how well does this work?

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kf4lne

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If it actually does what it says it does then it should be a good amplifier. most likeley it has a peak frequency range that the transistors are optimal for and it tapers off on either side. I would contact the seller and ask for specs that actually show where it is optimized and not just the general frequency range. Even with multiple transistors to amplify different ranges the frequency will still be peaked somewhere and it will taper off on either side of that peak.
 

kb2vxa

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Hi Asmitty and all,

When you get down to it you're asking a pointless question. It's just another mast head amplifier with the same characteristics as most DC to light preamps.

"Note that in urban settings or in areas near transmission towers boosting the signal by 20db of gain will overpower the front end of most scanners."

Now that's something to bear in mind, unless you live way out in the country with no transmitters for miles you'll probably do well. Note the operative here is "probably" because a preamp amplifies noise and signal, it can't tell the difference so the signal to noise ratio remains largely unchanged. Then there is that qualifier "largely" because every active circuit element (the IC in the preamp) makes noise of it's own. I'm just being technical, most are low noise but I don't see any noise figures in the specs.

"...for those who mount the pre-amp at the antenna mast (the preferred mounting method)."

That's because coax has loss and no matter how well shielded picks up some amount of noise that will be amplified along with everything off the antenna if the amp is in the shack. It's better to shove a hefty signal down the pipe and lose some of it than try to recover what's left and amplify noise with it.

The cardinal rule is NEVER try to make up for a lousy antenna system with an amplifier, that's asking for trouble. 80% of your scanner is on the roof, 15% is in between and 5% is in your "shack". Nothing beats a good antenna mounted as high as practical and good coax, you might not need an amp at all. If on the odd chance you do the way to go is use one to make a good antenna system better, it'll never change lead into gold.

Now watch me pick Dan apart just for fun.

"DISCLAIMER:My technical posts are for recreational use only."
I can see that.

"Use the information contained within this post at your own risk."
Like playing with dynamite with the fuse lit.

"If you are unsure how to use this information please contact a professional."
I'm sure you're unsure so contact me, I'm the REAL Wizard of Oz. Just be careful where, I'm sensitive in a few places and a bit ticklish.

To borrow another disclaimer, "Never try this at home, we're professional idiots."

Unless you run this or any other unit through a battery of tests with some very sophisticated and expensive instrumentation you'll never know it's exact operating curves. That's because most manufacturers consider it proprietary information and will never reveal engineering data. A simpler but less accurate way of spying it out is to disassemble the unit and look up the specs on the IC if the number hasn't been ground off, some go that far to protect industrial secrets. It's safe to assume the gain rolls off near the edges but what the curve looks like in between is anybody's guess no matter what the curves on the active element are with so many other circuit variables.

Now I ordinarily would make a comment about "Four Land" but that's a subject they work to death on QRZ, you REALLY don't want it to happen here. (;->)
 

k9rzz

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kb2vxa said:
80% of your scanner is on the roof, 15% is in between and 5% is in your "shack". Nothing beats a good antenna mounted as high as practical and good coax, you might not need an amp at all.
That hits the nail on the head. Put your money into a good antenna AND coax.

If you have an interest in a specific frequency range, you can buy pre-amps that are custom tweaked to that range (can't think of the brand name off hand).

John K9RZZ
 
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