> [snip]
> :Well that's not actually true... any wattmeter that is not op amp driven
> :is not a true peak reading meter. The Yaesu YS-60 is op amp driven and a
> :true peak reading meter and it sells for about 130.00. Its not a Bird,
> but :if you understand its limitations its a pretty good meter...
There is no requirement the meter have an "op-amp". The
requirement is the load across the storage capacitor be many
times the reactance of the capacitor at the lowest modulation
frequency, and the supply source charging the capacitor have
many times less impedance than the storage capacitor.
There many ways to do that, and an op-amp is just one way of
many.
The problem is an impedance ratio problem. The source needs to
be very low impedance and the load very high compared to the
capacitor impedance. That normally requires some active
components, or a very sensitive meter movement (with a 50 uA
meter you can come within a few percent of a Bird 43P on speech
with no active components).
73, Tom W8JI
w8ji@contesting.com
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|