is available to it. The radio
protocols used have very stringent error checking.
Of course it is recommended that the e-mail message be relatively
brief and not contain a huge attachment or large image. Having
said that a lot of text can be sent and small file attachments or
fairly small images can be sent.
A less expensive alternative will soon be available - Winmore
it does not have as robust error correction as Winlink.
Other means of passing traffic
Another means of passing a message is by HF radio. Many but not
all emergency agencies have this capability. HF radio can send
messages to isolated areas or out of an isolated area.
Once a message is passed to an isolated area then local
infrastructure can distribute the message to the proper
authorities.
If an area is isolated and can pass a message out of the area then
normal communications can distribute it.
Conclusion
In a scenario where normal means of communication are
disrupted, either overloaded or out of commission, the Amateur
Radio community has the capability to communicate into and
out of isolated areas by various means.
The Maritime Voice ( MAVCOM ) link system is the easiest way for
Amateur operators to pass message either as formal traffic
handling or tactical message handling.
The MAVCOM link system relies very heavily on our presence in
the Nova Scotia Provincial radio sites. A similar system is
supported by the provincial EMO in New Brunswick. PEI
currently relies mostly on Aliant and municipal sites through
MOU’s based on emergency communications.
The Amateur Radio systems and capabilities cover the Maritime
Provinces and beyond