Cell Phone Repeater Questions - Page 1
Forum section: electronics / general

author: hermitengineer
author_rank: Regular Contributor
timestamp: October 26, 2021, 03:08:55 am
content: I'm trying to gain as much understanding as I can about a cell phone repeater kit, in order to install it most effectively. So I thought I'd ask some general questions before deciding to take the plunge.First, I've heard that for direct communication, the phone and the tower will negotiate for some minimum amount of power which is still useful for the phone. Seems like the tower's goal is to give you maybe -100dbm wherever you are. Does a repeater affect this negotiation? One that I'm looking at says it will default to 65-70db of gain depending on frequency block, and only decrease if it gets oscillation, and a max downlink transmit of -2dbm. But will it attempt to make the signal anywhere near that strong? Or would it just continue to let the phone argue with the tower, acting as the proxy?Second, from what I understand, the signal strength drops by 20log10(distance). That means at 10 meters from the repeater antenna, you already lost 20db from transmit strength, and 100m away you're now at a 40db loss. Do I understand that correctly? Does FSPL for a directional antenna affect the loss vs distance, or does it just provide an offset to the starting strength? But still, at a friend's house, if I hold my phone against his repeater antenna mounted on the roof just above the dining table, it sees -80dbm. At table level, it's already -100dbm. That's less than 1m!

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 26, 2021, 03:14:07 am
content: Any reason to not just use the call over Wifi feature many newer phones have?

author: hermitengineer
author_rank: Regular Contributor
timestamp: October 26, 2021, 07:48:52 am
content: The place I'm interested in using it has no grid of any kind. We have a solar system for power, and definitely no internet or wi-fi without the phone.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 26, 2021, 12:34:58 pm
content: Try the low tech approach of getting an old satellite dish and putting the phone or mobile hotspot where the LNB goes.

author: hermitengineer
author_rank: Regular Contributor
timestamp: October 26, 2021, 08:14:53 pm
content: The nearest LoS tower is 60km away but also on the other side of a ridge 1km away. With a tall pole or tree (around 15m), I can peek over the ridge to see the tower. So it doesn't seem practical to try to use a phone while mounting it to a satellite dish, and I would rather not have to walk to the top of the ridge to do phone stuff.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 26, 2021, 10:25:16 pm
content: Perhaps look into satellite Internet service like Starlink instead?

author: SmallCog
author_rank: Frequent Contributor
timestamp: October 27, 2021, 02:51:00 am
content: I don't know what equipment you're looking at, and I'm far from an expert....Firstly to check for line of site get a location and height of your network on the tower (wont necessarily be at the top!) and use the viewshed feature on google earth to see if you'll get receptionHere in Australia I use CellFi Go repeaters installed on vehicles. Pretty sure they're available in other countries but perhaps under a different name - no idea if these are the model you're looking at.Australia is a big place, roughly similar to the US but most people live on the coast in the bottom right corner of the country. Out where I work there are a lot of cell towers a long way from another towerWhat I've observed with the CellFi units is that they'll hold onto a signal for a long time as you drive away from cellular reception. If you're as bored as I sometimes am on a long drive you'll see your signal bars on your phone dipping down, and once it gets down to 1-2 bars about 30km out of town all of a sudden bam the celfi kicks in and you're back up to full signal.In relatively flat terrain with a nice high powerful tower I've kept signal out past 90kmHowever.... They're not as good at finding a signal as keeping it. Driving back towards that same tower you're not going to suddenly get signal at that 90km mark. More like about 50km whereas you'd have gotten signal at 30km from the tower with just a phone.