What power is needed to drive PGXL's to achieve 1K PP and 1.5K PP via 8000 rigs in the CW Mode?

David43 · January 30

Mike-VA3MW · January 31

What is MEffA? And when to use MEffA, Mode AB, or Mode AAB.

MEffA was invented by 4O3A and stands for (Maximum Efficiency Algorithm) and this feature noticeably increases the efficiency of the amplifier when processing constant level tones or non-AM signals, such as CW, RTTY, FM or FT8 type signals.

It works by decreasing the drain Voltage on the amplifier devices, requiring more drive, which moves the amplifier closer to a higher efficiency “Class C” operation. It is only available in “AB” mode.

It is not applicable to amplify signals with a varying amplitude, such as SSB or AM. These modulation modes require the use of Mode “AAB” which provides maximum linearity, but at a lower efficiency than Mode “AB” because you are operating closer to operating the amplifier at Class “A”.

David Decoons, wo2x · February 1

MEffA can be left on all the time. It is only active in single tone modes such as CW and FT8. MEffA is not active on SSB.

73 Dave wo2x

Mike-VA3MW · January 30

What is PP? If you mean Peak to Peak, there is no Peak to Peak in CW mode. (just guessing that that is what you meant)

It varies by band and even amplifier.

Between 25 watts and up to 70 watts.

David43 · January 30

Just for clarification, since the AmpPO of the PGXL scale is in Peak to Peak (PP), my question is what has been observed for the driving power of an 8000 rig to achieve these power levels (1KW (PP) and 1.5KW (PP)).

David Decoons, wo2x · January 30

Also MEffA on or off will affect drive power.

Dave wo2x

David43 · January 30

David,

I have MEFFA on and would you expect the PGXL output power to be higher or lower if it was off?

Geoff AB6BT · January 31

David…Where do you see Peak to Peak indicated?

I have never seen that used as a way to measure power.

Usually power is measured as RMS or Peak.

Peak to Peak is often used as a way to measure voltage or current. For a sine wave the peak is the √2/2 or about 1.41 times the RMS value. Peak to Peak is twice that.

KD0RC · January 31

Hi David, according to the QST product review from Jan, 2021, it should take 40 or 50 watts depending on band. Their test setup required around 70 watts on 12 meters.

I seem to remember that the drive requirement goes up somewhat when MEFFA is engaged.

Are you seeing strange PGXL drive requirements?

David Decoons, wo2x · January 31

MEffA requires higher drive power.

I think MEffA is disabled on 6 and 160.

David43 · January 31

Mike,

If I select MEffA on the PGXL when operating in the CW mode should it be deselected when operating in the SSB?

Erik Carling EI4KF · February 1

With MEffA checked on in the settings, it will be on in AB mode and automatically deselected in AAB mode.

If you install the PGXL utility, the state of the amplifier is readily apparent:

On in CW / RTTY/ FT*/ FM and the display shows a red MEffA indicator and mode AB

Off in SSB and the display shows a shade of yellow MEffA indicator and mode AAB

What power is needed to drive PGXL's to achieve 1K PP and 1.5K PP via 8000 rigs in the CW Mode?

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