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Projects & Circuits Page

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"Promoting better On Air Audio Quality for EchoLink"

EL Mic Mod

Simple EL Interface circuit (with audio Band Pass)

"EASY DIGI" EL Mod

EL Audio Board

Audio Isolation/Band Pass Filter/DC Blocking circuit

EL Audio Isolation/Compression circuit

EL audio conversion (EL old software version)

EL PTT SW

3D Printed - 3.5mm Audio Switch Box (2in & 1out)

APRS Digital VOX Circuit

NOTE: Dave G4FRE/WWR2 Mod 02/14, he replaced the Darlington Transitor with a MOSFET 2N7000 (T2) for better PTT switching, this also means rewiring R5 & changing the resistor value as shown in the circuit above.

On Air TX Indicator

Power Supply Crowbar Circuit

DTMF FM900/FM92 Mic Mod

Baycom TCM3105 AX.25(Amateur X.25)Packet Modem

Battery Eliminator - UV5R

Battery Charger Mod to stop over heating - UV5R

Here is a Modification to fix the Heat problem on these Desk Top Chargers using HXN- WS, SC6038 and AM6138 IC's.
Just replace the 0.5 ohm resistor (PIN 7 IC) with a 1 ohm resistor, very simple, this will Half the Charge current, Double the Charge Time and Half the Power Dissipation / Temperature.
Approximately 400ma Charge current to 200ma Charge current.
Approximately 5hrs Charge Time to 10hrs Charge Time.
Approximately 1.2W Power Dissipation to 600mw Power Dissipation.
This lower the Temperature of the HXN-WS (SC6038, AM6138) IC from about 64°C to 32°C

Note: Some of these Desk Top Charger are not using these charging IC at all, now you have over voltage charging.

TESTED:
Red LED ON: Charging.
Red to Green LED changes @ 8.49 Volts.
Green LED ON: 9.97 Volts.
Maximum output Charge Voltage should be 8.4 Volts +/- 1%, NOT 9.97 Volts.

 

IC-290H Battery Backup

NBN FTTN Modem Fan Cooling Mod

NBN FTTN Modem cover bright LED Mod

NBN FTTN Modem Battery Backup

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