09-15-2009, 01:32 PM
OK so I tweaked the trimmer on the oscillator and moved the stations down a little on the dial.
The dial is now pretty accurate all the way up to about 1200, at which point stations are low (i.e. 1540 is at about 1450). It's almost like the very top of the dial is forshortened. I get all the expected stations, as compared to a digital radio that works, but the top ones a squeezed down on the dial. (this is the first time I've done a full spectrum comparison - All the ones I've previously spot checked ahve been fine, but I've never noticed the squeezing at the very top.)
My suspician is that this must be because the antenna tank trimmer needs tuning. I arrive at this conclusion through the idea that the oscillator should only adjust WHERE the stations are on the dial, but the antenna tank would control the spread of the band. I'm thinking that maybe the band pass of the antenna squeezes on the ends and it's currently adjusted so that it is above the middle so most of the dial is fine, but the top end is starting to get into the squeezed end.
Does this make sense?
Will adjusting the tank trimmer spread the band out properly (then allowing me to move it into proper position with the oscillator trimmer again)?
The dial is now pretty accurate all the way up to about 1200, at which point stations are low (i.e. 1540 is at about 1450). It's almost like the very top of the dial is forshortened. I get all the expected stations, as compared to a digital radio that works, but the top ones a squeezed down on the dial. (this is the first time I've done a full spectrum comparison - All the ones I've previously spot checked ahve been fine, but I've never noticed the squeezing at the very top.)
My suspician is that this must be because the antenna tank trimmer needs tuning. I arrive at this conclusion through the idea that the oscillator should only adjust WHERE the stations are on the dial, but the antenna tank would control the spread of the band. I'm thinking that maybe the band pass of the antenna squeezes on the ends and it's currently adjusted so that it is above the middle so most of the dial is fine, but the top end is starting to get into the squeezed end.
Does this make sense?
Will adjusting the tank trimmer spread the band out properly (then allowing me to move it into proper position with the oscillator trimmer again)?
