El 06/03/2010 8:34, Andy obrien escribió: > I was helping a ham get set-up for digital modes recently and turned > to the issue of interfaces for digital modes. I researched the price > for a Rigblaster Pro and was shocked that they sell for $299. My > friend settled for another interface that cost $69, new. I was > wondering about interfaces and wondering about whether the era of high > priced interfaces might be coming to an end. I'm not talking about > the ones that have extra features like electronic CW keying, high end > soundcards , etc etc. I'm thinking that a device that has connectors, > isolation circuits, pots, and a good solid enclosure, should be in the > under $100 range. I know you can build your own for $20 or so, It > is nice to see that many low price options exist nowadays. > Andy K3UK >
Mine is built using scrounged components, mostly. 1) A good quality japanese professional audio 10 k : 600 ohms transformer. Connected as step down, it doubles as an attenuator. Loaded with a 600 ohms resistor in the secondary. 2) Several 1:1 transformers. The last one I am using is ferrite pot core recovered from a dead modem, loaded with 1200 ohms and 2.2 nF in series gives insignificant square wave ringing on the edges when tested with audio generator / oscilloscope. 3) A 4N26 optocoupler with a red LED is series and a 2.2 k resistor. Also has a reverse bias protection shunt diode (1N4007 that was at hand) over the LED + optocoupler diode string. All contained in a small plastic box, from a discarded battery charger. I only paid for the new all metal stereo miniplugs that go to the PC soundcard. In use for at least a couple of years already. 73, Jose, CO2JA
