[Milsurplus] MAK progress.
Ray Fantini
RAFANTINI at salisbury.edu
Sun Jul 21 13:09:09 EDT 2019
Weekends are always good for progress, although this weekend was on the road most of yesterday collecting up some stuff for the mutt. Got a new drivers side mirror to replace the one that fell off on the way to Aberdeen this spring and picked up the correct Vietnam era antenna tuner and base for the VRC-43, the square one And not the more common round tuner. On the subject you would be surprised how much grief I have gotten about having a VRC-43 (RT-246) as opposed to having a VRC-46 (RTR-524) but that's another story.
The capacitor on the oscillator tank turned out to be 250pf going to assume the red, green and black dot decoded in resistor color code as two, five and zero with the third dot not being a multiplier but a digit. Saw many different explanations for reading Mica capacitors and found the real way to determine is by going old school again and using my old LRC Bridge. Swapped out to a 120 pf capacitor and using the Grid Dip meter found the LC circuit resonates well at 3.885 at just about the center of the coil and with the LC tank for the oscillator modified now have a working channel four on 3885. The PA tank had no issues being I had it strapped to the fourth or high end of its range and am getting a reliable 11 watts into 50 Ohms at 3.885, although I am 120 cycles low but for AM don't think that will be any issue.
The plate voltage drops down to about 375 volts for a plate current at resonance of just above 50 mills, figure that's about nineteen or twenty watts input power for around eleven watts at the antenna connector for a efficiency of just over fifty percent. Not bad for a AM transmitter. The broad range output tank has little issue matching fifty Ohms wonder how it will do on a shorter and higher impedance antenna.
The next issues will be the receiver rock when it gets here and last but not least what type of antenna gets paired with this? Anyone have any idea what type of antenna would be used on a WW2 motor launch?
Ray F/KA3EKH
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