Monday, April 17, 2006
New Echolink Interface
Last Saturday, after coming back from my saltmine, I figured out on how to add a monitoring speaker to my existing Echolink interface. Withe the addidtion, you'll be able to monitor both audio from echolink and also from the rig. However, if you are transmitting in a close proximity, you should switch off the active speaker. This is to prevent unwanted feedback that will affect your transmitted audio quality. You can use any active speaker sold in the coumputer shop for the monitoing speaker. Remember! you shall use only active speaker! that's mean the speaker must have a built-in amplifier. If you attach a passive speaker, the signal from the soundcard will not be able to drive the speaker and you'll possibly overload the soundcard and spoil it.
It all started when I blew my Icom BC-139 desktop charger for my Icom T90A handy. I was charging the handy and did not switch it off because I want to monitor the activity of V23. However, when one station came in, I accidently pressed the PTT and the charger went kaput. There was a nice smell of a burnt semiconductor.
Having the T90A without battery was really frustrating when V23 was active.
From the circuit, it is practically the same with the original circuit that we can find on the internet. However, with a close inspection, you'll find that I added another jack J4 and 2.2uF capacitor C5 connected in parallel with the soundcard line out jack (J5). You can choose to ommit the capacitor (C5) and just connect the jack J4 parallel with J5.
I also decide to draw the schematic with a connection for Kenwood TM-261A and Icom IC-208H with RJ45 connector. If you decide to construct this circuit, always remember to check the connection to the RIG. This is very important otherwise a small mistake is very costly.
Currently, this set-up is running fine with my Kenwood TM-261A and has no problem at all.
Good luck and please make sure you know what you are doing.