Keyboard Shortcuts
Likes
Search
Re: SX-110 Alignment Puzzle
¿ªÔÆÌåÓýI can't open deja vu on my cell phone. Most receivers with single crystal filters adjust the IF to the crystal frequency.? ?A very few,? like the Collins 51J series need to have an exact IF frequency due to the way the tuning is done but this is very rare.?? Despite the discussion about signal generator calibration and stability it should be possible to align a simple IF with a service grade generator.? The crystal establishes the frequency. Since the overall bandwidth of the IF is considerably wider than the crystal great precision is not necessary.?? In most cases the crystal stage will have input tuning, a loading adjustment to set broadest crystal bandwidth, and maybe a neutralizing adjustment to center the phasing notch.?? Some earlier receivers have essentially a fixed crystal bandwidth and fixed phasing adjustment.? These use the original Lamb circuit.? The adjustment procedure is rather different from the later Hammarlund type filter.? Can be confusing but I don't think the earlier filter was used after aboutb1950. -------- Original message -------- From: don Root <drootofallevil@...> Date: 11/10/22 11:59 AM (GMT-08:00) Subject: Re: [HallicraftersRadios] SX-110 Alignment Puzzle Hi Steve again I believe from previous posts re the sx-110, you are trying to understand and implement the original instructions,? rather than use newer? techniques. Due to your previous posts I have run into all kinds of stuff about crystals on the www; so thanks for the incentive. ? As to your specific query: My guess is that the note for step 2means¡. frequency of the crystal [ not just the IF transformers]? , and it does not say ¡°exact¡±? so is likely ballpark freq of ztal.? In the next step? I think it means the exact frequency of the that specific ztal in that specific circuit. I can only guess that for an older generator, you can adjust the frequency in small increments, but the readout of frequency is limited, so it will be hard to ¡°dial it in¡±, so I think their intent is keep the generator setting from step 2 , and use it [don¡¯t change it] to begin step 3 ?since step 3 is so sharp¡ just my guess. ? From some of my readings, step 2 cannot easily produce an ¡°exact¡± frequency, at least with equipment of the time.? ? As I read your attachment , I can only assume that IF you are using the Original crystal , the factory has set step 2 .. so it is not really necessary to repeat it; but if you change crystals [your situation?]? you should do step 2? This is my thought on what the instructions means; some others must have a better explanation. 73, Don VA3DRL ? ? From: [email protected] [mailto:[email protected]] On Behalf Of KW4H via groups.io ? All, ? The IF alignment procedure as spelled out in the SX-110¡¯s Operating and Service Manual is a little confusing in one spot (see attached). In step 2 you adjust the top slug of the first IF transformer (alignment point "A") for a dip on your output meter (a VTVM, usually) (while varying the generator frequency some) ¨C and the factory note says indicates that this alignment is to the frequency of the crystal. Fine -- I've found that null and know the frequency of that exact point. In the next step, however, you are asked to switch to sharp and ¡°adjust the generator frequency for maximum output¡± and that this is the ¡°exact frequency of the crystal¡±. So, which is it? I thought the frequency of the crystal was determined in step 2?? See the language in the factory note below step 2.? Thoughts? ? 73 ¨C Steve, KW4H
|