VoIP/IRLP Experiment Presentation
12 April 2003
Steve Hajducek, N2CKH
This presentation details how OMARC will provide access via the
145.110Mhz club repeater system to Internet based Voice over
Internet Protocol (VoIP). Specifically, the Internet Radio Linking
Project (IRLP) VoIP system will be utilized.
The method of providing VoIP using IRLP as detailed herein to the
users of the OMARC 145.110 repeater system on an experimental
basis is the simplest way possible to allow the membership to
experience the mode and to make their decision as to whether the
club should move forward to provide the capability on regular
This presentation will also detail how full, automated access could
be provided in the future, that would allow each member full
command and control of the IRLP should the club decide to
implement such a capability.
The idea is to allow for access to VoIP as easily and inexpensively
as possible on an experimental basis. To begin with, VoIP systems
have been around for a number of years now, KB2OPQ first
suggested that we implement such a system in OMARC many
years ago when the ARRL published the very first article on the
Since then the growth of various VoIP systems has been explosive,
so has the reception of VoIP within the hobby. There is however
both an open and the close mind attitude toward accepting new
technology within the hobby, which seems to be very close in both
camps as the recent ARRL poll results recently conducted on-line
and seen below indicate.
As you can see from the results of the ARRL survey, the two
current systems that are the most popular are EchoLink and IRLP.
The ARRL also published an article in the February 2003 QST
beginning on page 44 titled “VoIP and Amateur Radio” that details
the various VoIP systems currently in use. All of the systems are
similar in that they utilize VoIP, however there are big differences
between some of them.
In particular it is only IRLP that requires a radio on both ends of
the link, Echolink and the others allow for PC to PC and PC to
Radio, which the FCC frowns on. In addition only IRLP provides a
512 bit Pretty Good Protection (PGP) authentication algorithm so
prevent hacking into the system. Basically IRLP is as close as it
comes to traditional forms of RF, Land Line and Satellite linking
without the added costs and with the benefit of wider area
Regarding those recent ARRL survey statistics, looking at the
chart, you can also see that of those that responded to the survey of
which 5,774 did, 44.0% used a form of VoIP, with EchoLink and
IRLP almost tied, whereas 38.1% have a closed mind attitude !
Then 3.4% did not even know what it was and 14.4% have not
tried it, that can probably be attributed to the fact that they had no
access to try it out, only guessing though.
From the ARRL survey if one wants to draw any conclusions that
one could say represents the general attitude of the Amateur
community, which I really do not think polls can do, there would
seem to be an almost 50/50 split of open and closed minded
We have of course seen this attitude regarding AM vs. CW, SSB
vs. AM, FM repeaters vs. FM Simplex, Incentive Licensing, No-
Code Licensing etc. for years, many just don’t embrace change. In
my opinion (we all have one) we need to take steps that welcome
change to continue to evolve and exist, not to mention attract the
youth into the hobby, and VoIP is a very effective tool to
accomplish those goals.
At present there are nearly 900 IRLP nodes worldwide in 30
countries and there are 17 reflectors, each with ten (10) channels
for an effective total of 170 reflector channels.
9070 Alaska Reflector
9100 Toronto Reflector
9250 Western Reflector - Las Vegas
9300 Saskatoon Reflector
9350 Los Angeles
9400 Quebec City - GSM Only
9500 Sydney - Virtual PUB
9610 St. John's - GSM Only
9730 Indiana Regional
9800 Scandinavian Reflector
All Reflectors now have 10 channels as follows for 9200:
9200 will call primary channel
9201 will call channel 1
9202 will call channel 2
9203 will call channel 3
9204 will call channel 4
9205 will call channel 5
9206 will call channel 6
9207 will call channel 7
9208 will call channel 8
9209 will call channel 9
N2MO EXPERIMENT DETAILS:
As detailed in figure 1 below, an RF link to IRLP node 4040
located at the Lakewood hub of N2CKH will be provided as an in-
band RF link to the 145.110 repeater system using a modified GE
Phoenix transceiver as the link radio. This requires no radio
equipment or antenna installation at the 145.110 repeater site.
The easiest way to envision this is just think of the IRLP node as a
“regular user” of the repeater. The difference being that this
“regular user” will be a radio attached to the Linux based IRLP
server computer sending the audio feed of one or more other
repeaters linked in via IRLP world wide into the OMARC repeater
and taking what is being transmitted by local users of 145.110 and
re-transmitting that audio world wide to all systems linked in via
As an ARRL Auxiliary Official Observer I can guarantee everyone
that the method of in-band linking with the control operator
(myself or KC2KQG) at the Link Radio and IRLP server point of
control is 100 percent legal regarding FCC Part 97 requirements.
Both FCC Part 97 and the previously mentioned article in the
February 2003 QST beginning on page 44 titled “VoIP and
Amateur Radio” can be referenced as well. As long as a control
operator is present at the link radio at all times and is the only party
to have command and control it is legal.
HOW IT WILL WORK:
The premise of this connection to IRLP during the experimental
basis is simple, the control operator at the Link Radio will on a
weekly basis (Friday and Saturday nights between 8:00-10:00pm)
on schedule, will announce over the repeater what is going to take
place and allow anyone that desires the immediate use of the
machine to do so.
Then the control operator will place the OMARC 145.110 repeater
into an IRLP mode via DTMF signaling.
Then at the IRLP control point, the control operator will establish a
connection to the repeater with one of the IRLP Reflectors or
perhaps node to node for about two hours. During this time the
IRLP connection may be changed due to activity or lack of it as
During the IRLP connection, activity taking place on the particular
IRLP node connection will be retransmitted over our 145.110
machine and anyone locally can part take in the worldwide IRLP
hook up with the output of 145.110 being re-transmitted over IRLP
minus locally generated ID’s and brag messages.
Should anything take place either remote via the IRLP or locally on 145.110 that
would require intervention of the control operator, the link can immediately be
terminated via the keyboard of the IRLP Linux server PC by a single keystroke.
The Link Radio will have its own 3-minute timeout timer, this goes
beyond FCC Part 97 in this case. Also, during the course of each
such IRLP session via the club 145.110 repeater, the Link Radio
will also periodically ID in CW each 10 minutes during operation,
the callsign used will be N2CKH which will be re-transmitted
On the 145.110 repeater end, KC2CNB and N2CKH have already
discussed the needed configuration of the club repeater for this
experiment. During an IRLP session the hang time on the repeater
transmitter will be set extremely short and most or all of the brag
messages will be turned off. Perhaps a Special “IRLP Mode
Active” message along with the FCC required 20 WPM CW ID
will be active. This change over in the repeaters personality will
take place when control operator at the Link Radio places the
145.110 via DTMF tones into a pre-programmed IRLP mode.
After the IRLP session, the repeater will be placed back into
normal operating mode and personality.
145.110 HARDWARE CHANGES:
The only hardware changes needed at the 145.110 repeater for this
IRLP experimental capability is to configure the PL on the club
repeater transmitter to not be present when the repeater sends its
CW ID and any recorded messages (all of the recorded messages
must be redone to filter out PL tone content in the recordings).
The easiest and basically only way to do this with our current
controllers is to configure a hardwired mode that enables the PL
when ONLY when receiving a signal with PL content as the
repeater controllers do NOT support a programmable drop of PL
during periods of ID. This means simply that any user of the
145.110 repeater that is operating full CTCSS encode/decode will
hear all the activity except for the CW ID and brag messages.
Basically this is how the machine has behaved during the winter
when we pull encode off the transmitter to prevent our seasonal
desense problem, with the exception that brag message bleed
through as they have PL content recorded. We will also
configuring the long overdue sub-audible tone filter to strip off all
tone content from the receiver to the transmitter beyond the COR.
FUTURE OF IRLP ON 145.110:
What follows are the details of what can be implemented should
the membership make the decision to interface the club 145.110
repeater on a linked basis where the membership can then, on
demand, acting as the control operator, be able to bring up and
control the IRLP system themselves as desired for VoIP QSO’s
with their on-the-fly choice(s) of IRLP node connection.
Figure 2 above, details in full, the N2CKH/R planned hub in
Lakewood. In the framework of this scheme, the OMARC 145.110
repeater would be “Linked Repeater’s” at about 9 o’clock in the
The RF link would be provided over a dedicated half or full duplex
UHF link radio transceiver system donated to OMARC by N2CKH
to include the required tuned radio and directional antenna along
with feedline of his choosing.
In addition, the link radio pair would be coordinated by OMARC
via MetroCor for use with the N2CKH/R hub, which is
coordinated by ARCC Inc. With a full duplex radio, more control
is available, as is more equipment (UHF duplexer and cables) and
thus more complication. The benefit of full duplex would be two-
way control via the network, that is if the repeater controller at the
OMARC site supported such, which at present, it does not.
When this system is fully implemented, all of the features of the
N2CKH/R hub would be available via the OMARC 145.110
repeater, to include connection to other central NJ repeaters that
may be linked onto the hub, IRLP and NWS S.A.M.E. severe
(Note: The S.A.M.E. WX alerting system offered for donation to OMARC by
N2CKH at the 145.110 repeater site would be automatically disabled during liked
sessions due to redundancy.)
With the OMARC 145.110 repeater linked via UHF using the
repeater controller linking radio port, any OMARC member using
DTMF codes would be able to enable or disable the UHF link
radio port and once linked to the hub, would be able to
communicate with any system already on the linking hub, to
include directly making and breaking an IRLP connection if an
IRLP connection was not already active.
In figure 3 above, the details of just the N2CKH/R UHF omni-
directional linking hub as coordinated by ARCC can be seen. All
of the co-hosted repeaters at the Lakewood hub and the UHF
linking repeater will float on the Pacific Research repeater
controller bus as all of the co-hosted repeaters will use the same
make of controller. The AERIALS 443 repeater will also use a
Pacific Research (PR) controller. This will allow any user of the
network, from any point of access to issue common command and
control codes across the network machines using the PR
controllers. This would include the OMARC repeater should it
ever be upgraded to a PR controller. The OMARC control
operators would of course be provided with all the needed hub
control codes, many of the current OMARC control operators are
already control operators for the Lakewood hub and AERIALS.
In addition, all of the N2CKH/R and AERIALS repeaters will
support a mix of PL (CTCSS) and DPL (DCS) codes for various
command and control and user access features, this is already true
of the N2CKH/R 224.120 and 447.925 repeaters, which are the
only repeaters in the area to support DPL.
In figure 4 above, the lower right hand side of the figure depicts
the OMARC 145.110 repeater with the local S.A.M.E. system
integrated. The far left side of the figure depicts the N2CKH/R
linking hub in Lakewood and the center depicts any other 3rd party
repeaters that may be linked into the hub, such as the AERIALS
443 repeater and planned non-Lakewood N2CKH/R repeaters etc.
In figure 5 above, the entire N2CKH/R hub and all co-hosted
repeaters and 6m-satellite receiver system at the Lakewood hub are
represented. The lower right hand block represents the off site
linked systems. The system also features a single point of access to
a telephone line for 911 access on the RI-300 controller the
N2CKH/R 2m repeater is depicted on, that 911 access can be made
via any point of access to the system just as any other resource,
thus via an off site repeater such as the AERIALS 443 machine,
when on the hub could make a 911 autopatch. It is the needed new
RI-400 controllers that have been delayed which has slowed the
progress in completing the hub as detailed herein.
The system supports two IRLP nodes (4040 and 7280) with one
which will always on the linking hub for any local co-hosted or
remote system to utilize.
The two IRLP nodes at the hub can be bridged via the PR
controller back plane for special applications, such as bridging two
IRLP reflectors together. The system is extensible to add additional
local PR controllers and repeaters or more IRLP nodes or link
radios to bridge into other RF networks that can’t access the UHF
hub repeater for whatever reason. There is no limitation to the
number of remote systems that can be linked into the hub.
By the way, the UHF full duplex hub repeater is a 430/435Mhz
split and it is coordinated for use of an omni-directional antenna,
all remote linking radios coming into the hub must use directional
antenna and be cross coordinated with ARCC as the hub is based
in ARCC territory in Lakewood, Ocean County.
The entire hub can be controlled remotely via UHF control
receiver, via telephone line, via SSH secure shell over the internet
or any local repeater input or remote repeater linked into the hub.