[Elecraft] KPA1500 XCVR serial connection

[Paul Baldock]

The KPA1500 will just be listening. There will be 
no issue with the +6V from the TS-990 true RS232 
being heard by the KPA-1500 and PC, however I am 
concerned that the -6V from the true RS232 might 
get clamped close to 0V by the KPA-1500 input and 
so screw up communications between the TS-990 and 
the PC. Hopefully the KPA1500 has a reasonable 
input resistor and so clamping will be minimal.

- Paul

At 04:25 PM 2/28/2018, Don Wilhelm wrote:
>Paul,
>
>It is possible that short runs of "RS-232" can operate on TTL levels.
>There certainly is no problem at the 5 volt 
>level, that is entirely within the range of the + level valid RS-232 signals.
>
>The possible problem is with the low level.  A 
>proper RS-232 receiver should ignore levels 
>between -3 volts and +3 volts because it could be in a range defined as noise.
>However, all receivers are not designed to 
>ignore a 0 volts low level. The receiver on the 
>KX2 and KX3 as well as the XG3 (and probably 
>others as well) will interpret 0 volts as a low level.
>
>Note that the 'real' RS-232 spec is written for 
>very long communications lines.  Short lines (10 
>feet or so) can take liberties with the levels 
>if the receivers are such that they can tolerate 
>those switching levels yet will accept signals 
>with the full RS-232 voltage swings.
>
>Properly connected, you would need to have the 
>KPA1500 TxD disconnected and depend on the PC 
>application to poll the radio while the KPA1500 
>'listens' in to get its frequency information.
>Without the PC connection (and the KPA1500 TxD 
>connected, the KPA1500 will poll the radio for that information.
>
>RS-232 is point to point communications and not 
>multipoint, although there can be multiple 
>receivers listening to the communications, there can only be one driver.
>Sort of like ham radio - everybody can listen, 
>but if two operators transmit on the same 
>frequency, they will QRM each other and "data corruption" occurs.
>
>73,
>Don W3FPR
>
>On 2/28/2018 6:30 PM, Paul Baldock wrote:
>>The manual on page 24 says:
>>Serial: A Kenwood, Yaesu, Elecraft K2, K3, K3S, 
>>KX2, or KX3, or FlexRadio® transceiver that 
>>responds to IF; FA; FB; FT; polls with 
>>frequency and VFO information. The XCVR SERIAL 
>>connector is configured as TTL-level RS-232
>>Is it really TTL?. I planned to use this 
>>connected to the serial data line that goes 
>>between my Kenwood TS-990 and PC, such that the 
>>KPA1500 will catch the frequency data triggered 
>>by my logging program. This works great with 
>>the KPA500 which I assume  uses true RS232 
>>levels. If the KPA1500 does indeed use TTL 
>>levels will it capture the data, and will it 
>>not corrupt the RS232 levels between the PC and TS-990?