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)






EL Audio Board



Audio Isolation/Band Pass Filter/DC Blocking circuit



EL Audio Isolation/Compression circuit


EL audio conversion (EL old software version)





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.

Refer article - "An AFSK Interface for Android Smartphones" by Martin K0BXB - QST Magazine MAY 2012

projects 1\wolphilinkmanual.pdf



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 64C to 32C

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

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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