>The problem is that if you try to create a good hold time by simply
>making the RC time constant very long, it takes an age for the meter to
>drift back down again. It becomes far too slow to follow speech for
>example.
It rather depends what you consider useful. The 43P circuit takes forever to
fall back and just sits at the maximum reading when used with SSB. This is
good in contests as it stops the operator continually trying to "talk up"
the meter. What it really needs is some DC-DC converter to prevent its
excessive use of PP3s and a time out circuit in case it gets left on
overnight. There is no way of knowing what the chip is on the PCB as it is
potted.
Nowadays, this seems a good application for a microcontroller that could not
only do the PEP but also linearise the scale using a look up table allowing
any appropriate meter to be used with one of the readily available Bird line
sections. The meter could even set an overdrive alarm.
A useful addition would be the same circuit applied to amplifier
screen/anode/grid current metering.
--
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
|