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RE: When does a tuner need an alignment?

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fastcat

In Reply to: RE: When does a tuner need an alignment? posted by Steve O on September 29, 2018 at 14:11:43

Steve:

Thanks for the input!

If I were experiencing a higher than expected background noise level
with a station near the very far end of the tuning scale (88.7 in this case), would that possibly indicate a degree of misalignment?

Thanks!

Follow Ups:

RE: When does a tuner need an alignment? - Steve O 15:36:47 09/29/18 (4)
What you describe could be an alignment issue, esp if it developed gradually over time. It could also be the inability of the tuner to deal with HD broadcasts, mostly affecting vintage and tube types. Is the station broadcasting an HD signal?
- RE: When does a tuner need an alignment? - fastcat 16:27:45 09/29/18 (3)
  Steve:
  
  I do have a vintage tuner (Sansui TU-217), and the station does broadcast in HD too. Is there a way out that makes sense for this tuner, or similar?
  
  Thanks!
  - RE: When does a tuner need an alignment? - Steve O 17:16:18 09/29/18 (2)
    Difficult to do definitive remote troubleshooting and I'm not directly familiar with your tuner so I don't know for sure what the problem really is. However, if it truly is the HD issue there may a solution. A while back someone published a schematic for a relatively simple active low pass filter that could be inserted at the output of the FM detector that would filter out the HD junk prior to the stereo decoder. Building and installing the filter would requires a moderate degree of expertise. The bother of this solution must be traded off against finding a tuner inherently capable of dealing with HD while still meeting your sonic expectations. Based on the FM programming and audio quality in my area, it would have to be a very special tuner to warrant this kind of effort. Ultimately you are the only judge of the proper course of action for your situation.
    - RE: When does a tuner need an alignment? - fastcat 17:29:10 09/29/18 (1)
      Steve:
      
      I found an on-line article about FM tuner self noise with ND:
      
      http://www.ham-radio.com/k6sti/hdrsn.htm
      
      The catch for me would be figuring out where the FM detector ends, and the Stereo decoder starts, assuming that both are not inside a chip in my unit.
      
      Thanks!
      - RE: When does a tuner need an alignment? - Steve O 18:46:30 09/29/18 (0)
        
        In Reply to: RE: When does a tuner need an alignment? posted by fastcat on September 29, 2018 at 17:29:10
        
        That's the article and circuit I was referencing. The only modification I'd make would be to ditch the ancient TL071 and replace with a modern, wider band op amp. Answering your question about detector and MPX decoder and installation of a filter (if HD is really the problem) will require a schematic and possibly a board LO.

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