EMRFD Message Archive 10480

Message Date From Subject
10480 2014-11-21 06:56:50 timshoppa Peak-reading meters

Been a long time since I posted here! I actually had an on-the-air chat with W7ZOI a few months ago on 15M CW.

Right now I have a SWR/wattmeter using the directional coupler shown by KI6WX and I do great using this on CW because the meter reading is just the average power.

But as I venture into SSB I think I really need to adjust the time constants or maybe just need a new peak-reading circuit so this is more accurately peak-reading. At the moment I can send the directional coupler into a scope and I can see what I think of as "peak" on the scope, but this is nothing like the average that my meters read. Is there some "standard" peak-reading (sample-and-hold-then-decay) circuit used in SSB equipment used to drive meters?

Tim N3QE

10770 2015-02-09 09:26:47 timshoppa Re: Peak-reading meters
Coming back a little late, but finally found a circuit that works well for peak-reading meters for e.g. SSB speech. It is simple: an emitter follower on the RF detector output, the low output impedance of the emitter follower greatly reduces the time constant for charging while allowing the usual RC discharge curve. Look for example in the Ameritron AL-1500 manual at the power out metering.

Will do some SPICE modeling to show how it works :-).

Tim N3QE