Later in the Seven Cows series the characters are going to install a pirate radio station. This is illegal but the authorities are pinned down with other problems. Ideally, this station would be able to reach out ten or fifteen miles in the cardinal compass directions.
I know just a tiny bit about radios and radio waves. Tiny, tiny bit.
I suspect that I have readers who could whip off a functional concept while eating their Rice Crispies.
A few questions:
Which band? GMRS? Ham? CB? AM? FM? The FCC restricts "unlicensed" AM and FM stations to a transmission range of a few hundred meters.
The FCC also puts a minimum power requirement for licensed stations, I think 250W for AM and 100W for FM.
If something like GMRS what is the practicality of duplex repeaters on utility poles? Would they work by shifting privacy codes such that a listener could listen to channel xy and try privacy codes 13, 14 or 15 to find the best signal for their location?
If GMRS, what channels are least heavily used?
If GMRS, would the "network" also be able to function as two-way communication whereby one small patch of civilization can call for mutual aid?
If AM or FM, how much power would be required to transmit five miles? How about ten miles?
What questions am I not smart enough to ask but should be asking?
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ReplyDelete(ERJ writes: My bad. I fat-fingered the comment. Reproduced from the internet that never forgets)
Delete30 years ago I had a 20 watt AM transmitter that friends and I used for music that went about 16 miles in flat terrain. It takes a good transmit antenna. Easy and cheap to make and it was unlicensed radio. Just a lark, but was fun.
AM takes longer antennae (harder to hide), FM (depending on the frequency) takes shorter. GMRS would likely not be the best but would work.
It depends on what your goal is. Keep in mind that most people have AM or FM radios, so for a general audience it would need to be one of those two, or you would have to stockpile and give/ sell other radios.
ReplyDeleteIdeally, I would suggest MURS units, or at least MURS capable since you escape the restrictions of FRS/ GMRS in terms of antenna and power, but CB may be as good especially since the radios themselves are widely available. Keep in mind that like with GMRS there is a range of quality, features, and clarity depending on the manufacturer and price of the unit.
Your antenna height and design will make a big difference in how far your signal can be picked up (of course, the receiving antenna will also matter).
ReplyDeleteLike B above, I would suggest someone with lots more knowledge than myself to give you useful advice!
Amazon sells high-power FM transmitter. I bought one and use it - good audio quality.
ReplyDeletehttps://www.amazon.com/CZH-CZH-05B-Wireless-Broadcast-Transmitter/dp/B01JS39622
https://www.amazon.com/Retekess-Transmitter-Wireless-Broadcast-Christmas/dp/B01D44EP4K
https://www.amazon.com/Signstek-Broadcast-Transmitter-Antenna-Fashion/dp/B00CM2VPMQ
Your antenna is crucial - your transmitters power is of no use if it is connected to a mis-matched antenna.
One can build a much better antenna than that. Having said that, that is an easy and fast solution. You won't get 10 miles out of it though.
ReplyDeleteI have no idea regarding radio or electronics.....but my first thought was.....when the baddies finally find out about the radio station.....what's to keep them from hijacking the signal or homing in on the signal and eliminating the station......
ReplyDeleteSteve
Forgive the pun: Stay tuned in for future installments.
DeleteThat is how stories work. A problem begets a solution. The solution begets new problems.
Summarizing: Low power transmitters exist as engineered, proven designs built in factories that should give reliability rates similar to color TVs.
ReplyDeleteA power level of 15W-to-25W would give me the desired range if hooked to an antenna by a person with the skills and tools to tune it in.
It MIGHT be possible to feed the transmitter's signal into an amplifier and thence to the killer antenna.
It all hinges on having a person with the skills, the proper shielded cable and connection, the ability to elevate the proper antenna and tools like SWR meters etc.
Giant Disclaimer: This is not legal to execute today due to FCC rules.
Talk to a local ham operator about the gear he can run. High power amps and high-gain (efficient) antennas are part of that skill set.
ReplyDeleteGMRS or CB for wide availability of equipment. Use GMRS repeaters. FRM/GMRS repeaters are not that expensive. The license for GMRS is pretty cheap. The codes screen transmissions but do not make them private. For more money also consider WIFI using mesh routers. I have the idea, not yet tested, that I can set up a mesh network in my neighborhood and share camera access among neighbors. The equipment is on the shelf awaiting a free Saturday. Directional antennas are what you would use.
ReplyDeleteHorses for courses, different tech for different purposes...
ReplyDeleteAM or FM are good for broadcast info like "the Voice of Eaton Rapids" and even 10W FM can go a long way (Concord MA to Chicago one night).
CB, GMRS, FRS, and Ham allow two-way traffic for voice.
Meshed WiFi is great for data traffic like remote IP cameras but is a lot more cumbersome for voice..
I can see having all three, with the VoER broadcast starting late in the game if you want to bring in survivors.
Couple more things. If these people want decent point to point communication, check out Baofeng radios on Amazon. You really need the optional antenna upgrade and the larger battery pack is also nice but with these plus the programming cable (you only need one of these for all your radios), your cost is well under $100 each.
ReplyDeletehttps://www.amazon.com/BaoFeng-UV-5R-Dual-Radio-Black/dp/B007H4VT7A
Antennas - here is a link to an excellent 30 minute YouTube talk:
https://hackaday.com/2019/03/04/justin-mcallisters-simple-post-apocalypse-friendly-antennas/