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Scanner / Receiver Equipment Reviews - A forum for reviews of scanner and receiver hardware along with related accessories. Please read the forum Sticky before creating a thread.

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  #1 (permalink)  
Old 12-19-2014, 3:59 PM
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Default GRE Super Amplifier (Pre-Amp)

OMG OMG OMG OMG OMG OMG, this thing is so amazing.

$60, and it increases reception noticeably. I primarily listen to 800MHz, and the distant sites are low on the bars scale, and analog is scratchy. Popped the little amp on, and the bars on my PRO-197 went from 3-4 to 5, and the audio cleaned up, raised out of the mud, it was like magic!

But does it work on VHF......a little bit, it's slightly noticeable, but not the night and day (dusk/dawn) 800 difference.

Does it work on Motorola radios? Yes! Significant RSSI value increases. *be sure to TX enable radios prior to plugging this puppy on!* Best part is, I cannot discern any apparent audio hiss or other artifacts from the amp, the signal just goes up, and the analog RX clears up, and digital will go from broken and choppy to crystal clear. In testing around my room, it is easy to find spots where my not so sensitive 436HP receives at most a blip or two of digital garbage with one bar, flip the pre-amp switch and the bars go almost all the way up,a nd the digital traffic decodes perfectly.

I can't say enough about this product for 800Mhz. Of course, my work place is directly underneath an AT&T cell phone tower, so I will post an update as to how this puppy works when maxed out under the barrage of cell radiation.

Paul
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Old 12-19-2014, 11:00 PM
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Yes works great on 800 and UHF. I've been using one for years. However at VHF its easy to overload the receiver, depending on which receiver you use.
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Old 12-19-2014, 11:22 PM
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How many DB amp is it?
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Old 12-20-2014, 11:47 AM
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Originally Posted by scannermanner1 View Post
How many DB amp is it?
From 0 - 20db
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Old 12-20-2014, 2:11 PM
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Yes, they do indeed work. I've used them since the mid 90s. I didn't know they were still available, unless they started reproducing/redesigning them. I use one for marine traffic when the rivers flood & they (Ohio & Big Sandy ) converge nearly 2o miles and many hills away from me, but I hear all the panic & complaints.
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Old 12-21-2014, 1:39 PM
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Default Digital

will this Amp work on digital scanners
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Old 12-21-2014, 1:56 PM
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WILL work on digital, and I believe it is around 3-6db of gain given the audio/signal strength increases I see. Says 20db on the case....but that is not realistic.

If you are trying to monitor a distant system that is "in the mud", this may indeed clean it up enough to satisfy your ears, and even make incoherent voice traffic understandable.

Paul
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Old 12-22-2014, 12:00 AM
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Just tried the Super Amplifier in the area of cell phone towers.......unusable. Even with the gain turned all the way down, simply turning the unit on renders the signals mute. This still kicks butt for listening to distant systems assuming you have no cell towers or adjacent channel signals in the vicinity.

Paul
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Old 12-22-2014, 1:36 PM
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Quote:
Originally Posted by Anderegg View Post
*be sure to TX enable radios prior to plugging this puppy on!*

Paul
I think you mean "Disable"
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Old 12-22-2014, 11:31 PM
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Originally Posted by Anderegg View Post
Does it work on Motorola radios? Yes! Significant RSSI value increases...
Be careful there. An increase in RSSI is NOT a measure of whether a preamplifier is working properly. That only means it has gain. Put the primary purpose of a preamp is NOT TO PROVIDE GAIN.

It's to reduce the overall noise figure to something lower than the receiver by itself. If the NF of the preamp is higher than the receiver itself, then you'll see "more bars" on the receiver, but actual weak signals will be weaker and noisier. Or just plain gone.

The typical scanner noise figure is going to be 4-6 dB, and so the preamp MUST have a lower noise figure than that in order to actually improve weak signal reception. The GRE Super Amp does not have a published noise figure, so I'd be cautious about just plugging it in.

A Motorola radio with a sensitivity of around .2 uV is going to have a noise figure of around 1 dB, which is pretty damned good. I seriously doubt the GRE amp is better than that, so all you're getting out of the deal is more RSSI, and higher susceptibility to intermod. Actual weak signal reception would be reduced to about that of a scanner.
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Old 12-22-2014, 11:41 PM
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Be sure to hook it up to your SDR, it greatly improves ADS-B reception.
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Old 12-25-2014, 1:27 PM
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Very good amp! I have three of them. The nice thing about them is that you can adjust the gain.
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Old 01-03-2015, 6:52 AM
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Yes works great on 800 and UHF. I've been using one for years. However at VHF its easy to overload the receiver, depending on which receiver you use
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Old 01-06-2015, 5:36 AM
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Quote:
Originally Posted by zz0468 View Post
Be careful there. An increase in RSSI is NOT a measure of whether a preamplifier is working properly. That only means it has gain. Put the primary purpose of a preamp is NOT TO PROVIDE GAIN.

It's to reduce the overall noise figure to something lower than the receiver by itself. If the NF of the preamp is higher than the receiver itself, then you'll see "more bars" on the receiver, but actual weak signals will be weaker and noisier. Or just plain gone.

The typical scanner noise figure is going to be 4-6 dB, and so the preamp MUST have a lower noise figure than that in order to actually improve weak signal reception. The GRE Super Amp does not have a published noise figure, so I'd be cautious about just plugging it in.

A Motorola radio with a sensitivity of around .2 uV is going to have a noise figure of around 1 dB, which is pretty damned good. I seriously doubt the GRE amp is better than that, so all you're getting out of the deal is more RSSI, and higher susceptibility to intermod. Actual weak signal reception would be reduced to about that of a scanner.
Yeah, RSSI is pretty sketchy. My primary concern was to clean up 800MHz analog on a distant system, which I pump through WIN500 Android app to my car. The cleaner it is, and the more out of "the mud" the audio, the better it sounds coming through the Bluetooth car speakers. It does his remarkably well! But again, anywhere near a cell tower, and even set to the lowest gain, it will terminate reception completely for me.

Paul
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Old 01-07-2015, 1:42 AM
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Quote:
Originally Posted by Anderegg View Post
Yeah, RSSI is pretty sketchy. My primary concern was to clean up 800MHz analog on a distant system, which I pump through WIN500 Android app to my car. The cleaner it is, and the more out of "the mud" the audio, the better it sounds coming through the Bluetooth car speakers. It does his remarkably well! But again, anywhere near a cell tower, and even set to the lowest gain, it will terminate reception completely for me.

Paul
So, are you attempting to use a preamp in the car?

This is full of all sorts of potential problems, mostly nearby cell sites. I have measured signal levels from cell sites that are far in excess of what a relatively low quality preamp like the GRE amp can handle, especially without some filtering. I run some preamps in my vehicles for some ham band stuff, and it's always behind some pretty stiff filtering. At work, I don't connect any receiver or test equipment to an antenna unless it's behind a filter, particularly if there's a preamp involved. And what's needed for a filter is going to vary, depending on the circumstances.

Pretty sure you're better off without the preamp in most cases.
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Old 01-07-2015, 2:56 AM
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I bought one mainly for base station use, for boosting ow signal 800Mhz reception. I tested it out in my car, but in the vicinity of cell towers, it rendered those distant low signal systems completely DOA. Even with the gain turned all the way down, turning on the pre-amp would reduce the 2-3 bars to no bars, so vehicle use would not be recommended. I am fortunate enough that my home base station is in a cell dead spot. I have trouble not dropping cell calls at my residence, so no interference, and I can turn the gain all the way up, and it has no adverse side effects. I am happy to report tat analog audio quality when gained to maximum suffers no ill effects, it simply takes out the hiss and static as the bars go up.

Paul
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Old 01-10-2015, 1:36 AM
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Quote:
Originally Posted by Anderegg View Post
I bought one mainly for base station use, for boosting ow signal 800Mhz reception. I tested it out in my car, but in the vicinity of cell towers, it rendered those distant low signal systems completely DOA. Even with the gain turned all the way down, turning on the pre-amp would reduce the 2-3 bars to no bars, so vehicle use would not be recommended. I am fortunate enough that my home base station is in a cell dead spot. I have trouble not dropping cell calls at my residence, so no interference, and I can turn the gain all the way up, and it has no adverse side effects. I am happy to report tat analog audio quality when gained to maximum suffers no ill effects, it simply takes out the hiss and static as the bars go up.

Paul
If you really need a preamp for say the 800 MHz band, you are better off getting something that is tuned for just the band you need. The GRE amp is a very wideband amp that amplifies everything hitting its input jack.
This of course is bad as you don't really want to amplify things like FM broadcast radio.
All it will do is add more noise into your signal and overload the front end of your radio as you found when trying to use it while mobile.
I do use a preamp tuned for just the 800 MHz band but it only becomes useful for systems that I can barely hear with a yagi aimed at the system.
A good low noise amp with tuned input and output filters that only pass the 800 MHz band does make these systems monitorable.
For some systems that are noisy like weak signal static sounds, I only need a bandpass filter that blocks all but the band I want. Those type filters have no power needs so they don't add any noise into the signal, they simply block the bands I do not want. GRE scanners are famous for overloading their front ends if you live near FM radio stations. Get an FM band notch filter and many are amazed at how much better everything else sounds. They simply reduce the signal between 88 and 108 MHz to a level the scanner can handle thus allowing the signals you want to pass onto your speaker.

I had one of the GRE super amps but it was totally useless in my area due to all the other high power RF from paging systems and later, cell towers and Nextel.
I needed a signal from an 860 MHz trunked site though so I bought a PAR 800 MHz preamp and it made a system I could barely detect by ear, come in with zero decode errors. Still had a low signal strength overall but the low noise band specific preamp along with an FM notch filter allowed me to get what I was after. If I removed either device, I can no longer hear the system.

I generally stay away from wideband preamps and use passive filtering instead as that helps more than anything.
Especially on the GRE made radios and all older pre triple conversion receivers.
Even homemade stub filters can work wonders but they are hard to make if you only want to notch out 1 or 2 MHz of bandwidth. Stub filters are pretty wideband and you end up notching out frequency ranges you want.
They are a good starting point though and cheap to build for testing if a given frequency is responsible for desense or front end overload.
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Old 01-11-2015, 9:39 AM
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Love my GRE Amps,Ive got 3,,I get great results all around from VHF Lo all the way to 800meg..

I plan on adding 1 or 2 more(1 for each radio)...I recommend these hands down!

Hoping Whistler picks up the hint and adds this to their revamped GRE line...
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Old 02-02-2015, 7:31 PM
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I've got one I haven't used in years. Just tried with with my SDR dongle decoding ADSB and it significantly degraded my reception.
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Old 02-03-2015, 8:07 PM
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Has anyone used any of those EBL 9v lithium rechargeable batteries with these to see if they fit inside?

I've heard those EBL's are slightly larger than a normal 9v alkaline battery.Just curious if they will fit in the GRE.
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