On 7/14/2014 6:58 PM, Bob McGraw - K4TAX wrote:
Calculating power meters such as the LP-100A become a bit more costly.
Right. It also reads peak power with decent precision. That's important
if you want to be very competitive -- we are licensed for 1.5kW PEP, and
readying that peak power accurately is important if you want to be as
loud as possible in a contest, or in chasing DX.
AND the LP100A does a LOT more than measure power. See the link
previously posted. It is, for example, a vector power meter, meaning
that it reads the magnitude and phase of the voltage and current. This
allows it to compute the real power, and the complex impedance of the
load (in this case, the transmission line). For about $200 more, it can
handle a second coupler, so you can monitor two radios, or you can
measure the input and output of your power amp, as well as the complex
input impedance of your power amp. It can also read the voltage received
on an antenna down to -15 dBm (40 microwatts), so you can use it to
measure an antenna's pattern.
So while it ain't cheap, neither is a Bird 43, and Bird 43 needs slugs
for every power range and every frequency range. LP100A and coupler
calibration is specified at 5% at any frequency, 3% typical, traceable
NBS. So, as I see it, the LP100A is a real bargain!
My neighbor, N3ZZ, has a pair of LP100As in his very nice SO2R station,
where I've operated in several contests.
73, Jim K9YC
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