Would this Work As A Good Trap & Amp???

[zzdiesel]

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For scanner use?

 

[K9WG]

It should work however with 25dB gain you probably would overload the receiver pretty easily. Also it is a 75 ohm with F connectors. You would need to use adapters with it. For the price I would give it a try.

 

[zzdiesel]

Thanks for the reply. I would be feeding into a 3 way splitter into 3 radios; so there would probably be some loss.

 

[zz0468]

What's the noise figure? What's the IP3? What makes this a good choice to use with a scanner? Did you look at the specified frequency range?

 

[zzdiesel]

I'm sorry zz0468, but that's all over my head. That's why I was asking.

I just noticed the specs.

Amplifier Type Power Amplifier

Applications SATCOM; CATV

Primary Performance Specifications

Frequency Range 50.00 to 450 MHz

Minimum Gain 25.00 dB

Maximum Gain 25.00 dB

Amplifier Package Package Type Connectorized

Connectors Type F

Electrical Characteristics Nominal Impedance 75

Notes Amplifier 25db uhf/vhf/fm

 

[zz0468]

I'm sorry zz0468, but that's all over my head. That's why I was asking...

No problem!

Noise figure quantifies how much noise the amplifier creates on it's own. The lower the noise figure, the better. If you put a preamp in front of your receiver it MUST have a lower noise figure than the receiver itself, or it WILL actually degrade weak signal reception. The usual symptom is strong and moderate signals create "more bars" on the signal strength display, making the user think it's working. And weak signals are not heard at all.

An amplifier that doesn't specify it's noise figure is suspect. A scanner will typically have a noise figure of 4-6 db (I've measured some), so to achieve a real improvement, the noise figure of the preamp has to be better than 4 db (or whatever the receiver actually is) MINUS the loss of any interconnecting cables or filters between the preamp and the antenna. A 20 db gain, 2 DB noise figure preamp behind a filter or splitter with 2 db loss would barely be a wash, and might be even worse depending in the IP3.

IP3 represents "third order intercept". That's a measure of a preamplifiers immunity to overload that would cause it to generate it's own intermod. The higher the number, the better. The best commercial grade preamps can have an IP3 of 40dBm, or 10 watts of power hitting it before it goes non-linear and distorts.

A preamplifier without a rated IP3 specification is suspect, and might actually be worse than the receiver itself, which is one reason why so many people complain about interference when they try using a preamplifier. The other reason is simply too much gain. You only need enough gain to overcome the loss between the preamp and the receiver, and to overcome the (hopefully) inferior noise figure of the receiver itself. 25 db gain is entirely too much.

And as noted, the frequency range tops at 450 MHz, making any use above that frequency subject to uncertainty.

 

[zzdiesel]

You just helped to talk me out of this. My PSR-800 & Pro-197 overload just on the outdoor antenna.

 

[zz0468]

My good deed for the day!

 

[zzdiesel]

My good deed for the day!

Yup, and thanks.