WRP-2500 Pre-Amplifier Questions

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ka3jjz

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Preamps often cause more trouble than they're worth, particularly so if you are in an urban area. They can cause overloading and intermod issues, and increase overall noise levels.

You didn't say much about your antenna/coax situation; I'd start here before doing anything with preamps.

best regards...Mike
 

LtDoc

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I have to 'ditto' KA3JJZ's comment. Pre-amplifiers do have a use, but not all that often considering the sensitivity of most modern radio receivers. In general, an antenna system which is 'inadequate' tends to be the reason why a pre-amplifier would be useful. Spend the cost of that pre-amplifier on improving your antenna system would be my first suggestion.
The problem with the typical pre-amplifier is that they can not distinguish between a desired signal and an undesirable one, or noise. There are devices that can to that to some extent, but that ability means a large increase in price. That 'price' isn't just money, it's also clarity/quality of the resulting signals.
Mike's question about your antenna system is also pertinent. How can anyone comment or recommend some 'improvement' without knowing what's there now?
- 'Doc
 

Dewey

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I'm with Mike and Doc, and in addition, I do not think that that particular amplifier is well designed. I don't like anything that uses a phone jack for power. Phone jacks create a momentary short as the plug is plugged into the jack. You would have to get into the habit of plugging the jack into the amplifier before plugging the wall adapter in each time just to avoid the momentary short.

Dewey
 

gewecke

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I was wonder if anyone has this? WRP-2500 Pre-Amplifier for Wideband Scanners

I would like to get feedback from you guys see what you think. And if I did get it how would I hook it up to my scanner? It's a Uniden BCD996t.

Thanks for your help

Bryan
I would have to say unless it's a gaas-fet preamp, then I wouldn't bother with it. Gaas-fet devices have a very low noise figure allowing for the amplified signal to be higher than the noise floor.
You might be wiser to invest in a higher gain antenna arrangement?
73
n9zas
 

NFR85

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I have to 'ditto' KA3JJZ's comment. Pre-amplifiers do have a use, but not all that often considering the sensitivity of most modern radio receivers. In general, an antenna system which is 'inadequate' tends to be the reason why a pre-amplifier would be useful. Spend the cost of that pre-amplifier on improving your antenna system would be my first suggestion.
The problem with the typical pre-amplifier is that they can not distinguish between a desired signal and an undesirable one, or noise. There are devices that can to that to some extent, but that ability means a large increase in price. That 'price' isn't just money, it's also clarity/quality of the resulting signals.
Mike's question about your antenna system is also pertinent. How can anyone comment or recommend some 'improvement' without knowing what's there now?
- 'Doc
I have the regular antenna it came with the Uniden. I also bought a snoop antenna from someone it works ok but not as good. Thats all I have right now.
 

NFR85

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I would have to say unless it's a gaas-fet preamp, then I wouldn't bother with it. Gaas-fet devices have a very low noise figure allowing for the amplified signal to be higher than the noise floor.
You might be wiser to invest in a higher gain antenna arrangement?
73
n9zas
I'm a newbie to this so I have no idea what that is.
 

gewecke

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I'm a newbie to this so I have no idea what that is.
Gallium arsenide field effect transistor,(gaas-fet) is the heart of a GOOD preamp used to boost radio signals,but most of your run of the mill preamps won't use them due to the extra cost.
Remember; you won't be a newbie forever! Hang around us here at RR and you'll learn things whether you want to or not! :lol:
Good luck!
n9zas
 

NFR85

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Gallium arsenide field effect transistor,(gaas-fet) is the heart of a GOOD preamp used to boost radio signals,but most of your run of the mill preamps won't use them due to the extra cost.
Remember; you won't be a newbie forever! Hang around us here at RR and you'll learn things whether you want to or not! :lol:
Good luck!
n9zas
Where would I buy that, and how would I install it into my scanner?
 

gewecke

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Where would I buy that, and how would I install it into my scanner?
Unless you live out in the middle of nowhere'sville I wouldn't use any preamp at all, because as other posters here have said you would be inviting intermod (front end receiver overload)
which is not pleasant to listen to.
Instead, try investing more research and money into your radio's antenna! :)
n9zas
 

prcguy

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Having a Gaas-fet really has no bearing on being a good preamp or not, it depends on a combination of gain, noise figure, IP1 and IP3 ratings. Gaas-fets can have lower noise figure than similar silicon based transistors but many are way too small to be used as a wide band preamp without preselection.

The majority of wide band preamps I've seen lately run a little dinky RF IC that can be Gaas or silicon but are also too small to be useful, they amplify but also generate tons of IMD due to being run into oblivion from overload.

Angle Linear makes some of the best preamps when it comes to being overload proof and having the proper amount of gain and low noise figure for a particular application. These are almost always used after some sort of preselection even though Angle Linear preamps are more overload proof than most anything on the market today.

To date they have not made a wide band preamp (over about 200MHz BW) due to the hurdles of marketing an amp that will meet their goals of giving the customer an amp that will not fold when hooked to a broad band Discone like most other preamps will. Rumor has it they are working on a wide band preamp for our hobby but nothing has been announced yet.
prcguy

Gallium arsenide field effect transistor,(gaas-fet) is the heart of a GOOD preamp used to boost radio signals,but most of your run of the mill preamps won't use them due to the extra cost.
Remember; you won't be a newbie forever! Hang around us here at RR and you'll learn things whether you want to or not! :lol:
Good luck!
n9zas
 

prcguy

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I forgot to mention, the specs on the WRP-2500 preamp says it requires 12v @ 10-15ma. A typical high level preamp might require 12v @ 150 to 250ma, which makes me think the WRP-2500 is not going to work well unless your very far from any strong signals that will spank it.
prcguy
 

gewecke

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Having a Gaas-fet really has no bearing on being a good preamp or not, it depends on a combination of gain, noise figure, IP1 and IP3 ratings. Gaas-fets can have lower noise figure than similar silicon based transistors but many are way too small to be used as a wide band preamp without preselection.

The majority of wide band preamps I've seen lately run a little dinky RF IC that can be Gaas or silicon but are also too small to be useful, they amplify but also generate tons of IMD due to being run into oblivion from overload.

Angle Linear makes some of the best preamps when it comes to being overload proof and having the proper amount of gain and low noise figure for a particular application. These are almost always used after some sort of preselection even though Angle Linear preamps are more overload proof than most anything on the market today.

To date they have not made a wide band preamp (over about 200MHz BW) due to the hurdles of marketing an amp that will meet their goals of giving the customer an amp that will not fold when hooked to a broad band Discone like most other preamps will. Rumor has it they are working on a wide band preamp for our hobby but nothing has been announced yet.
prcguy
Well, I'm sure you blew the op away with all that,lol! I was trying to keep things somewhat simple since he said he's somewhat new to radio,but yeah for the most part your correct.
:roll:

n9zas
 

ka3jjz

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So let's get this back to where it belongs - Antennas. Bryan can you get something outdoors (best) or in an attic (next best)? What are you interested in hearing? Where are you (county/state is fine)? Do you need to watch for restrictive covenants or other idiocy like this that restricts outdoor antenna usage? Are you in an urban or rural type environment?

All of these questions, and more, will help folks make sound recommendations as to what to do next.

best regards..Mike
 

NFR85

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I live in Nashua,NH which i beleive is Urban. I could put an antenna on my roof, but I do not own a big ladder to put it up so i was thinking another alterative way.
 

ka3jjz

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Putting an antenna on the roof with all that snow would be highly dangerous; your safer bet is in the attic if you have one. Do you? What are you interested in hearing? You could later move the antenna outside when the weather improves.

How much vertical clearance in that attic, assuming you have one? That will narrow down the list of candidate antennas...

Safety first best regards..Mike
 

NFR85

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The attic is crawl space not even lol. The problem I'm having are towns that are very close to me that I should be getting clearer than I'm getting which is on the soft end.
 
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