[Elecraft] Tandem operation of KPA and ACOM 1500

[Jim Miller]

Just a note to document what I am planning for tandem (not simultaneous)
operation of my new acquired ACOM 1500 and my trusty KPA500/KAT500 combo.
I'm strictly single op and no SO2R here so a single feedline to my remote
antenna relay.

I bought the ACOM 1500 because I felt I needed additional power at times.
It is serving that need nicely. I'm slowly getting more accustomed to the
operation of a manual tune amplifier after a few years of automated
operation of the Electraft line.

But the KPA/KAT combo is nice for instant-on and quiet idling. I usually
leave my rig on all day if I'm in the house to grab the quick DX spot. At
the first spot of the day of course I need to wait 3 minutes plus tuning
time before getting in the pileup. I find that 3+ minutes torture. The ACOM
1500 fan is also a bit annoying.

So I've decided to put the KPA/KAT back in service in the following way.

Since I have a KANT3a in my K3S I will connect the KPA/KAT to ANT1 and the
ACOM 1500 to ANT2. Selection of the ANT line from the K3S will therefore
exclusively provide RF to one or the other.

Thanks to the internal preamp of the K3S the DIGOUT1 line is freed up to
provide a signal to switch the single feedline to the antenna farm between
the KPA/KAT and ACOM 1500 outputs. I haven't yet selected a legal limit A/B
relay but there appear to be several available. A separate relay also
driven by DIGOUT1 will switch the KEY line between the amps as well.

The KPA/KAT will connect via the AUX bus as usual to provide the former
automation including setting KPA per-band power levels. I'll need to put
the KPA in Standby to go "barefoot" and I already have the barefoot level
set to an appropriate value for the ACOM 1500. The normal drive power to
the KPA is also within the range of power I already use to tune the ACOM so
no problems there if I forget to put the KPA in Standby.

Since DIGOUT1 is per-band and per-antenna the appropriate setting will be
made for each. Of course DIGOUT1 being open collector it will need to be
pulled up and appropriate buffering added to ensure safe operation of the
relay coils.

So with two button presses I can switch between the two amps and the two
ANT connections eliminates the input switching relay and wiring.

Of course if a KPA1500/KAT1500 makes a debut all of this will be replaced
in a heartbeat!!!

Comments or suggestions welcomed!

73

jim ab3cv