[Elecraft] Looking to add LP700 to KPA1500 - ideas?

[Rick NK7I]

The KAT500 (and utility) can show the values used by the tuner to match 
the 50 ohm impedance of the radio.  Similar is possible either via the 
KPA1500 utility or the front panel of the KPA1500.

While it doesn't show the complex load; it gives enough to begin to 
figure out what the antenna is presenting (for use in apps like WinSmith 
etc) so one can make intelligent changes in the antenna.

I've used the utility for monitoring (and remote control) of the 
KPA500/KAT500 combo for years; now I'm using the KPA1500 utility for the 
same reason.

The KPA1500 presents a lot more useful information on the front panel 
(click on the menu button then the down triangle to select the menu you 
want).  Because my antennas are resonant, I park the amp display at 
power out, efficiency, volts and amps used and temp.  The power out on 
the utility also shows the reflected power in watts, nice to know.

If you put the LP sensor between the amp and the (not resonant) antenna, 
any mismatch will likely give you erroneous readings that would offer no 
value.  It would compare the antenna value (say 150 ohms of mixed 
reactance/resistance) to the tuner value (whatever is required to match 
to 50 ohms).  The worse the unmatched condition, the more useless the 
display becomes.  It wants to see 50 ohm in, 50 ohm out to provide 
accurate power readings.

So if your antennas demand a matching circuit (tuner), the LP sensor 
becomes less valued at the output of the amp.

73,
Rick NK7I

On 5/20/2020 9:41 AM, Andy Durbin wrote:
> "If it were mine, I would put the LP700 on the antenna line to monitor what is going on with the antenna itself."
>
> My LP-100A is between my KPA500 and my KAT500.  I want to know what load is being presented to the KPA500.   Neither the KPA500 not the KAT500 can display complex load values.  Since the LP-500 and LP-700 are intended to sample amplifier RF input and amplifier RF output I would expect the amplifier output sampling to be performed before the tuner.  But no, I don't know how to do that with a KPA1500.  It would seem to require an internal modification and two additional rear panel connectors.
>
> 73,
> Andy, k3wyc
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