Anyone every use a preamp to increase reception?

[dlbrock]

I recently purchased a Ramsey Wide-Band Pre-amplifier. Freq Range 1Mhz - 1Ghz.
http://www.grove-ent.com/PRE2.html
They claim that the noise figure is <3db and the average gain is 23db but when I hook this up to my scanner I don't pickup hardly anything and when I do there is a lot of ambient noice so much that I can barely hear what is being said. If I turn off the amp then the communication comes through very clear.

I am thinking about returning the unit but was wondering if anyone had any thoughts.

Thanks,

Doug

 

[Audiodave1]

Hello,
Depending on your RF enviroment and what antenna you are using it sounds like it is doing it's job. I just bought my 1st preamp, a used Grove PRE-5 to use on a VHF Yagi. I needed about another 10dB to pickup a far away county on VHF and guess what? It works great on my Optocom! Setting the volume to the 10'oclock position gives me enough juice but anything over this I get desense and pager intermod...but that is no surprise. 20dB is alot of gain for a consumer receiver to deal with.

I am also using it on a Discone during the day for Acars decoding (Split into 2 radios with a regular old CATV splitter) it does wonders here but the added noise is a problem at times, but it does the job feeding a 2005 and a 780.

Preamps can help but they are not, never and won't be a substitute for a good antenna in a reasonable RF area. If you live near FM stations or near cellular towers you are in trouble with a preamp as a signal far out of band (Say a TV station or FM station) from what your target is can destroy the entire radios reception. This could be your problem.

Search the site for more info like the above.

Dave

 

[mancow]

The key is to have it near the antenna not the radio. I have a preamp near an 800 yagi and it's a night and day difference.

I also have a gre model similar to what you have and occasionally use it near the other radio for general vhf/uhf stuff. It still helps but I have to keep it turned way down. Near the radio all you are doing is amplifying noise. I would put it at the antenna if I didn't use that one for transmitting ocassionally.

mancow

 

[brandon]

Just out of curiosity, how are you putting preamps up at the antenna? Do they have antenna mounted amps that can be controlled/powered remotely similar to a rotor?

I have a GRE pre-amp and it gave me mixed results. Most of the time it just overloaded everything. But it does make a difference when I put it on an 800 Mhz yagi I had laying around in the house. Obviously I'd like to test it with the antenna mounted outdoors which is why I am wondering about how to mount it at the antenna.

 

[Randall]

I recently purchased a Ramsey Wide-Band Pre-amplifier. Freq Range 1Mhz - 1Ghz.
http://www.grove-ent.com/PRE2.html
They claim that the noise figure is <3db and the average gain is 23db but when I hook this up to my scanner I don't pickup hardly anything and when I do there is a lot of ambient noice so much that I can barely hear what is being said. If I turn off the amp then the communication comes through very clear.

I am thinking about returning the unit but was wondering if anyone had any thoughts.

Thanks,

Doug

if everything comes through clear without it why do you think you need it?

 

[JohnWayne]

I will second the recommendation to use preamps only at the antenna. That way you are not amplifying as much noise as you would if it were next to the radio. You could mount any preamp next to the antenna if you can run power to it and weatherseal it I suppose. A good preamp usually costs $300-$600.

One key thing to remember is that preamps amplify everything, whether it is your intended signal or not. This is especially true if you get alot of intermod.

Jeff

 

[Al42]

I recently purchased a Ramsey Wide-Band Pre-amplifier. Freq Range 1Mhz - 1Ghz.
http://www.grove-ent.com/PRE2.html
They claim that the noise figure is <3db and the average gain is 23db but when I hook this up to my scanner I don't pickup hardly anything and when I do there is a lot of ambient noice so much that I can barely hear what is being said. If I turn off the amp then the communication comes through very clear.

Sounds as if the amp is being overloaded by something. It could be anything on any frequency - from the specs I'd say there's nothing even related to a tuned circuit in that amp.

 

[godspeed]

Suggestions

Three operating suggestions:

1.) As previously mentioned keep the preamp as near to the antenna as possible.

2.) I`m found the ramsey unit works best in conjunction with the radio shack variable attenuator (0-20db) just before the scanner. I use it to keep signal levels only as strong as needed and to adjust out overload.

3.) An inline FM filter before the preamp can do wonders as well in rejecting FM broadcast intermod which most likely WILL be a problem.

These three things have given me great performance from that unit. Hope that helps

Eric

 

[hcsotinstar]

I have a BC-785 in the mobile that I monitor an 800 Mhz trunking system with. The Rx sensitivity has been crappy from day one. Is anyone running a preamp on a mobile antenna? Preferably a preamp tuned only at 800 Mhz? I am really disappointed with the Rx sensitivity on this scanner.

Victor

 

[godspeed]

I`ve had dismal results in car with a preamp. Mainly due to noise picked up from the electrical system being amplified.

 

[doctordave]

Victor,

What sort of cable/antenna are you using?

 

[dlbrock]

I am using the Radio Shack whip antenna. It works the best of all antennas that I have tried but I live on the edge of coverage so I need to do something.

 

[W4KRR]

I recently purchased a Ramsey Wide-Band Pre-amplifier. Freq Range 1Mhz - 1Ghz.
http://www.grove-ent.com/PRE2.html
They claim that the noise figure is <3db and the average gain is 23db but when I hook this up to my scanner I don't pickup hardly anything and when I do there is a lot of ambient noice so much that I can barely hear what is being said. If I turn off the amp then the communication comes through very clear.

I am thinking about returning the unit but was wondering if anyone had any thoughts.

Thanks,

Doug

Return it. Sometimes preamps make your reception worse than if you had no antenna at all. This is due to the preamp overloading your scanner, as others have pointed out.

 

[Hoofy]

I am using the Radio Shack whip antenna. It works the best of all antennas that I have tried but I live on the edge of coverage so I need to do something.

Remember that when you are listening to vhf and uhf that these frequencies are line of sight frequencies and the height of your receiving antenna can make a tremendous difference. The higer the better in most cases especially if you're on a fringe area. And try to get the antenna in the clear as much as possible. Use good quality coax and use the highest gain antenna you can afford.
Hoofy

 

[godspeed]

yeah height makes a huge difference. My setup with the preamp and a duckie get me squat. but the setup hooked to my scantenna on the roof (with the same preamp setup) get me a ton and the occasional satellite.

 

[Hir8ed_2]

I`ve had dismal results in car with a preamp. Mainly due to noise picked up from the electrical system being amplified.

Sounds like you need to go to AutoZone and get a Capacitor to cut out the altenator and ignition interference...

 

[godspeed]

haha nah. I was just curious about the preamp while in the car. I keep it at home. the mobile antenna is sufficient when I`m on the move as is.

 

[hcsotinstar]

Anyone ever use a preamp to increase reception?

I am using a Radial / Larsen NMO 800 antenna with a Radial / Larsen NMO mount.
I've tried another mount and feedline on opposite side of the vehicle with the same
results.

Victor

Victor,

What sort of cable/antenna are you using?

 

[dlbrock]

Thanks for all the responses. Based upon advice, received here, I purchased an FM Trap and an RF attenuator. While the FM Trap didn't do anything for me, the RF attenuator was the trick. I just need a small amount of attenuation to keep from overloading the scanner front end. I am now picking up coms from 50 miles away.

Thanks again!

Doug

 

[kb2vxa]

Hi all,

"Do they have antenna mounted amps that can be controlled/powered remotely similar to a rotor?"

Yes, TV mast head amps are very common and the better ones have the FM broadcast band blocked. Power from a wall wart is sent up the coax with an in-line network that blocks the DC from everything downstream while passing the signals straight through. The advantage here is to overcome transmission line loss and noise by shoving the amplified signals down the coax rather than amplifying what's left plus noise at the receiver end.

Preamplifiers have numerous disadvantages which you see discussed here so you must weigh them against the advantages in the balance. They help in some cases but in others they either do nothing worthwhile or make bad things happen. You really have to do your homework on this one and remember that yor situation is unique, what's good for the goose isn't necissarily good for the gander.

The most important thing to remember is that 90% of your scanner is on the roof. In other words you must give the antenna and transmission line first consideration.