Matching the 6V6 link to a low pass filter

Continuing our discussion: “How do we get a low pass filter in the circuit between a link coil output (balanced) and a low impedance low pass filter (unbalanced)?” . The simplest way we found is to use a variable capacitor between – in series with – one leg of the link.  In our 6V6 transmitter design on 80 meters we have found the value needed is less than 250 pf.  The spacing between plates must be adequate to handle the power level. In our case,  running about 3 1/2 watts output using the Pastime Projects power supply spacing can be minimum.  We will be more detailed in the next email newsletter.  Using a watt meter and dummy load, we clearly see a peak in power when the match to the 50 ohm dummy load is best. And of course, the reflected power is minimum. There we are!  A low impedance output.  This is the way the vacuum tube mobile transmitters of yesteryear were tuned. The impedance of a mobile antenna is very low.  BCNU! Glenn NN8G


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