Ideas for investing in the Wireless

I am soon graduating electrical engineering, but have a passion for Radio Frequency, and also want to learn about possible investment opportunities and business ideas.

I have made a decent income recently by flipping amateur radio transceivers. I bought a pallet of 320 radios for 15 bucks a piece, and offered frequency programming and am almost through the pallet selling them at 50 bucks each.

I would like to move to investing opportunities in the commercial sector in radio communications such as 5G cellular, Low power FM broadcast stations, Land mobile radio, or whatever I can find with the lowest barrier to entry.

I am not necessarily interested in retail, selling cellphones, I would really like to get into the infrastructure side of things.

Let me know if anybody has other ideas to brainstorm on investment opportunities in the wireless sector. Here is my current list:

- Stocks. There are several 5G stocks, but I am not a fan of tying my money up in stocks, it's hard to determine if you are getting something under market value, and I much prefer investing in physical things.

- Flipping radios: I have been successful flipping radios for the amateur market, but this does not have much expanding due to the limited market size, there's only 800,000 hams in the US. Maybe if I were to become an official dealer for commercial land mobile radio, there would be much more room to scale up.

- Wireless Internet service provider- This seems highly dependent on location and current prices for what speed you get. It can be hard to find a market where you are competitive, but this could be lucrative in areas such as mountain towns and rural areas where cable and fiber is difficult to reach.

- FM broadcast low power stations- I have seen some of these for sale here and there for around $50K on the smaller markets, but those are only like 250 watt transmitters in little towns. It quickly scales up to 1M+ in big cities. My worry here would be that the FM market is a depreciating asset, and the money would start to dry up as advertisers leave. But if as a short term investment if I had good cashflow statements, maybe this could provide lucrative for a few years.

- Real Estate
There are mountaintop radio facilites with lots of antennas. I'm sure these facilities are multi-million. My main worry here is that the big facilities are NOT IDEAL for 5G networks, and there is not much demand anymore for wide area coverage, the market is all going micro cells. I would be worried about tenants leaving as the market for the land mobile radio, TV stations, and other odds and ends start leaving. This may be a good investment for rural areas where 5G millimeter will never work.

How would real estate even work for 5G micro cells, I think street lamps are owned by the city, and private investors can't just go buy street lamps. I've also seen cell companies completely replace the street lamps with their own.

- Cellular technology
This really feels like a dark, secret market that isn't accessible, you can't even find much info on the web how it all works. I can't think of any way to deploy, flip, or invest in the physical radio technology that cellular towers use. The closest I can see are contractors that deploy radios such as a verizon panel antenna, but they do not have any involvement in the technology itself.

SO, who has some other ideas to brainstorm on investing oppurtunites in growing wireless markets? I'd like to hear any thoughts or something one of you are doing to make $$$ on the air waves!!!