[ICOM] Computer Control Interface

Ed K1EP k1ep.list at gmail.com
Tue Dec 27 20:21:40 EST 2005


If you are using an opto to do CW keying via the UP/DOWN function, then you should be aware that the UP/DOWN sensing in the Icom is done by voltage.  That is, it senses the voltage on the UP/DOWN line.   The UP/DOWN line is also used for the 4 voice/CW memory keying but in that case, it senses 4 voltages.  What this means is, if you are using a transistor to key that line, whether it is the output of an opto or discrete transistor, you have to account for the Vcesat of the transistor in presenting the line with a voltage.  The UP/DOWN buttons have no voltage across them when they are on.  The Vce sat could be several tenths of a volt.  If you do the calculations, understanding the internal series resistance that is in the radio and the unloaded voltage, you can come up with 4 new values of resistance for the keyer and probably a new value for the UP/DOWN.  I have done that for the keyer with great success.  The only catch with the UP/DOWN, is that it only uses one resistance, with the other state grounding the line.  This may present a problem if the voltage detection is looking for something less that the saturation voltage of the transistor.  I have not done an UP/DOWN keyer, so I can't say whether it will work or not, but I have done computer controlled interfaces using the memory keyer with optos/transistors.  


At 12/27/2005 12:42 PM, you wrote:
>Bob,
>
>I was looking at the MFJ-1279 schematic and the CW out is using a Opto Isolator. In the past I remember an Opto isolator not being able to place a hard enough ground on the Icom UP / Down input.
>The AEA DSP-2232 users had to install a transistor to provide hard enough ground so the DSP-2232 would cause a frequency change, mostly to the IC-970. This was done for Doppler shift frequency tracking.
>I looked at the Buxcomm site but he has some much stuff it would take a week to find the product you are using listed.
>
>Gary K8IZ
>
>At 07:58 AM 12/27/2005, you wrote:
>>Ok I give up on this little project, it is quickly
>>becoming not worth my time.
>>
>>Is someone using an interface with an Icom PRO or II or
>>III that does all the soundcard modes and FSK modes along
>>with keying CW from A SINGLE COMM PORT that actually
>>works?
>>
>>I would like to know what your using so I can look into
>>getting one.
>>
>>What is recommended by you guys with the experience?
>>
>>
>>
>>  73 fer nw,
>>Bob AD5VJ
>
>----
>Your Moderator: Dick Flanagan K7VC, icom-owner at mailman.qth.net
>Icom Users Net: Sundays, 1700Z, 14.316 MHz
>Icom FAQ: http://www.qsl.net/icom/



More information about the Icom mailing list