too much gain

[ahuebel]

I have a question that I hope someone could answer or direct me to an answer.

The question is regarding how much is too much with respect to amplification.

The context is a system where off air cellular and PCS signal is brought into an amplifier/repeater and rebroadcast to multiple antennae inside a building to increase signal strength. This is basically a rudamentary distributed antenna system.

Let us assume we have a building where coverage is poor for 3 out of 4 carriers. There is a single donor antenna and a single amplifier. Even the carrier's signal that is already adequate will be amplified in such a brute force approach. What is the threshold whereby a signal is so strong it downs out signal from other carriers?

As I understand it CDMA has measures to distinguish signal even in such environments but let us assume it is a TDMA carrier that is being "drowned" out. What is that threshold?

I realize this can potentially be avoided with multiple donor antennas and amplifiers but for the sake of argument let's assume the above described approach.

I appreciate any help in advance!

 

[N_Jay]

I have a question that I hope someone could answer or direct me to an answer.

The question is regarding how much is too much with respect to amplification.

The context is a system where off air cellular and PCS signal is brought into an amplifier/repeater and rebroadcast to multiple antennae inside a building to increase signal strength. This is basically a rudamentary distributed antenna system.

Let us assume we have a building where coverage is poor for 3 out of 4 carriers. There is a single donor antenna and a single amplifier. Even the carrier's signal that is already adequate will be amplified in such a brute force approach. What is the threshold whereby a signal is so strong it downs out signal from other carriers?

As I understand it CDMA has measures to distinguish signal even in such environments but let us assume it is a TDMA carrier that is being "drowned" out. What is that threshold?

I realize this can potentially be avoided with multiple donor antennas and amplifiers but for the sake of argument let's assume the above described approach.

I appreciate any help in advance!

Systems of the kind you are describing are not legal unless authorized by the cellular carrier(s).

Since the output is going to an antenna they are a transmitter, and you must be licensed for the frequency to operate a transmitter.

I am not sure I understand the rest of your question.

In general you will need a directional antenna to pick up each carrier (since it is unlikely they are ALL in the same direction).

You will also need to set the gain so the signal radiated outside the buildings does not interfere with the direct signal.

The gain also has to be regulated to prevent the system from going into oscilation, or overload.

You also want to make sure the signal retuned to the cell site is not too strong.

 

[ahuebel]

Yes, I believe you did not understand my question. Perhaps it is a bit out of the scope of this forum but I assume there to be enough "radio" folks in here to provide some information.

At any rate, there is a point for a given receiver (cell phone) where an outside signal (from someone other than its carrier) is so strong, it cannot decipher signal from its own carrier. Most devices have a published receive sensitivity in a spec sheet.... this is a similar concept but on the other end of the "spectrum".

 

[N_Jay]

Yes, I believe you did not understand my question. Perhaps it is a bit out of the scope of this forum but I assume there to be enough "radio" folks in here to provide some information.

At any rate, there is a point for a given receiver (cell phone) where an outside signal (from someone other than its carrier) is so strong, it cannot decipher signal from its own carrier. Most devices have a published receive sensitivity in a spec sheet.... this is a similar concept but on the other end of the "spectrum".

There are lots of numbers. here is no one answer.

An on-channel sigal is usually considered stong enough to capture the receiver when it is 6dB over all other signals.

This is only true in FM, but other modlulatin forms have similar effects.
The 6dB number must include multipath and other variations in teh signal levels, so often you need 20dB to make sure the weaker signal does not beak through.

Then there is the adjacent channel rejection. This is teh difference between the level of a signal on an adjacent channel whent it can cause interference on the desired channel.

Thene thes is teh 3rd order intercept. This can be thought of an teh maximul signal anywhere in teh band that can cuase the receiver to become non-linear and start mixing signals in the front end.

Thene there are desensitation curves, that show the amount of degradation on the desired channel based on a particular strength signal elsewher in the band.

All these numbers will be different for each type of receiver and each type of modulation.

I am NOT trying to be a samrt-ass, just pointing out that your question has no clear answer.

So now my question?
Are you trying to install a amplifier to help get cellular coverage (Illegal for all but the carrier)
OR,
Are you trying to build a cellphone blocker (Illegal, period!)?

 

[ahuebel]

I appreciate your reply. This is a completely legal "project". Without getting into tremendous details, I work for an A&E firm and am involved in several projects designing radio and wireless systems for government agencies (mostly in the transportation industry). I do not like writing specifications without understanding all aspects of the recommendations. This is one such example. It is easy to read standards and concepts and say, it is best to do xyz. I am familiar conceptually with the items you mentioned but I would like to find out more detailed information including simulation, models, and other such explanations to provide tangible results given specific inputs.

I was actually not aware that you had to have carrier permission to do this. Manufacturers like Andrew and Powerwave make these amplifiers. It is only logical that you would have to register these transceivers with the FCC etc, since they are using licensed frequencies.

 

[CAT]

How about a passive antenna arrangement?

 

[N_Jay]

How about a passive antenna arrangement?

It is VERY difficult to get a passive to work well.

 

[AZScanner]

I was actually not aware that you had to have carrier permission to do this. Manufacturers like Andrew and Powerwave make these amplifiers. It is only logical that you would have to register these transceivers with the FCC etc, since they are using licensed frequencies.

Are you serious? Of course you will need the carrier's permission - they paid for the licensed frequencies! :shock:

I can go buy an Astro Saber and RSS to program it and register it with the FCC all I want - I still wouldn't be able to affiliate and transmit on the local DTRS without permission. If I even attempted it, they'd turn my radio into a brick and my occupation into "inmate". Your company is asking for hefty fines, lawsuits and jailtime for the person(s) responsible if you try and fire up a repeater on someone elses licensed channels. The FCC tends to frown on that sort of thing, especially when the "victim" is one of their pals in the wireless phone industry.

As for the models and simulations, I'm sure there are people on this board with the proper qualifications, but why would they give their knowledge away for free on a message board? The company I work for has undertaken a similar project for all their sites in Phoenix and has already spent millions of dollars in equipment and manpower to make it happen - and we're nowhere near done. I know one of the consultants on the project and he gets paid in the neighborhood of $150 an hour to do just what you are asking for. No way he'd do it for a penny less, let alone for FREE. :roll:
-AZ

 

[ahuebel]

Heh..alright. I see I am unable to accurately convey my requests. I am in no way asking for someone to provide me with detailed calculations or code. I am simply requesting direction and references, not for someone to do my work for me. Thanks for the input anyway.

 

[poltergeisty]

I appreciate your reply. This is a completely legal "project". Without getting into tremendous details, I work for an A&E firm and am involved in several projects designing radio and wireless systems for government agencies (mostly in the transportation industry). I do not like writing specifications without understanding all aspects of the recommendations. This is one such example. It is easy to read standards and concepts and say, it is best to do xyz. I am familiar conceptually with the items you mentioned but I would like to find out more detailed information including simulation, models, and other such explanations to provide tangible results given specific inputs.

I was actually not aware that you had to have carrier permission to do this. Manufacturers like Andrew and Powerwave make these amplifiers. It is only logical that you would have to register these transceivers with the FCC etc, since they are using licensed frequencies.

Your not a terrorist are you? Information like this would lead me to believe that you are trying to compromise cellular infrastructure. The information you request is some what questionable based on the fact that you work for a company that "designs" wireless systems. I would think this "company" would have the knowledge in solving such a problem or at least has dealt with it.

Don't get me wrong just a little odd. :shock:

 

[N_Jay]

Heh..alright. I see I am unable to accurately convey my requests. I am in no way asking for someone to provide me with detailed calculations or code. I am simply requesting direction and references, not for someone to do my work for me. Thanks for the input anyway.

Did you get my PM?

 

[N_Jay]

I appreciate your reply. This is a completely legal "project". Without getting into tremendous details, I work for an A&E firm and am involved in several projects designing radio and wireless systems for government agencies (mostly in the transportation industry). I do not like writing specifications without understanding all aspects of the recommendations. This is one such example. It is easy to read standards and concepts and say, it is best to do xyz. I am familiar conceptually with the items you mentioned but I would like to find out more detailed information including simulation, models, and other such explanations to provide tangible results given specific inputs.

I was actually not aware that you had to have carrier permission to do this. Manufacturers like Andrew and Powerwave make these amplifiers. It is only logical that you would have to register these transceivers with the FCC etc, since they are using licensed frequencies.

Your not a terrorist are you? Information like this would lead me to believe that you are trying to compromise cellular infrastructure. The information you request is some what questionable based on the fact that you work for a company that "designs" wireless systems. I would think this "company" would have the knowledge in solving such a problem or at least has dealt with it.

Don't get me wrong just a little odd. :shock:

Its not odd.
He said he works for an Archtechure and Engineering firm. Parts of a contract are often outside the expertise of the firm.
He needs to find a firm with the right experiance to subcontract to.

Hmmmm, where would one fine such a firm? :roll: :wink: :roll: :wink:

 

[AZScanner]

Your not a terrorist are you? Information like this would lead me to believe that you are trying to compromise cellular infrastructure.

I'm sure if he is a terrorist he will 'fess right up and tell you. :roll: :lol:

This whole thread is totally useless. To the original poster: We got the process rolling here by contacting our primary cellular provider and explaining what we wanted to do. They pretty much took it from there and advised us on how to proceed. I'd start there. Let them do the research and proposals - that's what you pay them for (and trust me, you will pay BIG $$$'s for this).

-AZ

 

[poltergeisty]

I'm sure if he is a terrorist he will 'fess right up and tell you. :roll: :lol:

I know that! I was just being sarcastic and was conveying my feel for the question. Seems odd though especially about this quote.

but I would like to find out more detailed information including simulation, models, and other such explanations to provide tangible results given specific inputs.

I am just a really suspicious person.(Or a PITA) Hope you enjoyed the laugh because this is on a terrorist list for something to do!

Maybe I'm just an idiot but why would a firm have a engineer search for answers on a scanner forum? :shock: I hold everything to the fire until I know it's truthfulness. It's my nature, sorry. You could say I have a Delta force type personality. That is to be suspicious of everything.

ahuebel, If your intentions are of a reasonable nature with no evil behind this project then I would like to apologize. I have to always find out the why. For all I know you could be a MIT grad who wants to get his name in the papers. :wink: Happened before.

 

[ahuebel]

I seriously debated even acknowledging some of these posts but I would like to just clarify something. I found this site by a recommendation from my old boss and have used the RR Database for work related purposes. You can scrutinize all day but I did not post here to have my integrity questioned. I had a thought that since this is a "radioreference" forum, perhaps I could post in the most general group within this forum and find someone with enough information to direct me to some study material or other references. I am not going to go into a debate of what I should know...the fact of the matter is, I know enough, and what I do not know I intend to learn. I realize now, this is not the forum to look in. I got some reasonable information from N_Jay and I appreciate that.

 

[poltergeisty]

All righty than! I don't care. I'm just a Pain in the ass hope you continue your search for answers as I do, Sorry. But I know that this info. is needed for overpowering a communication source and am concerned about the info. If other people helped you, cool props to them.

For the recored I don't think any one was questioning your integrity, Definition=

1. Steadfast adherence to a strict moral or ethical code.
2. The state of being unimpaired; soundness.
3. The quality or condition of being whole or undivided; completeness.)

But rather the PURPOSE!


And that is the truth. :evil:

 

[N_Jay]

I am just a really suspicious person.(Or a PITA) . . . .
. . Maybe I'm just an idiot but . . . . It's my nature, sorry. . . . ..

All righty than! . . . . I'm just a Pain in the ass . . . And that is the truth. :evil:

Ah, now we are getting somewhere! :twisted: :twisted: :twisted:

:wink:

 

[poltergeisty]

I am just a really suspicious person.(Or a PITA) . . . .
. . Maybe I'm just an idiot but . . . . It's my nature, sorry. . . . ..

All righty than! . . . . I'm just a Pain in the ass . . . And that is the truth. :evil:

Ah, now we are getting somewhere! :twisted: :twisted: :twisted:

:wink:

Getting somewhere? When you chop my thread. Mr. Butcher. :roll: :roll: :wink: :wink:

 

[N_Jay]

I am just a really suspicious person.(Or a PITA) . . . .
. . Maybe I'm just an idiot but . . . . It's my nature, sorry. . . . ..

All righty than! . . . . I'm just a Pain in the ass . . . And that is the truth. :evil:

Ah, now we are getting somewhere! :twisted: :twisted: :twisted:

:wink:

Getting somewhere? When you chop my thread. Mr. Butcher. :roll: :roll: :wink: :wink:

I did not chop it!
I trimmed it, keeping all the prime parts. :wink:

 

[flyingwolf]

I am just a really suspicious person.(Or a PITA) . . . .
. . Maybe I'm just an idiot but . . . . It's my nature, sorry. . . . ..

All righty than! . . . . I'm just a Pain in the ass . . . And that is the truth. :evil:

Ah, now we are getting somewhere! :twisted: :twisted: :twisted:

:wink:

Getting somewhere? When you chop my thread. Mr. Butcher. :roll: :roll: :wink: :wink:

I did not chop it!
I trimmed it, keeping all the prime parts. :wink:

Dont you just love when people quote an entire conversation only to add one thing?