James, These fast tuning birdies depend on the mode selected, the roofing filter selected, and the position of the shift control. If any of these was changed between the last time you looked and this time, that could account for a change between the two versions.
The birdie removal is not as simple as just finding the birdie and turning the knob. If you are tuning at the fast VFO rate (50 Hz per step), you may not be getting quite enough information to see and control what is happening. If you change the rate to 10 Hz per step with the Rate button, it is easier to see what is happening and easier to get the birdie removal working right. Here is an example. With the filter bandwidth set to 2.8 kHz, as you step through frequencies at 10 Hz steps you might hear birdies with the following pitches: 28135.30 - nothing heard. 28135.27 - 2700 Hz. 28135.28 - 2400 Hz. 28135.29 - 2100 Hz. 28135.30 - 1800 Hz. 28135.31 - 1500 Hz. 28135.32 - 1200 Hz. 28135.33 - 900 Hz. 28135.34 - 600 Hz. 28135.35 - 300 Hz. 28135.36 - nothing heard. At the 50 Hz tuning rate, you would only hear this birdie at two spots: 28135.30 - 1800 Hz. 28135.35 - 300 Hz. I assume that's what you meant by a "two-tone birdie". OK, with the dial tuned to 28135.30, use the SIG RMV feature. Depending on whether you turn the VFO A knob to the left or to the right, the birdies might be moved either up or down in pitch. Let's suppose you turned the knob in the direction that moves the birdie up in pitch, and that the shift is 1500 Hz (BTW, I have no idea whether that's the right amount, this is just a made-up example). Raising the pitch by 1500 Hz would remove the birdie at 28135.30 all right (it would now be at 3300 Hz, outside your bandpass), but it would change the birdie at 28135.35 to 1800 Hz, which does not remove it. This is the wrong direction to apply the correction for this particular birdie. If you tune at 10 Hz steps, this correction will produce new birdies at 28135.36-28135.39 that weren't even audible before. If you turn the knob in the opposite direction, though, the pitch of the birdie at 28135.30 will be lowered to 300 Hz, and there will be no birdie audible at 28135.31 or higher frequencies. This is almost, but not quite, good enough; so, turn the knob one more step in the same direction and that will eliminate the birdie from the entire range 28135.30 - 28135.39 . Now tune down one 10 Hz step to 28135.29. The birdie is still there at 2100 Hz - the previous adjustment did not affect it. Turning the knob to lower the pitch, like you did in the previous step, will not work - it will make this birdie worse. You need to turn the knob in the opposite direction, to raise the pitch. A one-step rotation will eliminate this birdie from the entire range 28135.20 - 28135.29 . So for this particular birdie, you had to apply two steps in one direction in one 100 Hz segment, and one step in the opposite direction in the adjacent 100 Hz step. Now suppose the birdie goes in the opposite direction, e.g.: 28135.27 - 300 Hz. 28135.28 - 600 Hz. 28135.29 - 900 Hz. 28135.30 - 1200 Hz. 28135.31 - 1500 Hz. 28135.32 - 1800 Hz. 28135.33 - 2100 Hz. 28135.34 - 2400 Hz. 28135.35 - 2700 Hz. In this case, you will need to use the opposite directions for correction compared to the previous case. You will have to raise the pitch of the birdies in 28135.30-39 by 2 steps, and you will have to lower the pitch of the birdies in 28135.20-29 by one step. I hope this helps you understand the birdie removal process better. 73, Rich VE3KI ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
