Radio Alignment Explained

What am I actually doing when I "align" a radio? What is the reason to do an alignment? If you watch the videos, and hear the signal getting stronger and see the meter increasing you may be wondering.... what the heck am I watching? I will try to explain it using a Hallicrafters S40-A schematic.

[@jenko701]

The best place to understand superhet is to look into Edwin Armstrong start from there then go to the technical stuff.

[@yanfishtwig2356]

thank you that finally put the whole thing together for me i knew parts of it but now the circuit is lit in my head

[@timtimeprojects3576]

Glad I could help. Have fun.

[@phs125]

This is what I understood. The thing at the end only accepts 455khz. So if I have everything aligned correctly, When I'm turning the dial, it's moving things inside the tuning capacitor, And it does 2 things at once. 1. It helps the antenna be it's best at 1000khz. 2. It makes the other thing produce exactly 1455khz. Then the 1455khz signal mixes with eveything coming through from antenna, and because the antenna is going it's best to push 1000khz through, They combine together and end up producing a range of frequencies, which are having a very good 455khz signal, but also some garbage we don't want. All the other garbage gets discarded by the filters, and you get a very pure 455khz signal at the end of all that. Which contains the signal which was originally in 1000khz. That 455khz signal goes through something else to be converted into sound, and into the speaker. So if you turn the dial to 1200khz, It 1. Makes the antenna be it's best at 1200khz 2. Make the radio produce a nice 1655khz signal. You get a 455khz difference, same deal, now you're listening to 1200khz station

[@phs125]

And the alignment of the colourful stuff, makes sure you're only taking 455khz further. And the alignment of screws in the tuning capacitor makes sure it favours the exact same frequency the dial is pointing at...

[@rayislooking2]

Great Video I learned a lot. Very well put and fairly easy to follow. I would like to see a video on what is a local oscillator? How the local oscillator works. How to test it,check it,adjust it. What components are used? Is "oscillator" the name for a circuit? Sorry for all the ?'s Thanks for sharing. Just1

[@timtimeprojects3576]

Questions are no problem. Just when I think I understand something I try to make it work and generate a ton of questions. On these old radios, an oscillator is a tuned or tank circuit consisting of a coil, a capacitor and an amplifier. Some use a crystal to control the frequency. Check Peter at TRX Bench. He does a great job at explaining oscillators and Phase Lock Loop.

[@rondeldebbio9219]

IF from the local oscillator and antenna frequency into the mixer , the result is 455khz which is modulated. True?

[@salmorreale7900]

So we have 1Khz, 1Khz +455, 1Khz-455, what is the fourth freq? Thank you for posting.

[@timtimeprojects3576]

Don't forget just 455.