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Tracy
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SJC EMCOMM Freqs
SJC1 - 147.210 + 114.8 Stockton (Stockton Pri)
SJC2 - 146.655 - 100.0 Tracy (County Pri)
SJC3 - 145.210 - 100.0 Tracy (County B/up)
SJC4 - 147.090 + 114.8 Lodi (North Pri)
SJC5 - 146.985 - 100.0 Manteca
SJC6 - 147.165 + 107.2 Stockton Club
SJC7 - 147.015 + 114.8 (East)
SJC8 - 147.105 + 67.0 Stockton
SJC9 - 146.895 - 114.8 Mt. Oso
SJC10 - 444.400 + 114.8 (East)
SJC11 - 444.325 + 94.8 Stockton (Stockton Pri)
SJC12 - 443.825 + 107.2 Mt. Oso
SJC13 - 444.575 + 107.2 Stockton (Pri)
SCJ14 - 444.850 + 114.8 Tracy (testing)
SJC15 - 444.500 + 114.8 Stockton
LLNL - 146.775 - 100.0 Livermore


Linked repeaters - SJC1/10 SJC2/LLNL SJC7/10

Tac1 - 146.550
Tac3 - 146.535
Tac4 - 146.430
Tac6 - 156.565
Tac7 - 146.590
Tac8 - 146.445
All simplex
2014 Frequency Plan
Disclaimer

Opinions expressed are my own. I hope they are useful, but policies and procedures vary widely from one location and group to another.

What I describe may not work for you and may even be unsafe. Always follow your local policies and procedures!

Also, unless specifically mentioned, this site is about VHF/UHF operations and not HF, which is very often different for very good reasons.

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N5FDL/CEVOL Repeaters

All PL 114.8 Unless Noted

Stockton: 147.210 + N5FDL and 444.500 + K6TRK (linked)

Copperopolis/Gopher Ridge: 147.015 + and 444.400 + N5FDL (linked)

Mt. Oso: 146.895 - N5FDL and 443.825 + PL 107.2

Affiliated Repeaters

Bear Mtn.: 146.090 + and 444.250 + WB6ASU (linked)

Mt. Delux: 145.210 - PL 100.0 WA6SEK (10mi S of Tracy)

All repeaters are open to all users.

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Sunday
Mar102013

A Morning of APRS EMCOMM Fun in Tracy

N6TCE’s portable digipeaterOn Saturday, Bob N6TCY, Brian N6ZZY and myself spent the morning driving around Tracy and San Joaquin county testing APRS coverage from our portable digipeaters and an iGate. This is a report on what we think we accomplished and how we plan to proceed. In an emergency, this is the type of installation we plan to use.

Vague map for coverage — click for larger imageWe were doing the testing on the NCPA alternate APRS channel, 144.410, using our own digipeaters and iGate, set up just for the test.

APRS, for new hams, is a system for transmitting location and other information over Amateur Radio. Digipeaters — sort of digital repeaters — are to APRS the same range-extenders that analog repeaters are to voice transmissions. iGates receive packets and post them to the Internet.

One of the digis was a Kenwood TH-D72 talkie, attached to a small beam, located at the same site as the 146.655 repeater. This is a location at about 1,800 feet (as I remember) in the Altamont Hills. The beam points toward Stockton, so it is aimed a bit north of Tracy.

Portable digipeater — FT-1500, KPC3+ and a batteryThe mobile digi was a Yaesu FT-1500, Kantronics KPC3+, battery-powered and connected to an Arrow Antenna j-pole at about 25 feet. Bob located this digi in South Tracy, along I-580, with a commanding view of the valley. (About 300 feet in elevation).

The iGate was located at Brian’s house in Tracy, and gatewayed our RF location reports into the APRS Internet data feed. It was not be apparent to Internet users that we were not on 144.390, the national APRS channel.

Once the infrastructure was set-up, Brian and I drove around using at least two APRS radios at all times. His was a Yaesu VX-8 talkie connected to an external antenna. I used an old Kenwood TH-D7A talkie, connected to a quarter-wave mag mount antenna. We both also had Yaesu FTM-350 mobile radios shooting packets at full-power.

We are still looking over the packet logs to see what was heard by which digi from where, so that will be the subject of an update in the future.

N6ZZY and N6TCE adjust radios in the jeepHere is what we think we learned:

1. A handful of users (in this case, four radios and two digis) can create an awful lot of traffic if frequent location fixes are required.

2. The iGate, connected to an outdoor antenna on Brian’s two-story house, worked great and did a fine job of making our position reports available to Internet APRS clients. It was nice to have the iGate beacon occasionally so we knew we could hear it.

3. We had a few reports from the Internet seemingly leak through the iGate and get transmitted on RF. Need to understand why that happened, but it was not a severe problem.

4. Having two digipeaters definitely improved our range, but we have to figure out which worked best where. It appears that within 8-10 miles, the local digi on I-580 picked up most of the packets, with the Altamont digi picking us up from as far as 25 miles on 5 watts.

5. We realized that none of us know as much about APRS or the settings on our radios to be really comfortable doing an exercise like this, but it was a start. Please be gentle in your comments.

6. Thank you, Northern California Packet Association, for creating the “alternate” APRS channel intended for situations where users need a quiet channel and are willing to bring their own infrastructure to get it. It is hoped that any use of the channel will be temporary in nature and permanent infrastructure will be limited. We don’t need another mess like 144.390.

We feel like we proved that the current configuration (two digis, one iGate) will work well across the Tracy area. Log analysis will tell us how well the I-580 digi worked with 5-watt signals (out to what distance?). The iGate did a good job of making us appear on Internet clients.

Speaking of which, if you have a smartphone and intact data network, apps like OpenAPRS (iOS) and APRSdroid (Android) are probably better ways to get your packets into the Internet feed than RF. However, packets sent over the Internet are generally only visible on other Internet clients. Your mobile radio operators will never see the packets generated by the smartphones. It also means that net control and others must use APRS apps and an Internet connection to see everyone’s location.

Depending on the circumstances, that may or may not pose a problem. More in a future post as we learn more.

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