10-05-2014, 09:37 AM
Fields, do not connect the counter directly to the grid of the 6A7. As mentioned previously, you are adding almost 40 pF capactance to the tuned circuit which will lower the actual freq. Use the 10 ten turn pickup loop as suggested. Regardless, the counter will always read 455 kHz higher because that is the IF offset, so all that indicates is that the IF is properly aligned..
What you really want to do is to check the full tuning range of the oscillator. With the tuning cap fully meshed, measure the freq. It should be 540 + 455 or about 1000 kHz. Then open the tuning cap completely and measure again. You should be at about 1700 + 455 or 2150 kHz. Adjust the J trimmer to set the low end, and the osc trimmer F for the high end. By going back and forth you should have both ends of the band at the right freqs. At that point, the dial calibration should agree across the band.
While the tuning cap plates can make small changes in freq, I doubt that much error can be attributed to bent plates. Just make sure the rotor and stator plates are centered within each other.
Your real problem may be the antenna tuned circuit is not tracking the osc. If you have been trying to align the padder trimmer J for max signal at 600 kHz and the ant circuit is off, then you have been misaligning the osc to compensate, causing the dial cal to be thrown off. You need to make the osc agree with the dial markings before trying to peak for max received signal.
What you really want to do is to check the full tuning range of the oscillator. With the tuning cap fully meshed, measure the freq. It should be 540 + 455 or about 1000 kHz. Then open the tuning cap completely and measure again. You should be at about 1700 + 455 or 2150 kHz. Adjust the J trimmer to set the low end, and the osc trimmer F for the high end. By going back and forth you should have both ends of the band at the right freqs. At that point, the dial calibration should agree across the band.
While the tuning cap plates can make small changes in freq, I doubt that much error can be attributed to bent plates. Just make sure the rotor and stator plates are centered within each other.
Your real problem may be the antenna tuned circuit is not tracking the osc. If you have been trying to align the padder trimmer J for max signal at 600 kHz and the ant circuit is off, then you have been misaligning the osc to compensate, causing the dial cal to be thrown off. You need to make the osc agree with the dial markings before trying to peak for max received signal.
