S-280 Shelter. How do I get Cellular/Radio Reception Inside?

Tinstar

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Have S-280 Shelter and cannot receive either cellular or radio signals once inside and door closed.

There are several devices available commercially that are advertised to bring the signals inside, but have read most are so so at best.
A friend spent over $500 on one model and he said it didn’t really help his reception at all.

What, if anything, are you guys using that actually works?
Commerically available or home brew.
I don’t mind spending the money, I just want something that actually works.
 

DieselAddict

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I'm in a place where cell service is a challenge. The frequencies that cell phones operate are very easy to block. Especially by metal. Where I live the problem is trees. My situation is horrible due to the ever changing nature of the environment. Your situation should be much more manageable assuming your signal outside is good.

Can you do some testing and show the difference in signal strength from outside versus inside the enclosure?
 

NDT

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It's funny that the whole reason for the radio shelters is to block interference (spurious radio signals). This is now your problem. The design is that desired signals would be brought inside via an antenna cable. Maybe this can be done for a AM/FM broadcast radio? For cellular, there are professional "repeater" devices made that work really well. We had to install one to get reception in a metal building. Was not cheap.
 

Tinstar

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While we are miles from town, the signal strength is good
4 bars

Leave door open while I’m inside it’s 2 bars

Close door.......nothing. Not even a hint.
 

Tinstar

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It's funny that the whole reason for the radio shelters is to block interference (spurious radio signals). This is now your problem. The design is that desired signals would be brought inside via an antenna cable. Maybe this can be done for a AM/FM broadcast radio? For cellular, there are professional "repeater" devices made that work really well. We had to install one to get reception in a metal building. Was not cheap.
As mentioned earlier, I know there are devices to bring service inside.

What I don’t know is which ones truly work and which ones don’t.
I know a few guys that have used them without much success.

Maybe a member here has built their own system and would share how it was done.

I thought about trying a simple appropriate antenna outside and another inside with the correct wire in between.
 

firefinder

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Tinstar,

As NDT said, the shelter is a purpose built Faraday cage! Hope this doesn't sound too simple, but the simple solution may solve the problem.

Might be easy to try a unity gain antenna arrangement. Use two good quality cellular antennas and a sufficiently long piece of coax cable with properly crimped connectors. Place one antenna on the outside of the shelter and one antenna inside the shelter. Make sure the coax cable is not un-necessarily bent, smashed or crimped when connecting the two antennas.
 

marchplumber

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Tinstar,

As NDT said, the shelter is a purpose built Faraday cage! Hope this doesn't sound too simple, but the simple solution may solve the problem.

Might be easy to try a unity gain antenna arrangement. Use two good quality cellular antennas and a sufficiently long piece of coax cable with properly crimped connectors. Place one antenna on the outside of the shelter and one antenna inside the shelter. Make sure the coax cable is not un-necessarily bent, smashed or crimped when connecting the two antennas.

I'm stupid here...................two antennas.................One to receive and one to transmit inside the shelter? Used as a signal "conduit"???? Just asking and looking to learn.
 

SCSG-G4

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I'm stupid here...................two antennas.................One to receive and one to transmit inside the shelter? Used as a signal "conduit"???? Just asking and looking to learn.
YES, YOU GOT IT! The signal will follow the outside antenna inside through the coax and then radiate out of the inside antenna. Ideally, you would put a powered booster along the line inside the shelter to increase the signal (before the interior antenna), so you would get four bars. The higher up the exterior antenna is above obstructions, the better the signal will be. A good recent example at the GA MV Rally was that I could get three bars standing in the MKT, with the phone about 8 feet off the ground, but only one bar two feet over and three feet down, standing on the ground.
 

marchplumber

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So, the incoming signals power is what is used to "broadcast" it from the other antenna? So, if weak on the outside antenna, wouldn't do much good without a booster inline? I don't normally do radio stuff, so this is outside of my area of expertise and it's really cool to learn. THANKS gentlemen!
 

Chainbreaker

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With an outdoor/indoor antenna arrangement you should also consider incorporating some type of lightning arrestor arrangement into your setup or you could potentially bring in more than just the cellular signal. There are some coax type connectors that have grounding lugs for this purpose.
 

BobbyT

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I'm stupid here...................two antennas.................One to receive and one to transmit inside the shelter? Used as a signal "conduit"???? Just asking and looking to learn.
Yes, it’s referred to as a passive antenna system, where the signal outside is fed into the box/building through the outside antenna, through the coax and out the inside antenna. It’s also a duplex situation that your phone transmits back out to the tower in reverse. It’s best to make sure the antennas you use are tuned for the frequencies that your carrier is using and keep you coax length as short as possible to reduce the amount of loss that’s added. But if you can gain at least one bar where you had none before, you should be good.

Also depending on what carrier you use, their network will be based on power or quality of the signal, so the amount of bars doesn’t equate to level of service that it used to mean. (I’m an RF Engineer, so I won’t bore everyone with detailed explanation :cool:)
 

Tinstar

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I know the shelter is designed to keep signals out.
Wanting to see what would work to bring signal in.

I was also thinking about doing the two antennas setup as I mentioned earlier.
It seems logical and is a lot less expensive than the commercial booster setups on the market.

Think I will try that route first.

Not really worried about lightning.
Too many trees and a steel container taller than than the shelter itself.
 

USAMilRet

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I know the shelter is designed to keep signals out.
Wanting to see what would work to bring signal in.

I was also thinking about doing the two antennas setup as I mentioned earlier.
It seems logical and is a lot less expensive than the commercial booster setups on the market.

Think I will try that route first.

Not really worried about lightning.
Too many trees and a steel container taller than than the shelter itself.
That is a false assumption on lightning. It seeks out the least path of resistance regardless of whether you are in the woods or not.

You have air to ground strikes, ground to air strikes, air to air strikes, and I am sure more as well.
 

Karl kostman

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I am pretty sure what firefinder came up with will work for you. As I was reading this I was trying to think of the same thing firefinder came up with but hadnt gotten to the how to DO IT yet, good job firefinder!
karl
 

m32825

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Sounds to me like this enclosure is acting as a Faraday cage. Isn't lightning going to run around the outside if it gets hit? The best path to ground isn't going to be the antenna going to air on the inside, is it? Inquiring minds want to know!

-- Carl
 

Chainbreaker

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Lightning sometimes acts in mysterious ways...there is the element of "side flash" where a strike let's say hits a tree and travels down the trunk but can create a side flash that finds another path to ground.

Here are some lightning/antenna grounding reference materials for inquiring minds:

https://www.repeaterstore.com/pages/signal-booster-antenna-grounding In particular, note this excerpt: "The metal frame or structure of a building. If none of the options above is feasible, you can ground by connecting to the metal structure of the building, as long as the structure is grounded."

https://www.bwcelectronics.com/articles/WP30A190.pdf
 

CMPPhil

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I don't know having someplace where I won't get Robo Calls, Sales Calls, Political Calls, on cell phone does not really sound that bad.

I used my S56 radio box as an office for years and the solution then was run the land line into the box. But you are correct radio shelters are dead without an outside antenna.

What are the optimum antenna lengths for cell phones?

Cheers Phil
 
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