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HP2DFA > TECH 15.10.26 16:11l 70 Lines 3764 Bytes #999 (0) @ WW
BID : 4544_HP2DFA
Subj: AEA PK-88 TNC HARDWARE MODIFICATIONS FOR APRS DIGIPEATERS
Path: DB0FHN<OE2XZR<OK1TOR<SR6DWH<SR1BSZ<EA2RCF<LU9DCE<K1AJD<VE3CGR<DM4RW<
HP2DFA
Sent: 261015/1404Z 4544@HP2DFA.#COL.PAN.CEAM BPQ6.0.24
AEA PK-88 TNC HARDWARE MODIFICATIONS AND FIELD HARDENING FOR APRS NODES
TECHNICAL AND PACKET/APRS INFRASTRUCTURE BULLETIN
SOURCE: SOFIA RICCI / SALINAS VALLEY REPEATER GROUP
VALID: 15-OCT-2026 ONWARDS
ISSUED VIA BPQ32 NODE HP2DFA-5 IN PANAMA
======================================================================
1. PROJECT OVERVIEW AND BACKGROUND
======================================================================
THE SALINAS VALLEY REPEATER GROUP (NORTHERN CALIFORNIA) HAS STANDARDIZED
ON VINTAGE AEA PK-88 TNC UNITS FOR MOUNTAINTOP APRS DIGIPEATER AND IGATE
BUILDOUTS (144.390 MHZ / APRS-IS). DESPITE EXCELLENT AM7910 BELL 202 MODEM
PERFORMANCE AND STURDY Z80 ARCHITECTURE, VINTAGE HARDWARE REQUIRES SPECIFIC
UPGRADES TO ENSURE LONG-TERM RELIABILITY AT UNATTENDED RADIO SITES.
======================================================================
2. BASELINE JUMPER CONFIGURATION
======================================================================
- JP1 & JP2 : LEAVE FACTORY DEFAULT (32 KB SRAM MEMORY MAPPING).
- JP3 : SET BETWEEN MIDDLE AND REAR PINS (KISS MODE OPERATION;
BYPASSES INTERNAL AX.25 STACK).
- JP4 : SET BETWEEN MIDDLE AND FRONT PINS (ROUTES INTERNAL AM7910
AFSK MODEM TO RADIO INTERFACE).
- JP5 : SET BETWEEN MIDDLE AND LEFT PINS (ACTIVE-LOW PTT FOR MOTOROLA
AND STANDARD COMMERCIAL RADIOS).
- JP6 : INSTALLED (CONNECTS BATTERY BACKUP TO 5BB RAIL FOR KISS MODE
PERSISTENCE ACROSS POWER CYCLES).
- JP7 : SET BETWEEN MIDDLE AND RIGHT PINS (SCC INTERRUPT ROUTING).
- JP8 & JP9 : LEAVE OPEN (SOLDER JUMPERS FOR DSR LOOPBACK AND SQUELCH).
- FIELD MODS: REMOVE ANY COMMON FIELD JUMPERS BETWEEN R5 AND R7 (RTS/DSR).
======================================================================
3. FIRMWARE REBURN AND BITROT MITIGATION
======================================================================
- EPROM REPLACEMENT: REPLACEMENT OF 30 YEAR OLD CHIPS WITH FRESHLY BURNED
VERSION E1744 (DATED AUGUST 23, 1991) PROMS.
- CHECKSUM VERIFICATION: ENSURES BOOT CHECKSUM PASSES WITHOUT SILENT BITROT
ERRORS OCCURRING OVER EXTENDED DEPLOYMENTS.
======================================================================
4. SUPERCAPACITOR REPLACEMENT FOR LITHIUM COIN CELL
======================================================================
- BATTERY REMOVAL: REMOVES THE SOLDERED-IN LITHIUM COIN CELL TO PREVENT
LEAKAGE AND DEGRADATION.
- SUPERCAP INSTALLATION: INSTALLS A 5.5V SUPERCAPACITOR (0.2 F TO 1.5 F).
- TRICKLE CHARGE CIRCUIT: PIGGYBACKS A 1K TO 10K RESISTOR OVER DIODE D7 TO
ENABLE TRICKLE CHARGING ON THE 5BB RAIL FROM MAIN DC POWER.
======================================================================
5. LM7805 BUCK CONVERTER UPGRADE
======================================================================
- THERMAL IMPROVEMENT: REPLACES THE HOT LINEAR LM7805 REGULATOR WITH A HIGH-
EFFICIENCY SWITCH-MODE BUCK CONVERTER MODULE.
- VOLTAGE OFFSET ADJUSTMENT: ADJUSTS MODULE OUTPUT TO 5.6V - 5.7V TO
COMPENSATE FOR DIODE DROPS (D5/D6). DIODE D4 IS REPLACED WITH A JUMPER WIRE,
AND FEEDBACK RESISTORS ARE MODIFIED OR FIXED WITH A DABB OF GLUE ON POTS.
======================================================================
6. DIRECT DC POWER OVER RADIO CABLE (P2.P4)
======================================================================
- ELIMINATING BARREL JACKS: FEEDS 12V DC DIRECTLY FROM MOTOROLA 16-PIN
ACCESSORY CONNECTORS TO PIN 4 OF THE PK-88 RADIO INTERFACE CONNECTOR.
- IN-RUSH LIMITING: PLACES A 1.5 OHM 1W RESISTOR IN-LINE ON PIN 4 TO PREVENT
THE TNC'S 1000uF FILTER CAPACITOR FROM BLOWING THE RADIO'S 2A AUX PICO FUSE.
NODE CONTACT MAIL: HP2DFA@GMAIL.COM / HP2DFA-5@BPQ32
73 DE HP2DFA-5 / BPQ32 NODE PANAMA
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