ARRL Affiliated
WPA Section

Mt. Davis, PA - Packet Radio Project

The following text and pictures were provided by Jim - NJ3T.

In June of 1998, Somerset County was hit by several tornados in a 3 day period. One such tornado practically leveled the town of Salisbury which is located in a valley in the southern most area of the county. Ham Radio volunteer operators were scrambled to assist in creating an Emergency Operations Center in Salisbury and maintain communications between the Salisbury E.O.C. and the Somerset Co. Emergency Management E.O.C. located in the north-central area of the county. The Red Cross was assisted in opening and maintaining communications at a shelter in Salisbury also.

Since Somerset County is mountainous various 2m and 440 mhz repeaters were used. Some of which were linked together for maximum coverage. When the Red Cross center in Johnstown, PA requested a packet radio station at the shelter in Salisbury to handle their traffic, we found that our local (LAN) packet node would not cover the Salisbury area and even though repeaters were strategically designated to aleve congestion, traffic had to be passed over a already congested system. As R.A.C.E.S. Radio Officer for our county I decided to develop a plan to enhance the packet radio systems coverage. After submitting a proposal to our county Emergency Management Agency and the Somerset County Amateur Radio Club the Mt. Davis Packet Radio Project was approved.

In the next few pages I hope to pass on my experiences related to this project. Also I would like to tell of the kind volunteers that helped with the project. I have tried to document the assembly of the system pictorially to assist me in describing the system, since my writing talents are limited. "A PICTURE IS WORTH A THOUSAND WORDS" a wise person once said. I hope you enjoy this short story as much as I have creating it.

PURPOSE
Our packet radio system consisted of a BBS (K3SMT:SMTBBS) with a 2m Node Port for users and a 220 mhz port for BBS to BBS forwarding located on a hill near the city of Somerset in the North Central area of the county. A EMA/RACES station located in the EMA office's EOC (N3VFG) runs a mail drop program for RACES messages. Both are on the frequency of 145.03 mhz. Users in the southern part of the county have marginal access to the BBS and can only connect to the RACES mail drop via the BBS's node port (K3SMT-3:SMST). On 220 mhz, BBS to BBS forwarding "backbone" system performance was good to/from the west but not so good to/from the south.

It was decided that the Mt. Davis project would consist of a 2m node on 145.03 mhz and a 220mhz node. Both would prove vital for enhancement of the overall network. Keeping the future in mind, a triband vertical and triplexer was included in the plans in case a node was needed in the 440 mhz band.


LOCATION

Mount Davis is the highest mountain in the state of Pennsylvania. It's elevation is 3313' ASL at its highest point which is located in a state park area. A lookout tower is situated near a plaque marking the highest point.. A few hundred yards (as the crow flies) across the top of the mountain from this point is where one of the counties 911 emergency operations towers exist. After studying a topo map and with permission from the counties E.M.A. director, Richard Lohr (N3VFG) my proposal included the use of this sites building and tower for the project.

EQUIPMENT

After conferring with numerous hams about the project it was determined that we needed a little more than the basic stuff needed for a node. Mainly due to the fact that it was sharing a building that housed professionally installed commercial emergency communications equipment that was installed to certain specifications ( it looked neat too !). It was decided that we needed a cabinet to mount the equipment needed for the nodes. Two vhf transceivers were needed along with two TNC's. A power supply heavy enough to handle three transceivers also would be needed. A triband vertical would also be installed on the tower and 1/2", 50 ohm hard-line would be used.

RESOURCES

After approaching the members of our local radio club with the idea an inventory of items was presented as available for the project. Some items were owned by the club, some by members themselves, and some would need to be purchased. The club owned a IC3AT HT and a small 25 watt rf amplifier. A member of the club had a GE Master II already crystalled for 145.030. It needed minor repair to the t/r relay circuit. He also had a MFJ1270 TNC. Things were looking up!

THE BOTTOM LINE !

After the antenna and hard-line was installed, it was decided to put the system together in my basement. A cabinet was purchased from Baer's Electronics (local Motorola dealer). It was a used cabinet and housed a cannibalized uhf repeater. After removing everything from inside and slopping the ole "Super Clean" to it I found I had a cabinet fit for the system.

Some Plexiglas covered the hole where the original control panel was fastened. Barry, N3XDZ came up with some 19" rack shelves that were rusted badly. A wire wheel in the drill press proved useful. A hand brush and sandpaper finished the rust removal. Some "X-O RUST" chrome paint helped too. I am not sure what these were originally manufactured for but they sure did come in handy for mounting the equipment to. You can see the "BEFORE and AFTER" above.

Small angle brackets were used to mount the GE to the 19" rack. This allows air to flow between the radio housing and the rack.

One rack shelf was used to hold the 220 mHz HT, Amp, and TNC. The Triplexer is partially in view to the left. The white rg8x line was attached to a dummy load for testing the nodes. --->>>

Amp not shown........

Summary: Both TNC's are MFJ 1270b's. The 2m node TNC is using x1j4 and has the MFJ 52b board in it which enables the indoor temperature sensor and the received signals Deviation/S-meter option, (I am still working on that). We have the temp. sensor reading and Deviation readings but I believe some kind of a s-meter driver circuit needs to be interfaced with the board. Did anyone ever get all the x1j4 / mfj-52b options working properly ??

The GE Master II was set at appx. 40 watts output. The IC3AT and Amp is measured at appx. 25 watts output. All transmit audio levels were set as close to 3.2kc dev. as possible. Both transceivers were bench tested and aligned before installation.

All DC lines were fused accordingly. The AC switch/fuse box used a 10 amp fast acting fuse.
The systems ID callsign was KB3BOD which was the SCARC call. Since then the club received a vanity callsign, K3SMT. Both nodes cover a wide area. Our goal of covering the southern parts of our county was met. A successful project !

MAP 1996

SMTBBS:K3SMT
MTD3:K3SMT-5 <------------> SMST:K3SMT-3 <----------------> JAIR:N3LZX-3
WVLINE :N2OCW-3 ---> MTD22:KC3XD-2 <----> SMTBBS (BACKBONE) <----> 03BBS:KA3JSD
/ \
N2OCW BBS N8YIB BBS
SMTBBS AND SMST ARE MSYS BBS/NODES LOCATED 3 MILES EAST OF SOMERSET PA.

MTD3 IS LOCATED ON MT.DAVIS, APPX 30 MILES SOUTH OF SOMERSET PA.

JAIR IS LOCATED NEAR THE JOHNSTOWN PA AIRPORT APPX 35 MILES NORTH OF SOMERSET PA.

MTD22 IS THE 220 MHZ BACKBONE NODE LOCATED AT MT.DAVIS. SMTBBS FORWARDS AND RECEIVES TRAFFIC FROM THE K8LG BBS IN NORTHERN WVA AND THE KA3OSC BBS BBS IN WESTERN PA.


MAP 2001
SMTBBS:K3SMT
MTD3:K3SMT-5 <------------> SMST:K3SMT-3 <----------------> JAIR:N3LZX-3
K8LG ---> MTD22:KC3XD-2 <----> SMTBBS (BACKBONE) <----> KA3OSC



MAP 2002
SMTBBS:K3SMT
MTD3:K3SMT-5 <------------> SMST:K3SMT-3 <----------------> JAIR:N3LZX-3
K8LG ---> MTD22:KC3XD-2 <----> SMTBBS (BACKBONE)

WE HOPE TO FIND ANOTHER BBS THAT IS WILLING TO FORWARD/RECEIVE TRAFFIC WITH US THROUGH MTD22 (223.66mhz) OR A 440MHZ NODE AT MT.DAVIS.

I want to take the time to tell you of all those who made this possible.

Rick, N3VFG The Somerset County EMA/911 Center Director for making this possible.

The Somerset County Commissioners.

Kevin, W3KKC for advice and expertise. Building and installing a standoff for the antenna. Installing the antenna and hard-line. "You would'nt catch me 10 feet up a tower let alone 160 feet !" TNX again Kevin ! Check out Kevin's Web pages for advice on building repeaters. http://www.kuggie.com/rbtip/

Sherm, KC3XD for donating his GE Master II and MFJ 1270b w/eprom for x1j4 and providing other eproms for x1j4 and TN208.

Brian, N3LZV and Barry, N3XDZ for advice, legwork, and help with installing the system at the site. Also for researching the site coverage after installation.

Joe, N3IAT for bench testing and aligning the transceivers, setting audio levels, etc.

Fred Baer (Baers electronics). Motorola dealer in the Somerset area.

Mark, KE3BE for the advice. Take a look at the spectrum analyzer !

The Somerset County Amateur Radio Club and all of it's members. Check out the clubs home pages.

Dave, KA3JSD for burning the eproms. Dave is sysop to the 03BBS in Mt. Pleasant, PA. Dave has always been there through "thick and thin" for our clubs bbs. Thanks Dave for the traffic ! Check out Dave's web pages for the Mt.Pleasant Amateur Radio Society. ~http://www.westol.com/~drath/ka3jsd.html

Larry, N2OCW and Ron, N8YIB for the advice and putting up with our experiments. Thanks for the traffic guys !

My family for putting up with the mess for a month !

Jim - NJ3T

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SOMERSET COUNTY AMATEUR RADIO CLUB, INC.
P. O. BOX 1241
SOMERSET, PA 15501

S.C.A.R.C. is a non-profit 501(c)(3) organization.