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Technical Tips from Mark W. Persons
Replacement RF Amplifier for a Continental 802B FM Exciter

If you have an RF amplifier in a Continental Electronics 802B FM Exciter that looks like this, you may have a problem.  Continental's answer is to replace the entire module for about $2000. 

There is an alternative.  If you look closely on the left side of the exciter, you will see the RF power amplifier circuit card has been rebuilt with new parts.  They include an 80 watt amplifier and a low pass filter with directional coupler from Broadcast Concepts.  That doesn't mean the exciter will make 80 watts.  The power output is limited by the exciter's power supply at 50 watts.

The rebuild project can be done for about $1000.

The low-pass filter has been replaced by a 150 watt model from Broadcast Concepts that is more compact, see photo below.     

September 28, 2016:  Here is a look at how a new RF amplifier fit to the left, a low pass filter in the middle and the original RF directional coupler to read forward and reflected RF power on the right.
The RF amplifier and low-pass filter came from Broadcast Concepts.  The amplifier has 40 dB of gain using an MRF173 transistor in its output stage.
Some 802B exciters have a directional coupler which can be reused when doing this update and some do not.  New directional couplers are available for this kind of rebuilding too.

March 16, 2015:
  Here is another example of a non-functional RF power amplifier in a Continental 802B FM Exciter. 

Transistors on the module failed and it could not be repaired.

It is one of three circuit designs that were short-lived.

See below:

Here is the power amplifier, modified with a Broadcast Concepts RF amplifier. 

The original amplifier card is still in place, but the amplifier portion is not being use.

However, the RF low-pass filter and directional coupler are still in the circuit. 

This simplified modification of the exciter and reduced the cost.

All was well in the end and the exciter was capable of delivering a full 50 watts to the transmitter it is driving.

The stories go on and on.  Stop in again sometime.  I'll leave the soldering iron on for you. 
Mark W. Persons   ham W0MH      

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