Radio Overhaul - Alignment page 3

Because the Sencore has a two level pilot signal I am able to adjust the stereo decoder to a finer degree.

I was able to adjust the stereo separation to a pretty high degree. That concludes the FM radio portion, now the AM.

I'll adjust the AM IF section first.

Again, signal injection and reading the output on the amps although since it's AM only 1 speaker channel is needed.

The AM IF is just adjusted by peaking. You would use a sweep method via signal generator and scope or spectrum analyzer with built in tracking generator if you were adjusting the AM IF on an aircraft radio or HAM radio in order to meet certain specifications, but on the standard broadcast band and on a consumer grade radio, peaking will do just fine. So here you adjust to achieve the tallest sine wave.

Next up is the adjustment of the pre-selector filter and antenna trimmer.

So now the signal is injected in the antenna jack and I will use the minimum power to still see a decent sine wave. In this case it's set to #6 on the output.

#6 is 3.5 uV. That's really good.

There is some noise, but you'd still the hear the broadcast reasonably well.

I did have to do quite some adjustment on the AM, if you recall the AM was dead in this radio and I had to open and repair one of the IF transformers. No doubt that changed the sensitivity. Now it should pick up loads of stations out here.