Antenna Pre-amp

[baybum]

Has anyone used the GRE Superamp (PRE01 from Grove)?
If so, have you been impressed with it ? What bands have you used it on and what bands does it do the best on?
Have you actually been able to bring in stations you could not hear before?


Thanks,

Mike

 

[TinEar]

I have a GRE that I got from Grove. I have no use for it at all. I've tried it both at the radio end and at the antenna and get no amplification from it at all. I suspect that because we live in this RF rich urban area, it just gets RF overload. On the 850 trunked band, it actually attenuates my signals so that where I had a weak control channel I had nothing with the GRE in line. I tried the Ramsey preamp before that and got a little amplification on the lower bands - up to about 160 mHz - and nothing but noise or attentuation at higher freeqs. The fine folks at Grove checked the Ramsey for me when I returned it and found no problem so it almost has to be because of RF overload that it wouldn't work here. By the way, if you're still interested in the GRE, I'll sell it for almost any reasonable offer. And I even have a 9V power supply for it which doesn't come with it when you buy the unit.

 

[N_Jay]

Receiver pre-amps are a tricky matter.

There are a number of reasons that they will not work in many applications.

Scanners are about the worst application since you have no filter ahead of the amp, and almost no filtering after the amp (due to the wide front end on a scanner).

I would bet that unless you are in a very rural environment, and/or have a long transmission line, you will find a preamp worthless (or worse).

P.S. thay should almost always go at the antenna end of the cable.

 

[doctordave]

Mike,

I used a commercial (high cost...forget the brand name) pre-amp some years ago and found that it caused horrific overload on 800, much noise in the 150's and maybe a slight improvement on 40 MHZ. Overall, I was very, very un-impressed....much like what others have alluded to here. For me, in Baltimore County, simply going with a high-gain 800 MHZ antenna (up from an average tri-bander) caused so much overload on 800 that I could barely copy the trunked system. Interesting concept that too much signal can actually be a bad thing in some cases.


Dave

 

[apex]

Antenna Pre-Amp

I have a GRE 3001 (the old base version).

I agree on the not much use in this metro area.

However using the GRE (w/RS 800mhz antenna) is the
only way I am able to monitor PG Co. EDACS North
from Howard Co. (on both BC 780xlt/BC 895xlt).

Jay

 

[N_Jay]

Mike,

I used a commercial (high cost...forget the brand name) pre-amp some years ago and found that it caused horrific overload on 800, much noise in the 150's and maybe a slight improvement on 40 MHZ. Overall, I was very, very un-impressed....much like what others have alluded to here. For me, in Baltimore County, simply going with a high-gain 800 MHZ antenna (up from an average tri-bander) caused so much overload on 800 that I could barely copy the trunked system. Interesting concept that too much signal can actually be a bad thing in some cases.


Dave

Signal level is not the issue.

You have signal to noise to worry about,
and adjacent channel and out of band desinsitization,
nad receievr quieting due to noise on the image frequency,
and non-linear mixing products in the amp and receiver.

Commercial systems never use an amp without a filter in front of it, and often have a filter after it.
Typically the gain of the amp is set to only slightly more than the loss through the filter and line.

The idea is as much to reduce the noise as it is to increase the the signal.

 

[doctordave]

Thanks for clarifying that.


Dave

 

[opus]

I run TV mast amps for my antenna runs. At first was also dissapointed due to the overload. But I was just sitting there pulling the power plug in and out to test the difference and I noticed that it instantly became good for a fraction of time. I guessed that was when the capacitors in the amps were discharging and reached a certain voltage. So I got a variable power supply and found that my Band V UHF TV antenna (what I use for 800MHz) actually runs best at around 12V instead of 18V as 'designed'. My VHF/UHF TV amp (use for mostly 400-500MHz) works great at 5V rather than 18V. In both cases I do get a noticeable improvement and am very happy.

I actually have these amps chained. The Band V UHF TV amp has an unamplified low pass input and can pass the power through on that line. I actually have my VHF/UHF amp feed into that input. Then I just run one line down to the shack. Only problem with this is that at the moment I need to choose either 5V or 12V depending on what I am listening too. I will be fixing that by putting a 5V regulator circuit across where the Band V amp passes the power onto its other input.

One problem is that FM signals (88-108MHz) are beating with our foreign language FM signals (152MHz) and thus causing bad intermod around 500MHz. I will be adding an FM trap to hopefully fix this, just like N_Jay says needs to be done in commercial systems.

Opus

 

[LarrySC]

First rule of thumb for a better signal. The best amp is a good antenna.

 

[scannerfreak]

With good cable...

 

[N_Jay]

With good cable...

You can have crappy cable if you have a good head end system.

Of course, I am speaking of a several thousand $$ commercial unit!