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SX-110 IF Alignment Question
开云体育So – this is something I’ve gone over and over again in the alignment instructions and I can’t find an answer.? Hallicrafters wants the IF aligned to the frequency of the crystal (which is almost certainly not going to be on exactly 455 KHz).? To identify the crystal frequency, you slowly sweep the signal generator above or below 455 KHz until you discover a sharp notch.? I’ve done that – no problem.? But, here’s the catch:? the location of that notch can vary rather signficantly with the position of the crystal phasing control, and there’s nothing in the alignment instructions about the correct position for the phasing control.? Been scratching my head over this, and so far I haven’t found any information about it online.? Anyone here run into this before and have an answer? ? 73 – Steve, KW4H |
开云体育
I'm a little foggy on this, but I believe you are supposed to set it for highest output I think
From: [email protected] <[email protected]> on behalf of KW4H via groups.io <reedsteve@...>
Sent: Thursday, November 3, 2022 2:26 PM To: [email protected] <[email protected]> Subject: [HallicraftersRadios] SX-110 IF Alignment Question ?
So – this is something I’ve gone over and over again in the alignment instructions and I can’t find an answer.? Hallicrafters wants the IF aligned to the frequency of the crystal (which is almost certainly not going to be on exactly 455 KHz).? To identify the crystal frequency, you slowly sweep the signal generator above or below 455 KHz until you discover a sharp notch.? I’ve done that – no problem.? But, here’s the catch:? the location of that notch can vary rather signficantly with the position of the crystal phasing control, and there’s nothing in the alignment instructions about the correct position for the phasing control.? Been scratching my head over this, and so far I haven’t found any information about it online.? Anyone here run into this before and have an answer? ? 73 – Steve, KW4H |
开云体育Scott.?You are trying to set the signal generator and the pitch control to the xtal frequency simultaneously.? The remarks column gives the procedure. The sig gen will peak at ?xtal freq, the pitch will dip to minimum. The correct spot is when they coincide. The pitch will attenuate the sig gen giving the “lowest peak” / “maximum dip”. 1. Adjust pitch to min.? 2. Adjust gen to peak.? 3. Repeat until 1and 2coincide.? Start at one end of pitch range and slowly move toward the other end. Do not reverse the pitch control.? 73 Dick. K9FFK Sent from my iThing which often corrects my typing and what I say.? On Nov 3, 2022, at 1:36 PM, Scott Petersen <s-petersen@...> wrote:
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开云体育FYI – I stumbled across this video, which helped answer some of my questions.? The focus was the SX62, but the principles and circuitry are nearly the same.? It was some of the best 30 minutes of crystal filter theory and alignment training I’ve ever run across.? Highly recommend. ? ? 73 – Steve, KW4H From: <[email protected]> on behalf of "KW4H via groups.io" <reedsteve@...> ? So – this is something I’ve gone over and over again in the alignment instructions and I can’t find an answer.? Hallicrafters wants the IF aligned to the frequency of the crystal (which is almost certainly not going to be on exactly 455 KHz).? To identify the crystal frequency, you slowly sweep the signal generator above or below 455 KHz until you discover a sharp notch.? I’ve done that – no problem.? But, here’s the catch:? the location of that notch can vary rather signficantly with the position of the crystal phasing control, and there’s nothing in the alignment instructions about the correct position for the phasing control.? Been scratching my head over this, and so far I haven’t found any information about it online.? Anyone here run into this before and have an answer? ? 73 – Steve, KW4H |
开云体育??Hmmm... a few more comments, Steve -? You align the IF's, peaking each at the frequency you've determined the crystal best "sings" at. For example, at least using a SA, for a 455 kHz crystal inject a sweep generated signal of, say, 450 to 460 kHz (not super critical +/-) into the mixer grid (loosely coupled) and look at the response at the detector at your widest filter setting. Your crystal is the tuning fork and whatever it rings at is the key it's in. It will almost never be 455.00 kHz. Make sure you have the phasing control adjusted such that no null appears on either side of your peak. You're hoping to see a perfect upside down ice cream cone on your scope - maybe just a scoop of mashed potatoes at the widest setting - ?with the top tip somewhere near 455 kHz. Whatever frequency your curve peaks at is the actual in-circuit resonance of your IF crystal. It will never be 455.000 in an old radio. No matter. Go about your IF alignment with your sig gen at your new "actual" crystal frequency. Your phasing control is best set with the knob at 12 o'clock and no null anywhere on the curve. Turning it clockwise or counterclockwise should initiate a sharp null going up or down one side or the other. Hammarlund goes into quite some discussion of this in their HQ-120/129/140/150 models. Halli may do the same, I don't know. Hammarlund was strangely very tight-fisted about using a spectrum analyzer back when almost nobody had one. Opinions vary. Many don't have or use any instrument and just twist the IF cores to their loudest. I do know the design, function, and schematics of these single crystal filters with switch settings are remarkably alike. Aligning a single conversion HQ Hammarlund "by the book" with a spec. an. for "symmetry, amplitude, and coincidence" on all settings of the bandwidth knob is like playing three dimensional chess through a German Enigma machine with the settings changing on each pass through. Dan WB4GRA On Nov 3, 2022, at 2:26 PM, KW4H via groups.io <reedsteve@...> wrote:
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