[Elecraft] Serial Port on K3

[N4CW at aol.com]

Jim, K9YC,
 
Let me address the questions you posed in your e-mail:
 
1. The K3 was powered directly from a 54-AH AGM battery using a  4-foot #10 
red/black wire pair (same as
what I use in the shack with an Astron RS-35M). 
2. The computer/laptop (IBM Thinkpad 390X -- with genuine RS232 serial  
port) is powered by a mobile
power supply specifically designed for the Thinkpads by IBM).
3. RF is not the issue here...the failure is obvious in receive mode...no  
rig control as manifested by no
frequency display/readout in N1MM Logger. So the antenna (an Outbacker  
Outreach with a 4-foot Hustler
mast extension on the base to resonate the antenna in the CW portion of the 
 band -- measured with an
MFJ-259B).
4. The serial cable is the same cable I use in the shack. A non-issue since 
 I tried another cable.
 
The point I tried to make is that IN THE CAR, I substituted an AC supply  
(AC thru75-Watt inverter/converter plugged into an Astron SS-30 power supply  
that produces 13.8 VDC -- receive mode on the K3 because of
power limitations) for the battery (unplug one, plug in the other, leaving  
all other cables attached) and the
laptop now communicated with the K3 (manifested by the proper frequency  
being displayed by N1MM Logger). The only thing that changed was the power  
source. 
 
 Ordinarily, I never power my K3 from other that more-than-adequate  
13.8-Volt DC supplies, but this was like an emergency/field day setup and it  
disclosed a problem. Now, you see my concern about the K3 serial port failing  
with a lowered supply voltage to the K3?
 
Thanks for your other suggestions.
 
Bert, N4CW