Scanner Pre-Amps

[nitetrain5]

I have the " Watson WRP-1300 " and " Jim M75 " pre-amps both purchased from ScannerMaster. Is there any benefit to using both of these at the same time, on the same scanner ?

 

[DaveIN]

Not really. You may increase the signal strength of the signal target, but you'll also increase the unwanted signals and noise giving you false hits or intermod.

Intermodulation
Process where multiple signals mix together. This may occur naturally outside of the receiver or in the front-end of the receiver. Either way, it results in the generation of a "false" frequency. The resultant audio of this signal is usually a combination of the audio portions of each signal involved.

Sometimes only one of the original signals can be heard making it appear to be an image.

This typically occurs when the initial stages of the receiver are "overpowered" by very strong, local signals. Radios with superior designs have better filtering which are better at keeping multiple signals from entering thereby helping to eliminate intermodulation.

Usually referred to as simply 'intermod'.

 

[N_Jay]

Multiple amplifiers are (almost) never any benefit in a receiver system.

The sensitivity is set by the first amplifier (mostly by the noise figure, not the gain) and all the second amplifier does is add noise, intermodulation and potentially overload the receiver.

 

[bgkoe]

I use one pre-amp with three antennas( one is a home brew) going into a good switch, then into the pre-amp. Using the pre-amp I've found that usually one of the antennas will bring in less noise, depending on which band I'm listening to. I'd rather lose the pre-amp than one antenna; antennas are more important, in my opinion.

 

[N_Jay]

I use one pre-amp with three antennas( one is a home brew) going into a good switch, then into the pre-amp. Using the pre-amp I've found that usually one of the antennas will bring in less noise, depending on which band I'm listening to. I'd rather lose the pre-amp than one antenna; antennas are more important, in my opinion.

You should not need the second amp unless something is wrong.

 

[nitetrain5]

Thanks for all your advice. By the way, I've noticed quite a difference using the amps....... Especially the Jim M75 !!

 

[ArtU]

Multiple amplifiers are (almost) never any benefit in a receiver system.

The sensitivity is set by the first amplifier (mostly by the noise figure, not the gain) and all the second amplifier does is add noise, intermodulation and potentially overload the receiver.

Yes N_Jay, I'd like to second that.

One of the best practices is to shop for an AMP is to look for Low Noise Amps (LNA) and get the lowest noise figures even if the gain is lower then one with a higher noise figure.