Pre-Amp Question

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Sjinndoawi

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I have the (Jim M75 ) pre-amp.. Now I have heard that Pre-Amps are not a good thing. Well I spent about 220.00 on it and want to use it on one of my BCD996t's to pull in the next county. Will it ruin the frontend of my scanner? It has varible gain control(-10dB to + 20dB) with band pass filters. Or does anyone know how I can use it on my system so that it will cause less harm to my scanner?
Now I did use it for about a week to get the next county and it worked very well. But once I heard that it will ruin my scanner I took it off. I really didn't notice any problems after it was off but I did mot get the other county like I did when it was on my 996t.

Any help would be nice

Brian
 

ka3jjz

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It won't 'ruin' anything - however, in certain cases, if you lived in an urban environment, preamps do have the habit of overloading the scanner, and can result in a condition where the scanner locks onto a false signal, and reduces sensitivity on freqs surrounding it - a very loose description of what is referred to as 'desense'.

Now, there's a few things working in your favor here. There's a variable gain control - use just enough gain to get that next county clearly, and no more than that. The bandpass filters might be quite useful if you start hearing things like FM broadcast and the like while using the amp.

Of course, we're assuming here that you've put up the best antenna you can, with good (no, I don't mean RS RG58U) coax as high as you can practically go. Only then should a preamp even be considered, frankly.

73 Mike
 

thewenk

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As has been said, it won't hurt your scanner. Since you already have it, try it and see what happens. You will know pretty soon if it gives you problems or helps. I've used preamps off and on for many years - sometimes they help and sometimes they cause reception or overload problems. It is usually dependent on your location and the frequencies you are trying to monitor.

Dave
 

Sjinndoawi

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Feb 12, 2007
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South Florida
Thanks guys

No, I use it in my house with a teleoscopic phase load antenna. And it really pulled the signal in from the other county with the preamp on it. But I do live in a city so I hope that it doesn't overload my scanner but when I use the preamp I didn't notice it. My roommate wont let me put up and outside antenna so I have the teleoscopic antennas and omnidirection discone which is a desk top verision.

Thanks
Brian
 

kb2vxa

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A preamp will ruin your scanner, give you herpes, and your nose will turn black and fall off.

If it worked once and did no harm you answered your own question.

Now which do you believe?

"What is a telescopic phase load antenna?"

There jus' ain't no such animal. He meant "base loaded" which is an electrically lengthened HF or low VHF portable or mobile antenna.
 
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