============================================ A R R O W R E P E A T E R S ============================================= WHAT WE USED TO HAVE: -------------------------- W8KJ Kevin J. Martin 146.97 ( 97 -vs- 96 & 20Khz bandplan) N8BJX Rick Green 224.38 W8MNT Blake Arnold 443.5 ???? Hugh Aller 439.25 ATV (Line "A") W8MNT Blake Arnold 902 ATV WD8DPA Mark Trav. Packet Digi on 220 MHz Dabbled in: 6 meter 10 meter (w/UHF crosslink) 1296 Weather RADAR BTW - Each had their own TRUSTEE Each had a seat on the Board (outnumbered the elected BoD) Hence why we now have a "Trustee Delegate" WHAT WE HAVE NOW: -------------------------- 146.96 -600 WB8TKL 224.38 -1.6 (WAAM) W8PGW 443.5 +5 W8RP AREDN W8RP Why do we have repaters? What do they do for us? ----------------------------------------------------- **** The *WHOLE* idea is to have antennas HIGH IN THE AIR (period!) -- THAT is how a repeater gives good coverage in the LOS bands -- But we are rarely LOS, so we depend upon 'reflections' -- MULTIPATH - Some relections arrive at the repeater 180 degrees out of phase because of different path lengths o Move your car 1/2 wavelength to go from solid to noisy The BASIC Repeater: -- In 1970's we BUILT repeaters from scratch Nothing was store bought / Plug-N-Play / Built with checkbook CONTROLLER was hard-wired LOGIC and/or RELAYS (Dana Whitlow built 2m controller discreate IC's) CPU's didn't exist - affordably... -- Sure, just hook a RX and a TX back to back. Uhhh.... NO !!! -- We need a COR How does SQUELCH work? TERM -- "Full Quieting" on FM Sample audio from DISC Hi-Pass filter - hi freq component of noise DC switch - set bias w/SQUELCH control So now we can key up the TX And that TX *MUST* handle 100% duty cycle !!! ...but wait! We need a HANG TIMER (3 to 6 seconds) (smack TX up/down) We need a TOT (3 minutes typical) FAILSAFE SHUTDOWN 1) TOT 2) Control Phone Line -or- over air command We should have a COURTESY BEEP (1 to 2 seconds) o Why a Courtesy Beep??? Also indicates reset of the TOT ...but wait! We need to ID the transmitter - Every 10 minutes (Part 97) - Usually done in CW, but can be done in Voice (digital "in mode") - No faster than 20wpm (but slower is nice for some) - But when? o Rules say WITHIN first 10 mins (220 rptr) o We prefer ID on first keyup (146 rptr) o DMR / D-Star / Packet Digi done "In Mode" ...but wait! So how DOES the audio get from RX to TX? - 3db rolloff per octave called PRE-EMPHASUS and DE-EMPHASUS for better FM modulation (not needed nor desired in RPTR) - Too tinny and the "old timers" can't hear it - Too bassy and the the audio sounds too muffled especially in noisy evironments such as in cars -- Hamtronics audio sucked! Tom Brey WB8COX designed Op-Amp audio shaping (FSA and COX each wired them up for 2m & 70cm) o Take audio from DISCRIMINATOR and pass to VARACTOR with some audio processing. Must also inject Courtsy beep and ID into audio stream. -- Motorola MSR2000 audio is conditioned for best performance for First Reponders (noise, sirens, fire engine pumps, etc.) -- We want "crisp audio" (96 has audible 'buzz' that is CPU noise) -- Fully deviated +-5KHz without clipping ...but wait! What about the RF? What about Interference between TX and RX? !!!!!!!!!!!!!! -- Front end saturation o Worse w/today's WIDEBAND receivers Commercial RPTRS have Tuned Front End B4 1st Mixer Helical Coil front end o No wiggle room to detect the desired signal o This is called "desense" because we have DESENSITIZED the receivers ability to discern a weak signal in the presence of a strong signal BASICALLY... Cavities to notch out TX energy - NOTCH out 146.96 from reaching the 36 receiver - PASS only 146.36 to the Receiver *** It's a whole presentation unto itself *** - >80 db ISOLATION is desired (82 db for a 25 Watt TX) - Usually about 1.5 to 3 db INSERTION LOSS on the RX cans ...but wait! What about *other* transmitters on the site getting into the RX? Rooftops and Towers are covered with TRANSMITTERS Paging, 154.25 fire dispatch, WTWR 98.3, WQKL 107.1 Use CAVITIES (a.k.a. "cans") to filter signals - Cavities to "pass" only the receive frequency (all other signals are outside the "passband") - $$ EXPENSIVE $$ high-Q filter - $$ CHEAP $$ 1/4-wave shorted stubb ...but wait! Can we combine the TX/RX onto one antenna? - PASS the TX freq on the TX string of cans - NOTCH the TX freq on the RX string of cans - Jumpers between cans are 1/8 or 1/4 of the *opposite* freq PROBLEMS: o Desense / Front End overload o Mixing products / Every diode/rust junction is a MIXER o IMD <--------------- !!!!!!! o Site noise / Motors / Lights (CFL at Chelsea) o Line loss o Insertion loss o LAND LORDS!!! Tower Plaza $400/month per repeater ($1200/mo) WTWR gave access in exchange for property maint. WVMO gave access in exchange for Weather RTTY !!! Don't abuse the relationship !!! COORDINATION BODIES: ============================ M.A.R.C. -- Michigan Area Repeater Council o Coordinates for lowest interference o Coord 6-meters up through 1.2 GHz o Band plan for LINKS and Packet o Keeps record of UHF links between repeaters o 2-meter 150-mile seperation o Work with neighboting State coordination bodies o QUADRANTS around the State o PL coordinated by Quadrants o We submit a TDS Report every 2 years to maintain our coord o 2M and 70cm are FULL!!! 220 *may* have openings + Uncoordinated like 5.15 get *NO* protections + FCC backs the Repeater Councils above uncoord. + 96 72 15 16 23 88 45 (Michigan does not use 5Khz) (no duplication across 144. 145, 146 segments) HELIAX PROJECT: ========================== The long awaited "Heliax Project": o Installed 8-bay 440 folded dipoles on 2-meter mast and found a damaged LMR400 line. FULL of water! Other lines suspected bad (2-meter IMD issues after rain) o W8RUR sold ARROW Heliax supply o Made up bundle of FIVE runs of 1/2" Heliax w/new conns o COULD NOT get reply from Radio Shop point of contact :( o AC8TO discovered why and paved the way to a new relationship o July 18th - 8 volunteers - 8-1/2 hours -- PICTURES!!!