how a tetra repeater works

[cerine]

i want to extend the radio coverage and I need to install a repeater to pick up the signal and broadcast it except I'm confused about how it works:
the repeater has a gain = 90 dbm and an output power = 37 dbm. for example the repeater receives a signal equal to -50dbm in this case how its output power will be calculated:
case 1: output power = received signal (-60dbm) + gain (90dbm)
-50+90=40 dbm = 10 watt
or
case 2: it suffices to capture a signal (greater than the minimum reception limit) so that the repeater amplifies it to its maximum power which is for this repeater equal to 37 dbm= 5 watt

 

[dazey77]

A repeater decodes what it receives and transmits it back out at its transmit power. It’s not an analogue amplifier so what comes out doesn’t change depending on if it receives a weak or strong signal, it always sends it back out at its transmitting power. So case 2.
obviously If what comes in is too low to be comprehended then you get the same or nothing out.
a repeater is logically a receiver paired with a transmitter, not an amplifier.

 

[mmckenna]

I think it would help if you shared a link to the "repeater" you are talking about.
What you are describing sounds more like a Bi-Directional Amplifier

 

[KevinC]

I think it would help if you shared a link to the "repeater" you are talking about.
What you are describing sounds more like a Bi-Directional Amplifier

Ugh...when I worked for a large PCS carrier (through an acquisition, not voluntarily) they referred to BDA's as repeaters. Through me off for awhile until I figured out what they meant.

 

[dazey77]

Good responses, hadn't occurred to me that he might not actually be talking about a repeater. Makes a lot of sense.

 

[cerine]

thank you for your help ,
i'm working with these two repeaters

ERDCHS1-385P37G90N - Excelwave | RF Repeaters

www.everythingrf.com

and 010048k_dat_digisel_gb

 

[mmckenna]

thank you for your help ,
i'm working with these two repeaters

OK, that helps.

Terminology is a funny thing. While they refer to that as a 'repeater', here in the USA, we'd call that a bi-directional amplifier.
Essentially the same thing, but a bit different using the terminology I'm comfortable with. They use a lot less power than what I'd call a 'repeater'. But that's OK, as long as we all understand what it is.

Looks like that's designed to improve indoor coverage of a TETRA system. It uses low power amplifiers to handle the uplink and downlink frequencies for the TETRA handsets.
Usually the amplification is carefully controlled to prevent self oscillation.

the repeater has a gain = 90 dbm and an output power = 37 dbm. for example the repeater receives a signal equal to -50dbm in this case how its output power will be calculated:
case 1: output power = received signal (-60dbm) + gain (90dbm)
-50+90=40 dbm = 10 watt
or
case 2: it suffices to capture a signal (greater than the minimum reception limit) so that the repeater amplifies it to its maximum power which is for this repeater equal to 37 dbm= 5 watt

Case 2 is likely the correct one. The self oscillation thing I mentioned above is usually the concern. Carefully controlling coverage is important, and having the output level controlled is part of that. If it says it puts out 37dBm, then that is likely it's maximum. Higher input on the customer side won't increase it.

 

[RFI-EMI-GUY]

I think there is an over simplification here.

With BDA amplifiers, the maximum power output, in this case +37 dBm, 5 watts is the aggregate power of all of the carriers which it is amplifying. So if you have 10 carriers, they each produce 0.5 watts. If 5 drop off the air, then 1.0 watt each.

This also is a simplification, because you want to be sure that the output is linear, not in compression and you must account for noise energy and undesired carriers that by nature will find their way into the system.

Follow manufacturers recommendations to a letter. If the documentation is lacking, pick another vendor...

 

[mmckenna]

I think there is an over simplification here.

It's what I do best….

 

[cerine]

It's what I do best….

thank you , i appreciate it

 

[cerine]

I think there is an over simplification here.

With BDA amplifiers, the maximum power output, in this case +37 dBm, 5 watts is the aggregate power of all of the carriers which it is amplifying. So if you have 10 carriers, they each produce 0.5 watts. If 5 drop off the air, then 1.0 watt each.

This also is a simplification, because you want to be sure that the output is linear, not in compression and you must account for noise energy and undesired carriers that by nature will find their way into the system.

Follow manufacturers recommendations to a letter. If the documentation is lacking, pick another vendor...

thank you , i appreciate it