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CRT6900N and QRM Eliminator X-Phase
The QRM Eliminator X-Phase has a PTT port to bypass circuitry of the Eliminator during Transmission to prevent damage.

The positive (12-Volt) central tap of the PTT RCA Port needs to be shorted to Ground to activate the bypass circuitry of the Eliminator to prevent damage to both Eliminator (mainly) and Rig. 

The problem is that the CRT6900N Rig (also known by many other names like AnyTone 5555N and Alpha 10 Max) does not have a PTT (Ground) Jack.

One would think that it would be a simple wiring up of the PTT function on the Microphone Jack but DON'T do that! It won't work and may cause damage to the Rig.

It was suggested that the voltage from the Red Transit LED be used to trigger a Transistor which, in turn, would be used to ground the positive terminal of the Eliminator.

I found that the voltage over or before or after the Red LED's Resistor and LEDs was either too erratic or too low to make any sense of. The Red/Green LED doesn't share a common Ground to chassis so this seemed to be too problematic and also hard to physically access.

I found a suitable point that gives 8 Volts on Transmit and was easy enough to get to and solder a wire.
I tried at first a Solid State Relay but it would activate the Eliminators TX LED but not its Internal Relay.
I then tried an Opto Isolator, it behaved pretty much the same and couldn't keep up and popped.

Using a BC547 Transistor produced promising results but the Transistor got hot.

With the help of a Radio Specialist (Andy Bosworth), I was told to use a couple of Resistors of suggested values but had no success. The Eliminator's TX LED would light up but not the Relay. Eventually, and through trial-and-error and trying 50 different values I got this working.

Andy mentioned that, in a normal situation, the values he provided should have worked but he was unfamiliar with the X-Phase Model I am using (pictured here).

So, with this in mind, I share the details here but take NO Responsibility for damage caused.


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