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Poweramplifier with QQE06/40

Frequency : 70MHz
Output power: 50 tot 100 watt
Valve: QQE06/40
Input power : 1-2 watt or 5-10watt
Pre-amp gain : 20dB

The purpose of this amplifier is to use it with a converted CB transceiver somewhere else on this site.

The chassis comes from a T-28/APT-1 VHF (90-220MHz)Jamming unit that dates back to WWII.

The poweramplifier makes 90 watt at 1.5 watt input power.
The amp can also used with an input power of 7 watt by using an input attenuator.
It has proved to be stabile under all circumstances.
The amplifier is finished and here are some pictures taken during building :

Top and bottom view:

The schematic is drawn by the use of kolourpaint :

Some blocks in the schematic:
- Pre-amp : 20dB preamplifier
- filter: mainsfilter from an old microwave oven
- low pass filter: ready bought filter for 70MHz 100 watt with RF detector
- ATT : 8 dB 10 watt attenuator

The preamp is build with a BFR92 transistor in a SOT23 housing. On the input of the pre-amp there is a bandfilter which is simulated with PUFF. The output of the pre-amp is a simple 100 ohm resistor output. The benefit of this output is that the gain is relatively low and the amp remains stabil. The pre-amp does about 20dB and can be very usefull.

Schematic diagram of the preamp: