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?
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