Receive amplifiers?

[KK4JW]

It's been awhile since I've done much scanning, but I'm dragging my 996XT out of mothballs in hopes of doing some air band scanning. I remember back in the day GRE made some really awesome amplifiers, what are you guys using these days?

 

[JoshuaHufford]

I use these myself,

Low noise preamplifiers and microwave Gunnplexers

Complete catalog of low noise preamplifiers and microwave Gunnplexers.

www.advancedreceiver.com

I've heard some say they are overpriced and don't perform well, I've had others say they are some of the best out there. I don't have any equipment that will test actual numbers, just real world experience, and I can say they work wonderfully for me. I have one I'm currently using that will allow me to decode a signal with 1% or less error rate, without it I can't decode anything.

 

[Ubbe]

I've used many different $5 to $200 amplifiers and they all have worked to improve reception more or less. The best ones I have used are the PGA103+ based amplifiers that has a very low noise figure and can handle big signals without creating intermod.

Amplifiers usually have a gain factor of 15dB to 30dB but a scanner receiver can't handle that sort of signals from the amplifer and needs to be antennuated so it is less than 10dB measured from the antenna. Depending of the RF enviroment at your location you might have to attenuate even more than that. A variable 0-20dB attenuator at the scanners antenna port would be ideal for to dial in the most optimum signal level. If you can receive a constant ATIS transmission it would be perfect to use to set the best signal/noise ratio.

VHF air are close to FM broadcast frequencies so if you plan to monitor that band then FM trap filters are usually neccesary to get better reception as strong broadcast signals could reduce the sensitivity of the receiver.

/Ubbe

 

[dlwtrunked]

(From about 50 years of experience) First the main reason to use a pre-amp is to improve the signal-to-noise via Friis Formula (use Google), not to just improve the gain. This usually requires signif-cant gain as well as a pre-amp with a low noise figure to be effective. (I do not think 10 dB is generally really enough but that may be due to receiver and location--I always use more despite an FM station 0.8 miles away but I do use filters.) Your goal is the improve the signal-to-noise. If nearby transmitters are going to then be a problem, notch filters are needed. Finding an optimal configuration requires some trial and error and will differ depending on the receiver and location. One should use a good FM broadcast band trap even if you are not tuning VHF air as FM broadcast stations can de-sense a receiver quite far away in frequency or generate inter-modulation causing problems on the desired frequency. Start with a good FM trap--sometimes that will improve reception across the spectrum by countering the de-sense problem in some receivers (I have seen that happen)--you will need to put one in front of the pre-amp anyway.

 

[prcguy]

The 1dB compression on those is really low and they will overload very easily.

I use these myself,

Low noise preamplifiers and microwave Gunnplexers

Complete catalog of low noise preamplifiers and microwave Gunnplexers.

www.advancedreceiver.com

I've heard some say they are overpriced and don't perform well, I've had others say they are some of the best out there. I don't have any equipment that will test actual numbers, just real world experience, and I can say they work wonderfully for me. I have one I'm currently using that will allow me to decode a signal with 1% or less error rate, without it I can't decode anything.