How to build a radio relay station?

[David lopez]

if i decide to build two relay stations 100 miles apart, what frequency or frequencies should i use to send a radio signal across 100 miles from 1 relay
station to the other relay station.

 

[berkeman]

if i decide to build two relay stations 100 miles apart, what frequency or frequencies should i use to send a radio signal across 100 miles from 1 relay
station to the other relay station.

It depends. Is it for commercial use, or just for a hobby? If it's not for commercial use, you can use HAM radio (probably the 3 meter band), assuming that you have a HAM radio license. You would likely use high-gain Yagi antennas at both ends of the link. See my footer for more information about getting your HAM radio license.

Otherwise, you could try to use the ISM band (microwave oven band around 2.4GHz), which does not require a license for certain power levels. You would need to use high-gain Yagi antennas at both ends of the 100 mile path, and you would need line-of-sight connection (like between a couple of hills that can see each other)...

http://cdn.everythingrf.com/live/yagi_antenna_1.jpg

 

[David lopez]

preferably the signal can travel through a town. the signal can travel from 1 relay station through a town to the other relay station.

 

[russ_watters]

preferably the signal can travel through a town. the signal can travel from 1 relay station through a town to the other relay station.

What does it mean for the signal to travel through a town and why would you want to do that? Is this for a real project? What, exactly, are you trying to do?

 

[sophiecentaur]

What, exactly, are you trying to do?

I think he's trying to tempt PF into yet another futile discussion about a project that is just a thought exercise. (But not thought out at all.)
Sorry if I appear grumpy but the OP has posted a string of questions in the same vein. These things never actually seem to get anywhere. When are we going to be honoured with reports of a working system?

 

[David lopez]

will the buildings in the town block the radio signal?

 

[berkeman]

preferably the signal can travel through a town. the signal can travel from 1 relay station through a town to the other relay station.

Not for 100 miles through a town. Buildings contain metal, which reflects and diffracts EM waves. Those redirections of the EM waves cause multipath interference at receivers, which significantly reduce performance and path/channel distance. Even when the obstructions are just trees and foliage, you will still get a lot of attenuation of the signal due to partial absorption (depending on the frequency of the EM being used).

Think about what existing 100 mile radio links look like. The antenna towers are on high hills, so they have line of sight to other towers on other hills. The highly directional antennas are aimed very precisely at their twin antenna on the other tower that they are linked to.

https://previews.123rf.com/images/a...tion-antennas-on-a-mountaintop-in-ecuador.jpg

And think about cell phone towers, which do communicate "in towns". Note how closely they are usually spaced together (less than a mile), and how tall they are to try to get good coverage despite foliage attenuation and building multipath issues...

https://cdn.shopify.com/s/files/1/1...ower_Locations_Near_Me_large.png?v=1523220152

 

[David lopez]

so if i want to send a radio signal over a distance of 100 miles with the fewest number of relay stations for hobby use, how do i do that? is there any particular frequency i should use? is there any antenna design i should use?
this must be something a hobbyist can build at home.

 

[David lopez]

preferably the buildings in any town don't block the signal.

 

[berkeman]

preferably the buildings in any town don't block the signal.

So you live here?

https://i2.wp.com/trekkingdays.com/wp-content/uploads/Igloo-village-near-Lake-Shikaribetsu-e1549372544137.jpg?ssl=1

Or maybe here?

https://ichef.bbci.co.uk/news/720/cpsprodpb/426D/production/_106150071_gettyimages-463719401.jpg

 

[David lopez]

what if i shorten the distance to 40 miles? can you build something at home that will send a radio signal over a
distance of 40 miles, with the fewest number of relay stations?

 

[berkeman]

what if i shorten the distance to 40 miles? can you build something at home that will send a radio signal over a
distance of 40 miles, with the fewest number of relay stations?

Get your HAM radio license, and you can do all that kind of stuff. Plus you can use your local HAM club as a learning resource. It's inexpensive and pretty easy to get your license. PM me if you need more information about how to do it.

http://www.k4amg.org/uploads/1/1/4/6/114601157/20190809-102014_orig.jpg

 

[russ_watters]

I think he's trying to tempt PF into yet another futile discussion about a project that is just a thought exercise. (But not thought out at all.)
Sorry if I appear grumpy but the OP has posted a string of questions in the same vein. These things never actually seem to get anywhere. When are we going to be honoured with reports of a working system?

Ahh, thanks, I hadn't seen the other threads (or maybe I did but didn't notice a pattern...). In that case we should be giving the OP a shorter leash on asking uselessly vague questions...

 

[zoki85]

so if i want to send a radio signal over a distance of 100 miles with the fewest number of relay stations for hobby use, how do i do that? is there any particular frequency i should use? is there any antenna design i should use?
this must be something a hobbyist can build at home.

For distances over 100 miles I'd recommend shortwave band, preferably around 10 Mhz. Get decent transceivers (they are not so cheap). For aerials, the simplest design would be 6-8 m long 1/4 wave vertical wire. Insulated litz cable or just a coax of sufficient length would do. Good luck

 

[davenn]

For distances over 100 miles I'd recommend shortwave band, preferably around 10 Mhz. Get decent transceivers (they are not so cheap). For aerials, the simplest design would be 6-8 m long 1/4 wave vertical wire. Insulated litz cable or just a coax of sufficient length would do. Good luck

AND an amateur radio license as has been said several times earlier

 

[Borek]

First of all: you do understand that radio communication is heavily regulated, and you need to stick to these regulations? You don't choose any frequency you can think off, you stick to frequencies and powers allowed for amateur communication. Otherwise you risk a rather unpleasant visit from the authorities.

 

[sophiecentaur]

Otherwise you risk a rather unpleasant visit from the authorities.

And years in the slammer.

 

[sophiecentaur]

I think it be only fair for OP to write down what he knows, so far, about this topic. He talks of what he has read but just what is that (performance figures and costs, for instance)? There is a vast amount of information about various styles of communications which is available to him so why are we all running round, pre-digesting and pre-selecting it all for him?
This thread is just a conversation between other PF members with no useful input from the OP. I'd prefer to be conversing with people who have all actually done some homework. (@David lopez !)

 

[zoki85]

You don't choose any frequency you can think off, you stick to frequencies and powers allowed for amateur communication. Otherwise you risk a rather unpleasant visit from the authorities.

Regulations and laws differ from country to country , from place to place. One should be careful and make sure not to break laws by illegal broadcasting. Speaking of risks I can tell you that I think it is more likely and unpleasant, if you live in (sub)urban area like I do, to experience a visit from angry neighbours...

 

[Vanadium 50]

I think it be only fair for OP to write down what he knows, so far, about this topic.

Too late. He's already moved on to another thread.