Is It Just Me?

[Nowhere-Man]

I learned tonight about FM conversion to AM amplitudes. I realised some ratio discriminators worked at an IF of 455 KHz but, checking my German set, its IF for ratio detection is 10.7 MHz. I was forced to go back and look at resonance curves. I have to work very hard to improve and I put down most of my progress to hard work. Maybe, as was said, I need to be aware the learning peaks of the brain tend to flatten as you age, although I'm very careful to limit dumbed down media and to exercise my thinking. At this stage my transistor knowledge lags my valve understanding. Diagnostic skills are poor. Repair needs more practice and time spent getting hands dirty.

[Nowhere-Man]

I had to find something a bit better explained for BFO image than the quagmire of ARRL. It turns out to be pretty basic. The BFO on a Ham receiver was set to a kilocycle above the IF. Let's say 456 Kilocycles. All ARRL had to say in plain English was a signal at 457 Kilocycles tuned in could interfere with the BFO. Till recently I didn't know what a BFO or CW was. The main thing I needed to understand was it used the IF. You can't really use amateur radio textbooks and not know how the BFO worked so I searched around. The textbook answer is the BF0 converts the superhet IF to an AF coded audio sound.

[Crackle]

I thought the BFO was only needed for the reception of sideband transmissions, to make the speech intelligible again. I dont think it is needed for normal AM reception.
Mike

[Doodlebug]

Can remember ohms law at present.
 Eventually, I will  still be able to keep 100k of my assets !

[Old Sparky]

A BFO (Beat Frequency Oscillator) sometimes known as a CIO (Carrier Insertion Oscillator) is only needed fro the reception of SSB (Single Sideband) sinnals, and possibly CW (Continuous Wave - or should that be Carrier Wave?) i.e. Morse Code. It should be disabled for AM reception. BFOs were often used in conjuction with Product Detectors in Receivers covering Amateur Bands, etc., where many, if not most, transmissions are SSB. The BFO is set to about + or - 1kHz of the IF, and tuned through a limited range to recover the modulation i.e. audio content. SSB can be Upper or Lower sideband with suppressed or reduced Carrier, hence the need to be able to tune above or below the IF.

[Nowhere-Man]

CW is an unmodulated carrier wave with no amplitude variation. It is merely broken in intervals so you just need to recapture the breaks as coded dots and dashes. The preliminary signal can first be converted to the IF. The BFO could be set to 171 KHz if the IF was 170 KHz and you'd get an audio output. The trouble with the ARRL is it segments the material but doesn't give context. Most other books focus more on understanding than isolated segments.

[peter scott]

There is a benefit to forgetting things too! It's the delight in rediscovering them as if for the first time.

Peter

[Alistair D]

I know that I knew that

Al

[Nowhere-Man]

The old saying by Einstein holds true. Try and explain it to a cleaner till it's understood. If they understand the explanation, it's fine. The number of times I tried explaining something I suddenly realised I didn't understand myself. I read once a teacher threw away all books that didn't use conventional current so the students wouldn't get confused. Yet confusion is part of learning or exposes gaps. Often any confusion comes later on and understanding may take time.

[Murphyv310]

Try and explain it to a cleaner till it's understood. 

I sincerely hope you are joking...... My wife is a cleaner and I find a statement like that somewhat demeaning, just because a person is a cleaner doesn't mean they are thick!!!