W2TRR . com

Thomas R. Ray, III - Ham Radio

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Recently, I decided that I needed to get into my local repeater (Newburgh, 146.430 RX [on my radio], 147.435 TX, 71.9PL) from the office or wherever using my laptop or smartphone.  In addition, there are a few members of the Orange County Amateur Radio Club that cannot easily get into the repeater at all times.  So....I have an old laptop of my son's that works, so I rebuilt the operating system and installed Echolink on it to run in Sysop mode.  Interfacing was fairly simple, and it works well.  To the right is the Echolink screen during a QSO with KC2VTJ connected to the W2TRR-R Echolink node. 

Right now, this is a "private", by invite, node to connect to.


This is the schematic for the interface between the computer and the Yaesu FT-1802M radio.  The computer being used does not have a com port, so I am using a USB to RS-232 adapter.  I have the Echolink program set to output PTT on the Request To Send (RTS) pin, pin 7 on the DB-9.  When Echolink wishes to key the radio, RTS goes high.  The resistor in series with the RTS pin is to limit current into the transistor.  The resistor from base to ground is to hold the transistor off when RTS is not active.  When RTS goes high (becomes active, which is actually a data 0 - RS-232 levels are -12V for a data 1, +12V for a data 0), the transistor turns on, taking the collector of the transistor to ground, connected to the emitter.  This takes the PTT pin on the radio to ground causing it to transmit. 

I am using two transformers to 1) isolate the computer from the radio and 2) to drop the audio levels.  The top transformer takes the audio output of the computer and drops the voltage, and sends the audio onto the mic input of the radio.  The bottom transformer takes the audio output of the radio, drops the voltage, and sends the audio onto the mic input of the computer.


I have the FT-1802M in a carrying case which I use as a portable APRS rig for remote operation.

This is the experimental interface.  The Echolink setup is presently set up temporarily.  Once I determine where it's permanent home will be, I will neaten up the interface and "make it real".  Bottom line is you don't need a fancy, expensive interface unit to put together an Echolink node.  The total parts cost was about $20.  I had the radio and antenna.  And I had a laptop kicking around.

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