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Old 7th Apr 2021, 3:01 pm   #16
jamesinnewcastl
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Join Date: Jul 2009
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 722
Default Re: Standard Beam Approach - Rebuild update

All

The next stage is to produce a signal fully representitive of the three transmitters to be found in the system namely the outer marker, the inner marker and the main 'Beam' transmitter.

I had a false start with some 555 circuits and googling 'controlled attenuator' unsucessfully. However googling 'controlled RF attenuator' produced a cheap chip on a small pcb for a few pounds that took 6 digital inputs and produced a wide range of attentuation. Naturally I had to wait 5 days for it to be shipped from China!

The final item pictured below is an Arduino on top of which is impaled a small vero board and impaled on that is the RF attenuator. Apart from taking the Arduinos outputs from 5 to 3.3V there is very little circuitry. All power is from USB (but I could add a 9V battery), 3.3V from the Arduino.

The simulator takes in a modulated RF from an external signal generator and performs the appropriate attenuation as required, namely:

Full on, Full off for specified periods - medium speed
Full on, Full off for specified periods - fast speed
One period of x amplitude and one period of y amplitude - X and Y being variable

The front panel controls are:

Select Outer/Inner/Beam function
Increase/decrease output
Left/Right variation
On/off (for battery if fitted)
USB Connection

The next part is to make a video of the R1125 in operation with the accurately simulated signals. I have also added a 1940's RAF earpiece to the rig so the sounds will be that little more accurate. (The price of these earpieces is astronomical!)

I'll produce a video soon and supply the link.

Cheers
James
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