What is Reddit's opinion of Modern Electronic Communication?

From 3.5 billion Reddit comments

This is a newer edition of the book I learnt RF stuff from back in the day: http://www.amazon.com/Modern-Electronic-Communication-9th-Edition/dp/0132251132

Not sure if it's going to be relevant enough for you without knowing precisely what you want to know, but might be worth a look to see.

I believe this book will answer all your questions https://www.amazon.com/Modern-Electronic-Communication-Jeffrey-Beasley/dp/0132251132/ref=mp_s_a_1_3?dchild=1&keywords=modern+electronic+communication&qid=1627528634&sr=8-3

1. In terms of requirements, I use an elderly IFR500 for day to day stuff, and have access to an Anritsu Sitemaster s362e for cabling and interference testing. If I want to just do some quick and dirty stuff, a $20 USB stick for a RTLSDR program works fine. The SDR is probably your best bet, given it's low cost but good feature set.

2. That depends on what you already know, and what you want to know. I'd look up primers on AM/SSB and FM/PM transmission/reception, then read into the theory before looking at "simple" circuits. I learnt mine over four years as a combination of on-the-job training, and modules at college. The books I use/used is an old edition of "Modern Electronic Communication" By Gary Miller and the ARRL Handbook , but I'm sure nowadays there's plenty more online you can learn from.

3. For wi-fi, it's usually (always?) in an "unlicensed" band. This means that anyone can use it, but there's no real protection against interfering signals. In your case, you probably want to try alternate channels, turn off your neighbour's wifi, or see if you can move to the 5GHz band (new equipment) if the current 2.4GHz band is full. The repeater could be making things worse (you need another channel and it will halve the available bandwidth). Quieting the noise will rely on you removing interfering transmitters (check for wireless/walky phones on 2.4G as well!), or installing shielding outside your house (like a Faraday cage, impractical though!). Adding amplifiers to your existing equipment isn't really practical (and may actually be unlawful), but replacing it with better equipment might be workable (some prosumer/commercial stuff is better than the average home equipment).

4. Your assumption isn't really useful in the context of your issue. Most RF signals will be filtered in hardware, or they wouldn't pass licensing/testing/etc. I can have a transmitter outputting 50W at 400MHz, and once you go 100KHz to one side you wouldn't really know it was running. Slap a decent hybrid combiner/band-pass filter on it, and suddenly you're transmitting at 12.5W (6dB loss) but 12.5KHz to a side and it's literally as if the transmitter doesn't exist. Take all the filtering components out of the final stage, and your 50W at 400MHz becomes 80W splattered all across the spectrum almost as if someone emptied a can of paint off a building onto the sidewalk...