An Explanation of PEP and the K4DPK PEP Adapter

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Suppose we tune up an amplifier to transmit a steady carrier of 1000 watts, read on an average-reading (not PEP) wattmeter.  Let’s then put the transceiver in CW and, while watching the wattmeter, send A SINGLE DOT. 

We know that the Dot was transmitted at the peak power level of 1 KW, but the highest the wattmeter needle indicated was only around 300 watts.  What caused this? 

Sure, that KW level signal went through the meter pick-up, and the electronics in the meter circuit detected it, but because of the MECHANICAL INERTIA of the meter movement, the needle moved so slowly that the signal ended before the needle reached the full value, or PEAK, it should have displayed.  Had we transmitted a longer signal by holding the key closed instead of simply sending one dot, the meter could have had time to accurately display the correct peak power level. 

Since voice syllables and CW characters are discontinuous in nature,  Average Reading Wattmeters (Non- PEP) just don’t show how much power we’re really running. 

The K4DPK PEP Adapter circuit detects the peak signals that are seen by the wattmeter sensing element, and stores them long enough to allow the meter the time to give an accurate display. 

Using the Adapter, the first sound into the microphone will cause the wattmeter needle to immediately climb to the correct peak power level and hover there as long as that peak continues to be reached by either voice syllables or CW characters.  Once speech (or CW) stops, the meter needle will slowly fall to zero.  This decay time is adjustable. 

WATTMETER ACCURACY: 

Accuracy and precision of the measuring instrument is not degraded by using a PEP Adapter.  In fact, accuracy is improved, since an average-reading wattmeter is totally inaccurate while in other than a key-down continuous carrier mode.  

Calibration of the wattmeter is unaffected by the addition of the K4DPK PEP Adapter.  Only the adapter need be calibrated, and that can be accomplished in less than a minute.

INSTALLATION AND OPERATION: 

Simple, straightforward instructions with drawings accompany each adapter.  Installation takes less than an hour.  The wattmeter sensing element is not disturbed. 

The adapter requires 8 – 15 volts DC.  This can come from a single 9 volt battery or a station supply.  If a wall-mounted plug-in supply is used, be sure the no-load voltage is correct.  Some of them soar when connected to light loads.

If you have further questions, contact k4dpk@comcast.net

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