I f your local store has the usual replacement series from ECG or
NTE - either the 3044 or 3045 works great. They have a
Darlington Pair output, so that you get a good clean on/off
I built all of mine into the serial connector at the computer. As in
most cases, there are pins that are not used in the connector, so you
can cut them off with a pair of dykes. Then, epoxy glue the opto-isolator
onto the area that doesn't have pins. A 1/4 watt, 1000 ohm resistor will
go from the Anode (pin 1) to what ever keying line is used.(Usually
the DTR line of a serial port, or the SLCT line of a parallel port.)
The cathode will then go to the computer ground for a serial port or
to the STROBE line of a parallel port.
Run the key line from you transceiver through the normal cable hole and
strain relief of the DB connector and tie to the output, Pins 4 & 5.
When you put the housing on the connector, it looks just like a normal
serial cable, very sanitary.
The Opto-isolator will switch considerably faster than you can send cw,
so there is no concern of character dropping.
Here and at the local contest stations, these have been in use for
about 7 or 8 years with no ill effects.
From: Paul Meier <wa7mig@Hevanet.com>
To: Del & Jan Seay <email@example.com>
Date: Friday, November 06, 1998 7:16 AM
Subject: Re: [TenTec] 301 Advice
>Thanks for the info, since I don't have any parts books can you recommend a
>couple of part numbers for the opto-isolator? Thats a good idea. Sure
>you could have found that schematic for the 4CX1500B's!!! Oh well, maybe
>next time. Thanks
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