Thank you for sharing the procedure. You sharing involves a lot of things that other people don't want to share with us and that is selfish on their part. THANKS, AGAIN!!!
Hi Tony. Measuring the THD is definitely the "icing on the cake". This is the step that separates the tech on the assembly line from the one with time and patience to really nail it. Lastly, with all the very high levels of composite clipping that most of the FM broadcasters use, this level of low THD is often not obtainable no matter what equipment is available to the end consumer because it's not there in the OTA signal. Even antenna bays are not aligned to spec and cause skewing of the sidebands, but few pay attention anymore. I think only the broadcasters that program classical music today are paying attention to the actual "quality" of the audio being modulated. Just an old man here waxing poetic. Keep up the great work and keep showing the viewer how it is done the right way. Far too much incorrect information on the internet now polluting the truth. 73 OM
Kudos to you Tony for making this video! This is one of the best explained and easy to follow videos I have seen on performing a visual FM alignment. Great job!
That's one of the best s curves I've ever seen doing a swept alignment. Great work. Now I know why I saw the PACO and asked about it a few vids back! Thanks again for the lessons!
Interesting and highly educational video. After seeing your alignment procedure with the wobbulator, now I remember why I prefer adjusting the IF with a spectrum analyzer/tracking generator.
I noticed that the dial indicator (at least for FM) tended to "see-saw" which would mean that getting the accuracy ultra-perfect would be dependent on which direction you were tuning the dial.
My first HiFi purchase was a Fisher tuner of this vintage, which I believe had the multiplex FM (I didn’t know what it was). My unit had a 2nd chassis mounted below the tuner chassis labeled ‘preamp.’ There was an eight pin connector between the two chassis. It sounded much better, and tuned much better, than the stereo Sansui that replaced it. It was 1971. I wish I had it still, even if it was monaural. 🙂
You should not have touched the tubing dial while tweaking the detector. That’s moving the goalposts. I would say your IF ended up too peaked, by the touchy tuning. You should have taken a closer look at the IF curves when you had them, instead of using the detector probe.
4:00 Kind of confusing how some engineers refer to TP as a "test point" on a schematic, while others refer to TP as a common "tie point" on an unused terminal on a valve, vacuum tube, or terminal strip. (edit: added timestamp)
I had to follow up question: with the 2015 THD meter, when measuring THD do you have to input a signal for it to look for? I know with a r&s unit I have and the HP audio analyzer you have to punch in the signal frequency for it to measure. I hope this question makes sense.
The 2015 has an auto mode, which automatically locks onto the fundamental frequency. You can also manually set it to a set fundamental. The 2015 also has a built-in low distortion signal generator, but I don't use it.
A Great demonstration with alot of "pitfalls" !! Trade secrets, I believe you were trying to say in the beginning of your intro. I figured alot of this out by just repitition of alignment sequence. Still, I won't spend $2K or more for a good 2015. Past that in my time. I enjoy the thorough style of your work, thank you.
